Making sense of nystagmus - can it be done?

Although a great number of sophisticated recording techniques and mathematical modeling theories have developed to evaluate and explain nystagmus, most cases can still be diagnosed after obtaining a careful clinical history and performing a thorough neuro-ophthalmologic examination. Presence of oscillopsia, vertigo, tinnitus, and/or nausea suggests an acquired condition. Congenital nystagmus is a benign condition but can co-exist with other ocular problems resulting in poor vision. Especially when a clear history of onset is not available or if the nystagmus is disconjugate, a careful search should be made for ocular or other nervous system pathology. Monocular or markedly asymmetric nystagmus in a child always warrants careful evaluation. We have reviewed the specific, recognizable, localizing types of nystagmus, all of which are present in the primary position. Down-beat and periodic alternating nystagmus in this group should alert the clinician to a possible cervicomedullary lesion, which frequently require metrizamid myelography combined with CT scanning or midsagittal cuts with MRI to demonstrate an abnormality, especially in adults. Convergence retraction nystagmus should draw the clinician's attention to the dorsal midbrain area and the possibility of a mass lesion. Acquired see-saw nystagmus is frequently accompanied by a bitemporal hemianopia and caused by large parasellar tumors expanding within the third ventricle, again prompting neuroradiologic investigation. Oculopalatal myoclonus is a delayed finding usually following a stroke involving the myoclonic triangle, manifested histopathologically by olivary hypertrophy. Vestibular nystagmus is the most common horizontal-torsional nystagmus present in the primary position. When the end-organ is involved, vertigo and nausea are prominent symptoms. When central, these symptoms are less pronounced and the direction of the nystagmus can change with changes in gaze. Acoustic neuromas and the lateral medullary syndrome of Wallenberg are subtypes of vestibular nystagmus with their own constellation of findings. Ocular dysmetria, flutter, and opsoclonus represent a continuum of increasing cerebellar malfunction. Dysmetria can be an early and subtle finding of the cerebellar system disease especially in multiple sclerosis. Opsoclonus, especially in a child, may be a remote effect of an occult neuroblastoma requiring CT evaluation of the adrenal region or can be a postinfectious symptom that responds to steroids. The onset of an intermittent monocular tremor in an otherwise healthy adult that results in a jelly-like vertical or torsional oscillopsia and diplopia represents superior oblique myokymia, which is a benign condition usually responsive to Tegretol.