Trigeminal Neuralgia

Question 1

Define trigeminal neuralgia.

Answer 1

Trigeminal neuralgia (TN) is a facial pain syndrome in the distribution of ≥1 divisions of the trigeminal nerve.

Question 2

Describe the characteristics of trigeminal neuralgia. (6)

Answer 2

It is characterised by some combination of..

• paroxysms of sharp, stabbing, intense pain
• lasting up to 2 minutes and/or a constant component of facial pain,
• without associated neurological deficit.
• unilateral
• typically mandibular or maxillary divisions
• face screws up with pain (hence tic douloureux)

Question 3

Is trigeminal neuralgia unilateral or bilateral?

Answer 3

Usually unilateral

BUT can be bilateral - this is more common in those who are symptomatic

Question 4

What infection can cause trigeminal neuralgia?

Answer 4

Outbreak of facial herpes zoster.

Question 5

What are some of the triggers for pain?

Answer 5

Washing affected area, shaving, eating, talking, dental prostheses.

Question 6

Who is the typical patient?

Answer 6

Incidence ~10 in 100,000 in UK

F>M

Increases with age >50yrs old;

Question 7

What is the aetiology of trigeminal neuralgia? (3 causes)

Answer 7

1. Compression of trigeminal nerve - 80-90% have focal compression by a vascular loop i.e. usually superior cerebellar artery
2. Demyelinating disease - e.g. 20x more common in MS.
3. Brainstem lesions - rare; amyloid or calcium deposition can occur along trigeminal sensory pathway

Other: chronic meningeal inflammation, zoster, skull base malformation (e.g. Chiari)

Question 8

What are the divisions of the trigeminal nerve?

Answer 8

• V1 - Ophthalmic division
• V2 - Maxillary division
• V3 - Mandibular division

Question 9

What investigations should you do in trigeminal neuralgia?

Answer 9

• Diagnosis is clinical

Other:

• Check oral cavity for dental pain
• Rule out TMJ dysfunction
• MRI - may exclude secondary causes like tumour, infarct, MS plaques
• Trigeminal reflex testing - early blink or early masseter inhibitor reflex in symptomatic TN.

Question 10

What is the management of trigeminal neuralgia?

Answer 10

• 1st line: Carbamazepine - start at 200mg/day in 2 doses PO increased to maintenance; max 1200mg/day. Alternatives include lamotrigine, topiramate or gabapentin.
• Refer to neurology if there is no response to treatment or atypical features (e.g. <50yrs)

Other:

• Microvascular decompression - vessels are separated from the trigeminal root.
• Ablative therapy - reserved for refractory cases and are associated with facial sensory loss ; mainly used for V2 or V3
• Motor cortex stimulation

Question 11

What is the prognosis with trigeminal neuralgia?

Answer 11

Chronic - variable remission and relapse

Many get relief with medication and therapeutic maneouvres

Question 12

What are some red flags suggesting an underlying cause?

Answer 12

• Sensory changes
• Deafness or other ear problems
• History of skin or oral lesions that could spread perineurally
• Pain only in the ophthalmic division of the trigeminal nerve (eye socket, forehead, and nose), or bilaterally
• Optic neuritis
• FH of multiple sclerosis
• Age of onset before 40 years

Question 13

How is TMJ syndrome distinguished from TN?

Answer 13

TMJ syndrome is usually bilateral and jaw opening may be restricted

Question 14

What are the complications of TN?

Answer 14

None

Post-operative complications may occur e.g. hearing loss, facial/corneal hypaesthesia, trigeminal motor weakness, CN palsies, meningitis