Abnormal Eye Movements

<p>　 Ocular flutter and opsoclonus are intermittent bursts of involuntary conjugate eye oscillations, in the horizontal and multidirectional planes, respectively, without intersaccadic intervals. Patients with ocular flutter/opsoclonus often present with oscillopsia and vertigo, sometimes with cerebellar ataxia and myoclonus. Ocular flutter/opsoclonus can be caused by various diseases, such as postinfectious encephalitis, paraneoplastic syndrome, and drug toxicity. Treatment of the causative disease is the primary goal of treatment, but in cases where they occur as a part of paraneoplastic syndrome, the prognosis for neurologic findings may be poor, regardless of the treatment status of the tumor. Ocular flutter/opsoclonus may originate from a loss of omnipause neuronal inhibition on burst neurons within the brainstem burst generator. In recent years, attention has been focused on a hyperexcitable or disinhibited state of the brainstem burst neuronal membrane.</p><p>　 Square wave jerks (SWJks) are abnormal eye movements that consist of unilateral saccades and intersaccadic intervals followed by a return to the original eye position. SWJks are also seen in normal subjects and are thought to be of little pathological significance in and of themselves per se. However, high-amplitude SWJks (Macro square wave jerks) may indicate central lesions, such as neurodegenerative diseases. They are thought to be caused by abnormalities in the ocular microsaccades mechanism.</p><p>　 Periodic alternating nystagmus (PAN) is a nystagmus in which the direction of the nystagmus alternates periodically at intervals of about two minutes. There are two types: congenital and acquired. Causes of acquired PAN include paraneoplastic syndrome and cerebellar degenerative diseases.PAN is thought to be caused by disruption of the inhibitory control from the cerebellum to the vestibular nucleus concerned with neural velocity storage mechanisms.</p>