Transient Anisocoria in an Otherwise Asymptomatic Child

Background: Anisocoria is an alarming sign on physical examination, often leading to extensive investigation in order to exclude life-threatening conditions.

Case Report: A 10-year-old boy attended the Pediatric Emergency Department with asymmetrical pupils, which were noted eight hours previously. His past medical history was notable for asthma, for which he was prescribed both salbutamol and ipratropium bromide (IB) inhalers via spacer and facemask. That morning, he referred to had done an IB inhalation in the dark, with dubious facemask adaptation. On examination, the child was well, with left mydriasis and both pupils reactive to light (Figure 1). Systemic and neurological examination were otherwise unremarkable. Head CT showed no acute lesions. Although an iatrogenic etiology was more likely, the child was admitted for overnight observation. By the next morning, the anisocoria had dramatically improved, and he was discharged with a scheduled appointment for the following day. 48 hours after the initial examination, the anisocoria had completely resolved (Figure 2).

Discussion: Being a direct antagonist at muscarinic cholinergic receptors, IB paralyses the parasympathetic fibers of the oculomotor nerve, leading to asymmetrical pupils. Although most reported cases of IB induced anisocoria occurred in children, usually due to facemask adaptation difficulties, it is still an infrequent condition. The possible etiologies for anisocoria and their severity pose a diagnostic challenge. History of asthma and IB inhalation, as well as otherwise unremarkable systemic and neurological examination, point towards an iatrogenic etiology.