Horner syndrome is a combination of signs and symptoms caused by the disruption of a nerve pathway from the brain to the face and eye on one side of the body. Typically, Horner syndrome results in a decreased pupil size, a drooping eyelid, and decreased sweating on the affected side of your face. Classically, the clinical findings include a triad of ipsilateral blepharoptosis, pupillary miosis, and facial anhidrosis.
Horner syndrome results from an interruption of the oculosympathetic pathway. Patients with Horner syndrome present with a slightly droopy upper lid and a smaller pupil on the affected side; less commonly, there is a deficiency of sweating over the brow or face on the affected side.
The oculosympathetic pathway has a long and circuitous course, beginning in the brain and traveling down the spinal cord to exit in the chest, then up the neck and into the orbit. Therefore, this syndrome with unimpressive clinical findings and insignificant symptoms may be a sign of serious pathology in the head, chest, or neck.
It is also present in some trigeminal autonomic cephalalgias (cluster), in thunderclap headaches, and in response to a stellate ganglia block. Horner's syndrome results from interruption of the sympathetic innervation to the eye. This interruption may occur at three anatomical levels along the sympathetic trunk pathway.
There are numerous causes of Horner's syndrome, including injury to the carotid artery, of which arterial dissection is the commonest pathology.
A painful horner could also be an alert of a lung Pancoast tumor (Pancoast or superior sulcus tumor consists of a wide range of tumors invading the apical chest wall and producing a characteristic syndrome named “Pancoast -Tobias syndrome.” The superior sulcus is an anatomical pleuro-pulmonary groove that is formed by the subclavian artery when it curves in front of the pleura and runs upward and lateral immediately below the apex).
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