Definition

Horner's syndrome consists of a ptosis (drooping of the upper eyelid), a small pupil and sometimes reduced facial sweating on the affected side. An interruption of the sympathetic nerve supply to the eye anywhere between the origin of the nerve in the brain to its end point in the eye will produce a Horner's syndrome.

Incidence/age

Horner's syndrome may occur as a congenital lesion (at or soon after birth) or as an acquired condition at any age.

Causes

A Horner's syndrome may be idiopathic with no known cause found. Known causes of Horner's syndrome include interruption to the sympathetic nerve in its course through the brain stem and spinal cord by conditions such as stroke, neck trauma, specific forms of migraine, multiple sclerosis and syringomyelia (abnormal development of the spinal cord). The sympathetic nerve may be interrupted in its passage from the spinal cord across the top of the lung and back up the front aspect of the neck by lesions such as lung cancer, thyroid tumour and trauma or surgery to the root of the neck. The sympathetic nerve may be interrupted in its final course from the root of the neck back up into the skull to reach the eye by lesions including abnormalities of the carotid artery or the blood vessels behind the eye, and nasopharyngeal cancer.

Signs/symptoms

The condition is usually unilateral. There is a mild drooping of the upper eyelid on the affected side (by 1-2 mm compared to the fellow eye). The size of the pupil is normally smaller on the affected side but the pupil reaction to light is normal. If the sympathetic nerve is interrupted in the brain stem, the spinal cord or the root of the neck then sweating on the affected side of the face will also be reduced. If the Horner's syndrome is congenital (present at or soon after birth) then the iris of the affected eye will be of lighter colour than the fellow eye (heterochromia).

Complications of disorder

There are no complications associated with either a congenital or idiopathic Horner's syndrome. It is however important to establish whether there is an underlying disorder present leading to the Horner's syndrome as early diagnosis and treatment may prevent the development of subsequent complications from the underlying disorder.

Tests

Eye drops may be used to confirm the presence of a Horner's syndrome; a) 4% cocaine drops are applied to both eyes. The normal pupil will dilate but the Horner's pupil will not. Subsequently drops can be used to determine approximately at what site the interruption to the sympathetic nerve has occurred; b) 1% hydroxyamphetamine drops are placed in both eyes. If the interruption to the sympathetic nerve is in the brain stem, spinal cord or the root of the neck (preganglionic) both pupils will dilate. If the interruption to the sympathetic nerve is between the root of the neck and the eye (post ganglionic) then the Horner's pupil will not dilate; c) 1:1000 adrenaline drops are installed into both eyes. In a preganglionic Horner's syndrome neither pupil will dilate. In a post ganglionic Horner's syndrome the Horner's pupil will dilate.

Where indicated tests to evaluate the cause of a Horner's syndrome may include magnetic resonance imaging of the brain, root of the neck or the internal carotid artery. Carotid angiography may be used to further evaluate suspected abnormalities of the internal carotid artery or blood vessels behind the eye.

Treatment

Medical

In cases of congenital Horner's syndrome there is no medical treatment that improves or reverses the condition. Treatment in acquired cases is directed towards eradicating the disease that is producing the syndrome.

Surgical

If the drooping of the upper eyelid in Horner's syndrome is a cosmetic problem then surgery may be undertaken to the upper eyelid to reverse the ptosis (drooping of the lid).

Outcome

Post ganglionic Horner's syndromes tend to occur from more benign causes. Early recognition of the syndrome and investigation of any possible underlying cause is important to prevent potential additional complications resulting from a possible underlying disorder.