Benign episodic mydriasis. Experience in a specialist neuro-ophthalmology clinic of a tertiary hospital.

INTRODUCTION Anisocorias are a relatively frequent reason for consultation in neuro-ophthalmology units. They remain a diagnostic challenge for specialists as they may be due to several etiological factors. In the absence of other accompanying symptoms, anisocorias are usually due to benign processes. Benign episodic mydriasis (BEM) is an isolated cause of intermittent pupil asymmetry, in which the pathophysiology is still not fully understood, and is predominant in young women with migraine. SUBJECTS, MATERIAL AND METHODS We describe the epidemiological and clinical characteristics of patients with BEM, assessed in a neuro-ophthalmology unit in a tertiary hospital. RESULTS A total of 7 patients were diagnosed with BEM, all of them females, with a mean age of 33 ± 10 yrs. The patients presented with pupil asymmetry (n = 5) and blurred vision (n = 2), and 6 of the 7 patients had unilateral involvement. The duration of impairment varied from a few minutes to 48 hrs. Four patients (57%) had a clinical history of migraine without aura. The episodes in these 4 patients were recurrent (75%), often lasted for a few minutes (75%), and had associated blurred vision (50%). The neuroimaging studies were normal. DISCUSSION BEM appears predominantly in young women. It is frequently related to a previous history of migraine, and the specialist must consider if it is a concomitant symptom of common migraine, migraine with aura, or ophthalmoplegic migraine. Although BEM has unilateral predominance, there may be alternation of the affected eye or even bilateral impairment during the same episode, which makes us question the adequacy of the term to describe the process. Imaging tests are not recommended in the absence of other accompanying symptoms, or in short-term episodes.