A 58-year-old hypertensive man presents with sudden onset of ipsilateral Horner syndrome, ipsilateral loss of pain and temperature over the face, contralateral loss of pain and temperature over the body, ipsilateral limb ataxia, and dysphagia. Which nucleus within the medullary tegmentum is the primary site of this infarct?
- A Nucleus ambiguus ✓
- B Dorsal motor nucleus of vagus
- C Gracile nucleus
- D Cochlear nucleus
Explanation
The constellation of findings — ipsilateral Horner, ipsilateral facial hemianalgesia (spinal trigeminal nucleus/tract), contralateral body hemianalgesia (spinothalamic tract), ipsilateral cerebellar ataxia (inferior cerebellopontine peduncle), and dysphagia/dysarthria — constitutes Wallenberg (lateral medullary) syndrome due to posterior inferior cerebellar artery (PICA) or vertebral artery occlusion. The nucleus ambiguus (motor nucleus for CN IX, X, XI) lies in the lateral medullary tegmentum and its involvement explains dysphagia/hoarseness; it is the principal motor nucleus damaged. The dorsal motor nucleus of vagus lies more dorsomedially and its isolated damage would not account for the full syndrome. Cochlear nuclei are pontine structures and the gracile nucleus is in the dorsal medulla.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
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