What is Horner's syndrome?

Horner's Syndrome: Clinical Features, Diagnosis, and Management

Horner's syndrome is a neurological disorder characterized by the classic triad of ptosis (drooping eyelid), miosis (pupillary constriction), and facial anhidrosis (reduced sweating), resulting from disruption of the oculosympathetic pathway, which may indicate potentially life-threatening conditions requiring urgent evaluation. 1

Clinical Presentation

Horner's syndrome presents with several distinctive features:

• Classic triad:

  • Ptosis (drooping of the upper eyelid)
  • Miosis (constriction of the pupil)
  • Facial anhidrosis (reduced sweating on the affected side)

• Additional features:

  • Pseudoenophthalmos (appearance of a sunken eye due to ptosis and reduced palpebral fissure)
  • Dilation lag (delayed pupillary dilation in darkness)
  • Upside-down ptosis (elevation of the lower lid)
  • Heterochromia (in congenital cases)

Anatomical Classification

Horner's syndrome is classified based on the location of the lesion along the oculosympathetic pathway:

1. Central (First-order neuron):

   • Lesion between hypothalamus and cervical spinal cord
   • Often associated with other neurological symptoms
   • Common causes: stroke, tumors, multiple sclerosis

2. Preganglionic (Second-order neuron):

   • Lesion between spinal cord and superior cervical ganglion
   • Common causes: lung apex tumors (Pancoast), trauma, surgical procedures

3. Postganglionic (Third-order neuron):

   • Lesion between superior cervical ganglion and eye
   • Common causes: carotid artery dissection, cluster headache, neck surgery

Etiology

The most common causes of Horner's syndrome vary by study methodology, but include:

• Iatrogenic causes: Surgical procedures in the neck and chest are the most common identifiable cause 2
• Vascular causes: Carotid artery dissection (often presenting with pain) 3
• Neoplastic causes: Lung apex tumors (Pancoast tumors), metastatic disease 4
• Traumatic causes: Neck trauma, birth trauma
• Idiopathic: No identifiable cause in approximately 40% of cases 2

Diagnostic Approach

1. Clinical examination:

   • Complete ophthalmic examination with emphasis on sensorimotor evaluation
   • Careful assessment for associated neuro-ophthalmic signs
   • Fundus examination to check for papilledema or optic atrophy 4

2. Pharmacological testing:

   • Apraclonidine test (0.5%) - preferred test to confirm diagnosis
   • Cocaine test (4-10%) - traditional test but less available

3. Imaging:

   • Targeted imaging based on suspected location and clinical presentation
   • MRI of brain, neck, and chest with special sequences as needed
   • CT angiography for suspected vascular causes

Management

Management depends on the underlying cause:

1. Urgent evaluation for new-onset Horner's syndrome, especially if associated with pain (may indicate carotid dissection) 3

2. Treatment of underlying cause:

   • Anticoagulation for carotid dissection
   • Surgical intervention for tumors
   • Management of stroke risk factors

3. Symptomatic treatment:

   • Prism therapy for associated diplopia
   • Botulinum toxin or strabismus surgery for persistent cases 4

Important Clinical Considerations

• Horner's syndrome associated with acute pain requires immediate evaluation for carotid artery dissection 3
• Superior sulcus (Pancoast) tumors often present with Horner's syndrome and arm pain 4
• In most cases where a cause is identified, the underlying condition is known before Horner's syndrome is diagnosed, but in an important minority, identifying Horner's syndrome leads to discovery of serious conditions like carotid dissection or tumor 2
• Pseudoenophthalmos in Horner's syndrome should be distinguished from true enophthalmos, which involves actual posterior displacement of the globe 1

Follow-up

• Regular ophthalmologic follow-up to monitor for changes
• Referral to appropriate specialists (neurology, otolaryngology) based on suspected cause
• Prognosis depends entirely on the underlying etiology

Horner's syndrome may be the first sign of a serious underlying condition, making prompt and accurate diagnosis crucial for optimal patient outcomes.