A patient has ptosis, miosis, and anhidrosis of the ipsilateral half of the face. This Horner syndrome involving facial anhidrosis suggests the sympathetic lesion is located at which level?

• A Post-ganglionic fibres (third-order neuron) distal to the superior cervical ganglion
• B Pre-ganglionic fibres (second-order neuron) in the neck between the superior cervical ganglion and cilio-spinal centre ✓
• C Central fibres (first-order neuron) in the hypothalamus–brainstem–spinal cord pathway
• D Nasociliary branch of the trigeminal nerve

Explanation

Sudomotor (sweat) fibres to the face travel with the external carotid artery branches from the superior cervical ganglion. Post-ganglionic (third-order) fibres for the eye travel with the internal carotid artery, so lesions distal to the superior cervical ganglion typically cause Horner syndrome WITHOUT facial anhidrosis (the sudomotor fibres have already separated). Facial anhidrosis implies the lesion is at the pre-ganglionic (second-order) level in the neck (between the spinal cord and superior cervical ganglion) where both pupillo-dilator and sudomotor fibres travel together.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.