Asymptomatic Transient Anisocoria
A 6-year-old girl with a history of asthma presented to the emergency department for an acute asthma exacerbation. She had been taking albuterol at home without much improvement. Her mother denied the presence of fever in the girl.
Physical examination findings were unremarkable except for the presence of mild respiratory distress, subcostal retractions, and expiratory wheezes.
She was treated with albuterol and ipratropium bromide inhaled nebulizer treatments and was given oral dexamethasone. Her asthma symptoms improved after several nebulizer treatments. She remained well appearing and without hypoxia, and she was being prepared for discharge.
On reassessment, however, she was noted to have unequal pupils. Her left pupil was 5 mm and nonreactive, while the right pupil was 3 mm and reactive. She was asymptomatic, with otherwise nonfocal neurologic examination findings, and was jumping around the room, ready to go home. Of note, her pupils had been equal and reactive at the time of the initial physical examination.
The girl remained asymptomatic but remarked that she felt like “something was getting in (her) eye” during the nebulizer treatment. Her mother was instructed to follow up with her pediatrician the next morning, and strict return instructions were given. On telephone follow-up approximately 24 hours later, the girl’s anisocoria had almost completely resolved.
Anisocoria is a concerning finding on physical examination and might suggest an impending neurologic emergency.1 Determining the cause might require costly studies such as magnetic resonance imaging. In an asymptomatic patient without recent history of trauma or concerning past medical history, pharmacologic causes should be considered.
In this case, given the girl’s otherwise normal neurologic examination findings and onset after administration of aerosolized ipratropium bromide, her anisocoria was believed to have been caused by the medication.
Ipratropium bromide has long been recognized as a cause of transient anisocoria, particularly in association with ill-fitting face masks, in children and adults.1-3 Proper face mask fit is particularly difficult for pediatric patients; the masks inevitably leak aerosol, leading to significant facial and eye deposition.4
Ipratropium bromide is an anticholinergic agent that is used frequently in the treatment of reversible airway disease owing to its bronchodilatory and antisecretory properties.1 It is a derivative of atropine, and the medication antagonizes muscarinic acetylcholine receptors, decreasing contractility of smooth muscle.5 When administered directly to the eye, ipratropium bromide paralyzes the parasympathetic nerve endings and results in unopposed mydriasis.5,6
In general, one-fifth of normal individuals have benign anisocoria with pupils that differ by 0.4 mm or greater but that exhibit normal reaction to light. The degree and laterality of anisocoria can vary over time.7
While brain imaging still is the most effective way to rule out structural causes of anisocoria, 1% pilocarpine drops have been shown to be an alternative.1,3,8 Pilocarpine administration will constrict a dilated pupil caused by oculomotor nerve palsy; failure to constrict confirms pharmacologically induced mydriasis. Adverse effects such as miosis, ciliary spasm, blurred vision, and photophobia have been reported with pilocarpine eye drop instillation.1
Pupil dilation usually resolves within 48 hours but can last up to 3 weeks after ipratropium is stopped.3,8 Other manifestations of ipratropium exposure include bilateral mydriasis, cycloplegia, blurred vision, dry eye, and in rare cases, acute glaucoma.3 Other pharmacologic causes of unilateral mydriasis include atropine-like agents, such as scopolamine and hyoscyamine, and plant species from the Datura genus, such as Jimson weed.7
References
1.Bisquerra RA, Botz GH, Nates JL. Ipratropium-bromide-induced acute anisocoria in the intensive care setting due to ill-fitting face masks. Respir Care. 2005;50(12):1662-1664.
2.Samaniego F, Newman LS. Migratory anisocoria—a novel clinical entity. Am Rev Respir Dis. 1986;134(4):844.
3.Wehbe E, Antoun SA, Moussa J, Nassif I. Transient anisocoria caused by aerosolized ipratropium bromide exposure from an ill-fitting face mask. J Neuroophthalmol. 2008;28(3):236-237.
4.Sangwan S, Gurses BK, Smaldone GC. Facemasks and facial deposition of aerosols. Pediatr Pulmonol. 2004;37(5):447-452.
5.Lust K, Livingstone I. Nebulizer-induced anisocoria [letter]. Ann Intern Med. 1998;128(4):327.
6.Bond DW, Vyas H, Venning HE. Mydriasis due to self-administered inhaled ipratropium bromide. Eur J Pediatr. 2002;161(3):178.
7.Moeller JJ, Maxner CE. The dilated pupil: an update. Curr Neurol Neurosci Rep. 2007;7(5):417-422.
8.Jannun DR, Mickel SF. Anisocoria and aerosolized anticholinergics. Chest. 1986;90(1):148-149.