54
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1 Faculty of Medicine, 
University of Ljubljana, 
Ljubljana, Slovenia
2 Department of 
Otorhinolaryngology and 
Cervicofacial Surgery, 
University Medical Centre 
Ljubljana, Ljubljana, 
Slovenia
Correspondence/
Korespondenca:
Saba Battelino, e: saba.
battelino@kclj.si
Key words:
benign paroxysmal 
postitional vertigo; central 
vestibular disorders; 
vertigo; Dix-Hallpike 
manoeuvre; calorimetry
Ključne besede:
benigna paroksizmalna 
vrtoglavica; centralne 
ravnotežne motnje; 
vrtoglavice; Dix-Hallpike-ov 
manever; kalorimetrija
Received: 23. 9. 2019
Accepted: 5. 11. 2020
eng slo element
en article-lang
10.6016/ZdravVestn.2985 doi
23.9.2019 date-received
5.11.2020 date-accepted
Neurobiology Nevrobiologija discipline
Review article Pregledni znanstveni članek article-type
Functional tests for assessment of the vestibu-
lar system – literature review and an example 
of our experience
Funkcionalni testi za oceno ravnotežnega organa – 
pregled literature in primer naših izkušenj
article-title
Functional tests for assessment of the vestib-
ular system Funkcionalni testi za oceno ravnotežnega organa
alt-title
benign paroxysmal postitional vertigo, central 
vestibular disorders, vertigo, Dix-Hallpike 
manoeuvre, calorimetry
benigna paroksizmalna vrtoglavica, centralne 
ravnotežne motnje, vrtoglavice, Dix-Hallpike-ov 
manever, kalorimetrija
kwd-group
The authors declare that there are no conflicts 
of interest present.
Avtorji so izjavili, da ne obstajajo nobeni 
konkurenčni interesi. conflict
year volume first month last month first page last page
2021 90 1 2 54 73
name surname aff email
Saba Battelino 1,2 saba.battelino@kclj.si
name surname aff
Metka Sluga 1
Manja Hribar 2
eng slo aff-id
Faculty of Medicine, University 
of Ljubljana, Ljubljana, Slovenia
Medicinska fakulteta, Univerza v 
Ljubljani, Ljubljana, Slovenija 1
Department of 
Otorhinolaryngology and 
Cervicofacial Surgery, University 
Medical Centre Ljubljana, 
Ljubljana, Slovenia
Klinika za otorinolaringologijo 
in cervikofacialno kirurgijo, 
Univerzitetni klinični center 
Ljubljana, Ljubljana, Slovenija
2
Functional tests for assessment of the 
vestibular system – literature review and an 
example of our experience
Funkcionalni testi za oceno ravnotežnega organa – 
pregled literature in primer naših izkušenj
Metka Sluga,1 Manja Hribar,2 Saba Battelino1,2 
Abstract
Vertigo and other balance disorders, which can have many different origins, are among the 
most common reasons for seeking medical care. The otorhinolaryngologist mostly deals with 
disorders of the inner ear and the vestibular nerve while, at the same time, identifying possible 
diseases of central origin as the cause of symptoms. To make a diagnosis, a combination of sev-
eral different tests is usually required so that the impairment of different parts of the vestibular 
system can either be confirmed or excluded. In general, we distinguish between tests to exam-
ine the semicircular canals and tests’ function to estimate the saccule and utricle’s function. We 
describe a clinical trial whereby we examined 1042 patients with a clear history of benign parox-
ysmal positional vertigo, which was diagnosed in 36%. Further tests, described in the following 
article, had to be performed. To interpret the test results, we often rely on the observation and 
measurement of eye movements. This requires knowledge of mechanisms of certain reflexes 
responsible for maintaining balance. At the same time, we have to consider the patient’s symp-
toms and complement the tests with other imaging examinations if necessary.
Izvleček
Težave z ravnotežjem sodijo med pogoste vzroke za obisk pri zdravniku, njihov izvor pa je lahko 
precej raznovrsten. Na področju otorinolaringologije se posvečamo predvsem okvaram notra-
njega ušesa in ravnotežnega živca ter nakažemo morebitno centralno prizadetost ravnotežnega 
sistema. Za postavitev diagnoze pogosto ne zadostuje zgolj ena preiskava, pač pa je po navadi 
potrebna kombinacija različnih testov, s katerimi potrjujemo ali izključujemo prizadetost posa-
meznih delov ravnotežnega sistema. V osnovi razlikujemo med testi, s katerimi ocenjujemo de-
lovanje polkrožnih kanalčkov, in testi za oceno delovanja sakulusa in utrikulusa. Predstavljena 
je klinična raziskava, v kateri smo pri 1.042 bolnikih z jasno anamnezo za benigni paroksizmalni 
pozicijski vertigo le-tega dokazali v 36 %. Nujno je bilo opraviti še dodatna testiranja, ki jih pred-
stavlja prispevek. Za razlago njihovih rezultatov se pogosto zanašamo na opazovanje in merje-
nje gibanja očesnih zrkel, pri čemer je pomembno poznavanje določenih refleksov za ohranjanje 
ravnotežja. Ob tem moramo upoštevati tudi simptome, ki jih navaja bolnik, in teste po potrebi 
dopolniti s slikovnodiagnostičnimi preiskavami. Natančne računalniške meritve in grafični zapisi 
danes nadomeščajo opazovanje s prostim očesom in subjektivno razlaganje opažanj preiskoval-
ca.
Cite as/Citirajte kot: Sluga M, Hribar M, Battelino S. Functional tests for assessment of the vestibular system 
– literature review and an example of our experience. Zdrav Vestn. 2021;90(1–2):54–73.
Slovenian
Medical
Journal
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Functional tests for assessment of the vestibular system
1 Introduction
Vertigo and other balance disorders 
are among the most common reasons 
for seeking medical care. Patients de-
scribe them as uncomfortable loss of 
orientation in space and a false feeling of 
movement of the body and/or the sur-
roundings, such as spinning, wobbling, 
or inclining. Their prevalence in the gen-
eral population is about 17%, and in the 
elderly above 80 years, it grows to 39% 
(1). Diseases of the vestibular part of the 
inner ear, together with the vestibuloco-
chlear nerve form part of the peripheral 
vestibular system, are slightly more fre-
quent than central nervous system dis-
eases (2). In the strict sense, the human 
balance system includes the vestibuloco-
chlear nerve and its ganglia, four vestib-
ular nuclei in the brainstem, cerebellum, 
and parts of the cerebral cortex (3). The 
reasons for its malfunction have varied 
origins and pathogenesis. When facing 
balance issues, otorhinolaryngology pri-
marily focuses on the inner ear and ves-
tibular nerve disorders.
Vestibular system dysfunction is gen-
erally manifested as a combination of 
sensory, oculomotor, postural, and au-
tonomous symptoms and signs: vertigo, 
gait abnormality (ataxia), nausea, and 
vomiting (1).
The patient’s medical history is first 
used to define the type of symptom, its 
duration, trigger factors, and a possible 
concurrent hearing loss, as well as con-
comitant chronic diseases, with systemic 
diseases often having a significant effect 
on balance. Next, we continue with an 
otoneurologic examination of the patient 
DOI: https://doi.org/10.6016/ZdravVestn.2985
Copyright (c) 2021 Slovenian Medical Journal. This work is licensed under a
Creative Commons Attribution-NonCommercial 4.0 International License.
and basic hearing tests. These are followed 
by assessing the balance function used to 
define disorders in individual structures 
responsible for maintaining balance.
2 Anatomy and physiology of 
the vestibular system
The vestibular system in the inner 
ear consists of three semicircular canals 
and the otolith organs. The semicircular 
canals (superior, posterior, and lateral) 
lie perpendicular to one another, always 
functioning in pairs (posterior with the 
anterior of the opposite side and both lat-
eral), and include cristas ampullae. These 
have gelatinous cups and detect angular 
acceleration through the changes in the 
endolymph current in the membranous 
part of the labyrinth with hair cells. In 
the inner ear’s vestibule, the otolith or-
gan comprises the saccule, which lies on 
the vertical plane, and the utricle, which 
lies on the horizontal plane. Its sensory 
organs, the maculae, sense linear accel-
eration and gravity (4). The vestibular 
system is connected to the eighth cranial 
nerve’s vestibular nerve through nuclei 
in the brain stem with the nuclei of some 
other cranial nerves, the cerebellum, and 
the cerebral cortex. The human brain does 
not contain a primary vestibular cerebral 
cortex area; however, it consists of sever-
al separate areas. These regions combine 
the balance, aural, visual, and somato-
sensory inputs (5). They demonstrate a 
strong right hemispheric dominance. The 
parieto-insular vestibular cortex (PIVC) 
was among the first areas to be defined 
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as vestibular, and after additional studies, 
the posterior insular cortex, the temporo-
parietal junction, the anterior insula, the 
pre- and postcentral gyrus of the parietal 
lobe, the ventrolateral part of the occipital 
lobe, and the inferior frontal gyrus with 
the inferior part of the precentral sulcus 
(5).
Understanding how the tests assess the 
vestibular system work is also essential to 
understand certain reflexes that ensure 
stabilization. The first among them is the 
vestibuloocular reflex, which stabilizes 
the image on the retina while the head 
moves by moving the eye bulb in the op-
posite direction, thereby retaining the 
image in the central part of the field of 
vision. Stimuli for the reflex mainly orig-
inate in the semicircular canals, then run 
through the vestibular nerve to the vestib-
ular nuclei in the brainstem. From there, 
the neurons connect with the nuclei of 
cranial nerves that ensure the movement 
of the extraocular muscles, moving the 
eye bulb appropriately (6).
In certain types of tests, the vestibu-
lospinal reflex is also essential. This is a 
combination of reflexes whose objective 
is to stabilize the body. When tilting the 
head, the semicircular canals on both 
sides become stimulated. The stimulus is 
transferred through the vestibular nerve 
and the vestibular centres along the lat-
eral and medial vestibulospinal tract, 
activating extensor muscles on the side 
towards which the head is tilted, and the 
flexor muscles on the other side. This en-
sures that the position of the body and the 
head are stabilized (3).
The most important indicator of the 
vestibular system function is spontaneous 
or evoked eye movements. By origin, we 
roughly divide them into ocular, periph-
eral vestibular, and central vestibular nys-
tagmus. Peripheral nystagmus is repeated, 
coordinated eye bulb movements around 
a horizontal or vertical axis, comprising 
a slow and fast phase, by which we also 
define its direction (7). Typical peripher-
al nystagmus is horizontal, it may have a 
rotational component, and it intensifies 
when the gaze fixation is removed (e.g., 
with closed eyelids, in darkness, or when 
using high-powered Frenzel’s’ goggles). 
The first-degree nystagmus occurs when 
gazing towards the fast component’s di-
rection, and the second degree also when 
gazing straight, while third-degree nys-
tagmus is present when gazing in all di-
rections (8). According to Alexander’s 
law, the amplitude of nystagmus increases 
when the eye moves towards the fast phase 
and decreases when viewing in the oppo-
site direction (9). By nystagmus onset, we 
divide them into spontaneous nystagmus, 
which is always pathologic, except in the 
most eccentric positions and optokinetic, 
and evoked by the movements of the body 
or by vibration stimulation of the inner 
ear (10). Every nystagmus that onsets 
without proper physiological stimulation 
is treated as abnormal, or the absence of 
nystagmus with appropriate stimulation 
(8). Nystagmus can be observed with the 
naked eye, or we can use glasses or a CCD 
camera that follows the pupils and logs 
the eye movement on a computer.
Because the vestibular system is not a 
single structure, every part must be test-
ed with different stimulation frequencies 
when there are balance issues. First, we 
stimulate the semicircular canals; then, 
we assess the saccule and the utricle func-
tion. The tests for assessing the vestibular 
system can be divided into the group of 
tests for assessing the function of semicir-
cular canals and the group for assessing 
the saccule and the utricle. They are sum-
marized in Table 1.
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Functional tests for assessment of the vestibular system
3 Test for the assessment of 
the vestibular system
3.1 Tests for the assessment 
of the semicircular canals
The tests for assessing the function 
of semicircular canals are divided by the 
speed with which the canals are stimu-
lated, as they have a different sensitivity 
to stimulation with low and high frequen-
cies (11). Caloric testing is among the very 
low-frequency tests. Low-frequency tests 
include rotation testing, while high-fre-
quency tests include the head impulse 
test. The medium-frequency dynamic vi-
sual acuity test (DVAT), the very high-fre-
quency vestibulo-collic reflex (VCR) test, 
and the vibration-induced nystagmus 
test (VIN) (11) are not performed at the 
Centre of Audiology and Vestibulology, 
Department of Otorhinolaryngology and 
Cervicofacial Surgery, University Medical 
Centre Ljubljana, Slovenia.
3.1.1 Caloric testing
Caloric testing is primarily intended 
for assessing the function of the later-
al semicircular canal. It is based on the 
principle that changes to the inner ear 
temperature trigger movement similar 
to turning the head. This results in the 
endolymph circulating within the lateral 
semicircular canal and, through the ves-
tibulo-ocular reflex, induces the response 
in the form of nystagmus, based on which 
we can assess the function of the lateral 
semicircular canal (12).
The examination procedure: the sub-
ject is placed supine, with the head ele-
vated at a 30-degree angle. Before we be-
gin the ear irrigation, we check whether 
the patient has spontaneous nystagmus 
in a standing or a sitting position using 
Frenzel’s goggles. Then, we irrigate the 
left ear canal with 30 °C water for half a 
minute, and for the next half-minute, we 
count or electronically log the twitches of 
the subject’s eye bulbs. After a brief pause, 
we repeat the procedure on the opposite 
ear. When stimulating with cold water, 
the nystagmus generally occurs in the 
opposite direction of the stimulated ear. 
Then, we repeat the procedure on both 
ears with water heated to 44°C, initiating 
the nystagmus in the stimulated ear’s di-
rection. If we do not initiate a response 
with ear irrigation in the first two tem-
peratures, we repeat the procedure with 
17°C water. When we cannot stimulate a 
response, even in this case, we can con-
clude that the labyrinth is not calorically 
stimulable (11).
This is one of the most frequently per-
formed balance tests conducted for verti-
go and instability, loss of hearing on one 
side, or any other suspicion of impaired 
function of the peripheral part of the ves-
tibular system.
When reading the results, it is import-
ant to compare both sides and consider 
the nystagmographic response’s absolute 
values, comparing it with average, i.e., 
normal values. An example of a caloric 
test result is in Figure 1.
When comparing both semicircular 
canals, we describe the paresis (labyrin-
thine paresis/predominance) and prepon-
derance (13). The semicircular canal’s pa-
resis is defined as at least a 20% difference 
in nystagmography response between 
both canals and represents a reduced 
function of one labyrinth concerning the 
opposite labyrinth (14). This is frequent 
with vestibular neuritis, Menièr’s disease, 
and tumours of the eighth cranial nerve, 
and can also onset with migraines and 
cerebrovascular diseases.  The directional 
preponderance describes the higher in-
tensity of the nystagmus in a particular 
direction than the other side by at least 
20–30%. Clinically, the preponderance 
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has several different implications. It may 
be present in entirely healthy people; it 
can reflect a single-side peripheral bal-
ance impairment on the opposite side, a 
central impairment, or even damage to 
the cerebral cortex (13).
Figure 1: Graphic display of caloric testing of the vestibular system. Less than 20% difference 
in the nystagmographic (i.e., paresis box) response between both sides indicates a normal 
response (A); a difference of more than 20% in the response between both sides indicates 
reduced function or paresis of one of the canals (B).
R – right; L – left.
Concerning the nystagmography re-
sponse’s absolute values, we describe hy-
per-, hypo-, and areflexia Hyperreflexia 
occurs when calorically stimulated nys-
tagmus exceeds the standard value. With 
peripheral vestibular disorders, it may 
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Functional tests for assessment of the vestibular system
occur on the opposite side of the affected 
location. The reason can also be a change 
in the ear, e.g., after a mastoidectomy or 
an eardrum perforation. With central 
vestibular disorders, hyperreflexia can be 
bilateral. An example of this is an impair-
ment of the cerebellum’s flocculus, which 
in its normal condition inhibits the neu-
rons of the vestibular core, thereby inhib-
iting the vestibulo-ocular reflex. When it 
is damaged, this inhibitory effect does not 
take place.
Hyporeflexia can result from differ-
ent causes, namely from drugs inhibit-
ing the labyrinth function or their toxic 
effect on the ear to systemic infection 
diseases, hypertension, brain tumours, 
and degenerative diseases of the central 
nervous system anxiety, also possibly due 
to the abuse of psychoactive substanc-
es. Areflexia, i.e., total unresponsiveness 
to caloric response, can be part of Usher 
syndrome resulting from bilateral periph-
eral vestibular loss or ototoxicity. In 20% 
of patients, the reasons for it remain un-
explained (15). However, it is not always 
related to a total loss of the balance func-
tion (13).
Despite frequent use, caloric testing 
has certain shortcomings. The effect that 
the ear irrigation has on the subject’s ear 
differs from person to person. This makes 
it difficult to compare the sensitivity of 
different people’s labyrinths concerning 
the absolute values of caloric stimulation 
responses. We can especially compare the 
sensitivity of both ears of the same sub-
ject, and even this calls for a certain level 
of caution, as the stimuli received by the 
left and the right ear are not entirely the 
same. Also, the frequency with which we 
excite the semicircular canals in this test is 
reasonably low. The vestibular system re-
sponds best to the head’s fast turns with a 
frequency of between 0.1 and 3 Hz. With 
caloric testing, we can only stimulate 
receptors up to a frequency of 0,003 Hz, 
which is significantly lower than the opti-
mum. We also do not know the stimula-
tion’s exact strength and must, therefore, 
be careful when interpreting results (16).
Certain subjects find the tests especial-
ly uncomfortable, as they can trigger ver-
tigo and nausea. If the examiner assesses 
that testing could trigger significant dis-
comfort in the examinee, testing should 
be stopped as soon as possible.
Seldom is caloric testing performed 
on both sides simultaneously. Only with 
the onset of nystagmus, i.e., with a differ-
ent stimulation results in one inner ear, is 
each ear tested separately (17).
3.1.2 Rotatory testing
The rotary chair test is also aimed at 
assessing the sensitivity of simultaneous-
ly stimulated lateral semicircular canals. 
The angular acceleration is used as a stim-
ulus (when the rotation begins and after 
it ends) when rotating the whole body. It 
is generally used in combination with ca-
loric testing, and if needed, the tests are 
supplemented with other vestibular sys-
tem examinations.
The rotary chair makes it possible to 
position the head at a 30-degree angle in 
which lateral semicircular canals are in 
a nearly horizontal position. The subject 
is then rotated ten times in one and ten 
times in the other direction, with a fre-
quency of approximately one rotation per 
second. Using nystagmographic goggles, 
we can watch the nystagmus during the 
rotation (rotatory nystagmus) and when 
stopped (post-rotatory nystagmus) and 
its persistence for each side of rotation 
(18,19).
Tests can consist of different protocols 
in which we rotate the subject in both 
directions with different frequencies and 
accelerations.
The main indications for rotatory 
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testing are bilateral paresis of the lateral 
semicircular canals, unsatisfactory re-
sults of the caloric testing, and the fact 
that small children being rotated in their 
parent’s lap can perform the test as well. 
The test assesses both vestibular systems 
at the same time. They provide the resid-
ual function data in patients with signs of 
bilateral failure of the vestibular system 
measured with caloric testing and the da-
ta on the central compensation of unilat-
eral paresis of the vestibular system (19).
3.1.3 Head impulse test
Unlike caloric and rotatory testing, 
where we stimulate and measure only 
the lateral semicircular canal function, 
all three canals are tested in the head im-
pulse test (HIT). Also, the frequencies in 
this test are higher than with the caloric 
test. This is an examination in which the 
vestibulo-ocular reflex (VOR) of each 
semicircular canal is measured separately 
during passive, quick and unpredictable 
head movements by 10 to 20 degrees in 
different directions (20).
First, the examiner merely monitored 
the subject’s eye movements by obser-
vation. Later, eye bulb movements with 
special wires installed on an eye via lens 
were introduced. The latest HIT version 
is called vHIT (video head impulse test), 
where light-weight and tightly fitting gog-
gles with a camera monitor the eye bulbs’ 
compensation movements during rapid 
head movements (impulses). The glasses 
are connected to software that marks the 
head and eye bulb movements, creating a 
graphic output from the data.
After proper positioning of the gog-
gles, the subject stares at a point approx-
imately 1 meter away on the wall in front 
of them. The subject’s head is turned 35 
degrees left or right, while their eyes re-
main focused on the point. The examin-
er then begins performing rapid sagittal 
head movements (up and down), stimu-
lating both vertical semicircular canals. 
The head first faces straight ahead; then, 
the examiner rapidly turns it left and 
right. This stimulates canals in pairs – 
both lateral together, the right anterior 
and the left posterior (RALP – with the 
starting position of head-turning left) 
and the left anterior and the right poste-
rior (LART – with the starting position of 
the head-turning right) at the same time. 
The examined person performs approxi-
mately 7 to 10 unpredictable head move-
ments individually in all directions. The 
whole procedure is called a head impulse 
paradigm (HIMP) (21).
With healthy subjects, there is smooth, 
compensatory eye bulb movement, re-
sulting from a well-functioning VOR. 
These maintain the focus on a fixed point 
(22) and are not visible to the examiner 
with the naked eye. Quite the opposite, 
patients with paresis of the semicircular 
canal exhibit corrective saccades at the 
Impulse’s end. When eye bulbs that had 
previously not been fixed on a point be-
cause of the impacted VOR, these occur 
with head movements, making a com-
pensatory move towards it. These are 
so-called overt saccades, which an exam-
iner notices when performing the test. 
These are clinical signs of the paresis of 
the canal. When moving the head to the 
impacted side, the left semicircular canal 
is affected, occurring when moving the 
head rapidly to the left. Some patients are 
capable of performing corrective saccades 
when the head is being turned. These are 
covert saccades that the examiner cannot 
see with their naked eye. They are essen-
tial for diagnosing impairments to the 
semicircular canal and can be measured 
with the vHIT test.
The graphic outputs of the head and 
eye bulbs’ movements, as shown in Figure 
2, are the same for healthy subjects, which 
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Functional tests for assessment of the vestibular system
means that eye bulbs with VOR appropri-
ately follow head movements. The chart 
allows us to calculate the so-called gain, 
i.e., the ratio between the speed of the 
slow, compensatory phase of the eye bulb 
and the speed of head movements. The 
gain value for healthy people is approx-
imately 1, i.e., sit should be above 0.79, 
meaning that the eye bulb movement’s 
speed follows head movements well (23). 
When there is the dysfunction of the 
semicircular canal, the VOR is impaired, 
and the graphic representation of eye 
bulb movement shows a record of com-
pensatory saccades. The gain is character-
istically lowered, generally much below 1.
Figure 2: Video Head Impulse Test (vHIT) results. Impulse right graph indicates a subject’s results with a normal function 
of the vestibulo-ocular reflex, where eye bulb movements appropriately follow the head movements. The Impulse 
left graph indicates the results in a patient with an impaired, left vestibulo-ocular reflex. This patient produces overt 
saccades to attempt to compensate for the reduced gain (24) appropriately.
There are numerous advantages of 
vHIT over caloric testing. With vHIT, we 
can measure the function of all six semi-
circular canals, while with caloric test-
ing we can only examine the function of 
the lateral ones. With caloric testing, we 
predominantly measure the asymmetry 
between the speeds of the slow phase of 
nystagmus with the same stimulation 
in both ears. The vHIT test also detects 
symmetrical, bilateral impairments of the 
vestibular system that appear as a normal, 
symmetric function of both canals in ca-
loric testing. vHIT is quick, objective and 
repeatable, and can be performed even 
during acute vertigo attacks. It can assist 
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in differentiating between vertigo from a 
stroke, i.e., central nervous system lesion, 
where test results are often normal, ver-
tigo resulting from peripheral vestibular 
neuritis, and vestibular dysfunction due 
to the Menière’s disease.
The protocol version called the 
Suppression Head Impulse Paradigm 
(SHIMP) also must be mentioned. It al-
so uses vHIT technology, but the subject 
does not fixate their gaze on a point on the 
wall during the test, instead of following a 
point that moves together with their head. 
Results of the SHIMP test are the oppo-
site of those of HIMP. At the end of an 
impulse, a healthy subject makes a bigger 
anti-compensatory saccade, while with 
patients who suffer from loss of vestibular 
function, we do not see the saccade. The 
vestibulo-ocular reflex attempts to avert 
the gaze from the moving point. With 
healthy subjects, VOR is suppressed, but 
with a delay of a few tenths of a millisec-
ond; therefore, VOR moves the gaze away 
from the point during this time. When the 
subject is instructed to follow the target, 
there is a conscious reflex suppression, 
causing an anti-compensatory saccade at 
the end of the Impulse (the SHIMPs sac-
cade), a sign of a well-functioning VOR. 
With patients with an impairment of the 
semicircular canal, and therefore the loss 
of VOR, it does not avert their gaze from 
the point, and, therefore, there are no an-
ti-compensatory saccades at the end of 
the Impulse (23).
The Functional Head Impulse Test 
(fHIT) is a version of the test based on 
recognizing an optotype briefly flashed 
on a computer screen. It is a function-
al measure of the vestibulo-ocular reflex 
function, mirrored with the ability to re-
tain visual acuity and to read during fast, 
passive head movements (25).
3.1.4 Dynamic visual acuity test
The dynamic visual acuity test (DVA) is 
a simpler version of the head impulse test. 
It is based on the fact that with the vestib-
ular system’s peripheral impairments, the 
retinal slippage during head movements 
is higher than usual. When the slippage 
speed is greater than 2–4° per second, vi-
sual acuity is reduced. By measuring visu-
al acuity during head movements, we can 
directly conclude an impairment of the 
vestibulo-ocular reflex and semicircular 
canals; however, we must first exclude any 
impairments in the eye bulb motor func-
tion that are not the result of an impair-
ment of the vestibular system. Performing 
the test includes performing a version of 
quick passive and active head movements 
while simultaneously measuring visual 
acuity using a Snellen chart. This verifies 
the vestibulo-ocular reflex function and 
can lead to a conclusion regarding a uni-
lateral or bilateral impairment of the ves-
tibular system (26).
3.1.5 The Dix-Hallpike test
This manoeuvre can confirm benign 
paroxysmal positional vertigo (BPPV), 
which is caused by free-floating otoliths 
in one or several semicircular canals. It 
can be performed on patients who feel 
short-term vertigo when changing their 
head position. At the start of the test, the 
patient sits on a bed, with the head tilt-
ed towards the tested ear at a 45-degree 
angle. The examiner then lies the patient 
down with a quick movement so that the 
subject’s head gazes across the edge of the 
bed, and the examiner extends it by 20 
to 30 degrees below the horizon. When 
performing this manoeuvre with a short 
pause, we can see the onset of typical nys-
tagmus, which does not persist for more 
than a minute with BPPV; however, it 
63
REVIEW ARTICLE
Functional tests for assessment of the vestibular system
may persist in a milder form sometime 
after the completion of the test. The test 
is then repeated on the opposite side. The 
impacted semicircular canal can be deter-
mined according to the direction of the 
nystagmus (11).
3.1.6 Videonystagmography (VNG)
The vestibular system function can 
be assessed with videonystagmography 
(VNG), where we analyze eye bulb move-
ments in detail using nystagmography 
goggles. They follow the movements of 
the eye with an infra-red camera (27). 
VNG includes three standard tests: the 
oculomotor test, the optokinetic posi-
tional test, and caloric testing. With the 
oculomotor test, we follow the eye mus-
cle motor function independently from 
the vestibular function. Oculomotor 
abnormalities could affect the results of 
vestibular function test results, which 
are interpreted based on eye movements. 
First, we verify spontaneous nystagmus’s 
presence without fixation (in the dark), 
then while fixing the gaze at a 30° angle. 
These are followed by tracking a moving 
point (smooth and saccadic following) 
and forming the optokinetic nystagmus 
when viewing moving lines, vertical 
and horizontal, separately. The comput-
er-generated results enable assessment of 
the nystagmus’ symmetry when rotating 
to the left and right, and we can compare 
the speed of eye bulb movement rela-
tive to the head’s speed. We can compare 
measurements recorded in a dark room 
(preventing the gaze from fixing) and the 
measurements recorded with a fixed gaze. 
Nystagmus with a fixed gaze, abnormal-
ities in gaze following, and optokinetic 
nystagmus generally occur in central ner-
vous system impairment. This is followed 
by a position test, where we observe the 
onset of nystagmus when the head and 
the body are tilted into different positions. 
Persistent nystagmus is non-specific and 
is not particularly helpful for determining 
the location of the impairment in the ves-
tibular system. We can also observe eye 
movements when performing the Dix-
Hallpike manoeuvre. Delayed nystag-
mus, rotational nystagmus, or weakened 
nystagmus in a particular position of the 
head point to BPPV, especially if the pa-
tient also manifests corresponding symp-
toms (28).
This is followed by performing the ca-
loric and rotational tests described above.
3.2 Tests for the assessment 
of the otolith organ
3.2.1 Vestibular-evoked myogenic 
potentials – VEMP
Vestibular-evoked myogenic poten-
tials (VEMP) are electromyographic re-
sponses evoked by sound, vibrations, or 
electricity, of the stimulated vestibular 
system (29). In this test, there are two 
types of electromyographic respons-
es. The cervical VEMP (cVEMP) runs 
through saccule stimulation, the inferior 
vestibular nerve (n. vestibularis inferior), 
the vestibular nuclei in the brain stem, 
and up to activating the vestibulospinal 
tract and the glossopharyngeal nerve nu-
cleus (n. IX, n. glossopharyngeus) with 
an inhibition response of the sternoclei-
domastoid muscle on the same side (the 
vestibulo-collic reflex). The ocular VEMP 
(oVEMP) runs through utricle stimu-
lation and the superior vestibular nerve 
(n. vestibularis superior), the vestibular 
nuclei, and the medial longitudinal fasci-
cle to the oculomotor nerve nucleus (n. 
oculomotorius) with excitation response 
to the opposite inferior oblique muscle 
(the otolith-ocular reflex). We measure 
the sternocleidomastoid muscle’s elec-
tromyographic response or the external 
eye bulb muscles’ response to the aural 
64
NEUROBIOLOGY
Zdrav Vestn | January – February 2021 | Volume 90 | https://doi.org/10.6016/ZdravVestn.2985
stimulation of the otolith organ.
Both otolith organs respond to stim-
ulation with loud, by air- or bone-trans-
mitted low-frequency tone. However, 
cVEMP is generally more specific for 
measuring the saccule function, and 
oVEMP for the utricle (30).
When cVEMP is performed using 
headphones, the saccule is stimulated, 
generally using 95–100 dB loud, short 
tones with a frequency of 500–1,000 Hz. 
Individual tones are played with 5-second 
pauses, and together approximately 200 
repeats per ear are produced. It is recom-
mended that one ear at a time is stimu-
lated. We place an electrode on the mid-
third of the sternocleidomastoid muscle 
to measure the muscle’s electromyo-
graphic responses to the aural stimuli, 
and these are then displayed on the com-
puter screen. Because the vestibulo-collic 
reflex causes an inhibition response of the 
sternocleidomastoid muscle, the subject 
must contract the muscle during the test. 
Via the same electrode, we also monitor 
the muscle contraction so that the sub-
ject can maintain the proper contraction 
during the test. If the muscle contraction 
is insufficient during the test, the VEMP 
responses are not suitable for analysis 
(31).
The most interesting parts of the test 
results depicted in Figure 3 are the char-
acteristic waves P13 and N23. They enable 
an analysis of various parameters, such as 
the latency and amplitude of both waves, 
the latency between them, the difference 
in latencies and amplitudes between ears, 
and the difference between their values 
and their threshold values.
oVEMP is conducted similarly, except 
the electrodes are placed beneath both 
eyes and on the forehead to measure the 
inferior oblique muscle’s electromyo-
graphic response. The patient must keep 
the gaze upwards during the examination 
Fi
gu
re
 3
: G
ra
ph
ic
 d
is
pl
ay
 o
f t
he
 re
su
lt 
of
 th
e 
cV
EM
P 
te
st
. T
he
 h
ig
hl
ig
ht
ed
 w
av
es
 a
re
 P
13
 a
nd
 N
23
 o
f t
he
 m
us
cl
e 
on
 th
e 
rig
ht
 si
de
 o
f t
he
 n
ec
k 
aft
er
 st
im
ul
at
io
n 
of
 th
e 
rig
ht
 e
ar
. A
fte
r s
tim
ul
at
io
n 
of
 th
e 
le
ft 
ea
r, 
th
er
e 
is
 n
o 
cV
EM
P 
re
sp
on
se
 o
n 
th
e 
m
us
cl
e.
to retain the inferior oblique muscle con-
tracted. The results show the frequency at 
which the response with the highest wave 
amplitude and latency occurs. The fre-
quencies through which we stimulate the 
vestibular system in oVEMP are similar 
to cVEMP, and the results reflect mainly 
the stimulability of the utricle (32).
A cVEMP test is used when diagnosing 
both peripheral and central lesions of the 
vestibular system (29). When diagnosing 
Menière’s disease or endolymphatic hy-
drops, we can lose the VEMP response to 
stimulation. With Menière’s disease, we 
can also notice the highest amplitude re-
sponse transition at usually 500–700 Hz 
to 1000 Hz. Comparing test results before 
and after an attack is especially crucial, as 
with endolymphatic hydrops, the cVEMP 
amplitude is restored at the impacted side 
after the attack. This also normalizes the 
frequency at which we get the response 
with the highest amplitude (33).
With vestibular neuritis, cVEMP can 
significantly assist in diagnosing the af-
fected location of the vestibular organ. 
The inferior vestibular nerve mainly sup-
plies nerve fibres to the saccule and the 
posterior semicircular canal, while the su-
perior vestibular nerve supplies nerve fib-
bers mainly to the lateral and the anterior 
semicircular canal and the utricle. With a 
pathological cVEMP, which is more spe-
cific for the saccule, in combination with 
normal results of the caloric test, specific 
for the lateral canal, we can conclude that 
the inferior vestibular nerve is affected 
(29).
With migraine patients suffering from 
vertigo, the cVEMP results can change in 
the sense of lower amplitudes (34). With 
a vestibular migraine, cVEMP can show 
extended latency and increased frequen-
cy at which the response with the high-
est amplitude occurs (similar to Menièr’s 
disease), which points to the possibility of 
65
REVIEW ARTICLE
Functional tests for assessment of the vestibular system
stimulation of the otolith organ.
Both otolith organs respond to stim-
ulation with loud, by air- or bone-trans-
mitted low-frequency tone. However, 
cVEMP is generally more specific for 
measuring the saccule function, and 
oVEMP for the utricle (30).
When cVEMP is performed using 
headphones, the saccule is stimulated, 
generally using 95–100 dB loud, short 
tones with a frequency of 500–1,000 Hz. 
Individual tones are played with 5-second 
pauses, and together approximately 200 
repeats per ear are produced. It is recom-
mended that one ear at a time is stimu-
lated. We place an electrode on the mid-
third of the sternocleidomastoid muscle 
to measure the muscle’s electromyo-
graphic responses to the aural stimuli, 
and these are then displayed on the com-
puter screen. Because the vestibulo-collic 
reflex causes an inhibition response of the 
sternocleidomastoid muscle, the subject 
must contract the muscle during the test. 
Via the same electrode, we also monitor 
the muscle contraction so that the sub-
ject can maintain the proper contraction 
during the test. If the muscle contraction 
is insufficient during the test, the VEMP 
responses are not suitable for analysis 
(31).
The most interesting parts of the test 
results depicted in Figure 3 are the char-
acteristic waves P13 and N23. They enable 
an analysis of various parameters, such as 
the latency and amplitude of both waves, 
the latency between them, the difference 
in latencies and amplitudes between ears, 
and the difference between their values 
and their threshold values.
oVEMP is conducted similarly, except 
the electrodes are placed beneath both 
eyes and on the forehead to measure the 
inferior oblique muscle’s electromyo-
graphic response. The patient must keep 
the gaze upwards during the examination 
Fi
gu
re
 3
: G
ra
ph
ic
 d
is
pl
ay
 o
f t
he
 re
su
lt 
of
 th
e 
cV
EM
P 
te
st
. T
he
 h
ig
hl
ig
ht
ed
 w
av
es
 a
re
 P
13
 a
nd
 N
23
 o
f t
he
 m
us
cl
e 
on
 th
e 
rig
ht
 si
de
 o
f t
he
 n
ec
k 
aft
er
 st
im
ul
at
io
n 
of
 th
e 
rig
ht
 e
ar
. A
fte
r s
tim
ul
at
io
n 
of
 th
e 
le
ft 
ea
r, 
th
er
e 
is
 n
o 
cV
EM
P 
re
sp
on
se
 o
n 
th
e 
m
us
cl
e.
66
NEUROBIOLOGY
Zdrav Vestn | January – February 2021 | Volume 90 | https://doi.org/10.6016/ZdravVestn.2985
the vestibular migraine originating both 
centrally and peripherally (35).
There are also reports on normal val-
ues of cVEMP and oVEMP with patients 
with a spinning feeling in the transversal 
or sagittal plane without rotational verti-
go (so-called idiopathic otolithic vertigo). 
cVEMP results can also help diagnose 
lesions of the central nervous system that 
affect areas included in the vestibulo-col-
lic or vestibulo-ocular reflex. The most 
often studied is multiple sclerosis which 
can be manifested with extended latency 
of P13 and N23 waves (36).
In combination with computed to-
mography (CT), oVEMP is most import-
ant in diagnosing the superior semicir-
cular canal’s dehiscence. It also plays an 
essential role in diagnosing BPPV. It can 
also be used for detecting other vestibu-
lar impairments in the event of vestibular 
nerve lesions, otolith diseases, and central 
nervous system lesions (37).
3.2.2 Subjective visual vertical test 
(SVV)
Patients with utricle impairment often 
do not have vertigo issues but instead de-
scribe a general instability during move-
ment, a feeling of swinging, and are more 
in danger of falling. In particular, the 
subjective visual vertical test (SVV) is in-
tended to test the utricular function. It is 
based on the assessment of the patient’s 
ability to determine true vertical, i.e., de-
termining how much the patient’s subjec-
tive (i.e., visual) vertical differs from the 
real (i.e., gravitational) vertical (38). The 
patient inspects a straight line in front 
and aims to position it vertically. The an-
gle between the subjective and the true 
verticality reflects the utricular function.
This test’s simple version is the buck-
et test, where the examiner encloses the 
subject’s whole visual field with a bucket. 
A straight line is drawn on the bottom of 
the bucket. In the beginning, the examin-
er turns the bucket so that the line on the 
bottom is not aligned with true verticali-
ty. Then the examiner slowly rotates the 
bucket, and the subject must say when the 
line is aligned vertically. There is an angle 
meter on the outside of the bucket that 
the examiner uses to measure how much 
the patient’s verticality differs from the 
gravitational. They can also use a weight-
ed string, installed on the outside bottom 
of the bucket, aligned with 0° on the angle 
meter. They can use it to read the discrep-
ancy of the subject’s verticality from true 
verticality (39).
A newer, digitalized version of the 
SVV test is increasingly replacing the 
bucket test. It consists of digital goggles 
that block all light, and on the inside, the 
subject sees a straight line. Using a wire-
less remote, they have to place the line 
into presumed true verticality. Setting the 
verticality occurs while the head is tilted 
at different angles, 0, 15, 30, and 45 de-
grees left and right. A gyroscope located 
in the goggles supports measuring the 
head tilt angle, ensuring the correct head 
position during testing. The higher the 
head-tilt angle, the more difficult it is for 
the subject to determine true verticality.
Results are measured using software, 
which records the angle of the tilt of the 
patient’s head and the angle of the dero-
gation of their verticality from true verti-
cality (Figure 4). Angle deviation beyond 
2° is defined as pathological, and the di-
rection of the deviation depends on the 
location of the vestibular system’s impair-
ment. With unilateral peripheral or pon-
tomedullary changes, the visual vertical is 
generally tilted to the affected side; with 
pontomesencephalic impairments, it is 
tilted to the opposite direction thalamic 
changes, it may be tilted to the affected 
or unaffected side. The test is described 
as especially useful in the literature when 
67
REVIEW ARTICLE
Functional tests for assessment of the vestibular system
diagnosing certain peripheral vestibu-
lar system lesions, such as BPPV and the 
unilateral vestibular loss, and in certain 
central nervous system lesions. It is also 
used as the follow-up instrument in the 
treatment of these diseases (39).
3.3 Balance assessment robot
Besides the tests mentioned above, we 
should also focus on the balance assess-
ment robot (BAR), developed by Slovenian 
researchers at University Rehabilitation 
Institute Soča (URI-Soča). This is a device 
for testing and enhancement the vestibular 
function of patients after a stroke. The pri-
mary objective of training with the robot 
is to reduce the number of patients’ falls. 
The training is based on the fact that when 
unpredictable forces (i.e., perturbations) 
act on a body during walking, an individ-
ual responds with a combination of ad-
justing their centre of pressure (COP) in 
the leg that is currently on the ground and 
by redirecting the raised leg to a location 
where it will be able to support the body to 
counteract the unpredictable force appro-
priately. With patients who have suffered a 
stroke, the mechanisms that provide such 
responses can be impaired. To learn how 
to perform the movements required to re-
spond appropriately, their training must 
consist of realistic situations that make it 
possible to lose balance. Depending on 
their physical impairment, they can then 
develop a good balance response. 
The device is essentially a combination 
of a treadmill and a movable frame that 
supports the patient’s pelvis. It has embed-
ded sensors for graphing the pelvis’s posi-
tion on a screen, the length of the step, the 
duration of steps, and the COP in the foot. 
It supports comprehensive measurements 
of steps and provides pressure jolts to the 
pelvis and assessing the response to them 
(40).
Fi
gu
re
 4
: G
ra
ph
ic
 d
is
pl
ay
 o
f t
he
 re
su
lts
 o
f t
he
 su
bj
ec
tiv
e 
vi
su
al
 v
er
tic
al
 te
st
 (S
VV
). 
Re
co
gn
iz
in
g 
su
bj
ec
tiv
e 
ve
rt
ic
al
ity
 w
ith
in
 2
° a
ng
le
 fr
om
 tr
ue
 v
er
tic
al
ity
 is
 
re
co
gn
iz
ed
 a
s n
or
m
al
 (l
eft
), 
w
hi
le
 a
ng
le
 d
ev
ia
tio
ns
 a
bo
ve
 2
° a
re
 p
at
ho
lo
gi
ca
l (
rig
ht
).
68
NEUROBIOLOGY
Zdrav Vestn | January – February 2021 | Volume 90 | https://doi.org/10.6016/ZdravVestn.2985
Training on this device consists of 
three phases. During the first phase, the 
patient walks straight along the tread-
mill while their position and movement 
are captured. The device exerts pressure 
on the pelvis when an abnormal gait is 
detected. This stimulates them to take 
all steps as equally as possible since they 
are otherwise asymmetric after a stroke. 
Meanwhile, the patient monitors their 
pelvis’s position on the monitor, striv-
ing to maintain it in the correct position. 
In the second phase, the patient walks a 
“virtual terrain” with a screen’s aid. They 
see their path on the screen, e.g., uphill, 
while the BAR exerts forces to the body 
that simulates walking uphill. In the third 
phase, the BAR provides unpredictable 
jolts from all directions while the patient 
is walking, and they have to respond to 
them appropriately to correct their pos-
ture and gait.
Exercise on the BAR is entirely safe 
and makes it easier to develop the whole 
vestibular system’s effective responses to 
unpredictable events.
3.4 Vestibular evoked potentials
Vestibular-evoked potentials (VsEPs) 
of the central nervous system are EEG 
responses, i.e., neurogenic potentials re-
corded with electrodes placed on the 
scalp when stimulating the vestibular sys-
tem. The vestibular system can be stim-
ulated with numerous quick and short 
head turns. The average of electronic neu-
ron responses and concurrent dissipation 
of background noise draws the curve of 
their path. The neurogenic response can-
not be measured for patients with an im-
pairment to the peripheral and/or central 
vestibular pathways. With these types of 
examinations, a frequent issue is the ar-
tifacts in the results, which also hinders 
the interpretation of the results; therefore, 
Tests for the assessment of the semicircular canals
Caloric testing By changing the liquid's temperature in the inner ear and observing the evoked 
nystagmus, we can assess the lateral semicircular canal dysfunction. 
Rotatory testing By rotating on a chair, we simultaneously stimulate both lateral semicircular canals. 
This provides the assessment of the residual function of the semicircular canals in a 
bilateral impairment of the vestibular system or provides an assessment of a central 
compensation of unilateral vestibular paresis.  
Head impulse test With rapid head movements in different directions, we stimulate all six semicircular 
canals in pairs. We monitor their function by changing vestibulo-ocular reflex, i.e., eye 
bulb compensation saccades during head movements. 
Functional head impulse test Using optotypes, we measure the ability to retain visual acuity during rapid head 
movements, thereby assessing the vestibulo-ocular reflex's function. 
A dynamic visual acuity test By measuring visual acuity during rapid head movements, we obtain the data on the 
impairment of the vestibulo-ocular reflex, i.e., the semicircular canals' function. 
The Dix-Hallpike test Using a special manoeuvre, we can evoke nystagmus in patients with suspected 
benign paroxysmal positional vertigo, and based on the result; we can assess the 
impairment of semicircular canals. 
Tests for the assessment of the otolith organ
Vestibular-evoked myogenic potentials Using short, loud tones, we stimulate the saccule or utricle and measure 
characteristic electromyographic responses of the sternocleidomastoid muscle or 
external eye bulb muscles. 
Subjective Visual Vertical test (SVV) By measuring the difference between the subject’s subjective and true verticality, we 
measure the utricular function. 
Balance assessment robot
The device makes it possible to measure exact steps and apply different forces to the 
body through the pelvis and is aimed at balance enhancement and practicing the 
steady gait for patients who have suffered a stroke. 
Vestibular-evoked potentials When stimulating the vestibular system with fast turns of the head, we measure the EEG of the cerebral cortex. 
Table 1: Classification of the vestibular system assessment test by the speed of stimulation and the inner ear’s 
anatomical location.
this method is seldom used to assess ves-
tibular system function (41).
4 Example of using several 
diagnostic tests
4.1 Patients and methods
We performed a retrospective anal-
ysis of the data for 1,042 patients who 
were treated for balance disorders at the 
Centre of Audiology and Vestibulology, 
Department of Otorhinolaryngology and 
Cervicofacial Surgery, University Medical 
Centre Ljubljana, Slovenia, between 2006 
and 2015, and who reported a typical 
history for short-term benign paroxys-
mal positional vertigo (BPPV). We per-
formed the Dix-Hallpike manoeuvre for 
diagnosing BPPV (11). We continued 
with the therapeutic Epley repositioning 
manoeuvre with a positive manoeuvre 
(11), and the patients were scheduled for 
a check-up within three weeks. Because 
determining which semicircular canal 
or canals are impacted can be difficult in 
clinical practice, especially with bilater-
al positive position tests, we divided all 
performed diagnostic maneuver results 
into positive (unilateral or bilateral) and 
negative. At the follow-up or even at the 
first examination, most patients had a 
caloric testing (i.e., bi-thermal frequency 
vestibulogram (VTG: Varitherm plus and 
Varioair)) performed, and in some vide-
onystagmography (VNG: Interacoustics 
VN415/VO425) has been performed (11). 
The patients’ data for whom we confirmed 
BPPV was then analyzed in more detail 
by age, sex, side of the impairment, the 
treatment success, level of repeatability, 
history of head injury, and osteoporosis. 
To alleviate the results’ interpretation, we 
assumed that the repositioning manoeu-
vre instructed at the first examination was 
successful for patients who did not attend 
69
REVIEW ARTICLE
Functional tests for assessment of the vestibular system
Training on this device consists of 
three phases. During the first phase, the 
patient walks straight along the tread-
mill while their position and movement 
are captured. The device exerts pressure 
on the pelvis when an abnormal gait is 
detected. This stimulates them to take 
all steps as equally as possible since they 
are otherwise asymmetric after a stroke. 
Meanwhile, the patient monitors their 
pelvis’s position on the monitor, striv-
ing to maintain it in the correct position. 
In the second phase, the patient walks a 
“virtual terrain” with a screen’s aid. They 
see their path on the screen, e.g., uphill, 
while the BAR exerts forces to the body 
that simulates walking uphill. In the third 
phase, the BAR provides unpredictable 
jolts from all directions while the patient 
is walking, and they have to respond to 
them appropriately to correct their pos-
ture and gait.
Exercise on the BAR is entirely safe 
and makes it easier to develop the whole 
vestibular system’s effective responses to 
unpredictable events.
3.4 Vestibular evoked potentials
Vestibular-evoked potentials (VsEPs) 
of the central nervous system are EEG 
responses, i.e., neurogenic potentials re-
corded with electrodes placed on the 
scalp when stimulating the vestibular sys-
tem. The vestibular system can be stim-
ulated with numerous quick and short 
head turns. The average of electronic neu-
ron responses and concurrent dissipation 
of background noise draws the curve of 
their path. The neurogenic response can-
not be measured for patients with an im-
pairment to the peripheral and/or central 
vestibular pathways. With these types of 
examinations, a frequent issue is the ar-
tifacts in the results, which also hinders 
the interpretation of the results; therefore, 
Tests for the assessment of the semicircular canals
Caloric testing By changing the liquid's temperature in the inner ear and observing the evoked 
nystagmus, we can assess the lateral semicircular canal dysfunction. 
Rotatory testing By rotating on a chair, we simultaneously stimulate both lateral semicircular canals. 
This provides the assessment of the residual function of the semicircular canals in a 
bilateral impairment of the vestibular system or provides an assessment of a central 
compensation of unilateral vestibular paresis.  
Head impulse test With rapid head movements in different directions, we stimulate all six semicircular 
canals in pairs. We monitor their function by changing vestibulo-ocular reflex, i.e., eye 
bulb compensation saccades during head movements. 
Functional head impulse test Using optotypes, we measure the ability to retain visual acuity during rapid head 
movements, thereby assessing the vestibulo-ocular reflex's function. 
A dynamic visual acuity test By measuring visual acuity during rapid head movements, we obtain the data on the 
impairment of the vestibulo-ocular reflex, i.e., the semicircular canals' function. 
The Dix-Hallpike test Using a special manoeuvre, we can evoke nystagmus in patients with suspected 
benign paroxysmal positional vertigo, and based on the result; we can assess the 
impairment of semicircular canals. 
Tests for the assessment of the otolith organ
Vestibular-evoked myogenic potentials Using short, loud tones, we stimulate the saccule or utricle and measure 
characteristic electromyographic responses of the sternocleidomastoid muscle or 
external eye bulb muscles. 
Subjective Visual Vertical test (SVV) By measuring the difference between the subject’s subjective and true verticality, we 
measure the utricular function. 
Balance assessment robot
The device makes it possible to measure exact steps and apply different forces to the 
body through the pelvis and is aimed at balance enhancement and practicing the 
steady gait for patients who have suffered a stroke. 
Vestibular-evoked potentials When stimulating the vestibular system with fast turns of the head, we measure the EEG of the cerebral cortex. 
Table 1: Classification of the vestibular system assessment test by the speed of stimulation and the inner ear’s 
anatomical location.
their check-ups. In this retrospective, the 
National Medical Ethics Committee ap-
proved the Republic of Slovenia’s clinical 
study (No. 0120-032/2016-2, March 21st, 
2016).
4.2 Results
We performed a diagnostic manoeu-
vre for BPPV on our subjects, and the 
expected typically evoked nystagmus oc-
curred in 376 (36%) of 1,042 patients, of 
whom 267 (71%) were women. Patients’ 
median age with a positive test was 58.5 
years (± 15, with a range between 16-92). 
Manoeuvres on the right side were positive 
with 188 (50%), and on the left side with 
145 (38.6%), bilaterally with 42 (11.1%) 
patients, while with one patient (0.23%), 
the only note is that the manoeuvre was 
positive, which can be interpreted as the 
presence of so-called subjective BPPV, 
i.e., the onset of vertigo without visible 
nystagmus. Repositioning manoeuvres 
were successful with 335 patients (89%). 
Improvements with occasional vertigo 
(with some depending on the position, 
with some not) or a feeling of instability 
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Zdrav Vestn | January – February 2021 | Volume 90 | https://doi.org/10.6016/ZdravVestn.2985
were mentioned by 20 (5.3%) patients, 
while with 21 (5.6%), there was no im-
provement. Test results were divided into 
normal results, vestibular system paresis, 
and central impairment. 52 (13.8%) pa-
tients had a recurrence of BPPV. With 40 
(10.6%) patients, the onset of BPPV oc-
curred after head trauma. 9 (2.4 %) pa-
tients had osteoporosis.
After performing appropriate thera-
peutic manoeuvres, 217 (57.7%) patients 
had VTG done, and 51 (13.6%) VNG. 
Among the patients whose vertigo was 
successfully eliminated, 204 (60.9%) had 
normal VTG and VNG results. For 20 
(6%), VTG proved vestibular system pa-
resis, while for 4 (1.2%), VNG established 
central vestibular impairments, and with 
2 (0.6%), there was a combination of ves-
tibular system paresis and central impair-
ment. With 105 (31.3%) patients without 
persistent vertigo, we could not perform 
the VTG or the VNG test. Among the 
patients who still had issues with BPPV 
after the therapeutic manoeuvres, VTG 
and VNG results were normal for 4 and 5, 
respectively, for a total of 9 (45%), while a 
total of 7 (35%), 2 with VTG and 5 with 
VNG, had paresis. For one patient (5%), 
VNG proved they had a central impair-
ment. Neither VTG nor VNG was per-
formed for 3 (15%) patients. Of the pa-
tients with persisting vertigo, 8 (38.1%) 
had normal results of both tests, 6 (28.6%) 
had a paresis, which was proven with a 
VTG, 5 (23.8%) had central vestibular 
impairments, which were proven with 
VNG, while 1 (4.8%) had a combination 
of paresis and central vestibular impair-
ments, also proven with a VNG test. We 
did not conduct additional tests on one 
(4.8%) patient from the group with per-
sistent vertigo. The results of these tests 
are compiled in Table 2.
5 Conclusion
The reason for short-term positional 
vertigo is not always BPPV, as we only 
diagnosed it in 36% of cases using di-
agnostic manoeuvres on patients with 
related issues. We did not perform a de-
tailed analysis on patients with negative 
diagnostics tests for BPPV in this study’s 
scope. Along with caloric testing and 
videonystagmography, the additional 
Diagnostic maneuver Therapeutic 
(repositioning) 
maneuver
VTG VNG
Positive/
pathologic
right left bilateral
335 (89%) 28 (12.9%) 18 (35.3%)
188 (50%) 145 (38.6%) 42 (11.1%)
Total
376 (36%)
Negative/
normal 666 (64%) 41 (11%) 189 (87.1%) 33 (64.7%)
Total 1.042 376 217 51
Table 2: The diagnostic manoeuvre was positive, i.e., pathological, for 376 patients (36%) of 1,042. Among these, 
repositioning manoeuvres were successful with 335 (89%) patients. Additional tests (VTG or VNG) were performed with 
268 (71.3%) patients with a positive diagnostic manoeuvre, and using tests; we were able to additionally define the 
source of the problem with 46 (12.2%) patients.
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Functional tests for assessment of the vestibular system
References
1. Brandt T, Strupp M. General vestibular testing. Clin Neurophysiol. 2005;116(2):406-26. DOI: 10.1016/j.
clinph.2004.08.009 PMID: 15661119
2. Brandt T, Dieterich M. The dizzy patient: don’t forget disorders of the central vestibular system. Nat Rev 
Neurol. 2017;13(6):352-62. DOI: 10.1038/nrneurol.2017.58 PMID: 28429801
3. Khan S, Chang R. Anatomy of the vestibular system: a review. NeuroRehabilitation. 2013;32(3):437-43. DOI: 
10.3233/NRE-130866 PMID: 23648598
4. Ekdale EG. Form and function of the mammalian inner ear. J Anat. 2016;228(2):324-37. DOI: 10.1111/
joa.12308 PMID: 25911945
5. Fasold O, von Brevern M, Kuhberg M, Ploner CJ, Villringer A, Lempert T, et al. Human vestibular 
cortex as identified with caloric stimulation in functional magnetic resonance imaging. Neuroimage. 
2002;17(3):1384-93. DOI: 10.1006/nimg.2002.1241 PMID: 12414278
6. Cullen KE. The vestibular system: multimodal integration and encoding of self-motion for motor control. 
Trends Neurosci. 2012;35(3):185-96. DOI: 10.1016/j.tins.2011.12.001 PMID: 22245372
7. Probst R, Grevers G, Iro H. Basic Otorhinolaryngology. New York: Thieme; 2006. p. 277.
8. Kavanagh KT, Babin RW. Definitions and types of nystagmus and calculations. Ear Hear. 1986;7(3):157-66. 
DOI: 10.1097/00003446-198606000-00007 PMID: 3487475
9. Jeffcoat B, Shelukhin A, Fong A, Mustain W, Zhou W. Alexander’s Law revisited. J Neurophysiol. 
2008;100(1):154-9. DOI: 10.1152/jn.00055.2008 PMID: 18450584
10. Newman-Toker DE. Symptoms and signs of neuro-otologic disorders. Continuum (Minneap Minn). 
2012;18:1016-40. DOI: 10.1212/01.CON.0000421618.33654.8a PMID: 23042058
11. Jacobson GP, Shepard NT. Balance function assessment and management. San Diego (CA): Plural 
Publishing Inc; 2016.
12. Jacobson GP, Newman CW, Kartush JM. Handbook of balance function testing. St. Louis, MO: Mosby Year 
Book; 1997.
13. Gonçalves DU, Felipe L, Lima TM. Interpretation and use of caloric testing. Rev Bras Otorrinolaringol (Engl 
Ed). 2008;74(3):440-6. DOI: 10.1016/S1808-8694(15)30580-2 PMID: 18661020
14. Jongkees LB. Value of the Caloric Test of the Labyrinth. Arch Otolaryngol Head Neck Surg. 1948;48(4):402-
17. DOI: 10.1001/archotol.1948.00690040414003
15. Brandt T. Bilateral vestibulopathy revisited. Eur J Med Res. 1996;1(8):361-8. PMID: 9360934
16. Jacobson GP, Shepard NT. Balance function assessment and management. San Diego,CA: Pluras 
Publishing; 2008.
definition of the origin of short-term 
positional vertigo would also be possible 
with newer tests described in this article, 
which can be used to more precisely con-
firm or exclude impairment of an indi-
vidual or several semicircular canals.
For all patients for whom the periph-
eral vestibular disorder has not been elu-
cidated or excluded, we will perform all 
the described tests to assess the function 
of distinctive parts of the vestibular sys-
tem. The results and the basic guidelines 
for treating patients whose medical his-
tory points to BPPV are shown below.
The significant progress in the devel-
opment of balance assessment tests de-
veloped over the past few years has made 
it possible to define the cause of the bal-
ance disorder more clearly. Continued 
research of the vestibular system is re-
quired to yield an even more detailed 
assessment of the results obtained from 
the existing tests. Regarding the patients 
we tested, we expect to increase the per-
centage of etiologically explained bal-
ance disorders through additional bal-
ance assessment tests. At the same time, 
we are looking to develop new tests that 
will utilize computer technology and 
functional-magnetic imaging to improve 
treatment and the possibilities for the 
rehabilitation of patients with vestibular 
disorders.
72
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Zdrav Vestn | January – February 2021 | Volume 90 | https://doi.org/10.6016/ZdravVestn.2985
17. Sataloff RT, Pavlick ML, McCaffrey JD, Davis JM, Stewart SM. Simultaneous binaural bithermal caloric 
testing: clinical value. Ear Nose Throat J. 2017;96(1):29-31. PMID: 28122101
18. Behrbohm H, Becker W, Naumann HH, Pfaltz CR. Ear, nose, and throat diseases: With head and neck 
surgery. Stuttgart: Thieme; 2009. DOI: 10.1055/b-005-148831
19. Maes L, Vinck BM, Wuyts F, D’haenens W, Bockstael A, Keppler H, et al. Clinical usefulness of the rotatory, 
caloric, and vestibular evoked myogenic potential test in unilateral peripheral vestibular pathologies. Int J 
Audiol. 2011;50(8):566-76. DOI: 10.3109/14992027.2011.576706 PMID: 21751944
20. Alhabib SF, Saliba I. Video head impulse test: a review of the literature. Eur Arch Otorhinolaryngol. 
2017;274(3):1215-22. DOI: 10.1007/s00405-016-4157-4 PMID: 27328962
21. MacDougall HG, McGarvie LA, Halmagyi GM, Rogers SJ, Manzari L, Burgess AM, et al. A new saccadic 
indicator of peripheral vestibular function based on the video head impulse test. Neurology. 
2016;87(4):410-8. DOI: 10.1212/WNL.0000000000002827 PMID: 27251884
22. Curthoys IS, Manzari L. Clinical application of the head impulse test of semicircular canal function. Hear 
Balance Commun. 2017;15(3):113-26. DOI: 10.1080/21695717.2017.1353774
23. Halmagyi GM, Chen L, MacDougall HG, Weber KP, McGarvie LA, Curthoys IS. The Video Head Impulse Test. 
Front Neurol. 2017;8:258. DOI: 10.3389/fneur.2017.00258 PMID: 28649224
24. Petrak MR, Bahner C, Beck DL. Video Head Impulse Testing (vHIT): VOR Analysis of High Frequency 
Vestibular Activity. [cited 2019 Sep 17]. Available from: http://www.hearingreview.com/2013/08/video-
head-impulse-testing-vhit-vor-analysis-of-high-frequency-vestibular-activity/
25. Versino M, Colnaghi S, Corallo G, Mandalà M, Ramat S. The functional head impulse test: comparing gain 
and percentage of correct answers. Prog Brain Res. 2019;248:241-8. DOI: 10.1016/bs.pbr.2019.04.028 PMID: 
31239135
26. Vital D, Hegemann SC, Straumann D, Bergamin O, Bockisch CJ, Angehrn D, et al. A new dynamic visual 
acuity test to assess peripheral vestibular function. Arch Otolaryngol Head Neck Surg. 2010;136(7):686-91. 
DOI: 10.1001/archoto.2010.99 PMID: 20644064
27. Falls C. Videonystagmography and Posturography. Adv Otorhinolaryngol. 2019;82:32-8. DOI: 
10.1159/000490269 PMID: 30947200
28. Furman JM, Goldstein A. Vertigo. In: Swaiman KF, Ashwal S, Ferriero DM, Schor NF, Finkel RS, Gropman AL, 
et al. Swaiman’s pediatric neurology: Principles and practice. 6th ed. Edingburgh: Elsevier; 2018. pp. 52-7.
29. Murofushi T. Clinical application of vestibular evoked myogenic potential (VEMP). Auris Nasus Larynx. 
2016;43(4):367-76. DOI: 10.1016/j.anl.2015.12.006 PMID: 26791591
30. Colebatch JG, Rosengren SM, Welgampola MS. Vestibular-evoked myogenic potentials. Handb Clin Neurol. 
2016;137:133-55. DOI: 10.1016/B978-0-444-63437-5.00010-8 PMID: 27638068
31. Akin FW, Murnane OD, Panus PC, Caruthers SK, Wilkinson AE, Proffitt TM. The influence of voluntary tonic 
EMG level on the vestibular-evoked myogenic potential. J Rehabil Res Dev. 2004;41(3b):473-80. DOI: 
10.1682/JRRD.2003.04.0060 PMID: 15543465
32. Rosengren SM, Colebatch JG, Young AS, Govender S, Welgampola MS. Vestibular evoked myogenic 
potentials in practice: Methods, pitfalls and clinical applications. Clin Neurophysiol Pract. 2019;4:47-68. 
DOI: 10.1016/j.cnp.2019.01.005 PMID: 30949613
33. Seo T, Shiraishi K, Kobayashi T, Mutsukazu K, Fujita T, Saito K, et al. Revision of a furosemide-loading 
vestibular-evoked myogenic potential protocol for detecting endolymphatic hydrops. Acta Otolaryngol. 
2017;137(12):1244-8. DOI: 10.1080/00016489.2017.1355565 PMID: 28749204
34. Roceanu A, Allena M, De Pasqua V, Bisdorff A, Schoenen J. Abnormalities of the vestibulo-collic reflex 
are similar in migraineurs with and without vertigo. Cephalalgia. 2008;28(9):988-90. DOI: 10.1111/j.1468-
2982.2008.01641.x PMID: 18624802
35. Murofushi T, Ozeki H, Inoue A, Sakata A. Does migraine-associated vertigo share a common 
pathophysiology with Meniere’s disease? Study with vestibular-evoked myogenic potential. Cephalalgia. 
2009;29(12):1259-66. DOI: 10.1111/j.1468-2982.2009.01860.x PMID: 19911463
36. Shimizu K, Murofushi T, Sakurai M, Halmagyi M. Vestibular evoked myogenic potentials in multiple 
sclerosis. J Neurol Neurosurg Psychiatry. 2000;69(2):276-7. DOI: 10.1136/jnnp.69.2.276 PMID: 10960289
37. Weber KP, Rosengren SM. Clinical utility of ocular vestibular-evoked myogenic potentials (oVEMPs). Curr 
Neurol Neurosci Rep. 2015;15(5):22. DOI: 10.1007/s11910-015-0548-y PMID: 25773001
38. Michelson PL, McCaslin DL, Jacobson GP, Petrak M, English L, Hatton K. Assessment of Subjective Visual 
Vertical (SVV) Using the “Bucket Test” and the Virtual SVV System. Am J Audiol. 2018;27(3):249-59. DOI: 
10.1044/2018_AJA-17-0019 PMID: 29946701
39. Cohen HS, Sangi-Haghpeykar H. Subjective visual vertical in vestibular disorders measured with the 
bucket test. Acta Otolaryngol. 2012;132(8):850-4. DOI: 10.3109/00016489.2012.668710 PMID: 22667824
40. Matjačić Z, Zadravec M, Olenšek A. Feasibility of robot-based perturbed-balance training during 
treadmill walking in a high-functioning chronic stroke subject: a case-control study. J Neuroeng Rehabil. 
2018;15(1):32. DOI: 10.1186/s12984-018-0373-z PMID: 29642921
73
REVIEW ARTICLE
Functional tests for assessment of the vestibular system
41. Rosengren SM, Colebatch JG. Vestibular evoked potentials (VsEPs) in patients with severe to profound 
bilateral hearing loss. Clin Neurophysiol. 2006;117(5):1145-53. DOI: 10.1016/j.clinph.2005.12.026 PMID: 
16497555