- Round , regular , symmetric , and reactive to light = midbrain intact
- Unilateral dilated and fixed = CNIII compression (uncal herniation / Pcomm aneurysm)
- Bilateral dilated and fixed = hypoxic ischemic encephalopathy, opiate withdrawal, and intoxication with barbiturates, atropine, scopolamine, or glutethimide.
- Pinpoint and reactive = pontine damage, opiate or cholinergic toxicity
- Midposition fixed or irregular = focal midbrain lesion
- Unilateral small pupil or isolated miosis ( especially with ipsilateral ptosis , facial anhidrosis , and enophthalmos )= Horner’s syndrome (consider
carotid or vertebral artery dissection)
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Rana, Abdul Qayyum, and John Anthony Morren. Neurological Emergencies In Clinical Practice. London: Springer, 2013. Print.