How to assess the 9th (Glossopharyngeal) and 10th (Vagus) cranial nerves?

Clinical Examination of Cranial Nerves IX and X

Test CN IX (glossopharyngeal) and CN X (vagus) together by assessing the gag reflex, observing palatal elevation with phonation ("say ah"), evaluating swallowing function, and checking for uvular deviation—the uvula deviates away from the side of the lesion. 1

Motor Function Assessment

Palatal Elevation Test

• Ask the patient to say "ah" while observing the soft palate and uvula directly. 1
• The soft palate should elevate symmetrically, and the uvula should remain midline. 2
• With unilateral vagal palsy, the uvula deviates toward the intact side (away from the paralyzed side) due to unopposed muscle contraction. 2
• The affected side of the palate will appear lower and move less than the normal side. 1

Gag Reflex Testing

• Touch the posterior pharyngeal wall on each side separately with a tongue depressor. 1
• CN IX provides the sensory (afferent) limb, detecting the stimulus on the posterior pharynx. 1
• CN X provides the motor (efferent) limb, causing pharyngeal muscle contraction and palatal elevation. 1
• Loss of the gag reflex with impaired sensation suggests CN IX involvement, while absent motor response with intact sensation suggests CN X pathology. 1

Critical pitfall: The gag reflex can be absent in up to 20% of normal individuals, so its absence alone is not diagnostic—always correlate with other findings. 3

Sensory Function Assessment

Posterior Tongue and Pharynx

• Test taste on the posterior one-third of the tongue using sweet, salty, sour, or bitter substances. 1
• CN IX provides both general sensation and taste (special sensory) to the posterior third of the tongue. 1
• Assess for oropharyngeal pain, which may indicate glossopharyngeal neuralgia or nerve lesion. 1, 4
• Loss of sensation accompanied by impaired taste on the posterior tongue and palate signals CN IX dysfunction. 1

Functional Assessment

Voice Quality and Phonation

• Listen for hoarseness, breathy voice quality, or nasal speech suggesting vocal cord paralysis. 4, 3
• Ask the patient to sustain the vowel "eee"—a weak, breathy voice indicates vocal cord weakness from vagal involvement. 3
• Hoarseness specifically suggests recurrent laryngeal nerve dysfunction, a branch of CN X. 4

Swallowing Evaluation

• Observe the patient swallowing water—coughing, choking, or difficulty suggests dysphagia from CN IX/X dysfunction. 5, 3
• CN IX innervates the stylopharyngeus muscle (elevates the palate), while CN X provides motor innervation to most pharyngeal and laryngeal muscles. 1
• Dysphagia with aspiration is the main functional consequence of combined CN IX/X palsy. 5, 6

Critical pitfall: Isolated recurrent laryngeal nerve palsy (a CN X branch) causes hoarseness without dysphagia, while proximal vagal lesions cause both. 2

Anatomical Localization

Brainstem vs. Peripheral Lesions

• Brainstem lesions affecting the nucleus ambiguus cause ipsilateral palatal weakness with associated brainstem signs (crossed sensory/motor deficits, ataxia). 2
• Intramedullary pathology includes infarction, demyelination, neoplasms, and syringobulbia. 2
• Peripheral lesions at the jugular foramen typically involve CN IX, X, and XI together (Vernet syndrome), causing palatal weakness, vocal cord paralysis, and trapezius/SCM weakness. 4
• Jugular foramen pathology includes schwannomas, paragangliomas, meningiomas, and metastases. 1

Key Clinical Patterns

• Glossopharyngeal neuralgia presents as severe oropharyngeal and otic pain triggered by swallowing—this is typically from neurovascular compression but requires imaging to exclude tumor. 1
• Tonsillar pain with loss of gag reflex and impaired posterior tongue sensation indicates CN IX lesion. 1
• Isolated vocal cord paralysis without other deficits suggests recurrent laryngeal nerve pathology, requiring imaging from skull base to mid-chest. 2, 4

When to Image

Order contrast-enhanced MRI of the orbits, face, and neck (or MRI head plus neck) for any confirmed CN IX or X deficit. 1, 4

• Use thin-cut high-resolution sequences through the posterior fossa, jugular foramen, and neck. 1
• For CN X evaluation specifically, imaging must extend to mid-chest to evaluate the recurrent laryngeal nerve course. 2, 4
• Add CT neck with contrast to assess bony skull base and jugular foramen anatomy. 1