Horner's syndrome

Horner's syndrome
Miosis.jpg
Left-sided Horner's syndrome
Synonyms	Bernard-Horner syndrome (BH), oculosympathetic palsy

Horner's syndrome, or oculosympathetic paresis, is a rare neurological condition characterized by a constellation of symptoms resulting from disruption of the sympathetic nerve supply to the eye and surrounding facial structures. This nerve pathway starts in the hypothalamus of the brain, descends to the cervical and upper thoracic spinal cord, and then ascends to the face along the internal carotid artery.

Symptoms and Signs

The classic triad of Horner's syndrome includes miosis (constriction of the pupil), partial ptosis (drooping of the upper eyelid), and anhidrosis (loss of sweating) on the same side of the face as the affected sympathetic pathway. Other symptoms may include enophthalmos (inward displacement of the eye) and blood vessel dilation on the affected side.

Causes and Pathophysiology

Horner's syndrome results from an interruption in the sympathetic nerve supply, which can be caused by various conditions such as stroke, trauma, tumors, or neurologic damage from surgery. The syndrome can be classified by the location of the lesion along the sympathetic pathway: first-order neuron lesions occur in the brainstem or cervical spinal cord; second-order neuron lesions occur in the sympathetic chain in the upper chest; and third-order neuron lesions occur along the internal carotid artery or within the cavernous sinus in the skull.

Diagnosis

Diagnosis of Horner's syndrome is based on clinical observation of the characteristic symptoms. Pharmacological testing with topical cocaine or apraclonidine can confirm the diagnosis by demonstrating an abnormal response in the affected pupil. Imaging tests such as MRI or CT scans may be required to identify the underlying cause of the syndrome.

Treatment

Treatment for Horner's syndrome focuses on addressing the underlying cause of the nerve disruption. There is no specific treatment for the syndrome itself, but the symptoms can be managed and may resolve over time if the cause is treated effectively.

External links

• 
  Diagram showing autonomic innervation of the eye related to Horner's syndrome
• Example of Horner's syndrome in a cat
  Example of Horner's syndrome in a cat