Horner syndrome

Head | Neurology | Horner syndrome (Disease)


Horner syndrome refers to a constellation of signs produced when sympathetic innervation to the eye is interrupted. Lesions at any point along the sympathetic pathway may result in Horner syndrome.

Signs found in all patients, regardless of the level of interruption include mild-to-moderate ptosis owing to denervation of the sympathetically controlled Müller muscle, slight elevation of the lower lid (upside-down ptosis) due to denervation of the lower lid muscle analogous to the Müller muscle in the upper lid, and miosis and dilation lag, where pupillary dilation after psychosensory stimuli is slower in the affected pupil than the unaffected pupil.

Depending on the level of the lesion, impaired flushing and sweating may be found ipsilaterally. Iris heterochromia (with the affected eye being hypopigmented) is seen in congenital Horner syndrome or Horner syndrome that occurs in children younger than 2 years. Iris heterochromia also may occur in long-standing Horner syndrome.

Causes and Risk factors

Horner syndrome can be caused by any interruption in a set of nerve fibers that start in the part of the brain called the hypothalamus and travel to the face and eyes. Sympathetic nerve fiber injuries can result from: injury to one of the main arteries to the brain (carotid artery), injury to nerves at the base of the neck called the brachial plexus, migraine or cluster headaches, stroke, tumor, or other damage to a part of the brain called the brainstem, tumor in the top of the lung.

Diagnosis and Treatment

Blood tests and imaging tests are performed to determine the cause of the syndrome. Treatment depends on the cause of the problem. There is no treatment for Horner syndrome itself. ...