Nystagmus - Specific Types
BPPV: triggered by positional changes.: Posterior canal[β¦] (most common): Dix-Hallpike β mixed upbeat/torsional nystagmus toward affected ear; Horizontal canal[β¦]: supine roll test β horizontal nystagmus.
Vestibular neuritis: acute onset, beats contralateral[β¦] to lesion side, unidirectional, intensifies as patient looks toward fast-phase side. Physiologic endpoint nystagmus: normal in far lateral gaze, small amplitude, fatigues quickly; disappears at 75% mark.
Downbeat[β¦] nystagmus: cerebellar flocculus/tonsils[β¦] dysfunction. Progressive imbalance, vertical oscillopsia, gaze-evoked nystagmus in lateral gaze.
Treatment: trial dalfampridine (4-AP)[β¦]; avoid bifocals (forces downgaze).
Periodic alternating[β¦] nystagmus: spontaneous horizontal nystagmus reversing direction every minute or two ("null period").
Cerebellar nodulus/uvula[β¦].
Treatment: baclofen[β¦].
Pendular nystagmus: often seen with MS[β¦]; heavy posterior fossa/brainstem paramedian involvement.
Seesaw[β¦] nystagmus: one eye rises and incycloducts while the other depresses and excycloducts. Mesodiencephalic junction or optic chiasm area lesions.
Upbeat nystagmus: midline brainstem (e.g., Wernicke's encephalopathy[β¦]).
Treat empirically with IV thiamine[β¦]. Oculopalatal tremor: presents with oscillopsia or imbalance months after a posterior fossa insult (cavernoma, surgery).
Hits the Guillain-Mollaret triangle[β¦]. Pathway: inferior olive β contralateral cerebellar dentate β wraps around red nucleus β down via central tegmental tract β back.
MRI: T2 FLAIR hyperintensity of the inferior olivary nuclei[β¦].
