Nystagmus

NYSTAGMUS AND ITS TYPES
  • Nystagmus is rhythmic oscillatory movement of eye and has two components slow and fast.
  • It can be of vestibular or ocular in origin.
  • Vestibular Nystagmus is of two types:
  1. Central Nystagmus:when lesion is in the central neural pathways (Vestibular nuclei, brainstem and cerebellum)
  2. Peripheral Nystagmus:when it is due to lesion of labyrinth or VIllth nerve.
  • (Cochlear problems is associated with hearing loss and not nystagmus)
  • In destructive lesions eg. trauma to labyrinth, the nystagmus is towards the opposite side.
  • In irritative lesions eg. serous labyrinthitis, fistula of labyrinth, the nystagmus is towards ipsilateral side.
  • Difference between Central and Peripheral Nystagmus

Peripheral Nystagmus Central Nystagmus
Form of Nystagmus Torsional with Horizontal or Vertical Component Purely Horizontal or Vertical or pure Torsional .
Direction of Nystagmus Direction fixed Direction changing
Latency 2-20 seconds No Latency
Duration Less than 1 minute More than 1 minute
On Visual Fixation Nystagmus disappears Does not disappear
Accompanying symptoms Tinnitus, vertigo present Tinnitus,Vertigo not present
Fatiguability Fatiguable Non fatiguable
Example BPPV, labyrinthitis, Meniere's disease labyrinthine fistula Vertebrobasilar insufficiency, tumours
CHARACTERISTICS OF NYSTAGMUS IN DIFFERENT PATHOLOGIES
  • Stimulation of posterior semicircular canal produces Torsional vertical nystagmus.
  • Optokinetic Nystagmus occurs when the patient looks straight.
  • Unilateral homonymous hemianopia with saccadic pursuit movements and defective optokinetic nystagmus.The lesion is most likely to be in the Parietal lobe.
  • Cerebellar hemisphere is the site of lesion in unilateral past pointing nystagmus.
  • Miners nystagmus is of Rotatory type.
  • Spontaneous vertical nystagmus is seen in the lesion of Midbrain/Medulla.
  • Superior semicircular canal lesion leads to torsional vertical upbeat nystagmus
  • Posterior semicircular canal lesion leads to torsional vertical downbeat nystagmus
  • Medullary lesions lead to pure torsional nystagmus
  • Pure vertical nystagmus is seen in medullary lesion or vertebrobasilar insufficiency.
  • Pure horizontal nystagmus is seen in cerebral lesions.
  • Down beat nystagmus occurs from lesions near craniocervical junction (in posterior fossa near foramen magnum) e.g. Chiari malformation , in cerebellar or brainstem stroke , lithium or anticonvulsant intoxication, alcoholism, and multiple sclerosis.
  • Upbeat nystagmus is associated with damage to pontine tegmentum from stroke, demylination or tumor.
INVESTIGATIONS IN A CASE OF NYSTAGMUS.
  • Illuminated frenzel galsses (+20 lenses) are useful for abolishing fixation and thus revealing peripheral vestibular nystagmus
Caloric test-
  • Helpful in case of Peripheral Nystagmus.
  • It is an attempt to discover the degree to which the vestibular system is responsive and also how symmetric the responses are, between left and right ears. It is a test of the lateral semicircular canals alone -- it does not assess vertical canal function .
  • Cold stimulation causes nystagmus towards opposite side while warm stimulation causes Nystagmus towards same side.
  • In canal paresis either there is a reduced or absent response (causes of U/L canal paresis are-U/L vestibular Schwannoma or vestibular neuritis).
  • B/L absence of caloric nystagmus is seen in case of amminoglycoside ototoxicity or postmeningitis
Electronystagmography (ENG) :
  • Records involuntary movements of the eye caused by a condition.
  • It can also be used to diagnose the cause of vertigo or balance disorder by testing the vestibular system.
  • The comparison of results obtained from various subtests of ENG assists in determining whether a disorder is central or peripheral.
Exam Question
  • Nystagmus that occurs when the patient looks straight is Optokinetic Nystagmus.
  • Nystagmus is absent in a brain stem dead patient.
  • A patient has a right homonymous hemian-opia with saccadic pursuit movements and defective optokinetic nystagmus.The lesion is most likely to be in the Parietal lobe.
  • Cerebellar hemisphere is the site of lesion in unilateral past pointing nystagmus.
  • In caloric test,Cold stimulation causes nystagmus towards opposite side while warm stimulation causes Nystagmus towards same side.
  • Spontaneous vertical nystagmus is seen in the lesion of Midbrain/Medulla.
  • Central Nystagmus changes the direction,with no fatiguability,no latency and does not disappears on visaul fixation.
  • Peripheral Nystagmus has fixed direction,latency and fatiguability present and disappears on Visual Fixation.
  • Cochlear problems is associated with hearing loss and not nystagmus.
  • In destructive lesions eg. trauma to labyrinth, the nystagmus is towards the opposite side.
  • Stimulation of posterior semicircular canal produces Torsional vertical nystagmus.
  • Miners nystagmus is of Rotatory type.
  • Illuminated frenzel galsses are useful for abolishing fixation and thus revealing peripheral vestibular nystagmus
Don't Forget to Solve all the previous Year Question asked on Nystagmus