A 40-year-old man develops hoarseness, nasal regurgitation of fluids, and deviation of the uvula to the right. Palatal elevation is absent on the left, the left gag reflex efferent limb is lost, and tongue protrusion and facial movement are normal. Which nucleus is involved?

• A Left hypoglossal nucleus
• B Left spinal trigeminal nucleus
• C Left solitary nucleus
• D Left nucleus ambiguus ✓

Explanation

The nucleus ambiguus gives motor fibres to the pharyngeal and laryngeal muscles through cranial nerves IX, X, and the cranial root of XI. Its lesion causes ipsilateral palatal and laryngeal paralysis, hoarseness, dysphagia, and loss of the efferent limb of the gag reflex, with the uvula deviating to the intact side. Tongue protrusion is mediated by the hypoglossal nucleus, which is clinically normal here, excluding option A.

Reference: Snell's Clinical Neuroanatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.