Trigeminal
neuralgia
- Also known as
Tic Douloureux
- Increases
with age, usu >50
- Incidence
4-13/100,000
Aetiology
- Three types:
- Idiopathic –
no known cause
- Classic – neurovascular
compression by aberrant artery
- Secondary –
other underlying cause
- Tumours - Schwanoma, meningioma
- AVM
- Multiple
sclerosis (2-3% of cases) – demyelination at
- Post
herpetic
·
Root entry zone is thought to be particularly prone
to demyelination injury due to the transition from peripheral myelin (Schwann
cell) to central (oligodendroglia).
·
Demyelination results in damage to ion channels, especially
sodium, with subsequent upregulation and ectopic impulse generation.
·
Classic form said to make up 80-90%
o
Due to aberrant vascular loop
o
Usually Superior cerebellar artery (SCA) or Anterior
inferior cerebellar artery (AICA)
·
Risk factors
o
History of migraine
o
Diabetes
o
Low vitamin B12
Clinical
- Sudden,
brief, recurrent episodes of pain in distribution of TGN
- Can be one or
more branches of TGN – V1 rarely affected (~5%)
- Usually
unilateral – if bilateral not at the same time
- 1 to several
seconds
- Stabbing or
electrical like pain
- Can have
facial spasm (hence old name for the disease: tic douloureux)
- Does not wake
patient at night (unlike some other pain syndromes)
- Triggered by
touch, often near midline in nerve distribution
- Other
trigger: chewing, talking, brushing teeth, cold air, smiling, and/or
grimacing
- Usually have
intermittent course with episodes lasting weeks or months
- May be dull
pain between episodes
DDX
●
Persistent atypical facial pain (atypical facial
pain)
●
Persistent dentoalveolar pain (atypical odontalgia)
●
Acute shingles, herpes zoster infection
●
Glossopharyngeal neuralgia
● Dental
▪ Cracked or fractured tooth
▪ Caries or pulpitis
●
TMJ disorders
●
Headache disorders:
▪
Unilateral neuralgiform headache with conjunctival
injection and tearing (SUNCT)
▪
Cluster headache
▪
Cluster-tic syndrome
▪
Primary stabbing headache
▪
jabs and jolts syndrome
Diagnosis
- History and
examination
- higher risk
of secondary cause: Young patients, sensory loss, bilateral
Diagnostic criteria:
- Paroxysmal
attacks of pain lasting from a fraction of a second to two minutes,
affecting one or more divisions of the trigeminal nerve
- Pain has at
least one of the following characteristics:
- Intense,
sharp, superficial, or stabbing
- Precipitated
from trigger areas or by trigger factors
- Attacks are
stereotyped in the individual patient
- There is no
clinically evident neurologic deficit
- Not
attributed to another disorder
Imaging
- No evidence based guidelines
- However MRI probably warranted in patients with high
risk of secondary cause, as above.
Electrophysiology studies
- TGN reflex
studies have some utility in detecting secondary cases
Treatment
• Carbamazepine
o NNT to attain significant pain relief <2
o
Relief at 1 year >50% (?~75%),
Long term ~31%
o Number needed to cause minor and major adverse effects 3 and 24.
- ~27%
ceased due to adverse effects in one study
o
Usual maintenance dose 600-800mg daily
• Oxcarbazepine
o Probably equally effective as carmabazepine
o Dose 900-1800mg daily
o
Slightly more tolerable (~18% cessation due to
side effects)
• Other
medications with some evidence:
o
Baclofen
o
Lamotrigine
o Pregabalin
o Phenytoin
o Botox (25-100units spread over affected dermatome)
• Other
medications that have been used:
o
Pimozide (severe side effects)
o
Valproate
o
Clonazepam
o
Gabapentin
o Topiramate
o
Lacosamide
o IV lignocaine or phenytoin may be trialled in severe cases
• Medications for which there is no evidence:
o Anti-cGRP injections – trials negative
o Opiates
Surgery
• Microvascular decompression
o Involves placing a sponge between nerve and the artery
o Most effective if there is vascular compression, less effective if there is contact without compression and less effective again if there is no compression
o Up to 90% pain relief at 1 year
o Mortality 0.2%, Hearing loss in 7%
• Percutaneous procedures on the Gasserian ganglion
o Destroy the nerve, will result in sensory loss
o Radiofrequency ablation, thermocoagulation, glycerol injection, balloon microcompression
• Sterotatic radiosurgery (Gamma Knife)
o Targets trigeminal root
o Take 6-8 weeks to work
o Relief in 69% of patients at 1 year
o Sensory loss in up to 37% and other sensory symptoms in up to 13%
Prognosis
• Poor data on long term prognosis
• 7-27% of patients are referred for surgery implying that remainder have reduction in pain over time when treated with medical therapy
References:
Ashina S, Robertson CE, Srikiatkhachorn A, et al. Trigeminal neuralgia. Nat Rev Dis Primers. 2024;10(1):39. Published 2024 May 30. doi:10.1038/s41572-024-00523-z