Trigeminal neuralgia (TGN), a severe unilateral paroxysmal facial pain, often severe enough to be frequently described the most painful condition, even reported to induce suicidal thoughts. Its nickname of Suicide Disease (Myth), is misplaced and carried across generations without substantiating evidence. While the severity of pain may bring in suicidal thoughts, but there is no conclusive evidence of a significant suicide rate.
Incidence:
TGN is a rare condition with differing incidence / prevalence data varying between 4-13 per 100,000 population each year, with higher prevalence over 50 year olds and females. However, data from Indian subcontinent is at odds to other published literature with a male preponderance noted in Indian literature published between 1960-1980. The possible cultural differences in Indian subcontinent (data reporting and collecting) may have contributed to this significant variance in prevalence.
Cause of TGN:
TGN is mostly idiopathic (no identifiable cause) and a small proportion (<10%) is secondary to multiple sclerosis (1-5% of MS patients), tumor or cyst in the cerebellopontine angle.
Sophisticated imaging techniques (MRI) in the recent past have frequently identified compression of trigeminal nerve exit point from the brain by a small artery (less commonly vein) in over 80% of idiopathic TGN. The sustained arterial compression of the nerve exit site accumulated with aging results in damage to the nerve wrapping layer (demyelination).
The exact consequence of demyelination and resulting TGN is unclear, with the most promising hypothesis being nerve fiber damage from compression by an adjacent artery.
Diagnosis of TGN
TGN remains entirely a clinical diagnosis, not requiring an MRI scan (Myth 2). Imaging is usually undertaken to rule out organic pathology if clinical examination (numbness, bilateral disease, younger patient) suggests a possible secondary cause. The increasing recognition of nerve wrapping damage at the nerve exit site from the brain by small arteries as a cause for idiopathic TGN and the availability of high-resolution contrast-enhanced imaging techniques are commonly undertaken before contemplating surgical treatments.
Diagnostic Criteria
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Paroxysm of unilateral pain lasts under 2min in 1-3 divisions of the trigeminal nerve
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Pain characteristics (at least one):
- Intense, sharp, stabbing
- Precipitated by trigger zones
- Each attack is similar in character, location, trigger
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Normal neurological examination
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No other disease/cause identified to explain the pain
Background pain between paroxysms and mild sensory loss are features of atypical TGN (a refractory form of the disease).
Your doctor well versed with managing facial nerve pains may be in a position to distinguish TGN from other potentially confusion conditions like trigeminal neuropathy, Cluster headache, SUNCT ( the worst headache ever), other neuralgias and neck related headaches.
Imaging in TGN
Trigeminal neuralgia is a clinical diagnosis, meaning there is no need for expensive scans/tests. Since 5-10% of TGN have a secondary cause identified, investigations are dependent on clinical examination identifying atypical features (e.g. Dental x-rays, sinus x-ray / CT scan).
Investigations are done to:
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Clarify the differential diagnosis; for example, by taking dental x rays
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Magnetic Resonance Imaging to detect secondary TGN, particularly with a view to surgical cure
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Identify artery compressing nerve exit site from the brain before contemplating surgical treatment. Interestingly, 3-12% incidence of compressing artery in asymptomatic individuals, imaging studies for artery compression are only considered in clinically diagnosed patients, rather than to make a diagnosis.
Conventional MRI is good at ruling out sinus, CP angle tumors/cysts and multiple sclerosis. Artery compression needs a more complex specialized MRI scanning sequence.
Treatment of TGN
Carbamazepine remains the drug of choice for TGN. Its use has been traditional and based on old small studies of debatable quality. Based on the best available evidence including Cochrane reviews, guidelines continue to recommend Carbamazepine as the first line of treatment. Nearly 70% gain reasonable good benefit from it. Oxy-carbamazepine has a better side-effect profile and is likely to be better tolerated. Cognitive side-effects are common and hematological side-effects warrant regular monitoring of blood counts.
In spite of unproven benefits for other anti-epileptic, alternative antiepileptic mediations are tried (with acceptable reasoning/logic) in patients intolerant of Carbamazepine. These include lamotrigine, phenytoin and gabapentin among others.
Surgical procedures for Trigeminal Neuralgia
TGN surgical treatment can broadly be classified into two categories Microvascular decompression (major brain operation) and palliative destructive procedures of trigeminal ganglion/nerve (Non-surgical needle procedures).
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Microvascular decompression (MVD) aims at relieving nerve roots arterial compression and hence provides pain relief. The palliative destructive procedures involves heat (Radiofrequency burn), chemical (glycerol), physical (Balloon Compression) or radiation-induced (stereotactic radiosurgery Gamma knife) nerve exit site partial destructive lesions. Apart from the Gamma knife technique, the ablative procedures involve accessing the trigeminal neural path through the foramen ovale.
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Palliative destructive procedures: RF thermal ablation has better results with a higher incidence of numbness, while balloon compression causes jaw weakness. The Radiofrequency ablation procedure provides good pain relief for well over 3 years. The cost and risk of major brain surgery especially in elderly people are prohibitive in considering major brain surgery (Microvascular decompression -MVD) which does provide better results without numbness 80-90% pain relief with a 10% recurrence rate over 10 years-20 years.
Your Pain Specialist is well placed to discuss your treatment options and assist you with a helping hand in you fight against pain. They can help you in managing your pain killers based on their vast experience and guide / provide a suitable procedure to control your pain.
