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Pupil Examination for a Patient in Coma

Pupil Examination in a Comatose Patient Pupil assessment is a vital part of the neurological exam in coma—it helps localize brainstem lesions, differentiate structural vs metabolic causes, and even predict prognosis. Here's how clinicians approach it: 🔍 What to Examine Size: Measure in ambient and dim light Normal: 2–4 mm in bright light, 4–8 mm in darkness Pinpoint: Suggests pontine lesion or opioid overdose Mid-dilated: May indicate midbrain damage Unilateral dilation: Could be uncal herniation (Hutchinson pupil) Shape: Round, oval, or irregular Oval pupils: Often linked to midbrain compression Equality: Check for anisocoria (unequal pupils) Reactivity to light: Brisk: Normal Sluggish: May suggest metabolic or toxic cause Fixed: Indicates severe brainstem injury or pharmacologic dilation 💡 Light Reflex Testing Direct response: Shine light in one eye—observe constriction Consensual response: Opposite eye should also constrict Swinging flashlight test: Detects relative afferent pupillary defect (RAPD) 🧠 Localization Clues Pupil Finding Possible Lesion Pinpoint pupils Pontine hemorrhage or opioid toxicity Mid-dilated, fixed Midbrain lesion Unilateral dilated, fixed Uncal herniation compressing CN III Small, reactive pupils Metabolic encephalopathy Oval pupils Midbrain compression Bilateral nonreactive mydriasis Terminal brainstem failure 🧪 Additional Reflexes Ciliospinal reflex: Pupillary dilation in response to neck pain—tests sympathetic pathway Accommodation reflex: Often absent in coma due to lack of voluntary effort ⚠️ Important Considerations Drug effects: Anticholinergics, opioids, and inhalers can alter pupil size/reactivity Pre-existing conditions: Ocular surgery, trauma, or congenital anomalies may affect findings Prognosis: Early non-reactive pupils post-cardiac arrest often indicate poor outcome #Coma