![]() ![]() In: Walsh and Hoyt Clinical Neuro-ophthalmology, 6th ed, Miller, NR, Newman, NJ, Biousse, V, Kerrison, JB (Eds), Williams & Wilkins, Baltimore. Anatomy and physiology of the autonomic nervous system. Neuro-Ophthalmology Illustrated, Thieme Verlag, Germany.Ħ. American Association of Neurological Surgeons. “Anisocoria.” Stedman’s Medical Dictionary, 27th ed. (2000).Ĥ. “Traumatic Brain Injury”. However it is useful to understand the anatomy and physiology and the other possible causes of unequal pupils.ģ. Summary: A fixed dilated pupil in the pre-hospital setting is presumed to be a sign of uncal herniation until proven otherwise and should be treated accordingly. 1 We report a patient who developed transient unilateral mydriasis and prolonged sedation after the use of dexmedetomidine as an adjunct for general anesthesia. Summary of the pathophysiology of anisocoria. summarising the pre-hospital causes of anisocoria.įig 1. Learning points: Obvious direct trauma and fake eyeballs aside, below is Fig 1. 5, 6Įach eye’s sensory pathway is linked with its counterpart by partial crossover of fibers in the Edinger-Westphal nuclei which accounts for the consensual response to light. The pupil will respond to circulating catecholamines but dilation is controlled by sympathetic fibres originating from the superior cervical ganglia. Pathophysiology: Pupillary size is governed by the balance of actions of two opposing muscle groups of the iris: the dilator and sphincter pupillae controlled by the autonomic nervous system.Ĭonstriction of the size of the pupil is mediated via parasympathetic (cholinergic) nerve fibers that travel superficially with the third cranial nerve. The head CT performed at the trauma centre revealed no gross intracranial pathology requiring neurosurgical intervention, but did show a right-sided retrobulbar haematoma, which was thought to account for his unilateral fixed dilated pupil.Ĭhallenge: To understand the pathophysiology of pupillary signs and when a “blown” pupil might not be a consequence of uncal herniation. His pupillary signs did not improve with a bolus of hypertonic saline bolus and hyperventilation in transit. He received an RSI and bilateral thoracostomies. The more seriously injured victim had obvious right-sided facial and thoracic injuries, had a blown right pupil and a GCS 3 (with no external signs of head trauma). 4Ĭase: Our HEMS team was called to a rural trauma involving two motocross riders. 3Ī “blown” pupil is the colloquial term used by medics to refer to a fixed unilateral mydriasis. There are also many pre-hospital causes of a unilateral miosis a constricted pupil. 1 In my mind he still gets a tube and the paramedic can do it, but he only gets “ one shot“?!? 2Īnisocoria is characterised by unequal pupil sizes, but not necessarily as a consequence of mydriasis a dilated pupil. The condition is typically accompanied with other signs and symptoms, including. His reduced level of consciousness and blown pupil might just be due to a copious amount of mind-bending drugs and the accident as a school-boy which left him with a unilateral pupillary defect. Benign episodic unilateral mydriasis causes temporary mydriasis of one eye. Take caution if you ever get tasked to a pre-hospital trauma at David Bowie’s house.
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