What is trigeminal neuralgia?
Trigeminal neuralgia is a condition characterised by severe facial pain. The pain itself has very specific features. These include being almost invariably on one side of the face or the other. The pain itself is of a shooting, almost electric shock (lancinating) nature. There are, therefore, periods which may last for weeks or months when the pain is not present but the nature of the condition is that it often returns and over the years becomes both more severe and more frequent. Another characteristic of trigeminal neuralgia is that it is commonly triggered by such day-to-day events as eating, brushing your teeth and even being exposed to a breeze against your face. Perhaps as characteristic as the nature of the pain is the potential severity thereof. The experience of the surgeons of the Brain and Spine Clinic, managing hundreds of patients with the condition over the years, makes them ideally suited to appreciate the severity and distressing nature of the pain.
Difficulty with diagnosis
Unlike a number of medical conditions, trigeminal neuralgia is diagnosed almost exclusively on the basis of the history (the description of the type of pain), rather than on a scan. It is sometimes misdiagnosed leaving patients suffering for an undue period of time. In particular, the origin of the pain is often ascribed to dental problems. Equally, by no means all facial pain is trigeminal neuralgia, and it is only trigeminal neuralgia that lends itself to the option of neurosurgical intervention. Therefore a crucial part of the consultation is for us to determine whether we consider the facial pain from which you suffer to be trigeminal neuralgia or not.
Trigeminal Neuralgia Treatment
In terms of treatment, whilst the surgical options are perhaps uniquely effective in the world of neurosurgery, the first line of management is drug therapy. Specifically, Carbamazepine (Tegretol) is dramatically effective in treating the pain to the point that complete resolution of the pain with this drug is almost diagnostic of the condition. There are a range of other drugs that may be effective in trigeminal neuralgia, although there efficacy is rather less than that of Carbamazepine. It is also a characteristic of drug therapy with Carbamazepine that over the years, the doses required to maintain remission increase. It is, therefore, not uncommon for the individual sufferer to find that intolerance develops to the drug with a variety of side effects including nausea, drowsiness and instability. Some patients find that even on low doses of Carbamazepine they are unable to tolerate the side effects. It is in these situations that surgical options should be considered. These are discussed in below, in the treatment section.
In those patients who are either intolerant or fail medical treatment of trigeminal neuralgia, there are several very good surgical options for the treatment of this condition. Before considering these, it is useful to understand the reasons that people develop trigeminal neuralgia.
By far the most common reason for trigeminal neuralgia is compression of the trigeminal nerve (the nerve of facial sensation) by a blood vessel. It is not thought that blood vessels migrate onto the nerve but rather that they have always been there are in some people their presence causes a breakdown on insulation within the nerve. Loss of insulation of the individual fibres making up the nerve (analogous to an electrical cable) causes short-circuiting in the nerve. As a consequence, a simple touch stimulus to your face can get amplified into a dramatic painful response, namely trigeminal neuralgia. In a tiny proportion of people with trigeminal neuralgia, there can be spontaneous breakdown of the insulation within the nerve without a blood vessel pressing on it, typically due to a neurological condition called multiple sclerosis. It is, however, a tiny minority of people with trigeminal neuralgia who have multiple sclerosis.
Bearing this in mind, the surgical treatment options for trigeminal neuralgia fall into two categories:
1. Decompressive procedure (microvascular decompression or MVD).
This procedure very simply aims to remove the causative blood vessel from the trigeminal neuralgia. Once the blood vessel is removed, the insulation within the nerve can be restored and the condition can be considered to be cured. As a consequence, the long term pain relief rates of microvascular decompression are over 90%. This extremely high success rate makes microvascular decompression the most successful surgical intervention for trigeminal neuralgia. Andrew King and Scott Rutherford have recently published their surgical results for microvascular decompression in trigeminal neuralgia and these are summarised below. Your appropriateness for a microvascular decompression will depend upon whether there is indeed a blood vessel on your trigeminal nerve. This is established by carrying out a high definition MR scan which has a very high sensitivity for picking up the presence of a blood vessel. If a blood vessel is confirmed to be pressing on your trigeminal nerve, then a microvascular decompression will be offered to you by your neurosurgeon. On vary rare occasions, no blood vessel is evident on an MR scan, in which case your surgeon will discuss the second category of procedures with you which are detailed below.
A microvascular decompression is achieved by approaching the trigeminal neuralgia from an incision behind the ear on the affected side of the head. A small window of bone is removed from the skull which allows us access to a part of the brain cavity called the cerebellopontine angle. This is where a variety of nerves emerge from the brain to supply and head and neck function, including the trigeminal neuralgia, the nerve of facial sensation. The nerve and offending blood vessel are identified and then using microsurgical techniques, the two are separated. A variety of methods are used to keep the nerve and blood vessel apart including using specially fashioned slings and Teflon cushions. I microvascular decompression usually entails 3 or 4 days in hospital. It is a very safe procedure when carried out by an experienced surgeon, with complications being very rare. However, these do include tiny risks of harm to the nerves in the cerebellopontine angle which can result in facial numbness, deafness, facial weakness and/or double vision. Thankfully, the risks of these are no more than 1% and your surgeon will discuss this in far greater detail with you.
2. Ablative procedures.
These are procedures that are designed to create a degree of damage to the trigeminal nerve. These may be considered if you have no causative blood vessel pressing on the trigeminal nerve or if for medical or other reasons, you do not wish to consider a microvascular decompression. Your surgeon will offer you one of 2 options:
a. Trigeminal glycerol injection.
This involves injecting glycerol which mildly damages the nerve. This injection needs to take place under general anaesthetic, although it takes no longer than 20 minutes and, therefore, can be done as a day case procedure. The initial success rates in our hands are over 80%, as they are in the international literature. A glycerol injection tends to provide temporary relief but this relief may be effective for many years. There are risks that go with such a procedure which include a tiny risk of infection or bleeding. Given that we are setting out to create some damage within the nerve, there is a chance that some facial numbness can ensue. This is unpredictable and if it were to occur, it can be temporary or permanent.
b. Stereotactic radiosurgery.
This involves highly targeted radiotherapy being directed onto your trigeminal nerve. As with a glycerol injection, this is intended to create harm within the nerve and it carries very analogous success rates to a glycerol injection (of the order of 80% resolution or substantial improvement in your trigeminal neuralgia). It does not involve any anaesthetic but the targeting mechanism of the stereotactic radiosurgery does require fixation of a special frame to your skull. This is done using local anaesthetic following which you would have a scan to map out your trigeminal nerve before undergoing the radiotherapy. There is usually a delay of a few months before the benefits are felt, although it can be sooner than this. As with a glycerol injection, there is a risk of facial numbness which can be temporary or permanent but this risk is low particularly with a first time ablative treatment.
As part of our rigorous process of surgical outcome review, we carried out a detailed analysis of our outcomes of patients undergoing surgical management of their trigeminal neuralgia in 2012. This looked at results of all operations performed over a 3-year period. During this time we carried out 54 microvascular decompressions and 25 glycerol injections. Our results are as follows:
- Microvascular decompression
> Complete relief of neuralgia in 91%
> Partial relief of neuralgia in 6%
> Recurrence of pain only occurred in 3 patients whose trigeminal neuralgia was not
related to multiple sclerosis (recurrence rate of 6%)
- Trigeminal glycerol injection
>Complete relief of neuralgia in 50%
> Partial relief of neuralgia in 38%
> A recurrence rate of neuralgia in 1/3 of patients
For each of these procedures our complications rates were low (equivalent or better to other large surgical series which have been published).
Another important aspect of this study was to review factors which we have used in our practice to guide surgical decision-making. Statistical review of a variety of these factors validated our approach to choosing a surgical intervention as they were found to have a significant impact on surgical outcomes. These included age, sex, presence of a compressive blood vessel, character of the neuralgia, duration of pain and any previous intervention.
Your surgeon in the Brain and Spine Clinic will help guide you through this very important treatment decision offering you advice that his considerable experience provides, but also recognising that it is always a very individual decision.