The lower cranial nerves — glossopharyngeal (IX), vagus (X), spinal accessory (XI), and hypoglossal (XII) — exit the brainstem through the jugular foramen and adjacent canals. They share much of their course in the upper neck and are often affected together by lesions at the cranial base or in the posterior fossa. Their dysfunctions produce bulbar findings — dysphagia, dysphonia, dysarthria, neck weakness, tongue deviation — that are clinically significant in their own right and can be localized with care. This page covers the anatomy, examination, and syndromes of CN IX, X, XI, and XII.

CN IX — Glossopharyngeal Nerve

Functions

• Motor: stylopharyngeus muscle (a single muscle); pharyngeal constrictors (shared with CN X).
• Sensory: taste from posterior 1/3 of tongue; general sensation from posterior tongue, pharynx, tonsils, middle ear, carotid body.
• Parasympathetic: to parotid gland (via tympanic nerve → otic ganglion → auriculotemporal nerve).

Anatomy

• Nuclei in the medulla (nucleus ambiguus for motor; nucleus solitarius for sensory; inferior salivatory nucleus for parasympathetic).
• Exits the brainstem in the postolivary sulcus.
• Passes through jugular foramen with CN X and XI.
• Descends in the neck.

Examination

• Gag reflex (sensory limb CN IX, motor limb CN X).
• Taste testing of posterior tongue (rarely formally tested).
• Difficulty swallowing.

Glossopharyngeal Neuralgia

Lancinating pain in the throat, base of tongue, ear — provoked by swallowing, talking, yawning. Analogous to trigeminal neuralgia but rare. Can be associated with vagal symptoms (bradycardia, syncope) when severe (vasovagal mechanism). Treatment: carbamazepine, oxcarbazepine; microvascular decompression if refractory.

CN X — Vagus Nerve

Functions

• Motor: muscles of palate, pharynx, larynx (the soft palate, pharyngeal constrictors, vocal cords).
• Sensory: pharynx, larynx, external auditory meatus, dura of posterior fossa.
• Parasympathetic: heart (slows rate), lungs (bronchoconstriction), GI tract (down to splenic flexure).

Anatomy

• Nucleus ambiguus (motor), dorsal motor nucleus (parasympathetic), nucleus solitarius (sensory), spinal trigeminal nucleus (external ear sensation).
• Exits brainstem in postolivary sulcus.
• Passes through jugular foramen.
• Descends in carotid sheath with internal carotid artery and internal jugular vein.
• Recurrent laryngeal nerves branch off in the upper neck and recur:
  • Right recurrent laryngeal nerve loops under the right subclavian artery.
  • Left recurrent laryngeal nerve loops under the aortic arch (vulnerable to mediastinal pathology — aortic aneurysm, mediastinal tumor, lung cancer, thyroid surgery).
• Recurrent laryngeal nerves supply most laryngeal muscles. Superior laryngeal nerve supplies cricothyroid and sensation above the vocal cords.

Examination

• Soft palate elevation: ask patient to say “ah” — the soft palate should elevate symmetrically. Unilateral palatal weakness: uvula deviates AWAY from the side of weakness (toward the intact side that pulls more strongly).
• Gag reflex (motor limb is CN X).
• Hoarseness suggests recurrent laryngeal nerve dysfunction.
• Dysphagia (especially for liquids) suggests pharyngeal weakness.
• Nasal regurgitation suggests palate weakness.
• Listen for breathy or hoarse voice.

Vagal Lesions by Location

• Nucleus ambiguus (medulla): ipsilateral palate, pharynx, larynx weakness. Often with other medullary signs.
• Jugular foramen: CN IX, X, XI together. Vernet syndrome.
• Below jugular foramen: vagus alone, or with CN XII (Collet-Sicard syndrome — IX, X, XI, XII).
• Recurrent laryngeal nerve alone: hoarseness, breathy voice, ineffective cough, sometimes aspiration. Causes: thyroid surgery (most common iatrogenic), lung cancer (especially left RLN by mediastinal nodes), aortic aneurysm, mediastinal tumor.
• Bilateral recurrent laryngeal nerve injury: severe — vocal cords paralyzed in adducted position, airway compromise.

CN XI — Spinal Accessory Nerve

Functions

Motor only: sternocleidomastoid (SCM) and trapezius muscles.

Anatomy

• Spinal portion: arises from anterior horn neurons in upper cervical cord (C1-C5).
• Ascends through foramen magnum.
• Joins briefly with cranial portion (vagal fibers that travel with CN XI through jugular foramen, then rejoin vagus).
• Exits jugular foramen with CN IX and X.
• Descends in the neck to innervate SCM and trapezius.

Examination

• SCM: turning head against resistance — the SCM on one side turns the head to the OPPOSITE side. Weak right SCM = difficulty turning head to the left.
• Trapezius: shrugging shoulders; lateral abduction of the arm above 90° (trapezius rotates scapula). Weakness produces drooping shoulder, weak shrug.

CN XI Lesions

• Often iatrogenic — lymph node biopsy in posterior triangle of neck.
• Penetrating trauma.
• Jugular foramen tumor.
• Brainstem lesion (usually with other findings).

Critically, sternocleidomastoid receives ipsilateral cortical innervation for head turning (i.e., the left cortex turns the head to the right via the left SCM — paradoxical seeming). A cortical lesion may therefore produce SCM weakness on the IPSILATERAL side of the lesion (the side of the SCM that the lesioned cortex was driving). This is one of the rare ipsilateral motor effects of a cortical lesion.

CN XII — Hypoglossal Nerve

Functions

Motor only: tongue muscles (intrinsic and most extrinsic muscles).

Anatomy

• Nucleus in dorsal medulla.
• Exits brainstem in the preolivary sulcus.
• Passes through hypoglossal canal.
• Descends in the neck to the tongue.

Examination

• Inspection of tongue at rest: atrophy, fasciculations (LMN signs).
• Protrusion: deviates TOWARD the side of weakness (the intact genioglossus pushes the tongue toward the weak side).
• Listen for dysarthria (the hypoglossal is essential for clear speech).

Hypoglossal Lesions by Location

• Cortex / corticobulbar: contralateral tongue deviation. Hypoglossal nuclei receive bilateral innervation for most actions, with predominantly contralateral for the genioglossus protrusion movement. A cortical lesion produces contralateral tongue deviation on protrusion, often as part of a hemiparesis.
• Hypoglossal nucleus (medulla): ipsilateral tongue atrophy, fasciculations, weakness; tongue deviates toward affected side on protrusion. Often with contralateral hemiparesis (medial medullary syndrome — Dejerine syndrome).
• Hypoglossal canal: ipsilateral CN XII palsy. Skull base tumors, fractures.
• Neck: surgical injury (e.g., carotid endarterectomy), tumor, infection. Can be isolated or combined with other lower cranial nerves.

Jugular Foramen and Related Syndromes

The clustering of cranial nerves at the cranial base produces named syndromes when multiple nerves are affected together:

Common causes of jugular foramen syndromes: glomus jugulare tumor (paraganglioma), schwannoma, meningioma, metastasis (especially nasopharyngeal carcinoma), trauma, infection.

Bulbar vs Pseudobulbar Palsy

Bulbar Palsy

Lower motor neuron lesion of the lower cranial nerves — nuclei (in the medulla) or peripheral nerve. Features:

• Dysarthria with nasal, breathy quality.
• Dysphagia.
• Tongue atrophy, fasciculations.
• Absent or decreased gag.
• Flaccid soft palate.
• Often with associated extremity LMN signs (motor neuron disease, especially ALS bulbar onset).

Pseudobulbar Palsy

Upper motor neuron lesion of corticobulbar tracts bilaterally. Features:

• Dysarthria — explosive, strangled, “hot potato” voice.
• Dysphagia (UMN — preserved or exaggerated gag reflex).
• Tongue spastic — not atrophic, no fasciculations; slowed movements.
• Brisk jaw jerk (UMN).
• Emotional incontinence (pseudobulbar affect): pathological laughing or crying — emotional displays disconnected from inner feeling.
• Often with extremity UMN signs.
• Causes: bilateral capsular strokes, ALS (combined UMN and LMN), MS, vascular dementia.

Examining Bulbar Function — Quick Workflow

1. Listen to speech: nasal vs strangled vs breathy.
2. Inspect tongue: atrophy, fasciculations, deviation on protrusion.
3. Test palate: “Ah” — symmetric elevation? Uvula deviation?
4. Gag reflex: intact, brisk, or absent?
5. Swallowing: water swallow if safe.
6. Test SCM (head turn against resistance), trapezius (shrug).
7. Listen for stridor or breathy voice (vocal cord paralysis).
8. Check jaw jerk (brisk in pseudobulbar palsy).
9. Test cough — weak in vagal lesions.

🔍 Did You Know?

The uvula deviation rule for vagal lesions can confuse learners because the deviation is AWAY from the side of weakness, not toward it. Here is why: the soft palate normally elevates symmetrically because both sides pull equally during phonation. If one side is weak (vagal nerve injury on, say, the right), the right side cannot pull as strongly. The intact left side continues to pull normally, dragging the uvula and the midline of the soft palate toward the LEFT (the intact side). Result: the uvula deviates toward the LEFT — AWAY from the affected right side. This is opposite to the tongue, where the tongue deviates TOWARD the side of the weak hypoglossal nerve (because the intact genioglossus on the other side pushes the tongue forward and the weak side cannot resist, so the tongue tip swings toward the weak side). The two rules — “uvula away, tongue toward” — must be memorized correctly because they are commonly tested and easily confused. The general principle: a deviation occurs because the intact opposing muscle has unopposed action. For the palate, the strong side LIFTS its own side up; for the tongue, the strong side PROTRUDES its own side forward. Hence the apparent direction reversal.

Pitfalls and Pearls

• Palatal weakness: uvula deviates AWAY from the affected side.
• Hypoglossal weakness: tongue protrudes TOWARD the affected side.
• SCM is unusual: a cortical lesion can produce ipsilateral SCM weakness (because cortical control of head-turning SCM is ipsilateral).
• Recurrent laryngeal nerve injury: hoarseness, breathy voice, weak cough. Left RLN more often affected by mediastinal disease.
• Bilateral RLN injury: airway emergency.
• Bulbar palsy (LMN): atrophy, fasciculations, absent gag, flaccid palate.
• Pseudobulbar palsy (UMN): brisk jaw jerk, no atrophy, exaggerated gag, emotional incontinence.
• Bulbar onset ALS: prominent dysarthria, dysphagia, tongue atrophy with fasciculations. Often progresses to involve limbs.
• Jugular foramen syndromes: combinations of IX, X, XI (Vernet); add XII (Collet-Sicard) or Horner (Villaret).
• Glossopharyngeal neuralgia: lancinating throat pain — treat like trigeminal neuralgia.
• Carotid endarterectomy can injure CN X or XII in the neck.
• Nasopharyngeal carcinoma classically presents with multiple lower cranial nerve palsies + headache + Horner.
• Glomus jugulare tumor: pulsatile tinnitus + lower cranial nerve palsies + cherry-red mass behind tympanic membrane.
• Stroke in the lateral medulla (Wallenberg): ipsilateral palate, pharynx, larynx weakness (nucleus ambiguus); + other classical features (Horner, ataxia, crossed sensory).

References

1. Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology. 7th ed. Wolters Kluwer; 2017.
2. Campbell WW. DeJong’s The Neurologic Examination. 8th ed. Wolters Kluwer; 2019.
3. Wilson-Pauwels L, Stewart PA, Akesson EJ, Spacey SD. Cranial Nerves: Function & Dysfunction. 3rd ed. People’s Medical Publishing House; 2010.
4. Wirth A, Lichter PR. Dysfunction of the lower cranial nerves. Continuum (Minneap Minn). 2009;15(4):69-86.
5. Ropper AH, Samuels MA, Klein JP, Prasad S. Adams and Victor’s Principles of Neurology. 11th ed. McGraw-Hill; 2019.