![]() ![]() ![]() ![]() Third order neuron or postganglionic lesion: These include lesions of the superior cervical ganglion (trauma, radical neck dissection or jugular vein ectasia), lesions of the internal carotid artery (ICA) in the neck and skull base (dissection, thrombosis, invasion by tumors or iatrogenic from endarterectomy or stenting, base of skull malignancies), lesions of ICA in the cavernous sinus (thrombosis, aneurysm, inflammation or invasive tumors) and lesions of the sellar and parasellar regions (invasive pituitary tumors, metastatic tumors, paratrigeminal tumors). Third order neuron or postganglionic lesion Preganglionic (second order neuron) Horner’s: These include lesions of the thoracic outlet (cervical rib, subclavian artery aneurysm), mediastinum (mediastinal tumors), pulmonary apex (Pancoast's tumor), neck (thyroid malignancies) or the thoracic spinal cord (trauma) or surgical procedures in this region including radical neck dissection, jugular vein cannulation, thoracoscopy or mediastinoscopy, chest tube placement and other thoracic surgical procedures. Preganglionic (second order neuron) Horner’s The etiology remains unknown in 35-40% of cases.Ĭentral (first order neuron) Horner’s: These include lesions of the hypothalamus, brainstem and spinal cord such as stroke (classically the lateral medullary syndrome), demyelination (such as multiple sclerosis), neoplasms (such as glioma), or other processes such as a syrinx (syringomyelia or syringobulbia). The etiology of Horner’s syndrome varies with the patient age and site of lesion. Pupillary constriction is produced by parasympathetic (cholinergic) fibers that travel with the third cranial (oculomotor) nerve.The vasomotor and sudomotor fibers to the face exit the superior cervical ganglion and ascend in the external carotid artery.The fibers (long ciliary nerve) innervate the dilator muscles of the iris and the smooth muscle (Müller’s muscle) in the upper and lower eyelid (inferior retractors).Here, the oculosympathetic fibers exit the internal carotid artery in close proximity to the trigeminal ganglion and the sixth cranial nerve and join the 1st division of the trigeminal nerve to enter the orbit. The third order (postganglionic) neuron for the orbit enters the cranium within the adventitia of the internal carotid artery into the cavernous sinus. The superior cervical ganglion is located near the angle of the mandible and bifurcation of the common carotid artery. The second order (preganglionic) neuron destined for the head and neck exits the spinal cord and travels in the cervical sympathetic chain through the brachial plexus, over the pulmonary apex and synapses in the superior cervical ganglion. The descending sympathetic tract is in close proximity to other tracts and nuclei in the brainstem. The first order (central) neuron descends caudally from the hypothalamus to the first synapse in the cervical spinal cord (C8-T2 level-also called the ciliospinal center of Budge). Pupillary dilation is mediated by a three-neuron sympathetic pathway that originates in the hypothalamus. The pupil is innervated by sympathetic and parasympathetic fibers. Horner's syndrome results from a lesion to the sympathetic pathways that supply the head and neck, including the oculosympathetic fibers. In a population based study of Horner’s syndrome in the pediatric age group, the incidence of Horner’s syndrome was estimated to be 1.42 per 100 000 patients younger than 19 years, with a birth prevalence of 1 in 6250 for those with a congenital onset. 1.4.3 Third order neuron or postganglionic lesion.1.4.2 Preganglionic (second order neuron) Horner’s.1.4.1 Central (first order neuron) Horner’s.1.3.3 Third order (postganglionic) neuron.1.3.2 Second order (preganglionic) neuron. ![]()
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