![]() Although rare, damage to the superior cervical ganglion can occur as a complication of anterior or posterior cervical spine surgery, or surgery involving the thoracic outlet or lung apex. ![]() These axons then enter the orbit upon the short and long ciliary nerves (branches of V1, the ophthalmic division of CN V - the trigeminal nerve) to synapse on the dilator pupillae muscle, causing pupillary dilation.Īny disruption along the three neuron pathways can result in loss of pupillary dilation. The third-order postganglionic neurons travel along the periarterial carotid plexus through the cavernous sinus. The superior cervical ganglion appears opposite the second and third cervical vertebrae, near the angle of the mandible and the bifurcation of the common carotid artery. The second-order neuron, the preganglionic sympathetic neuron, exits the spinal cord through the ventral roots and ascends through the thorax, near the lung apex and subclavian vessels, onto the superior cervical ganglion. The first-order neuron begins in the hypothalamus and descends through the midbrain to synapse onto the spinal cords ciliospinal center of Budge, found between C8 to T2. The pupillary dilation pathway is a sympathetically driven response to stimuli and is a three-neuron pathway. ![]() In addition to Horner syndrome, chronic opiate abuse can cause miosis. Topical cocaine in a person with Horner syndrome will lead to minimal or no dilation at all. Topical cocaine in a person without Horner's syndrome will cause pupillary dilatation. One of cocaine's mechanisms of action is to block the reuptake of norepinephrine at the neuromuscular junction. It is essential to avoid damaging the superior cervical ganglion during cervical surgery, as such damage could prompt the development of Horner syndrome.Īlthough Horner syndrome is predominantly a clinical diagnosis, in more subtle cases, administration of topical cocaine to the eye for confirmation secondary to cocaine's sympathetically activating qualities is an option. The pupillary dilation pathway is a three-neuron pathway disruptions anywhere along the oculosympathetic pathway may cause Horner syndrome, which is a classic triad of ptosis, miosis, and anhydrosis of the face due to loss of sympathetic innervation. It is for this reason that pupillary dilation may result from any physical or emotional stress that triggers the autonomic sympathetic nervous system, which is mediated by the hypothalamus. The pupillary dilation pathway is a sympathetically driven response beginning in the hypothalamus and ending with the contraction of the dilator pupillae muscle.
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