[Episodic benign unilateral mydriasis. Clinical case in a girl]

Pupil asymmetry is an alarm signal which should lead to investigation to rule out severe underlying neurological disorders. Among its causes are tumors, aneurysms and hernia of the uncus. The differential diagnosis should also include other conditions such as Adie's tonic pupil, the Pourfour de Petit syndrome and local disorders such as closed angle glaucoma or segmental spasm of the iris dilator muscle. In practice however, exposure to mydriatic substance is one of the commonest causes. Another cause of this sign is benign episodic unilateral mydriasis. This uncommon condition has been defined as an isolated benign cause of pupil asymmetry. The underlying physiopathology is not always clear and may involve either parasympathetic deficiency or sympathetic hyperactivity affecting the iris. Usually related to migraine, some authors classify it as a limited form of ophthalmoplegic migraine, although some cases have been described with no accompanying headache.

We describe a case of benign episodic unilateral mydriasis in a six-year-old girl who presented with intermittent episodes of pupil asymmetry with no other neurological symptoms.

We underline the rarity of this condition in children with no simultaneous headache.