• 11 SECTIONDisorders Saccadic

Ocular Bobbing

Key Facts

•Vertical conjugate oscillation of eyes in a comatose patient

•May represent disinhibition of automatic midbrain vertical eye movement centers

•Common causes:

•pontine hemorrhage or infarct

•metabolic or anoxic encephalopathy

Clinical Findings

•Typical ocular bobbing:

• fast downward movement followed by slow upward drift to primary position

•horizontal eye movements absent

•Ocular dipping:

•slow downward movement followed by fast upward movement

•horizontal eye movements often intact

•Reverse bobbing:

•fast upward movement followed by slow downward drift to primary position

•horizontal eye movements often intact

•Reverse dipping:

•a slow upward drift followed by a fast downward movement

•horizontal eye movements often intact

Ancillary Testing

•In bobbing, brain imaging often shows intrinsic brainstem lesion

•If brain imaging is negative, consider metabolic or toxic conditions

Differential Diagnosis

•Acquired binocular pendular nystagmus

•Epileptic nystagmus

•Upbeat or downbeat nystagmus

Treatment

• Depends on underlying condition

Prognosis

• Depends on underlying condition

• 12 SECTION Disorders Pupil

Tonic Pupil

Key Facts

•Affected pupil constricts segmentally and more to a near target than to direct light (light–near dissociation) • Affected pupil redilates slowly on changing

fixation from a near to a distant target (tonicity) • Affected pupil constricts following instillation of <1/8% pilocarpine (parasympathetic denervation supersensitivity)

•Common causes:

•presumed viral or postviral dysautonomia affecting ciliary ganglion or ciliary nerves (Adie tonic pupil) • sometimes also dorsal root ganglia are damaged causing impaired deep tendon reflexes (Holmes–Adie syndrome)

•Uncommon causes:

•retinal laser photocoagulation • orbital tumors, surgery, or trauma

• widespread neuropathies, including Guillain–Barré syndrome, Riley–Day syndrome, hereditary neuropathies, amyloidosis, syphilis, pandysautonomias

•No treatment except sometimes bifocals (see below)

Clinical Findings

•Anisocoria with affected pupil larger or smaller than fellow pupil in dim light

•Affected pupil constricts minimally to direct light within days of onset

•≥8 weeks after onset, affected pupil does not constrict normally to direct light but constricts slowly on viewing a target at reading distance (tonic light–near dissociation) • May have temporary loss of accommodation • Slit-lamp examination shows segmental immobility of iris sphincter (segmental palsy) and subtle transillumination defects (iris atrophy) • Deep tendon reflexes may be absent (Holmes–Adie syndrome) • Corneal sensation in affected eye may be reduced, but there are no other pertinent ophthalmic findings • Sometimes evidence of retinal photocoagulation or orbital tumor, trauma, or surgery

Ancillary Testing

•Affected pupil constricts to dilute (<1/8%) pilocarpine • Neurologic or autonomic testing may show evidence of widespread neuropathy • Serologic test for syphilis may be positive

Differential Diagnosis

•Pharmacologically dilated pupil • Third cranial nerve palsy • Iris atrophy from trauma, intraocular surgery, inflammation, congenital anomaly

•Botulism

Treatment

•Patients with deficient or tonic accommodation may benefit from bifocals

• Patients with widely dilated pupil may benefit from periodic instillation of dilute pilocarpine

Prognosis

•Accommodation recovers fully within weeks • Affected pupil becomes smaller within months but never regains normal constriction to light • If only one pupil is affected at presentation, the other pupil may become affected within months to years • Patients rarely have lingering ophthalmic symptoms

A

B

C

D

Fig. 12.1 Tonic right pupil. (A) In darkness, the right pupil is dilated. (B) In brightness, the right pupil does not constrict but the left pupil constricts normally. (C) When a target is viewed at reading distance, both pupils constrict, although right pupil constricts slowly (tonic near response) and segmentally. (D) After instillation of 1/10% pilocarpine

in each eye, the right pupil constricts (cholinergic denervation supersensitivity) but the left pupil does not.

Pupil Tonic