Should cranial nerves (CN) 9 and 10 be evaluated together or separately?

Cranial Nerves IX and X Should Be Tested Together

The American College of Radiology recommends testing CN IX and CN X together by assessing the gag reflex, observing palatal elevation with phonation, evaluating swallowing function, and checking for uvular deviation. 1

Rationale for Combined Testing

The glossopharyngeal (CN IX) and vagus (CN X) nerves are tested together because:

• It is often impossible to separate the individual contribution of each nerve clinically, as many examination techniques provide a composite functional measure of both nerves 2
• Both nerves emerge from the medulla oblongata and share overlapping motor, sensory, and parasympathetic functions that are difficult to distinguish at the bedside 2, 3
• The nerves travel in close anatomical proximity through the jugular foramen, making them vulnerable to combined injury from single lesions 4, 1

Practical Combined Examination Approach

Motor Function Tests (CN IX and X Together)

• Observe palatal elevation by asking the patient to say "ah" - the soft palate should elevate symmetrically with the uvula remaining midline 1
• Check for uvular deviation - with unilateral vagal palsy, the uvula deviates toward the intact side due to unopposed muscle contraction, away from the lesion side 1, 5
• Test the gag reflex by touching the posterior pharyngeal wall bilaterally - this assesses both the sensory component (CN IX) and motor response (CN X) 1
• Evaluate swallowing function - dysphagia indicates combined CN IX and X dysfunction 2, 3

Individual Sensory Testing (CN IX Alone)

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

Individual Motor Testing (CN X Alone)

• Assess voice quality for hoarseness suggesting vocal cord paralysis due to CN X involvement 6
• Perform laryngeal examination if isolated vocal cord paralysis is suspected, as this indicates recurrent laryngeal nerve (branch of CN X) pathology 1

Clinical Syndromes Involving Both Nerves

Vernet syndrome involves CN IX, X, and XI as they traverse the jugular foramen together, presenting with combined deficits 6

Collet-Sicard syndrome involves CN IX, X, XI, and XII from lesions just below the skull base, causing even more extensive lower cranial nerve dysfunction 6

Anatomical Localization Principles

• Brainstem lesions affecting the nucleus ambiguus cause ipsilateral palatal weakness with associated brainstem signs like crossed sensory or motor deficits 1, 5
• Peripheral lesions at the jugular foramen typically involve CN IX, X, and XI together, causing palatal weakness, vocal cord paralysis, and trapezius/sternocleidomastoid weakness 1
• Isolated vocal cord paralysis without other deficits suggests recurrent laryngeal nerve pathology, requiring imaging from skull base to mid-chest 1, 5

Common Pitfall to Avoid

Do not assume isolated CN X pathology when only hoarseness is present - the recurrent laryngeal nerve can be injured anywhere along its long course from brainstem to mid-chest, including by thoracic pathology like aortic aneurysm or mediastinal masses 1, 5