Nystagmus

Convergence–retraction “Nystagmus”

Key Facts

•Repetitive convergence and retraction saccades of both eyes provoked by attempted upgaze or by viewing an optokinetic strip moved downward

•Not a true nystagmus (because nystagmus is never initiated by a saccade)

•Co-contraction of all extraocular muscles produces repetitive saccades

•Always associated with impaired upgaze

•Caused by a lesion of the dorsal midbrain region (see Dorsal midbrain [pretectal] syndrome)

Clinical Findings

•Repetitive convergence and retraction saccades of both eyes provoked by attempted upgaze or by viewing an optokinetic strip moved downward

•Impaired upgaze and other signs of dorsal midbrain dysfunction

•Patient experiences brow ache whenever convergence–retraction “nystagmus” is provoked

• 10 SECTION

Ancillary Testing

• MRI usually discloses an abnormality of the dorsal midbrain region

Differential Diagnosis

• Nothing else looks like this

Treatment

• Directed at underlying condition

Prognosis

• Depends on underlying condition

Fig. 10.18 Convergence–retraction “nystagmus”. On attempted upgaze, the eyes do not move upward very much. Instead, they converge and retract a few times. This reaction looks like clonus elicited at the ankles when the Achilles deep tendon reflex is tested in a patient with an upper motor neuron lesion.

A B

Fig. 10.19 Pineal germinoma causing convergence–retraction “nystagmus”. Postcontrast (A) sagittal and (B) axial T1 MRIs show enhancing (high signal) mass (arrows) in the pineal region that infiltrates the tectal plate.

“Nystagmus” retraction–Convergence

• 10 SECTION Nystagmus

Voluntary “Nystagmus”

Key Facts

•Voluntary bursts of back to back saccades in horizontal plane

•Not a true nystagmus (because nystagmus is never initiated by a saccade)

•Episodes are brief and tiring to the patient

•May be used to simulate illness

•Mistaken for ocular flutter or opsoclonus but distinguished by lack of accompanying neurologic findings (tremor, titubation, myoclonus, ataxia)

Clinical Findings

•Bursts of quick, quivery oscillations in both eyes, usually initiated by convergence

•No other ophthalmic or neurologic findings

Ancillary Testing

• None needed

Differential Diagnosis

•Congenital nystagmus

•Peripheral vestibular nystagmus

•Sidebeat nystagmus

•Ocular flutter or opsoclonus

•Habit spasms (tics)

Treatment

•Explanation to patient of the voluntary nature of this phenomenon and/or reassurance

Prognosis

• May be used repeatedly to simulate illness