• 9 SECTIONDisorders Gaze Cerebral

Ping Pong Gaze

Key Facts

•Arrhythmic slow conjugate horizontal movement of the eyes from one side to the other in a comatose patient

•Caused by severe ischemic or metabolic insult to both cerebral hemispheres

•Damaged cerebral hemispheres cannot control pontine gaze generators, which discharge automatically to move eyes back and forth

•Often mistaken for epileptic nystagmus

Clinical Findings

•Conjugate horizontal eye movements taking about 5 s to complete full cycle

•Patient typically unresponsive except to painful tactile stimuli

Ancillary Testing

•CT or MRI may show extensive damage to both cerebral hemispheres

•Normal MRI suggests metabolic or toxic damage, which may be shown with blood and urine tests

Differential Diagnosis

• Epileptic nystagmus

Treatment

• Directed at underlying disorder

Prognosis

•Irreversible if ischemic damage

•May be reversible if metabolic damage

• 10 SECTION Nystagmus

Physiologic Nystagmus

Key Facts

•Horizontal or horizontal–torsional jerk nystagmus at extremes of horizontal gaze to both sides that is considered a variant of normal function

•Often confused with pathologic nystagmus but usually distinguishable by noting clinical findings

Clinical Findings

•Fast phase in direction of gaze

•Nystagmus amplitude is low and equal in amplitude in both directions of gaze

•Nystagmus amplitude may be greater in abducting than in adducting eye

•Nystagmus stops after four or fewer beats (unsustained)

•No oscillopsia during the nystagmus

•No nystagmogenic medications or drugs

•No other pertinent abnormalities on examination

Ancillary Testing

• All tests normal (but not necessary)

Differential Diagnosis

•Congenital nystagmus

•Sidebeat nystagmus

Treatment

• None

Prognosis

• Nystagmus may appear on some examinations and not on others