![]() ![]() S for Sentral, T for Torso (pre-ganglionic) and C for Cervical (post-ganglionic). The causes can be remembered as the 4 Ss, 4 Ts and 4 Cs. Post-ganglionic lesions do not cause anhidrosis. Pre-ganglionic lesions cause anhidrosis of the face. Central lesions cause anhidrosis of the arm and trunk as well as the face. The location of the Horner syndrome can be determined by the anhidrosis. These post-ganglionic nerves then travel to the head, running alongside the internal carotid artery. They then enter into the sympathetic ganglion at the base of the neck and exit as post-ganglionic nerves. The sympathetic nerves arise from the spinal cord in the chest. The journey of the sympathetic nerves to the head is relevant for the causes of Horner syndrome. Horner syndrome is caused by damage to the sympathetic nervous system supplying the face. Light and accommodation reflexes are not affected. They may also have enopthalmos, which is a sunken eye. Posterior communicating artery aneurysm.This is called a “ surgical third” due to the physical compression: This may be due to:Ī full third nerve palsy is caused by compression of the nerve, including the parasympathetic fibres. Third nerve palsy can be idiopathic, without a clear cause.Ī third nerve palsy with sparing of the pupil suggests a microvascular cause as the parasympathetic fibres are spared. Therefore, cavernous sinus thrombosis and a posterior communicating artery aneurysm can cause compression of the nerve and a third nerve palsy. It travels through the cavernous sinus and close to the posterior communicating artery. The oculomotor nerve travels directly from the brainstem to the eye in a straight line. Therefore third nerve palsy causes a dilated fixed pupil. The oculomotor nerve also contains parasympathetic fibres that innervate the sphincter muscle of the iris. Therefore third nerve palsy causes a ptosis. It also supplies the levator palpebrae superioris, which is responsible for lifting the upper eyelid. Therefore when these muscles are no longer getting signals from the oculomotor nerve, the eyes moves outward and downward due to the effects of the lateral rectus and superior oblique still functioning without resistance. It supplies all of the extraocular muscles except the lateral rectus and superior oblique. ![]() The third cranial nerve is the oculomotor nerve. It causes a “ down and out” position of the eye. Divergent strabismus (squint) in the affected eye.Argyll-Robertson pupil (in neurosyphilis).This is usually temporary and associated with migraines. Tadpole pupil is where there is spasm in a segment of the iris causing a misshapen pupil. This can cause a hole in the iris causing an irregular pupil shape. This is usually associated with poorly controlled diabetes and diabetic retinopathy.Ĭoloboma is a congenital malformation in the eye. Rubeosis iridis (neovascularisation in the iris) can distort the shape of the iris and pupil. This could be caused by cataract surgery and other eye operations.Īnterior uveitis can cause adhesions (scar tissue) in the iris that make the pupils misshapen.Īcute angle closure glaucoma can cause ischaemic damage to the muscles of the iris causing an abnormal pupil shape, usually a vertical oval. Trauma to the sphincter muscles in the iris can cause an irregular pupil. They are stimulated by the sympathetic nervous system using adrenalin as a neurotransmitter. The dilator muscles of the pupil arranged like spokes on a bicycle wheel travelling straight from the inside to the outside of the iris. The fibres of the parasympathetic system innervating the eye travel along the oculomotor (third cranial) nerve. They are stimulated by the parasympathetic nervous system using acetylcholine as a neurotransmitter. There are circular muscles in the iris that cause pupil constriction. The pupil is formed by a hole in the centre of the iris. 2003 110(8):1606-14.Īmerican Academy of Ophthalmology.There are a number of conditions that can cause abnormally shaped or sized pupils. Pupil size and quality of vision after LASIK. Schallhorn SC, Kaupp SE, Tanzer DJ, Tidwell J, Laurent J, Bourque LB. Ocular manifestations of drug and alcohol abuse. Pupillary reactivity as an early indicator of increased intracranial pressure: the introduction of the Neurological Pupil index. doi:10.3892/ol.2017.5648Ĭhen JW, Gombart ZJ, Rogers S, Gardiner SK, Cecil S, Bullock RM. Iris metastasis as the first sign of small cell lung cancer: a case report. March 23, 2016.īrigham And Women's Hospital. Pupillary disorders including anisocoria.Īmerican Academy of Ophthalmology. What kinds of eye examinations are there? April 20, 2016. Anisocoria and an array of neurologic symptoms in an adult with Ewing sarcoma. ![]() Safe and sensible preprocessing and baseline correction of pupil-size data. Mathôt S, Fabius J, Van Heusden E, Van der Stigchel S. A model of the entrance pupil of the human eye. ![]()
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