Horner's syndrome

Overview

Horner's syndrome is a neurological condition caused by the disruption of the sympathetic nerves supplying the eye and surrounding facial muscles. It is characterized by a classic triad of symptoms: ptosis (drooping of the upper eyelid), miosis (constricted pupil), and anhidrosis (absence of sweating) on the affected side of the face. The syndrome can result from a variety of underlying conditions that affect the sympathetic pathway at any point from the brain to the face.

Causes

Horner's syndrome is not a disease itself but a sign of an underlying medical issue. The causes are typically grouped based on the location of the lesion along the sympathetic chain:

• First-order (central) neuron lesions: Stroke, brainstem tumor, multiple sclerosis, spinal cord injury

• Second-order (preganglionic) neuron lesions: Pancoast tumor (lung apex), trauma to the neck, thyroid or cervical surgery

• Third-order (postganglionic) neuron lesions: Carotid artery dissection, cluster headaches, neck trauma

In some cases, the cause may be idiopathic (unknown).

Symptoms

The hallmark symptoms of Horner's syndrome are typically seen on the affected side of the face and include:

• Ptosis – mild drooping of the upper eyelid due to loss of sympathetic tone

• Miosis – constricted pupil that does not dilate well in dim light

• Anhidrosis – decreased or absent sweating on the same side of the face

• Enophthalmos – the appearance of a sunken eyeball (less common)

Symptoms may vary depending on the location and cause of the nerve disruption.

Diagnosis

Diagnosis of Horner's syndrome involves a combination of clinical evaluation and imaging studies to determine the location and cause of the sympathetic disruption. Steps typically include:

• Detailed neurological and ophthalmologic examination

• Pupil dilation tests using apraclonidine or cocaine drops to confirm sympathetic dysfunction

• Imaging studies such as MRI, CT scan, or MRA to detect tumors, carotid dissection, or brainstem lesions

Identifying the underlying cause is essential for proper management.

Treatment

Treatment of Horner's syndrome focuses on addressing the underlying condition that disrupted the sympathetic pathway. Depending on the cause, treatment options may include:

• Medications or surgery for tumors, infections, or vascular issues

• Management of stroke or spinal cord injuries

• Observation if the cause is benign and self-limiting

The eye-related symptoms themselves do not usually require specific treatment unless they cause functional or cosmetic concerns.

Prognosis

The prognosis of Horner's syndrome depends on the underlying cause. If the cause is benign and treatable, symptoms may resolve partially or completely. In cases where the underlying condition is serious or irreversible, the symptoms may persist. Horner's syndrome itself is not life-threatening but may be a sign of a potentially serious medical condition that requires prompt attention.