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

Assessment of Cranial Nerves IX (Glossopharyngeal) and X (Vagus)

Test CN IX and CN X together through a systematic evaluation of motor function (palatal elevation, gag reflex, uvular position), sensory function (posterior tongue sensation and taste), and voice quality, as these nerves share anatomical proximity and functional overlap. 1

Motor Function Testing

Palatal Elevation Test

• Ask the patient to say "Ah" while observing the soft palate with a tongue depressor and light. 1
• The soft palate should elevate symmetrically, and the uvula should remain midline during phonation. 1
• With unilateral vagal palsy, the affected side of the palate appears lower and moves less than the normal side. 1
• The uvula deviates away from the side of the lesion—toward the intact side—due to unopposed muscle contraction on the healthy side. 1, 2

Gag Reflex Assessment

• Touch the posterior pharyngeal wall on each side separately with a tongue depressor or cotton swab. 1
• The normal response is bilateral pharyngeal muscle contraction with elevation of the soft palate. 1
• CN IX provides the sensory (afferent) limb, while CN X provides the motor (efferent) limb of this reflex. 1

Voice Quality Evaluation

• Listen for hoarseness, breathy voice quality, or nasal speech, which suggest vocal cord paralysis from vagal dysfunction. 1, 3
• Ask the patient to cough forcefully—a weak, ineffective cough suggests vocal cord weakness from CN X dysfunction. 1

Swallowing Function

• Observe the patient swallowing water or their own saliva. 1
• Difficulty swallowing (dysphagia) indicates dysfunction of the pharyngeal muscles innervated by CN IX and X. 4, 5

Sensory Function Testing

Posterior Tongue Sensation and Taste

• Test taste on the posterior one-third of the tongue using sweet, salty, sour, or bitter substances to assess CN IX function. 1
• CN IX provides both general sensation and taste to the posterior third of the tongue. 1
• Loss of sensation accompanied by impaired taste signals CN IX dysfunction. 1

Pharyngeal Sensation

• CN IX provides general sensation to the posterior pharynx and posterior tongue, while CN X provides visceral sensation to the pharynx and larynx. 1
• Assess for oropharyngeal pain, which may indicate CN IX involvement, particularly in glossopharyngeal neuralgia. 1, 3

Anatomical Localization Patterns

Brainstem Lesions

• Lesions affecting the nucleus ambiguus cause ipsilateral palatal weakness with associated brainstem signs (crossed sensory or motor deficits). 1, 2
• Intramedullary lesions include infarction, demyelination, neoplasms, motor neuron disorders, and syringobulbia. 2

Peripheral Lesions at the Jugular Foramen

• Peripheral lesions at the jugular foramen typically involve CN IX, X, and XI together (Vernet syndrome), causing palatal weakness, vocal cord paralysis, and trapezius/sternocleidomastoid weakness. 1, 3
• This pattern reflects the close anatomical proximity of these nerves as they traverse the jugular foramen. 3, 6

Isolated Recurrent Laryngeal Nerve Pathology

• Isolated vocal cord paralysis without other deficits suggests recurrent laryngeal nerve pathology, requiring imaging from skull base to mid-chest. 1, 2
• The vagus nerve has the longest course of any cranial nerve, making it vulnerable to pathology along its entire length. 1, 3

Critical Pitfalls and Caveats

• Always image any confirmed CN IX or X deficit with contrast-enhanced MRI of the orbits, face, and neck, with thin-cut high-resolution sequences through the posterior fossa, jugular foramen, and neck. 1, 3
• For vocal cord paralysis, imaging must extend from skull base to mid-chest to visualize the full vagal course. 1, 2
• Glossopharyngeal neuralgia presents as severe oropharyngeal and otic pain triggered by swallowing, typically from neurovascular compression, but requires imaging to exclude tumor. 1
• Single lesions frequently cause multiple cranial neuropathies due to close proximity of nerve nuclei, segments, and exit sites. 3
• Autonomic nerve fibers may travel with multiple cranial nerves, meaning loss of specific function can indicate involvement of more than one cranial nerve. 3