• 11 SECTIONDisorders Saccadic

Ocular Flutter and Opsoclonus

Key Facts

•Bursts of involuntary back to back binocular conjugate saccades that take eyes away from primary position • In ocular flutter, the trajectory is strictly in the horizontal plane; in opsoclonus it may be in any plane • Caused by dysfunction of pontine pause cells that normally prevent involuntary conjugate eye movements

•Common causes in children:

•postviral autoimmune disorder • paraneoplastic disorder associated with metastatic neuroblastoma

•Common causes in adults:

•postviral or paraneoplastic encephalitic manifestation of metastatic lung, breast, or ovarian cancer

•Uncommon causes:

•drug toxicity (lithium, amitriptyline, cocaine, phenytoin) or poisoning (toluene, thallium, chlordecone, organophosphates, strychnine) • hyperosmolar coma

• brainstem hemorrhage • multiple sclerosis

•Treatment of underlying cancer may improve neurologic manifestations

•Adrenocorticotropic hormone (ACTH), corticosteroid, plasmapheresis, or immunoglobulin treatment may improve on natural course of paraneoplastic and postviral encephalitis

Clinical Findings

•Bursts of involuntary back to back binocular conjugate saccades that take eyes away from primary position • In ocular flutter, the trajectory is strictly in horizontal plane; in opsoclonus it may be in any plane

•Associated with:

•brief muscle contractions (myoclonus) at joints • head and trunk oscillations (titubation) • extremity tremor • ataxia

Ancillary Testing

•Brain imaging usually negative • Lumbar puncture may disclose mild pleocytosis or protein elevation

•In children with metastatic neuroblastoma, the following may be positive:

•urine catecholamines • chest, abdomen, and pelvis imaging • MIBG nuclear medicine scan

•In adults, primary cancer may become apparent with structural (MRI) or metabolic (PET) scanning

Differential Diagnosis

• Ocular dysmetria • Voluntary nystagmus • Square wave jerks

Treatment

•Treatment of underlying cancer may improve neurologic manifestations • ACTH, corticosteroid, plasmapheresis, or immunoglobulin treatment for paraneoplastic and postinfectious encephalitis

Prognosis

•Postviral autoimmune disorder: eye findings resolve within months, but ataxia and cognitive dysfunction may persist • Adult paraneoplastic disorder: findings usually do not resolve and survival time is short • Neuroblastoma with ocular flutter or opsoclonus has better prognosis than neuroblastoma without ocular flutter or opsoclonus

Fig. 11.3 Ocular flutter. Involuntary rapid saccades move the eyes conjugately off target. As the movements are limited to the horizontal plane, this is called ocular flutter.

Fig. 11.4 Opsoclonus. The conjugate saccadic eye movements occur in horizontal and vertical planes.

Opsoclonus and Flutter Ocular

• 11 SECTIONDisorders Saccadic

Ocular Dysmetria

Key Facts

•Refixational eye movements lead to conjugate saccadic ocular oscillations

•Usually accompanied by extremity, gait, or speech ataxia

•Reflects cerebellar system dysfunction

Clinical Findings

•When eyes make a refixational movement, they oscillate before settling on the target

•Usually accompanied by ataxia

•Eye movements do not cause visual symptoms

Ancillary Testing

• Brain imaging may show lesions of brainstem or cerebellum

Differential Diagnosis

•Voluntary nystagmus

•Congenital nystagmus

•Ocular flutter or opsoclonus

Treatment

• Directed at underlying condition

Prognosis

• Depends on underlying condition