Differential Diagnosis in Neurology

5.9. Cranial Nerve IX

Anatomy

• Emerges dorsal to the inferior olive in close relation to X and XI (spinal accessory nerve; distal or within the jugular foramen nerves widen to form the superior and inferior petrous ganglion)
• Upper neck: IXth is between the ICA and jugular vein (anterior to Xth nerve)
• Innervates: stylopharyngeus (elevates the pharynx; occasionally innervates the superior constrictor (rather than vagus). Innervates the cricopharyngeus muscle (external pharyngeal sphincter)
• Parasympathetic fibers: origin inferior salivary nucleus (near superior pole of X); leaves the nerve at the petrous ganglion; travels with the tympanic nerve (petrous bone) and superficial petrosal nerve to the otic ganglion. Post ganglionic fibers travel with the auriculotemporal branch of V to innervate the parotid gland
• Sensory fibers: afferents from posterior 1/3 of tongue, tonsils, nasopharynx, inferior surface of soft palate, uvula, eustachian tube, tympanic cavity; small area in front of the tragus and small part of anterior wall of external auditory meatus
• Taste: posterior: 1/3 of the tongue; cell bodies are in the petrous ganglion, terminate in the nucleus tractus solitarius
• Carotid sinus nerve:
  • Afferents of chemoreceptors of carotid body
  • Baroreceptors of carotid sinus wall
  • Project to the nucleus of the tractus solitarius

Clinical Aspects of IX Nerve Lesions

• Involved with vagus nerve:
  • Taste involved posterior 1/3 of tongue
  • Decreased gag reflex
  • Decreased salivary secretion from the parotid gland
  • Transient hypertension after bilateral surgical section
  • Bonner syndrome (intramedullary involvement):
    • VIII, IX, X involvement
    • Vertigo dysphagia, dysarthria
    • Contralateral hemiplegia
    • IX nerve involvement
    • Syringobulbia, stroke, tumor, inflammatory
  • Paroxysmal lacrimation (Bogorad syndrome):
    • Abnormal lacrimation, normal production of saliva
    • Following middle ear surgery; the lesser superficial petrosal nerve to the parotid is damaged
    • Aberrant innervation from the parasympathetic fibers (from otic ganglion) now innervate the lacrimal gland; also seen in Bell's palsy with lesions proximal to geniculate ganglion (preganglionic fibers to lacrimal, nasal, palate, pharyngeal, submandibular and sublingual glands travel conjointly)
    • Sphenopalatine ganglion-postganglionic parasympathic supply to the lacrimal gland

Glossopharyngeal Neuralgia

• Idiopathic or secondary to structural lesion
• Males and females have equal incidence; onset 40–60 years of age
• Stabbing unilateral pain
• Pain radiates to the base of the tongue; faucial (tonsils); may radiate into X sensory area; in or behind the external auditory meatus; beneath the angle of the jaw
• Trigeminal and glossopharyngeal neuralgia may occur concurrently
• Hacking cough may accompany the paroxysms of pain
• Triggers: swallowing, talking, pressure on the tragus or auricle, sneezing, coughing, moving the head
• Associated: salivation, flushing, sweating, tinnitus, lacrimation, tachycardia, hypertension and vertigo; rare seizures or cardiac asystole (cardio depressor nerve)
• Bradycardia and syncope: afferent impulses to brainstem vasomotor center that excite X; pacemaker prevents bradycardia but not a fall in blood pressure; therefore syncope still occurs.
• Pain occurs 2–3× per year; lasts a few minutes or occurs over several days
• Differential diagnosis:
  • Occlusion of the ICA
  • Elongation of stylomastoid process
  • Tumors of the posterior fossa (25%)
  • Tortuosity of PICA (pressure on the nerve)
  • Local infection
  • Neck trauma

Carotid Sinus Hypersensitivity

• General features:
  • Syncope with head and neck movement
  • Tight collar
  • Stretching the neck
  • Response to carotid massage:
    • Decrease of heart rate of 50%
    • Asystole greater than three seconds
    • A fall in blood pressure of 50 mmHg
  • Cardioinhibitory form: decrease of heart rate
  • Mixed form: heart rate is maintained in the face of decreased blood pressure
  • Vasodepressor form; hypotension alone

Differential Diagnosis of IX Nerve Syncope

• Digoxin
• B-adrenergic blockers
• Biliary disease (high bilirubin depresses SA and AV node)
• Elderly patients (atherosclerosis)
• Takayasu's disease
• Carotid body tumor (chromaffin)
• Tumor infiltration around the sinus
• Post carotid endarterectomy
• Elicitation of cardiodepressor reflex: ventricular fibrillation has occurred; R > L side

Vascular Disease

• Wallenberg's syndrome (PICA)
• Cavernous hemangioma, AVM, telangiectasia, hemorrhage
• Aberrant vertebral artery or PICA with nerve compression
• Bonner's syndrome

Tumors of the IXth Nerve

• Glomus jugulare
• Schwannoma
• Meningioma
• Chordoma
• Metastatic disease
• Jugular foramen syndrome (Vernet) IX, X, XI are affected

Peripheral Nerve/Neuromuscular Junction

• Diphtheria
• AIDP
• CIDP
• Meningeal involvement (infection, tumor, pachymeningitis)
• Tabes dorsalis (carotid and baroreceptor dysfunction)
• Hencken's syndrome: loss of taste posterior 1/3 of the tongue and pharynx
• Lesions within the retropharyngeal or retroparotid space:
  • Nasopharyngeal cancer
  • Abscesses
  • Adenopathy
  • Aneurysms
  • Trauma (birth injury)
  • Surgical procedures (head and neck carcinoma)
  • Carotid endarterectomy
  • Pure glossopharyngeal syndrome:
    • Minimal dysphagia
    • Depressed gag reflex
    • Ipsilateral palatal weakness
    • Loss of taste of the posterior 1/3 of the tongue
    • IX sensory distribution loss
  • Associated syndromes:
    • Collet–Sicard: IX, X, XI, XII
    • Villaret's: IX, X, XI, XII sympathetic chain, occasionally VI
  • Basilar skull fracture
  • Bogorad syndrome: crocodile tears from aberrant regeneration of lesser superficial petrosal nerve