Horner Syndrome

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  • Horner syndrome is a constellation of neurologic signs and symptoms manifested as a classic triad of ipsilateral miosis, eyelid ptosis, and anhidrosis of the ipsilateral midface and/or neck (with iris heterochromia in children).
  • It is caused by the interruption or lesion along the sympathetic nerve supply to the head, neck, and eye.
  • Oculosympathetic pathway anatomy:
    • First-order neuron: Sympathetic nerve fibers originate in the hypothalamus, descend through the brainstem, and synapse at the ciliospinal center (of Budge) located at approximately the C8–T2 levels of the spinal cord.
    • Second-order neuron: exits the spinal column at the T1 level primarily, arches over the apex of the lung and under the subclavian artery, ascending to the superior cervical ganglion at the level of the carotid bifurcation and angle of the jaw
    • Third-order neuron: ascends along the adventitia of the internal carotid artery, through the cavernous sinus in proximity to cranial nerve (CN) VI, and joins CN VI to innervate the iris dilator muscle and Müller muscle in the eye
  • System(s) affected: nervous, skin/exocrine
  • Synonym(s): Bernard-Horner syndrome; Bernard syndrome; Horner syndrome; cervical sympathetic syndrome; oculosympathetic syndrome; oculosympathetic paralysis; oculosympathetic deficiency; oculosympathetic paresis


  • Predominant age: none
  • Predominant sex: male = female



Etiology and Pathophysiology

  • The constellation of signs and symptoms will be produced when sympathetic innervation is lesioned anywhere along the track producing ipsilateral Horner syndrome.
  • Syndrome characteristics based on lesion locations:
    • Central or preganglionic lesion (complete syndrome):
      • First-order Horner syndrome (central): lesion located in the sympathetic tracts in the brainstem or cervicothoracic spinal cord; most common cause (MCC) lateral medullary infarction which present Horner syndrome as part of Wallenberg syndrome
      • Second-order Horner syndrome (preganglionic): due to trauma or surgery involving spinal cord, thoracic outlet or lung apex
    • Peripheral postganglionic lesion (incomplete syndrome, given by anhidrosis): third-order Horner syndrome; lesions usually located in internal carotid artery (e.g., dissection, thrombosis, cavernous sinus aneurysm, surgical endarterectomy, or stenting)
  • Sympathetic fibers innervating sweat glands and vasodilatory muscles branch off before the cervical sympathetic ganglion traveling along the external carotid artery, so distal lesions will not result in anhidrosis; idiopathic (40%), congenital, or acquired
  • Best classified by which order neuron is affected as mentioned above and by age (pediatric vs. adult)
  • Etiology adult:
  • First-order neuron (13%)—central mostly located in hypothalamus/brainstem (lateral medulla)/spinal cord (cervical thoracic):
    • Arnold-Chiari malformation
    • Basal meningitis (e.g., syphilis)
    • Tumors
    • Cerebral vascular accident: lateral medullary (Wallenberg) syndrome
    • Cervical cord trauma
    • Demyelinating disease (multiple sclerosis)
    • Intrapontine hemorrhage
    • Neck trauma
    • Pituitary tumor
    • Syringomyelia
    • Unintended subdural placement of lumbar epidural catheter
  • Second-order neuron (44%)—preganglionic: pulmonary or thoracic upper lesions
    • Aneurysm/dissection of aorta
    • Central venous catheterization
    • Chest tubes
    • 1st rib fracture
    • Lymphadenopathy (Hodgkin, leukemia, tuberculosis, mediastinal tumors, sarcoid)
    • Mandibular tooth abscess
    • Neurofibromatosis types I and II
    • Pancoast tumor or infection of lung apex
    • Proximal common carotid artery dissection
    • Trauma/surgical injury
  • Third-order neuron lesions (43%)—postganglionic lesions located in superior cervical ganglion, internal carotid artery, skull base lesions, cavernous sinus lesions
    • Carotid cavernous fistula or other pathology
    • Carotid endarterectomy or carotid artery stenting
    • Cluster headaches
    • Internal carotid artery dissection
    • Herpes zoster
    • Lesions of the middle ear (acute otitis media)
    • Lyme disease
    • Nasopharyngeal cancer
    • Tonsillectomy
    • Raeder paratrigeminal syndrome
  • Etiology children: Common causes are birth-related injuries (in neck and shoulder), neuroblastoma (paraspinal), vascular anomalies, and chest surgical interventions.
  • MCC birth-related: associated injury to lower brachial plexus presenting ipsilateral forearm and hand weakness (Klumpke paralysis)
  • Drugs: acetophenazine, alseroxylon, bupivacaine, butaperazine, carphenazine, chloroprocaine, deserpidine, diacetylmorphine, diethazine, ethopropazine, etidocaine, guanethidine, influenza virus vaccine, levodopa, lidocaine, mepivacaine, mesoridazine, methdilazine, methotrimeprazine, oral contraceptives, perazine, prilocaine, procaine, prochlorperazine, promazine, propoxycaine, reserpine, thioproperazine, thioridazine, trifluoperazine

Rare autosomal dominant inheritance

Risk Factors

  • Most common: apical bronchogenic carcinoma (Pancoast tumor) in smokers
  • Aneurysm of the carotid or subclavian artery
  • Injuries to the carotid artery high in the neck
  • Dissection of the carotid arteries
  • Carotid artery occlusion
    • 15% of patients with carotid artery occlusion develop ipsilateral Horner syndrome.
    • May occur without evidence of cerebral ischemia, neck injuries, or operative procedures
  • Cluster headaches
    • 20% have an ipsilateral Horner syndrome.

Commonly Associated Conditions

  • Wallenberg syndrome
  • Pancoast tumor
  • C8 radiculopathy

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