XXX. Vertigo and nystagmus
Practicals
Department of Physiology LF MU

•rhythmic eye-bulb movements, 2 components: slow deviation to one side and fast twitch to the
opposite side (slow is vestibular, fast from brainstem structures)
•Nystagmus at rest (unprovoked) – vestibular system, neural pathways  or cerebellum is affected by
some pathological process
•Direction of the nystagmus is determined according to the fast twitch
Nystagmus
Optokinetic_nystagmus.gif

The Vestibular System
structure


The Vestibular System
•The vestibulo-ocular reflex (VOR) stabilizes retinal images during head motion by counter-rotating
the eyes at the same speed as the
head but in the opposite direction
•Semicircular canals (kinetic sensor)
•cristae ampullares, specialized for responding to rotational acceleration of the head
•Utriculus, sacculus - maculae staticae
(static sensor)
•linear acceleration, head position in the gravitational field
Obrázek2.png

•Each semicircular canal contains an ampulla containing hair cells embedded in sensory epithelium
called
crista ampullaris
•Cilia of hair cells project
into gelatinous cap
called cupula
•Head rotation results in
inertial movement of
endolymph in opposite
direction, which inflects cilia
•
•
The Vestibular System – Semicircular canals
C:\Users\Johanka\Desktop\výuka\prezentace k praktikám ppt\Nové verze praktik\Nystagmus a reakční
doba\obrázky\M9780323045827-008-f024.jpg
http://users.atw.hu/blp6/BLP6/HTML/C0089780323045827.htm

Semicircular canals: sensory transduction
E:\306\images\blks 6th ed\images\008026.jpg
•Steriocilia maintain directionality on both sides of the head
•Bending towards kinocilium → opens mechanically gated cation channels → K+ influx → depolarization
•Bending away from kinocilium → closes channels that are open during resting state →
hyperpolarization
•

Obrázek1.png
•Head rotation results in inertial movement of endolymph in opposite direction
•With turning of the head, hair cells on one side of the body send excitatory signals to the brain
while hair cells on the opposite side are inhibited
•Each channel is associated with a pair of peculiar muscles that moves the eye in its plane
Obrázek2.png

•semicircular canals are stimulated by:
•post-rotational
•Caloric (application of external auditorial tube either with cold=27 C or warm=47 C water)
•Galvanic (stimulation with electric current)
Tests for provocation of nystagmus

•Examined subject with eyes closed and head inclined frontally by about 30 degrees is sitting in
the swivel chair – lateral channel is in horizontal plane
•Rotate the chair 10 times during 10 s and than suddenly stop chair
•The rotation is suddenly stopped and movements of subject’s eyes are observed
•Observe post-rotational nystagmus
•Slow eye movement – initiated from vestibular system, in direction of endolymphe flow
•Fast eye movement – initiated from brain stem, returns the bulb to the starting position
(direction of nystagmus)
•
•Various head inclinations stimulate different channels – influence on plane and direction of
nystagmus
Post-rotational nystagmus

•In practical: direction (horizontal, vertical, diagonal, rotational) – according to the fast eye
movement
•Other possible parameters
•amplitude (in degrees)
•frequency (Hz)
•duration (s, min)
•
Evaluation of the post-rotational nystagmus in practicals
head inclination
direction of rotation
plane of nystagm
direction of nystagmus
frontally by about 30°
on the left by 90°
on the right by 90°
maximally back
maximally frontally

•Vertigo (dizziness)– subjective loss of stability in space, rotation of surrounding space or
rotation of body in space
•connected with objective symptoms – disturbances of equilibrium and nystagmus – by stimulation of
the labyrinths
•Hautant test (differential diagnosis of vestibular, cervicogenic, and ischemic dysfunction)
•subject closes eyes and stretch arms forwards
•tonic deviations of the arms are associated with deviation of the body in the same direction
•deviations of the arms are in direction of impaired labyrinth (according to the slow part of
nystagmus)
•In practical: Hautant test after rotation – observe the direction of the arms deflection in the
relation to the direction of rotation
Vertigo