Overview

Horner’s syndrome is a rare neurological condition that affects the eye and surrounding facial muscles. It occurs due to disruption of the sympathetic nerves that supply the eye and facial structures. This disruption leads to a characteristic group of symptoms including drooping of the upper eyelid (ptosis), constriction of the pupil (miosis), and lack of sweating (anhidrosis) on the affected side of the face. Horner’s syndrome is not a disease itself but rather a clinical sign of an underlying issue affecting the sympathetic nervous pathway. It can result from various causes, ranging from benign conditions to serious life-threatening disorders. Identifying and treating the underlying cause is crucial in the management of Horner’s syndrome.

Causes

Horner’s syndrome results from damage or disruption along the oculosympathetic pathway, which runs from the brain to the face and eyes. Depending on where the disruption occurs, it is classified into three types:

• First-order (central) lesions: Damage occurs within the brain or spinal cord. Causes include stroke, brainstem tumors, multiple sclerosis, and neck trauma affecting the upper spinal cord.
• Second-order (preganglionic) lesions: The damage is located between the spinal cord and the superior cervical ganglion. Causes include tumors in the lung apex (Pancoast tumor), neck trauma, or surgery affecting the chest or neck region.
• Third-order (postganglionic) lesions: The disruption occurs after the superior cervical ganglion. Causes include carotid artery dissection, cluster headaches, migraine, or skull base tumors.

Other possible causes include birth trauma in newborns, infections, and idiopathic cases where no clear cause is identified.

Symptoms

The main symptoms of Horner’s syndrome are usually restricted to one side of the face and include:

• Ptosis: Drooping of the upper eyelid on the affected side.
• Miosis: Constricted pupil that remains smaller compared to the other eye.
• Anhidrosis: Decreased or absent sweating on the affected side of the face.
• Enophthalmos: The eye may appear sunken, although this is often due to the drooping eyelid rather than true displacement of the eyeball.
• Facial flushing: Some individuals experience redness or warmth on one side of the face.
• Heterochromia (in children): In congenital Horner’s syndrome, the affected eye may have a lighter-colored iris due to impaired pigmentation.

Diagnosis

Diagnosing Horner’s syndrome involves identifying the characteristic eye and facial changes and determining the location and cause of nerve disruption. The diagnostic approach includes:

• Clinical examination: A thorough eye and neurological exam to identify the classic signs (ptosis, miosis, anhidrosis).
• Pupil dilation tests: Pharmacological testing using eye drops like apraclonidine or cocaine drops can confirm Horner’s syndrome by showing a reversal of pupil size difference.
• Imaging studies: Depending on the suspected level of the lesion, MRI or CT scans of the brain, neck, chest, and upper spine may be performed.
• Carotid artery evaluation: In cases where carotid artery dissection is suspected, ultrasound or angiography may be used.
• Additional tests: Based on findings, further tests may include chest X-rays (for lung tumors), blood work, or lumbar puncture (if infection or inflammation is suspected).

Treatment

Treatment of Horner’s syndrome focuses on addressing the underlying cause rather than the syndrome itself. Options include:

• Treatment of underlying condition: Managing strokes, tumors, trauma, or infections depending on the identified cause.
• Carotid artery dissection management: Anticoagulation or surgical repair in cases of arterial dissection.
• Surgical intervention: In cases involving tumors or compressive lesions, surgery may be required to remove the underlying cause.
• Symptom management: While Horner’s syndrome symptoms are generally mild, cosmetic surgical options (such as eyelid surgery) can be considered in selected cases if ptosis is bothersome.

Prognosis

The prognosis of Horner’s syndrome depends largely on the underlying cause. If the cause is benign or treated effectively, the condition may partially or completely resolve over time. In cases of congenital Horner’s syndrome, symptoms such as heterochromia are permanent, though other signs may improve. When associated with serious conditions like carotid artery dissection, stroke, or cancer, the outcome depends on timely diagnosis and treatment of the primary condition. Overall, Horner’s syndrome itself is not life-threatening, but it serves as a crucial indicator of potentially serious underlying diseases that require medical attention.