Benign episodic unilateral mydriasis. Clinical characteristics

To describe the clinical features of the syndrome of neurologically isolated episodic unilateral mydriasis.

Information was obtained by reviewing the case records of 24 patients evaluated by the author and collected by polling other neuro-ophthalmologists.

Nineteen patients were women. The median age was 31 years. Fourteen patients had migraines. The median interval between onset of events and evaluation was 6 months. The median duration and frequency of events were 12 hours and two to three per month, respectively. Most patients did not identify any factor that could precipitate an occurrence. The most common associated symptoms during an episode included visual blur in 15 patients, headache in 9, and orbital pain in 5. Eleven patients were examined during an attack. Three patients who were examined had impaired near vision, four had impaired accommodative function, and six had an anisocoria that increased with added ambient light. None of these patients had a tonic pupil or cholinergic agonist-induced pharmacologic mydriasis. Five other patients examined during an attack had normal vision and unimpaired direct light reactivity of their large pupil. No neurologic disorder was identified after neurodiagnostic testing, clinical evaluation, and natural history observation.

The syndrome of idiopathic episodic unilateral mydriasis probably comprises a heterogeneous group of conditions that result in parasympathetic insufficiency of the iris sphincter in some patients, and sympathetic hyperactivity of the iris dilator in others. Patients with episodes similar in characteristics to the ones described in this survey appear to have a benign neurologic prognosis, and do not require further neurodiagnostic studies.