05/26/2025
❇️ Horner Syndrome = Disruption of sympathetic innervation to the face and eye.
🔹 Classic Triad (Mnemonic: "PAM is H***y")
✔️ P – Ptosis (mild upper eyelid droop – ↓ superior tarsal muscle)
✔️ A – Anhidrosis (↓ sweating on affected side)
✔️ M – Miosis (constricted pupil – unopposed parasympathetic tone)
🔹 Anatomy: Sympathetic Pathway (3-Neuron Chain)
1st-order (Central): Hypothalamus → Spinal cord (C8–T2, ciliospinal center of Budge)
2nd-order (Preganglionic): Exit spinal cord → Travel over apex of lung → Synapse in superior cervical ganglion
3rd-order (Postganglionic): Travel along internal carotid artery → Eye & face
🔹 Causes by Lesion Location
🔸 Central (1st-order)
Brainstem stroke, spinal cord trauma, syringomyelia
🔸 Preganglionic (2nd-order)
Pancoast tumor, thyroid surgery, neck trauma
🔸 Postganglionic (3rd-order)
Carotid artery dissection, cavernous sinus pathology, cluster headache
🔹 Associated Findings
✔️ Anhidrosis affects entire face in central/preganglionic lesions
✔️ No anhidrosis in postganglionic lesions (sweat fibers travel with external carotid)
✔️ Ipsilateral facial flushing may be seen
✔️ Dilated pupil fails to dilate in darkness (sympathetic failure)
🔹 Diagnosis
✔️ Clinical (look for PAM triad)
✔️ Pharmacologic testing:
Co***ne test (fails to dilate pupil)
Apraclonidine test (denervation hypersensitivity → reverses miosis)
✔️ MRI or CT to localize lesion
