A 52-year-old man presents with sudden onset left-sided face and right-sided body loss of pain and temperature sensation, hoarseness, dysphagia, and ipsilateral Horner's syndrome. MRI shows an infarct in the territory of the posterior inferior cerebellar artery. Which structure, when damaged, produces the ipsilateral facial sensory loss in this syndrome?

• A Spinal trigeminal nucleus and tract ✓
• B Main sensory nucleus of trigeminal nerve
• C Trigeminal motor nucleus
• D Mesencephalic nucleus of trigeminal nerve

Explanation

Wallenberg (lateral medullary) syndrome results from PICA territory infarction affecting the lateral medulla. The spinal trigeminal nucleus and tract descend into the upper cervical cord and carry pain and temperature from the ipsilateral face; damage here produces ipsilateral facial hemianesthesia. The crossed body deficit (right body) is due to compromise of the lateral spinothalamic tract before it decussates in the spinal cord. The main sensory nucleus handles discriminative touch and lies more rostrally in the pons.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.