Trigeminal & Glossopharyngeal Neuralgia

Two cranial neuralgias with an almost identical pain quality and management ladder, covered together here. See facial pain for the broader differential.

Trigeminal neuralgia

Recurrent, unilateral, shock-like pain in one or more divisions of the trigeminal nerve. Due to demyelination or neurovascular compression.

Request imaging to exclude a structural cause (specific trigeminal nerve/ganglion views), especially with sensory loss — which suggests trigeminal neuropathy rather than classic trigeminal neuralgia.

Management: drugs are first-line. If ineffective, consider surgery (microvascular decompression, percutaneous rhizotomy, stereotactic radiotherapy/gamma knife). Carbamazepine has stronger evidence but oxcarbazepine is often better tolerated.

• First-line: carbamazepine MR 100mg PO BD, increase as tolerated every 7 days to max 400mg BD.
• Second-line: oxcarbazepine 300mg PO BD, increase after 7 days to max 600mg BD.
• Third-line: baclofen 5mg PO BD (increase every 4 days to 10–20mg TDS); gabapentin 300mg PO nocte (increase every 3–7 days to 600–1200mg TDS); lamotrigine (slow titration schedule to max 100mg BD); phenytoin 300mg PO daily; pregabalin 75mg PO nocte (increase every 3–7 days to 150–300mg BD).

Glossopharyngeal neuralgia

“The trigeminal neuralgia of the throat” — pain in the tonsillar fossa, or sometimes deep in the ear or the back of the tongue. It’s rare — around 0.2–1.3% of all cranial neuralgias, with an incidence of roughly 0.7 per 100,000 population — and is often misdiagnosed as trigeminal neuralgia because the pain quality is so similar; the two conditions can also coexist in the same patient.

Presentation

Precipitated by chewing, swallowing (particularly cold liquids), talking or yawning — pain is brief (seconds, up to about 2 minutes), severe, and sharp/stabbing or shock-like, felt below the ear, in the tonsillar fossa, base of tongue or posterior pharynx. Onset is usually middle-aged to older adults; one large case series found 57% of patients were over 50. Accompanied by syncope in ~2% — the glossopharyngeal nerve carries baroreceptor/chemoreceptor afferents from the carotid sinus and body (via Hering’s nerve), so nerve irritation during an attack can trigger an amplified vagal reflex causing bradycardia, hypotension and cardiac dysrhythmia (probably via cardiac arrhythmia); when cardiovascular features dominate without much pain, this is sometimes called non-neurologic (vago-)glossopharyngeal neuralgia. Most patients have a single episode with spontaneous remission (~74% in one large series); only around 12% have bilateral pain.

Secondary causes to consider, beyond the idiopathic/essential form: vascular compression at the nerve root (the most common identifiable cause), demyelinating disease (e.g. multiple sclerosis), inflammatory/autoimmune disease (e.g. Sjögren syndrome), peritonsillar or intraoral infection, intracranial space-occupying lesions (especially cerebellopontine-angle or medullary tumours), and Eagle syndrome (an elongated >25mm or calcified styloid process/stylohyoid ligament compressing the nerve).

Investigation

Exclude a structural cause: oropharyngeal malignancy, peritonsillar infection, vascular compression — consider imaging. MRI/MRA is the most useful study — it best shows neurovascular compression (most often from the posterior inferior cerebellar artery), plus demyelinating lesions or a posterior fossa tumour; a plain cervical spine X-ray or CT can show an elongated/calcified styloid process if Eagle syndrome is suspected. Baseline bloods (FBC, ESR/CRP, ANA) help exclude infection, inflammation or malignancy. If syncope has occurred, arrange cardiology assessment (ECG, Holter, echo) to characterise the arrhythmia.

Differential diagnosis: trigeminal neuralgia (most easily confused — distinguished by pain location and trigger: facial/light-touch-triggered in trigeminal neuralgia versus throat/swallowing-triggered here), Jacobson (tympanic) neuralgia when pain is isolated to the ear, temporal arteritis, and temporomandibular joint dysfunction.

Treatment

Same ladder as trigeminal neuralgia:

• First-line: carbamazepine 100mg BD, increasing every 7 days according to response, up to 400mg BD. Better efficacy evidence but less well tolerated — drowsiness, ataxia, SJS/DRESS, induces metabolism of hormonal contraceptives (use Mirena, DMPA or copper IUD instead), neural tube defect risk (avoid in pregnancy — category D). Response can take up to 2 weeks to assess; roughly 70% of patients get pain control initially, though efficacy can wane over time. A Cochrane review of carbamazepine across trigeminal neuralgia, diabetic neuropathy and post-stroke pain found the trial evidence itself is of poor quality (small, short studies) and could not be relied on to quantify benefit precisely — carbamazepine remains the best-studied and first-choice agent in practice despite that evidence gap, but around 65% of patients on it have at least one adverse event, roughly double the placebo rate.
• Second-line: oxcarbazepine 300mg BD, increasing every 7 days up to 600mg BD. Generally better tolerated — drowsiness, GI upset, SJS/TEN, also induces contraceptive metabolism, unclear pregnancy safety (category D).

If drug therapy fails or isn’t tolerated, a glossopharyngeal nerve block (diagnostic local anaesthetic block first, to confirm the pain source) can be useful before considering chemical neurolysis or radiofrequency ablation — these interventions carry a real risk of bradycardia/hypotension from vagal stimulation, so are done by an experienced proceduralist. Bilateral blocks are avoided (risk of complete vocal cord paralysis).

Refer to neurology if poor response or tolerance — surgery may be considered — microvascular decompression (for confirmed vascular compression) is the most-used surgical option; alternatives include radiofrequency rhizotomy, nerve resection, or — specifically for Eagle syndrome — resection of the styloid process (stylectomy). Persistent dysphagia and voice hoarseness are the main risks of intracranial nerve-resection approaches.

Prognosis is variable: bilateral pain, multiple severe bouts, and constant (rather than paroxysmal) pain are poor prognostic features. Only around a quarter of patients ultimately need surgery; most remain manageable with drug therapy alone.