耳鼻喉科Otolaryngology topic eleven: Otoneurology & vestibular system

Otoneurology & vestibular system

1. Central pathways

-- vestibulo-ocular reflex (VOR) : CN3,4,6

-- vestibulo-spinal reflex (VSR): lateral tract for extremities, medial tract for central muscles

-- vestibulo-vegetative reflex (VVR) : GI related

2. Dizziness and DDx

Duration is the key!

-- seconds: benign paroxysmal positional vertigo, superior semicircular canal dehiscence(SSCD, induced by noise, DDx by CT), perilymphatic fistula 
-- minutes: vertebrobasilar insufficiency ; migraine-related vertigo

-- hours: meniere’s disease
-- days: vestibular neuritis, labyrinthitis

3. Nystagmus
-- slow phase: speed, pathologic direction
-- fast phase: descriptive direction
-- transverse: inner ear problems
-- vertical: CNS problem
-- spontaneous
-- gaze (Brun's nystagmus: ─, cerebellopontine; down-beat nystagmus: ↓, Arnold-Chiari malformation = narrow foramen magnum)
             > uni-directional: inner ear, 
             > multi-directional: brain, variable intensity
-- normal ones: optokinetic nystagmus, caloric-test induced(COWS)

*** Closing the eyes, darkness, Frenzel glass, ENG would help the observation of nystagmus.

4. Coordination tests

Equilibratory
-- Romberg: eye close-->proprioception
-- Romberg on foam: eye close--> vestibule
-- tandem Romberg: similar to Romberg on foam

Non-equilibratory (cerebellum function)
-- circle drawing: dyssynergia
-- some for dysmetria
-- some for dysdiadochokinesia
-- smooth persuit
-- saccades

5. ENG and caloric test
(│right side wave angles-left side wave angels│/ sum of both-side wave angles ) x 100%
normal: <20. the side with smaller angle-->weaker function

6. Other tests
-- cervical vestibular myogenic potential
-- ocular vestibular myogenic potential
-- posturography
-- rotational chair test