Anisocoria - is it always sinister?

Acute anisocoria or unequal pupil size suggests impending neurologic emergency unless proven otherwise. Anisocoria can be caused due to benign physiological, pharmacological or congenital abnormalities or sinister causes like tumor, hemorrhage or herniation causing raised intracranial tension. With detailed history, physical examination and close monitoring unnecessary investigations can be avoided. An 11-year-old boy with childhood asthma on preventers was admitted and treated in pediatric intensive care unit (PICU) for life threating exacerbation of asthma. After 72 hours of admission his pupils were found to be unequal with a normal sensorium with no evidence of papilledema or raised intracranial pressure (ICP), anisocoria was postulated to be induced by accidental exposure to nebulized ipratropium. Ipratropium was stopped and he was closely monitored with a plan for imaging in case of worsening. However, anisocoria improved and by 24 hours child’s pupils were equal in size. To confirm the diagnosis of Ipratropium induced anisocoria from trauma or nerve damage, 1% pilocarpine can be instilled into the dilated eye which fails to constrict. Though anisocoria is a medical emergency, it can also stem from benign causes which should be diligently sought to circumvent inadvertent interventions.