Horner syndrome

Last updated: April 27, 2022

Summarytoggle arrow icon

Horner syndrome (HS) is a neurological disorder characterized by a symptom triad of miosis (an abnormally small pupil), partial ptosis (drooping of the upper eyelid), and facial anhidrosis (absence of sweating). This condition results from lesions that interrupt the ipsilateral sympathetic nervous supply to the head, eye, and neck. Most cases of HS are idiopathic, but conditions such as brainstem stroke, carotid dissection, and neoplasm are occasionally identified as the cause of HS. Because of the wide array of possible causes, diagnosis of the underlying disorder frequently poses a challenge and requires a systematic approach. Once the lesion has been identified, treatment should be tailored to the specific cause.

Pathophysiologytoggle arrow icon

Type Anatomical trajectory Typical lesion


  • Hypothalamus (first-order oculosympathetic neuron) brainstem, cervical, and thoracic spinal cord → ciliospinal center (C8–T2)



Clinical featurestoggle arrow icon

Remember the symptoms of Horner syndrome by the great HORNs of the PAMpas deer: Ptosis, Anhidrosis, and Miosis.

Referencestoggle arrow icon

  1. Miller N, Kanagalingam S. Horner syndrome: clinical perspectives. Eye and Brain. 2015: p.35.doi: 10.2147/eb.s63633 . | Open in Read by QxMD

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