Trigeminal Neuralgia
Trigeminal neuralgia (TGN) is a severe disabling pain condition which affects the nerve supply to the face, mouth, teeth and eye, causing extreme pain which can last for many years and can difficult to treat. It sometimes referred to as the ‘suicide disease’, due to the sudden, severe attacks of face, eye and mouth pain. It is characterised by recurrent episodes of electric shock-like pains in one side of the face in the distribution of one or more divisions of the fifth cranial (trigeminal) nerve, which is the nerve that supplies sensation in our face and mouth. The shock like pains of trigeminal neuralgia typically are triggered by innocuous stimuli such as brushing teeth, wind or cold air. The underlying cause in many is thought to be increased numbers of pain signals (electrical activity) from the nerve due to problems with the insulating coating.
How is it diagnosed?
Diagnosis is clinical i.e based on the symptoms. There are many different kinds of facial pain syndromes, the management of which is different - typically specialists involved in the diagnosis and care of patients with facial pain includes neurologists, maxilla-facial surgeons, pain doctors, and neurosurgeons. Once a clinical diagnosis of TGN is established investigations should then undertaken to investigate the cause. This usually means having an MRI scan of your head with and without contrast. If you cannot have an MRI scan CT scans can be arranged. Imaging of the brain is performed to look for potential underlying causes of your TGN, compression of the trigeminal nerve by an adjacent artery or a structural brain lesion such as a tumour or demyelinating plaques (for example in multiple sclerosis).
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What treatments are available?
As outlined above there are many causes for trigeminal neuralgia and treatments recommended therefore varies. Â Pain medications often play a central role in managing the pain of trigeminal neuralgia regardless of the underlying cause and some of these are outlined in the section below. If no underlying cause such as a tumour or demyelinating condition is seen you may be referred to a Neurosurgeon for a discussion on peripheral nerve procedures and/or microvascular decompression and the sections below cover these forms of treatment.
Medications
There are a wide variety of pain medications that can help with managing the pain of TGN and many people manage well with these without needing intervention.
Commonly used medications include:
- Carbamazepine
- Oxcarbazepine
- Gabapentin
- Pregabalin
- Lamotrigine
- Baclofen
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These are typically guided by your neurologist, pain physician and/or GP
Peripheral nerve procedures (rhizotomy)
These are typically considered for people with TGN that is not well controlled with medications, or those who cannot manage with the side effects that sometimes these medications can have (for example fatigue and poor concentration) who either do not have a clear surgical target such as a compressive adjacent artery or tumour or who do but would prefer trying a less invasive approach.
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Peripheral nerve procedures, otherwise known as rhizotomy encompasses a number of surgical techniques that are performed by passing a cannula through a gap in the base of the skull where the origin of the devisions of the trigeminal nerve (called a ganglion) sits. The ganglion can then be treated using one of several options:
•Radiofrequency thermocoagulation rhizotomy, which applies heat therapy to the ganglion.
•Mechanical balloon compression, which uses a catheter to compress the ganglion.
•Chemical (glycerol) rhizolysis, which involves the injection of 0.1 to 0.4 mL of glycerol into the area around the ganglion.
These procedures are performed under general anaesthetic and are typically performed as a day case procedure.
Up to 90% of people with TGN treated with one of these procedures can have initial pain relief. This tends to reduce over time to pain free rates of between 65-85% after 1 year and approximately 50% by 5 years. They can be repeated.
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The main risk of rhizotomy procedures is that they are not effective (i.e do not result in a significant improvement in your pain). There is a risk of meningitis (seen in approximately 0.2 percent of people), of injury to a nearby artery (maxillary) requiring repair and/or blood transfusion, dural leak leading to CSF leak (leak of fluid from the brain) and those of the general anaesthetic which includes a small risk of stroke and to life. Up to 12% of people have numbness in their face on the side of the injection afterwards and this can be long-lasting. A small percentage of patients can develop a different type of pain syndrome int he face called anaesthesia dolorosa. This tends to be more commonly seen in people who have had a number of procedures. If you are considering a rhizotomy your Doctor will run through all the risks, benefits and alternatives in full detail - this is just an overview.
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An alternative to these injections is to undergo radiosurgery treatment to the trigeminal ganglion. The best evidence for this to date is when a type of machine called 'Gamma Knife' is used. This form of treatment is performed with you awake in a specialist centre, lesions in the trigeminal nerve are generated using focussed radiation. Typically it takes a month or so for the treatment to start showing benefits in terms of pain relief. Pain relief after one year occurs in approximately 75-80% of patients, and 50% at three years. Numbness in the face can occur after treatment in up to 40% of people, anaesthesia dolorosa is rare.
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Microvascular Decompression
Microvascular decompression is a neurosurgical operation that is performed under general anaesthetic, suitable for patients with TGN who have a vascular loop in contact with/distorting the trigeminal nerve. A craniotomy (opening) at the back of the head behind the ear is performed and the vascular structures that are compressing or distorting the nerve (seen on MRI scans) are separated away from the nerve. It is the most effective long term treatment of trigeminal neuralgia at this time, with evidence showing that pain relief occurs in 90% initially, and remains in approximately 75% of patients after 5 years.  Typically this procedure requires a hospital stay of 2-3 days during which time people often have increased headaches and some unsteadiness on their feet. Generally there is a recommended recovery time of 6 weeks away from work and not to travel by aeroplane in that period.  For more information on this please see the section on 'What is it like to have a neurosurgery operation?'. The risks of the procedure include it not working, those of a general anaesthetic including a small risk of stroke or to life, infection (superficial/deep/meningitis), leak of CSF from the wound requiring repair and/or CSF diversion, double vision, hearing loss, facial weakness, facial numbness, unsteadiness.