Intro to nystagmus
Nystagmus. The word originates from the Greek for “nodding,” as in “to be sleepy.” But this BrainWaves podcast makes you feel anything but. Led by Dr. Ali Hamedani, also responsible for an earlier and incredibly thorough episode on painless ophthalmoparesis, this interview covers many of the basic principles of this description of efferent eye function.
By convention, nystagmus can be divided into either jerk or pendular forms. Jerk nystagmus is defined by its fast phase in the horizontal, vertical, or rotational planes (e.g., right-beating nystagmus in right maximal gaze, or rotational nystagmus toward the left shoulder), whereas pendular nystagmus is either horizontal or vertical (e.g., vertical pendular nystagmus). Symptomatically patients may complain of nothing at all, or they may endorse dizziness, vertigo, diplopia, or jumping of the environment (oscillopsia). And when you see these eye movements, it makes all too much sense that a patient would complain that their visual environment is bouncing from one side to the other.
Often benign, nystagmus encompasses a variety of eye movements whose main feature includes a rhythmic biphasic oscillatory eye movement with slow and fast components. If the movement is not oscillatory, or it lacks both a slow or fast phase, the movements may be called nystagmoid (e.g., ocular flutter, opsoclonus). These processes will be covered in subsequent episodes. As in all neurologic conditions, the appreciation of nystagmus variants is important for lesion localization. While many forms of nystagmus may not localize consistently to one region of the brain (e.g., upbeat nystagmus may occur in lesions of the cerebellar vermis, midbrain or medulla), some have high localizing value:
|Periodic alternating||Horizontal: first in one direction, then stops, changes direction, usually cycles over 3 minutes.||Baclofen||Cerebellar nodulus, cervico-medullary junction|
|Downbeat||Fast phase downward. Usually most noticeable on down or lateral gaze.||3,4-diaminopyradine, 4-aminopyradine, clonazepam||Cervico-medullary junction, cerebellar flocculus|
|See-saw||One eye intorts and falls as the other extorts and rises, then alternates, kind of, like a see-saw.||Baclofen, clonazepam||Parasellar (optic chiasm), midbrain (inC, sparing riMLF)|
|Oculopalatal myoclonus or acquired pendular nystagmus||Pendular oscillation of the eyes and palate (“clicking noise”)||GBT, Memantine, VPA, clonazepam||Central tegmental tract|
|Congenital Motor||Horizontal pendular and jerk nystagmus. Less with convergence. Often latent worsening.||Associated w/ many visual pathway d/o but not caused by visual loss.|
|Superior oblique myokymia||GBT, CBZ, propranolol|
|Oculomasticatory myorhythmia||Slow convengence pendular eye movements with simultaneous jaw contractions.||Ceftriaxone||Whipple’s|
|Congenital Sensory||Pendular||GBT, Memantine|
|Upbeat||Fast beat upwards||Cerebellum, medulla, midbrain|
|Convergence retraction||Rapid convergence and retraction movements on upgaze.||Dorsal midbrain|
|Rebound nystagmus||Horizontal, gaze-evoked; few beats of nystagmus in the opposite direction upon return to primary position.||Cerebellum|
|Brun’s nystagmus||Large amplitude, low frequency with ipsilateral gaze. Small amplitude, high frequency with contralateral gaze.||Cerebellopontine angle|
|Spasmus nutans||Dissociated, asymmetric (occasionally monocular), high-frequency, low-amplitude pendular nystagmus. Assoc with torticollis and titubation.||Exclude chiasmal glioma and craniopharyngioma|
|Opsoclonus||Continuous random directional saccades||Corticosteroids, ACTH, IVIG, clonazepam||Post fossa, assoc with neuroblastoma in kids; in adults, other toxic, metabolic, parainfectious, & paraneoplastic syndromes of cerebellum and pons|
|Ocular flutter||Back-to-back horizontal saccades without an interval||Posterior fossa (cerebellum or PPRF), other causes similar to opsoclonus|
|Ocular Bobbing||Fast downward with slow upward return.||Pons (usually a hemorrhage)|
For more info, I’ll refer you to Dr. Hamedani’s detailed descriptions. Although his fund of knowledge may be dizzying, I think you’ll find this episode accessible regardless of your level of training.
The content in this episode was vetted and approved by Robert Avery.
Liu GT, Volpe NJ, and Galetta SL. Neuro-ophthalmology: Diagnosis and management, 2nd ed., pp. 587-610. Elsevier, 2010.