Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4433_Библиотеки_им_академика_М_И_Перельмана
.pdf
324 BALANCE FUNCTION ASSESSMENT AND MANAGEMENT
https://t.me/medicina_free
Figure 13–32 illustrates rotational findings from
a patient with a compensated complete unilateral
peripheral vestibulopathy. In patients such as this, vestibular gain has been centrally compensated; however,
phase abnormalities continue to persist. The persistence of phase abnormalities is a result of impairment
in the velocity storage mechanism. This centrally distributed system acts as a neural integrator to enhance
the low frequency performance of the vestibular system beyond what would be expected based on cupular
mechanics. Significant unilateral vestibular impairments disrupt the normal functioning of the velocity
storage mechanism and consequently reduce the efficiency of the VOR for low frequencies (Goldberg, 2000;
Goldberg et al., 2012). This loss of velocity storage has
the effect of increasing VOR phase leads, generally for
low frequency stimuli below 1.0 Hz. In cases where the
unilateral peripheral vestibulopathy is severe or complete, VOR phase abnormalities may be more inclusive
of frequencies greater than 1.0 Hz.
Bilateral Peripheral Impairments
SHA testing is extremely useful in describing and
quantifying the severity of bilateral vestibular loss. Figure 13–33 shows rotational results from a patient with
partial bilateral vestibular dysfunction. As can be seen,
there is significantly reduced gain at 0.01 and 0.02 Hz
with recovery of function at higher frequencies. At the
frequencies where gain is significantly low, phase and
symmetry measures should be interpreted with caution. This pattern of partial bilateral loss at low frequencies is a relatively common finding and will often
be accompanied by reduced caloric responses. In these
cases, abnormally low but measurable VOR responses
are often accompanied by corresponding prolonged
phase at the same frequencies. Symmetry measures
obtained from patients with bilateral peripheral
impairments in the absence of spontaneous nystagmus
are typically within normal limits. Patients manifesting
a complete vestibular loss or labyrinthine areflexia (i.e.,
no response at any frequency) are relatively uncommon
(Figure 13–34). Finally, it is important to keep in mind
that, because VOR phase and symmetry measures are
calculated from VOR gain, in cases where VOR gain is
below 10% to 15%, such measures of phase and symmetry should be performed with caution.
Central Impairments
Pure central lesions are often difficult to isolate using
SHA testing. More commonly, mixed lesions will be
suggested, as both a reduction of peripheral afferent
vestibular input and central lesions can produce the
more common SHA abnormalities of abnormal VOR
phase lead and VOR asymmetry. Mixed lesions are
figure 13–32. Common SHA results for unilateral labyrinthine hypofunction. Results for VOR gain (A), VOR phase
(B), and VOR symmetry (C) from 0.01 through 0.64 Hz. Normal VOR gain and symmetry in the presence of abnormal
low-HZ VOR phase provides good evidence for effective compensation.
13. ROTATIONAL VESTIBULAR ASSESSMENT 325
https://t.me/medicina_free
figure 13–33. Common sinusoidal harmonic acceleration (SHA) results for bilateral labyrinthine hypofunction.
Results for VOR gain (A), VOR phase (B), and VOR symmetry (C) from 0.01 through 2.0 Hz. Abnormal response
regions are indicated by the gray regions for each results graph.
figure 13–34. Common SHA results for bilateral labyrinthine areflexia. Results for VOR gain (A), VOR phase (B),
and VOR symmetry (C) from 0.01 through 2.0 Hz. Since VOR phase and symmetry are calculated form VOR, these
parameters should be interpreted with caution under such conditions.
326 BALANCE FUNCTION ASSESSMENT AND MANAGEMENT
https://t.me/medicina_free
often suggested when concomitant central findings are
identified, such as abnormal ocular motor findings.
There are, however, specific SHA response patterns that
have a greater proclivity secondary to a central lesion.
First, abnormal VOR phase leads that are isolated to
the mid-to-high frequencies suggest an inappropriate
recruitment of the central neural integrator mechanism
(velocity storage) that would normally not require
recruitment of such processes during higher frequency
head movements. Second, VOR asymmetries in the
absence of any peripherally induced spontaneous nystagmus may suggest a central pathology, similar to that
of an isolated caloric directional preponderance. Such
an SHA result may suggest a lack of central compensation mechanisms for a unilateral peripheral vestibular
insult, particularly when VOR gain remains uncompensated. Finally, significantly increased VOR gain,
most commonly for low rotational frequencies, may be
associated with a central lesion, similar to that of hyperreactive caloric responses. Although not ubiquitously present with increased VOR gain, a decrease in
VOR phase lead, or even a phase lag, may be present
in such cases, as problems involving uncontrolled cerebellar modulation of VOR gain cause concomitant
problems with central velocity storage mechanisms and
tend to shorten low frequency VOR phase leads (Figure
13–35).
Sinusoidal Harmonic Acceleration
Clinical Summary
Overall, the SHA provides the examiner with a number
of useful applications. These include documenting the
degree of bilateral vestibular loss, tracking compensation when caloric testing is impossible, monitoring
vestibular function in patients being administered vestibulotoxic medications, and assessing young children.
However, SHA is best utilized in the context of other
tests, including ocular motor and VST, as well as other
vestibular function testing (e.g., videonystagmography,
vestibular evoked myogenic potentials, video head
impulse test, dynamic posturography).
figure 13–35. Central SHA pattern for VOR gain (A), VOR phase (B), and VOR symmetry (C) from 0.01 through
0.64 Hz. Borderline hyperlabyrinthine VOR gain for 0.01 Hz with a concomitant decrease in VOR phase is
identified.
13. ROTATIONAL VESTIBULAR ASSESSMENT 327
https://t.me/medicina_free
ADVANTAGES AND LIMITATIONS
TO
ROTATIONAL TESTING
As with any clinical assessment measure, the advantages and limitations of rotational testing can be significant. As such it is critical to understand the specific
benefits and limitations as they relate to rotational
assessment. Table 13–5 summarizes the advantages
and limitations to rotational assessments.
Advantages of Rotational
Vestibular
Rotational testing offers some distinct advantages for
assessing the vestibular system. There are eight primary advantages for performing rotational testing.
First and most important, rotational testing provides
exacting stimuli that are precisely controlled. Second, because the stimulus is precisely controlled, the
recorded response exhibits an extremely high degree
of repeatability (Brey, McPherson & Lynch, 2008a; Furman et al., 1994, 2000; Maes et al., 2008). This advantage
alone allows rotational testing to effectively monitor
vestibular physiology during recovery or deterioration
from vestibular disease or toxicity. Third, rotational
stimuli are far less noxious than other stimuli (i.e., the
caloric stimulus). Although slower rotational stimuli
can produce slight vegetative symptoms of nausea and
Testing
vertigo, the degree of subjective vertigo present during
most rotations is often minimal, making rotational testing more tolerable for patients. Fourth, rotational testing allows for the assessment of children when caloric
irrigations are often contraindicated (Cumberworth,
Patel, Rogers, & Kenyon, 2006; Cyr, 1991; Fife et al.,
2000; Phillips & Backous, 2002). Although precise objective measures may not always be obtained due to the
inability of fitting infrared goggles to a child’s or even
infant’s head, the observation (or lack thereof) can provide a binary decision of an intact VOR while the child
is seated on a parent’s lap (Cyr, 1991). Fifth, rotational
stimuli assess the vestibular system at frequencies that
approach those encountered during normal daily life
activities and are, therefore, a more functional measure
(see Figure 13–1) (White, 2007). Sixth, rotational testing
allows for the precise calculation of the timing relationship (or phase) of the VOR to head movement. This is
an important parameter of the VOR as it is a representation of the velocity storage of the system and indirectly
reflects central vestibular function (Shepard & Telian,
1996). Seventh, rotational testing provides a measure
of investigating bilateral vestibular lesions (Shepard
& Telian, 1996). It is well documented that a bilateral
absence of any VOR in response to caloric irrigations
does not necessarily mean a complete absence of vestibular function. Often, vestibular decrement will first
appear for lower frequencies prior to higher frequency
involvement (opposite that of cochlear dysfunction)
(Brey et al., 2008a). In light of this, caloric testing may
Table 13–5. Advantages and Limitations of Rotational Assessments
Advantages Limitations
Precisely controlled stimuli
High degree of stimulus and response
repeatability (when tasking is consistent)
Tolerable stimulus/less noxious than
caloric stimuli
Pediatric friendly
Broad, more natural stimulus frequency
range
Able to measure central contributions to
the VOR (phase, time decay constants)
Able to confirm/evaluate bilateral
vestibular loss
Monitor/examine central compensation
process
Difficult (but not impossible) to lateralize
unilateral vestibular lesions; particular
mild paresis
Equipment cost
Directly stimulates only a portion of the
peripheral vestibular system (horizontal
semicircular canal); however, the
response reflects both peripheral and
central contributions)
Response can be complex and not
always straightforward to interpret
328 BAlAnCE FunCtion AssEssmEnt And mAnAgEmEnt
https://t.me/medicina_free
not provide an adequate stimulus needed to produce
or confirm a vestibular response. Finally, rotational
testing allows for the determination of the progress
of central compensation following vestibular insult or
vestibular rehabilitation (Paige, 1989; Shepard & Telian,
1996). This is often documented by a recovery in the
sensitivity (gain) of the VOR response back to normal
levels. However, other subtle abnormalities frequently
remain even following effective compensation, such as
a permanent deficit in the timing (or phase) of the VOR
(Shepard & Telian, 1996).
Limitations of Rotational Vestibular Testing
The primary limitations of rotational testing are few;
however, they are significant. First and most relevant
is that the laterality of a vestibular lesion cannot always
be determined from rotational testing (Baloh, Sills, &
Honrubia, 1979). Because both vestibular labyrinths are
rotated simultaneously within the head, both excitatory
and inhibitory responses are simultaneously generated
(Brey et al., 2008a). Therefore, determining an independent response from a single labyrinth (horizontal semicircular ) is challenging. Simply stated, a reduction in
VOR sensitivity may be secondary to a lack of inhibition from the trailing ear or a lack of excitation from the
leading ear. Although this limitation can be addressed
through high velocity step testing (see Appendix IV),
the lack of lateralizing peripheral vestibulopathies is
duly noted. This is probably the most significant weakness of rotational testing, and often the first and foremost criticism offered from clinicians. However, with
the advancement of new tests like chair head impulse
testing, this limitation may only be a transient hurdle.
A second limitation is that rotational equipment
is extremely expensive and sizable, which does not
make purchasing the equipment very feasible for
most clinicians or facilities. At the time of this publishing, the approximate cost of a basic rotational system is ~$120,000 for a chair and lightproof booth, and
~$75,000 for a boothless version. The primary cost of
the chair is due to the highly specialized torque motor.
Other features can be added onto the purchase (e.g.,
off-vertical axis motors, higher frame-rate goggles,
specialized analysis research software), which can
quickly inflate the cost of a rotational system above
$250,000. Although boothless chairs and virtual LED
goggles assist in alleviating some of the cost and space
considerations, vestibular equipment is, in general,
expensive. A comprehensive vestibular lab is generally associated with a well-funded research university,
a well-funded clinical site, or a government facility. In
addition, a comprehensive vestibular lab is often only
present in more urban or metropolitan areas. Because
of these issues, such well-funded comprehensive vestibular labs are few when considering the comprehensive clinic per capita ratio. Unfortunately, rotational
chairs are some of the higher priced pieces of vestibular
equipment in the lab and consequently often the first
piece of vestibular test equipment eliminated from the
budget when considering all the vestibular tests currently available.
A third limitation is that standard rotational testing
directly stimulates only a portion of the peripheral system, specifically the horizontal semicircular canal and
the superior vestibular nerve branch. Consequently,
the vertical semicircular canals and the maculae fail to
contribute to the observed VOR response and are not
directly evaluated. The limited anatomical contributions to the observed VOR response during rotational
testing create challenges when using the output to
adequately reflect the physiology from the remaining
peripheral sensory end organs of the vestibular system
(i.e., the vertical semicircular canals and the maculae).
This challenge is similar to making assumptions of the
physiologic response of the entire vestibular periphery (all five sensory end organs) based solely on the
caloric test. Although rotational testing does offer
valuable and unique insight into central functioning of
the neural integrator and velocity storage, the results
generated must be interpreted as representing only a
portion of the peripheral system contributing to the
overall response.
One final limitation to rotational testing is that
analysis of the response can be complex and often
requires a great deal of experience and training to fully
interpret the array of results that are generated from all
the various tests. Given the paucity of rotational equipment available, this is a problem that may be inherent
to the lack of exposure and/or training that can effectively be given to students and clinicians. Moreover,
the shortage of rotational chairs in standard vestibular
clinics has likely created a void in the dissemination
of research and clinical findings that has circuitously
and intrinsically contributed to a blunting of its clinical demand. In addition, there is also a secondary
obstacle that has almost certainly led to the shortage
of rotational testing in more general routine clinical
practice. This obstacle is the cost-to-benefit ratio of
the equipment versus reimbursement. It would be a
severe omission not to recognize that the lower insurance reimbursement for rotational testing compared
with the equipment cost has likely contributed to the
scarcity of rotational test equipment available in routine vestibular testing facilities.
13. ROTATIONAL VESTIBULAR ASSESSMENT 329
https://t.me/medicina_free
CHAPTER SUMMARY
deliver. A clinical summary of abnormal results during SHA testing is detailed in Tables 13–6 and 13–7.
Supplemental tests such as VOR suppression, eccenRotational assessment with SHA testing, particularly in conjunction with other rotational assessments
described separately in Appendix IV, can provide
invaluable diagnostic insight into peripheral and central vestibular function that no other test can equally
Table 13–6. Abnormalities Associated with SHA Testing
Sinusoidal Harmonic Acceleration (SHA) Test Abnormalities
Parameter Abnormal Result Possible Interpretation Rule Out
With concomitant abnormal phase lead at low
1.
Hz & asymmetry
of asymmetry
Low VOR gain for low
Hz (<0.04–0.08 Hz)
GAIN
Low VOR gain for all
Hz
2. With no phase abnormalities but abnormal
symmetry, possible irritative or stable lesion (side
uncertain)
No other abnormalities & normal spectral purity,
3.
compensated
1. BVL given eyes open during test (symmetry and
phase cannot be interpreted)
2. Vestibulotoxic medication, aging (usually
>65–70 years), rare degenerative disorders of
the brainstem and/or cerebellum (especially if
caloric data are normal)
tric SVV testing, vestibular-visual enhancement, and
recent advancements regarding chair impulse testing
can significantly augment the diagnostic power for the
identification of vestibular pathology. These tests are
discussed in Appendix IV.
— uncompensated UVL on side
Insufficient
alerting
UVL is likely
Insufficient
altering,
restricted E
fixation
OM,
High
VOR gain for all
or most
↑ Low Hz Phase lead
PHASE
↑ High Hz Phase lead
↓ Low/High Hz Phase
lead/lag
SYMMETRY Asymmetric SPV
1. Cerebellar lesion (associated ocular motor
abnormalities)
2. Has been observed in migraine and hydrops
Peripheral vestibular end-organ lesion/vestibular
1.
nuclei lesion
2. With concomitant asymmetry, uncompensated
UVL (on side of asymmetry)
Acute vestibular end organ lesion; vestibular
3.
hydrops
CNS lesion; (look for associated ocular motor
1.
abnormalities)
1. CNS lesion; (associated ocular motor
abnormalities); consider lesions involving
brainstem or posterior cerebellum; cerebellar
nodulus
1. Two or more consecutive abnormal Hz; similar to
DP on caloric testing (non-localizing with respect
to site-of-lesion unless secondary to spontaneous
nystagmus)
2. With low Hz phase lead, uncompensated
peripheral lesion on side of asymmetry
Medications;
stimulants
Compare with
Step Tests &
calorics
Lateral medullary
syndrome
Unstable lesion
with normal
phase findings
330 BALANCE FUNCTION ASSESSMENT AND MANAGEMENT
https://t.me/medicina_free
tab le 13–7. SHA Abnormalities Associated with Site-of-Lesion
Sinusoidal Harmonic Acceleration (SHA) Test Abnormalities
Site-of-Lesion Possible Response Rule Out
1. Initial loss of VOR gain can involve low, mid, and high
frequencies with a greater impact towards the lower
frequencies.
2.
VOR gain can return to normal and often does for the
higher frequencies over days or months.
Increased low frequency phase leads that remain even
3.
following compensation (secondary to a permanent
change in central integrator processing).
4.
UNILATERAL
PERIPHERAL
Asymmetrical “bias” often is present due to afferent
asymmetry. At first, fast-phase components of the
vestibular nystagmus are ipsilesional but may change
over time and is, therefore, a poor indicator of laterality of
lesion.
5. The severity of the abnormal response will often co-vary
with the severity of the peripheral lesion.
6. SHA gain and symmetry may be entirely within normal
limits with an isolated low-frequency
suggesting a compensated unilateral pathology.
Decreased spectral purity
is often associated with
the onset of a unilateral
lesion, which may
contribute to the initial
decrease in overall gain;
rule out anti-dizziness
medication effects if
patient’s remain on
pharmacology treatment.
VOR phase lead
ILATERAL
B
CENTRAL
1. Low, mid, and high-frequency gain is reduced below
normal limits.
2. When gain is within normal limits, it almost is always
confined to the higher frequencies suggesting an
incomplete bilateral vestibular loss.
3. Phase leads are often randomly distributed, particularly at
low frequencies.
4. Phase and symmetry data should be interpreted with
caution when gain falls below 0.15 (15%).
5. Spectral purity is often poor, particularly for frequencies
where gain is poor.
1. Hyperactive gain may involve any frequency but often
occurs in the low frequencies where central control
(velocity storage) is in higher demand (i.e., cerebellar
site-of-lesion).
2. Hypoactive gain with no concomitant peripheral
indicators (rare).
3. Isolated mid-to-low frequency phase leads (or sometimes
involving the entire frequency range), suggesting an
inappropriate processing of central velocity storage
mechanisms for frequencies where the neural integrator is
not required.
4. Bias (asymmetry) may or may not be present
Insufficient altering,
restricted E
differentiate peripheral
and central with
concomitant results
(ocular motor, etc.)
Compare with step test
& caloric data; central
pathologies rarely
cause abnormalities
isolated to a single test —
identify concomitant
abnormalities across tests
(ocular motor, etc.).
OM, fixation;
Source: Adapted from Wall, 1990.
13. rotAtionAl vEstiBulAr AssEssmEnt 331
https://t.me/medicina_free
We began this chapter suggesting that rotational
assessment should be the primary test of vestibular function (Arriaga et al., 2005). Although the best
approach is a comprehensive vestibular assessment,
in a current model of medical care, where the balance
between the cost of medical care and medical benefit
is under constant scrutiny, the advantages of conducting a comprehensive rotational assessment is appealing. Rotational testing continues to hold a unique
position in the comprehensive vestibular assessment.
Between its natural acceleration stimuli and its detailed
outcomes measures, its analyses are unparalleled for
the identification of peripheral and central vestibular
disease. As with all things, as rotational testing continues to advance in the twenty-first century, it will
be essential to stay current with our understanding
of the various assessment techniques and outcomes
measures associated with normal and abnormal vestibular function.
referenCes
Arriaga, M. A., Chen, D. A., & Cenci, K. A. (2005). Rotational
chair (ROTO) instead of electronystagmography (ENG) as
the primary vestibular test. Otolaryngology–Head and Neck
Surgery, 133(3), 329–333.
Baloh, R. W., Sills, A. W., & Honrubia, V. (1979). Impulsive
and sinusoidal rotatory testing: A comparison with results
of caloric testing. Laryngoscope, 89, 646–654.
Brey, R. H., McPherson, J. H., & Lynch, R. M. (2008a). Back-
ground and Introduction to whole body rotational testing. In G. Jacobson & N. Shepard (Eds.), Balance function
assessment and management (pp. 253–280). San Diego, CA:
Plural Publishing.
Brey, R. H., McPherson, J. H., & Lynch, R. M. (2008b). Tech-
nique, interpretation, and usefulness of whole body rotational testing. In G. Jacobson & N. Shepard (Eds.), Balance
function assessment and management (pp. 281–317). San
Diego, CA: Plural Publishing.
Coats, A. C., & Smith, S. Y. (1967). Body position and the
intensity of caloric nystagmus. Acta Otolaryngologica, 63(6),
515–532.
Cumberworth, V., Patel, N., Rogers, W., & Kenyon, G. (2006).
The maturation of balance in children. Journal of Laryngol-
ogy & Otology, 121, 449–454.
Cyr, D. G. (1991). Vestibular assessment. In W. Rintelmann
(Ed.), Perspectives in audiology series: Hearing assessment
(2nd ed., pp. 739–803). Boston, MA: Allyn & Bacon.
Fetter, M., Hain, T. C., & Zee, D. S. (1986). Influence of eye and
head position on the vestibule–ocular reflex. Experimental
Brain Research, 64(1), 208–216.
Fife, T., Tusa, R., Furman, J., Zee, D., Frohman, E., Baloh, R.,
. . . Eviatar, L. (2000). Assessment: Vestibular testing tech-
niques in adults and children: Report of the therapeutics
and technology assessment subcommittee of the American Academy of Neurology. Neurology, 55, 1431–1441.
Furman, J. M., Goebel, J. A., Hamid, M. A., Hanson, J., Hon-
rubia, V., Peterka, R., . . . Wall, C. (1994). Interlaboratory
variability of rotational chair test results. Interlaboratory
Rotational Chair Study Group. Otolaryngology–Head and
Neck Surgery, 110(4), 400–405.
Furman, J. M., Goebel, J. A., Hamid, M. A., Hanson, J., Hon-
rubia, V., Peterka, R., . . . Wall, C. (2000). Interlaboratory
variability of rotational chair test results II: Analysis of
simulated data. Otolaryngology–Head and Neck Surgery,
122(1), 23–30.
Goldberg, J. (2000). Afferent diversity and the organization of
central vestibular pathways. Experimental Brain Research,
130, 277–297.
Goldberg, J. M., Wilson, V. J., Cullen, K. E., Angelaki, D. E.,
Broussard, D. M., B
Oxford University Press.
Hirsch, B. E. (1986). Computed sinusoidal harmonic accelera-
tion. Ear and Hearing, 7(3), 198–203.
Jacobson, G., McCaslin, D., Grantham, S., & Shepard, N.
(2016). Within and between measure relationships between
balance function tests — illustrative cases. In G. Jacobson &
N. Shepard (Eds.), Balance function assessment and manage-
ment (pp. 833–855). San Diego, CA: Plural Publishing.
Jacobson, G. P., & Newman, C. W. (1990). The development of
the Dizziness Handicap Inventory. Archives of Otolaryngol-
ogy-Head and Neck Surgery, 116(4), 424–427.
Leigh, R. J., & Zee, D. S. (2006). The neurology of eye movements
(4th ed.). New York, NY: Oxford University Press.
Maes, L., Dhooge, I., D’haenens, W., Bockstael, A., Keppler,
H., Philips, B., Swinnen, F., & Vink, B. (2008). Normative
data and test-retest reliability of the sinusoidal harmonic
acceleration test, pseudorandom rotation test and velocity
step test. Journal of Vestibular Research, 18, 197–208.
McCaslin, D. L. (2012). Electronystagmography and videonystag
mography: ENG/VNG. San Diego, CA: Plural Publishing.
Miles, R. D., & Zapala, D. A. (2015). Vestibular function mea-
surement devices. Seminars in Hearing, 36(1), 49–74.
Paige, G. D. (1989). Nonlinearity and asymmetry in the human
vestibule-ocular reflex. Acta Otolaryngologica, 108, 1–8.
Phillips, J., & Backous, D. (2002). Evaluation of vestibular
function in young children. Otolaryngologic Clinics of North
America, 35, 765–790.
Shepard, N. T., & Telian, S. A. (1996). Practical management
of the balanced disordered patient. San Diego, CA: Singular
Publishing Group.
Stockwell, C. W., & Bojrab, D. I. (1997). Background and tech-
nique of rotational testing. In G. Jacobson, C. Newman, &
J. Kartush (Eds.), Handbook of balance function testing, (pp.
237–248). San Diego, CA: Singular Publishing Group.
Van Nechel, C., Toupet, M., & Bodson, I. (2001). The subjec-
tive visual vertical. In P. Tran Ba Huy & M. Toupet (Eds.),
Otolith function and disorders (pp. 77–87). New York, NY:
Karger.
ütner–Ennever, J. A., . . . Minor, L. B.
-
332 BAlAnCE FunCtion AssEssmEnt And mAnAgEmEnt
https://t.me/medicina_free
Wall, C. (1990). The sinusoidal harmonic acceleration rotary
chair test. Theoretical and clinical basis. Neurologic Clinics,
8(2), 269–285.
White, J.A. (2007). Laboratory tests of vestibular and balance
function. In G. Hughes & M. Pensak (Eds.), Clinical otology
(3rd ed., pp. 132–149). New York, NY: Thieme.
Wilson, V. J., & Jones, J. G. (1979). Mammalian vestibular physi-
ology. New York, NY: Plenum Press.
Zalewski, C. (2018). Rotational vestibular assessment. San Diego,
CA: Plural Publishing.
14
https://t.me/medicina_free
The Video Head Impulse Test (vHIT)
Ian S. Curthoys, Hamish G. MacDougall, Leigh A. McGarvie,
Konrad P. Weber, David Szmulewicz, Leonardo Manzari,
Ann M. Burgess, and G. Michael Halmagyi
ABBREVIATIONS
BVL, bilateral vestibular loss;
Contralesional, the side opposite to the actual or
suspected lesion;
Ipsilesional, on the same side as the actual or
suspected lesion;
LARP, left anterior — right posterior;
RALP, right anterior — left posterior;
UVL, unilateral vestibular loss;
INTRODUCTION
In many clinics around the world the video head
impulse test (vHIT) of semicircular canal function is
the first test given to patients reporting symptoms of
dizziness or vertigo, because it quickly gives clinically
valuable information and is such an innocuous test.
However, it is unusual in that it is the clinician who
delivers the test stimulus, not some machine. So, in
order to carry out the test and interpret the results, it is
vital to understand the rationale. In this chapter we set
out the rationale, explain how the test should be conducted and how the test results should be interpreted,
including a section on the neural basis of vHIT. For
HIT, head impulse test;
vHIT, video head impulse test;
VOR, vestibulo-ocular reflex;
HIMP, head impulse paradigm test;
SHIMP, suppression head impulse test;
LH, left horizontal canal;
RH, right horizontal canal;
ITG, intratympanic gentamicin
readability we have kept references to a minimum, but
Curthoys and Manzari (2017), Halmagyi et al. (2017),
and Halmagyi and Curthoys (2018b) refer to the very
extensive literature on head impulse testing.
Why Measure Eye Movements to Test the
Semicircular Canals of the Inner Ear?
A very basic reflex, the vestibulo-ocular reflex (VOR),
ensures a stable image on the retina and clear vision
during head movements. Receptors in the semicircular
canals are activated by any head rotation, and neural
input from those receptors drives the eyes via short fast
pathways so that the eye movement compensates for
333
Соседние файлы в папке Библиотека им академика М.И. Перельмана