Sympathetic Pathway of the Face and Eyes

Sympathetic Pathway:

The sympathetic pathway to the eye and face is a three-neuron pathway.
Targets of sympathetic pathway to the eye and face include the following:
  1. Sweat Glands —> Facial Sweating
  2. Superior tarsal muscle & inferior tarsal muscle —> Upper eyelid elevation & lower eyelid depression respectively
  3. Dilator pupillae muscle —> Pupil dilation
  4. Facial vasculature —> Vasoconstriction
Horner’s Syndrome represents the classic triad of ptosis, miosis, and anhidrosis caused by disruption to the sympathetic innervation to the eye and face. Additionally, due to innervation to the inferior tarsal muscle, patients also experience lower eyelid depression.

Horner’s Syndrome

  1. Perform detailed history to establish timeline, possible inciting event, and other associated symptoms
  2. Perform a thorough general and neurologic exam to further help in localizing the lesion(s) responsible
  3. To confirm Horner’s syndrome:

    • Cocaine 4% or 10%: No longer performed readily in the US. Cocaine blocks reuptake of norepinephrine released by the neuromuscular junction of the iris dilator muscle. If there is sympathetic denervation at any level of the pathway, upon dropping cocaine in both eyes, the unaffected eye will dilate and the affected eye will stay the same, worsening the anisicoria.

    • Apraclonidone: Within 24-28 hours the denervated dilator muscle of the iris develops hypersensitivity to alpha-1 stimulation. Apraclonidine is an alpha 1 and 2 agonist. If administered to normal eye, there is no change to pupil size. When administered to affected eye, hypersensitivity to alpha-1 stimulation leads to abnormal dilation of the pupil. 

  4. Localization (if not made clear by history, review of systems, and exam)

    • Hydroxyamphetamine:  Administration in the eye leads to release of norepinephrine in healthy third order neurons. If affected eye dilates, the lesion is affecting the 1st or 2nd order neurons. If the lesion is affecting the third order neurons, the pupil will not dilate
  5. Imaging based on earlier table’s recommendations

How to work up a Horner’s Syndrome

Disclaimer: The information provided here is intended for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of your physician or other qualified health provider with any questions you may have regarding a medical condition.