Trigeminal neuralgia is one of the facial pain conditions, and it manifests along the three
divisions of the trigeminal nerve, which is how the brain gets representation of the sensation
in the face. So you have three divisions: one along the jaw, one along the cheek below the eye,
and one above the eye and into the forehead. So, the neuralgia can manifest in one or all three of
these divisions and it's described as one of the most painful pain conditions in existence. So,
it goes from the patient being quite comfortable to suddenly having multiple shocks of what we call
lancinating, so as if the face is being pierced or as if there were electrical shocks in the face.
There can be a run of those and then it stops, and then it can be another run and then it stops. So,
the description of that is is paroxysmal, that's the term that doctors use for it.
It comes really strongly and then it disappears completely and then comes again.
So, it's important we tease it out. There are a lot of other facial pain conditions
which are very similar, or are crucially subtly different and respond to different treatments. So,
certainly the diagnosis of trigeminal neuralgia in the first place is a very important first step.
So, why it occurs, we don't yet know. In 50 percent of patients, approximately, there is a
blood vessel pushing against the nerve just as it enters the brain, and our main operation for this
is to create a bit of space and a bit of a buffer between the blood vessel and the nerve so it's not
pushing on the nerve anymore. But, as I say, that occurs in only about 50 percent of patients, so
the others aren't clearly understood. Multiple sclerosis can also produce trigeminal neuralgia
and that can be from changes within the nerve, but also changes within the brain.
In terms of what's happening to manifest this horrible pain, it's thought that there's a
jump of electricity along the nerve in an uncontrolled fashion just at the point where
it reaches the brain, where you change from the wrappings around the peripheral nerves
that go into the face to the wrappings around the nerves of the brain. So, that interface
is a point of potential weakness and a point of electrical chaos. That's the prevailing theory.
In terms of actually triggering it, and for someone who already has trigeminal neuralgia,
there are multiple different triggers, but they tend to be quite classic.
So, touching the face, cold wind against the face, chewing, brushing the teeth, and cold drinks.
So, the most important treatment is medication. So, carbon mesopine or tegratol is the commonest
medication, and it's one of the features that most diagnostically pure trigeminal
neuralgias respond to. Other medications can be added to that if it's insufficient or the
patient has adverse effects from the tegritol which is limiting how much they can receive.
In terms of when I come in, so the neurosurgical treatments, the reason for intervening is when
the painkillers aren't doing enough and the pain is very intrusive and very frequent,
or, to increase the medications, the adverse effects that are created that are not
tolerable for the patients. So that's when our neurosurgical interventions are important.
In terms of our neurosurgical options, there are three broad options: number one is surgery,
and that's at the base of the skull behind the ear, where we drill a small window in the skull
and tease the blood vessel away from the base of the brain. That's called a micro, because
it's under the microscope, vascular because it's a blood vessel decompression, where we're taking the
pressure off that nerve. That has the closest to cure rate, but of course,
it is an open operation that we do and some patients would prefer to avoid open head surgery.
Another option is Gamma Knife radiosurgery. So, this is relatively
younger than the microvascular decompression surgery. It was pioneered in the 90s and the
early 2000s. Gamma Knife is a sophisticated form of radiation, and, rather than the
cancer-treating radiotherapy, where a whole wave of radiation goes over the brain, Gamma Knife
supplies multiple innocuous rays in different directions, and where they cross over is where
they provide a noxious dose, so in that way the brain can receive very little radiation, but the
targets the trigeminal nerves can receive a big dose of radiation. The aim of that is to create
changes within the nerve. So, this leap of current is inhibited. So, it's a day-case procedure,
and entails applying a frame to the head. But, otherwise, with the gamma radiation,
you can't feel. So, the actual treatment itself is painless after the frame's gone on.
In terms of the outcomes, it's not quite as good as surgery, but it has a much lower risk profile.
So, although the risks of surgery are low in the current era, there's still an important risk
of stroke or wound healing problems, with Gamma Knife it's incisionless. We don't open the head.
The patient comes in in the morning and they've gone home by lunch time. You could call it a
day-case or even an outpatient procedure. They may have some headache for a couple of days afterwards
when the frame comes off, but that settles down and paracetamol is all they need to get through
that ordinarily. The important thing about Gamma Knife is, whereas the surgery and other
treatments such as through the face can give you instant improvement in the pain, we have to be
a little bit patient with the Gamma Knife effect because Gamma Knife is more of a gentle treatment.
It takes a little bit longer to have its full therapeutic profile reached, so, it's about
one month. Some patients can say the next day it gets better, or within a week, but they tend to
be the exception. It's usually about a month that patients notice to see an improvement. I certainly
don't make a judgement on whether the Gamma Knife has worked for at least three to six months. So,
the changes that occur in the nerve are subtle and progressive, and it ramps up during that period.