Vestibular

Vestibular

Examination of Eye Movements

·        Nystagmus:

o   Peripheral cause: fine, unidirectional, horizontal or rotatory

o   Beats to the side opposite the lesion, worse when looking to that side

o   Named for the direction of the fast phase

o   Is inhibited by fixation (ie will be quicker if you close one eye and try fundoscopy on the other)

o   Bi-directional or vertical nystagmus is always central in origin

·        Control of eye movement: 

o   Saccades: voluntary quick refixation eye movement. If hypometric then undershot ® number of small saccades to catch up. Hypermetric saccades ® overshoot ® reverse saccade 

o   Parietal lobe controls ipsilateral smooth pursuit and contralateral saccades. Impairment over 70 may be normal

o   Impaired pursuit also due to cerebellar and brainstem lesions

·        Vestibulo-ocular reflexes:

o   Eye movements to compensate for head movement: maintain stable picture on retina

o   Doll‟s eye: eyes stay focused on target when head moves

Benign Paroxysmal Positional Vertigo (BPPV)

·        Usually posterior semicircular canal. Due to debris in canal (CaCO₃ crystals). Usually cause unknown or aging, but may follow trauma or infection. Fluid movement ® distorted stimulations to nerve due to particles ® different input from 2 vestibular end organs

·        Posterior canals are in the snow-plough position, and are the lowest. Collect debris from the anterior and horizontal canal

·        Leads to ­ discharge to ipsilateral superior oblique and contralateral inferior rectus ® torsional nystagmus

·        Can also be due to horizontal semicircular canal

·        Symptoms:

o   Brief attacks of vertigo precipitated by certain head movements (eg getting into or out of bed, rolling over). Less severe when repeated

o   May spontaneously remit and relapse

o   Hallpike manoeuvre: Rotatory or torsional nystagmus beating toward affected ear when tipped down, after a brief latent period (5 – 10 secs). If immediate then ?central cause. Last about 20 secs and reoccurs again when sitting up. Effect fatigues with retesting (material disperses in process of testing)

o  Usually resolves over weeks or months

o  No cochlear symptoms

·        Treatment:

o  Drug therapy not helpful

o  Canalith Repositioning: induce symptoms ® shifts particles into a chamber not sensitive to movement

o  For right ear: sit on edge of bed, turn head 45 degrees to the left, lean all the way down to the right then quickly through 180 degrees to the left, then back to upright. May be easier with eyes closed. Repeat after 2 – 3 minutes. Do every three hours

Acute Peripheral Vestibulopathy

·        = Acute labyrinthitis

·        Symptoms: acute and continuous vertigo, worse with any movement, lasting several days with nausea and vomiting, but no auditory or neurological symptoms

·        Signs: unsteady walking (eg heel-toe). Fine horizontal/rotatory nystagmus beating away from the lesion. Vestibulo-ocular reflex is absent/impaired on passive head rotation toward the lesion, requiring voluntary eye movement to regain fixation (catch-up saccade)

·        Most likely to be horizontal canal affected

Other

·        Vertigo may follow Head injury.  Eg temporal bone fracture tearing 8^th nerve

·        Infarct with occlusion of the internal auditory artery ® affects hearing and balance

·        Chronic bilateral vestibulopathy ® imbalance and oscillopsia (sensation of the world moving on head movement) due to inadequate vestibulo-ocular reflex. Usually due to gentamycin toxicity

·        Migraine may have vestibular symptoms

·        MS: vertigo is a classic feature