<prompt> Horners syndrome. All true exceptaEURMiosisAnhydrosisHyperchromatic irisApparent exophthalmos  <response>: Apparent exophthalmoses Ref: Adams victor principles of neurology 8e p. 2541 Horners syndrome is a classic neurologic syndrome whose signs include: -- Miosis, - Ptosis, and - Anhidrosis Also called oculosympathetic paresis, a Horners syndrome can be produced by a lesion anywhere along the sympathetic pathway that supplies the head, eye, and neck. Neuroanatomy Horners syndrome can result from a lesion anywhere along a three-neuron sympathetic adrenergic pathway that originates in the hypothalamus - The first-order neuron - Descends caudally from the hypothalamus to the first synapse, which is located in the cervical spinal cord levels C8-12, also called ciliospinal center of Budge. - The second-order neuron - Travels .from the sympathetic trunk, through the brachial plexus, over the lung apex. It then ascends to the superior cervical ganglion, located near the angle of the mandible and the bifurcation of the common carotid aery. - The third-order neuron - Then ascends within the adventitia of the internal carotid aery, through the cavernous sinus, where it is in close relation to the sixth cranial nerve. The oculosympathetic pathway then joins the ophthalmic VI division of the ,fifth cranial nerve trigeminal nerve. In the orbit and the eye, the oculosympathetic fibers innervate the iris dilator muscle as well as Mullers muscle, a small smooth muscle in the eyelids responsible for a minor poion of the upper lid elevation and lower lid retraction. Clinical features The classic signs of a Horners syndrome are: ? - PtosisQ - Miosise - A n hidrosisQ The degree of anisocoria is more marked in the dark than in light. - There is associated dilation lag, an asymeetry in papillary redilation between the two eyes when the light source is moved away .from the eye. - The homers pupil will redilate more slowly by 15 to 20 seconds than the normal pupil. The ptosis is minor less than 2 mm and occurs as a result of paralysis of the Mullers muscle, which is innervated by the sympathetic pathway. The lower as well as the upper lid is affected producing the so-called upside-down ptosis. Anhidrosis is present in central or preganglionic first or second order lesions. The sympathetic fibers responsible for facial sweating and vasolidation branch off at the superior cervical ganglion from the remainder of the oculosympathetic pathway; thus, anhidrosis is not a feature of postagangkonic or third-order lesions. This sign is .frequently not apparent to patients or clinicians. A congenital Horners syndrome should be suspected when anisocoria is associated with heterochromia unequal iris color, with the affected iris being lighter. - This occurs because formation of iris pigment in the first several months of age is under sympathetic control. This may only be apparent if the natural color is relatively dark. ETIOLOGY The etiology of Horners syndrome in adults relates to the lesion location. First-order syndrome central Lesions of the sympathetic tracts in the brainstem or cervicothoracic spinal cord can produce a first-order Homers syndrome. Lateral medullary syndromes M.C. - Brainstem disease stroke, tumour, demyelinating disorder - Syringomyelia - Cervical cord trauma including surgery - Spinal cord tumour - Diabetic autonomic neuropathy - Multiple sclerosis Second-order syndrome preganglionic - Trauma or surgery involving spinal cord, thoracic outlet lung apex. - Pancoast tumour - Carotid and Aoic aneurysm and dissection - Lumbar epidural anaesthesia. Third-order syndrome Postganglionic - Lesions of internal carotid aery such as - Dissection, thrombosis - Otitis media - Cavernous sinus mass Surgery for raynauds syndrome cervical sympathectomy may cause trauma to cervical spinal cord. 