![]() Key history to obtain include: recent head, neck, or eye trauma past ocular procedures use of eyedrops or other topical medication and the presence of other neurologic symptoms. 2,6,9 An initial focused history and examination can help delineate between these three categories. 9Īnisocoria can be subdivided int0 three broad categories: (1) pathologic large pupil, (2) pathologic small pupil, or (3) physiologic pupil size difference. Autonomic innervation of the eye and associated anatomic structures. 2,10 Unilateral interruptions anywhere along these pathways, including the brain, nerve chains, neuromuscular junction, or muscles can lead to anisocoria. 10 Upon contraction of the dilator papillae, the pupil dilates. 2,10 The carotid plexus then follows the path of the external carotid artery through the cavernous sinus before innervating the dilator papillae muscle across a norepinephrine synapse (Figure 3). 2,10 From there, the sympathetic chain extends cephalad before giving rise to the carotid plexus. The sympathetic fibers start in the hypothalamus and extend down the spinal cord before exiting at C8-T2 and synapsing on the paravertebral sympathetic chain. While pupillary dilation is also initiated in the brainstem, it results from sympathetic input. Parasympathetic and sympathetic pathways with associated anatomy responsible for pupillary constriction and dilation. ![]() Upon iris sphincter contraction, the pupil constricts. The parasympathetic fibers travel alongside the oculomotor nerve (CN III) before innervating the iris sphincter muscles across an acetylcholine neuromuscular end plate (Figure 2). Pupillary constriction is initiated in the brainstem and is controlled by parasympathetic signals. Unequal pupils found on examination consistent with anisocoria. For that reason, the emergency clinician must understand how to obtain the appropriate history, examination, and workup when anisocoria is found on examination.įigure 1. 1-6 However, anisocoria can point to dangerous pathologies, so its presence on physical examination should prompt a thorough evaluation. 1-4 Physiologic anisocoria is not associated with a disease process and can be persistent or self-limiting and unilateral or of variable laterality. 1-3,5 Physiologic anisocoria is the most common cause of anisocoria, with a pupillary size difference most commonly less than or equal to 1 mm. 3,4 It is estimated that physiologic anisocoria, also called simple or essential anisocoria, is present in 10-30% of the population. 1-4 The possible etiologies for anisocoria are broad and can range from benign conditions to potentially life-threatening pathologies. What is the relevance of the patient’s pupillary size difference and how does it pertain to this patient’s workup? How is anisocoria evaluated in the ED and how is the clinician to determine the relevance of this physical examination finding?Īnisocoria is a condition defined by pupils of unequal sizes (Figure 1). When asked about the difference in pupil size, the patient reports that she first noticed it this morning. The rest of her neurologic examination is normal, and the patient’s visual acuity is at her baseline. On examination, she has lid lag of her left eye. Examination is notable for bruising over her left neck and asymmetrical pupils, with her left pupil measuring 2 mm, and her right 6 mm. Her pain developed overnight and was still present upon waking this morning. The patient was able to ambulate after the incident and declined EMS transport for medical evaluation. She was wearing her seatbelt and did not lose consciousness. The patient reports that last night she was the driver involved in a moderate-speed motor vehicle collision in which airbags did not deploy. The pain is unilateral, moderate, and has been progressive over the last 24 hours. Louis) Marina Boushra, MD (Cleveland Clinic Foundation, EM-CCM Attending) CaseĪ 33-year-old female with no significant past medical history presents to the emergency department (ED) with left-sided face and neck pain. ![]() Louis) // Reviewed by: Jessica Pelletier, DO (EM Education Fellow, Washington University School of Medicine in St. Louis) Aaron Lacy, MD EM Attending Physician, Washington University School of Medicine in St. Authors: Emilie Lothet, MD (EM Resident Physician, Washington University School of Medicine in St.
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