There are two forms of facial pain that can be helped by gamma knife treatments.
The first is trigeminal neuralgia, and the second
is glossopharyngeal neuralgia.
So, with classic trigeminal neuralgia,
we don't quite understand the full reasons for
for why it occurs in about 50 percent of patients.
There may be a blood vessel next to the point where the trigeminal nerve joins the brain,
what we call neurovascular conflict.
And, as the blood vessel beats against the nerve, the hypothesis triggers this
abnormal facial pain.
In the other 50 percent of patients,
we don't fully understand why.
There is this abnormality of conduction, although we think this is a result of the
transition from the wrappings around the peripheral nerve, as it is outside the brain, when it
joins the brain, a different sort of wrapping is present.
So, that little junction is where we think there's little escape of electrical information,
which triggers the pain and the abnormal sensations in the face.
Glossopharyngeal neuralgia is similar to trigeminal neuralgia,
but the distribution is different.
It pertains
to the glossopharyngeal nerve.
The glossary nerve gives sensation at the back of the tongue, the inside and back
the throats,
and along the angle of the jaw and into the ear.
Trigeminal neuralgia is far
more common than glossopharyngeal neuralgia.
The patients with facial pain who can benefit from the Gamma Knife or neurosurgical treatments
are those who have been through an appropriate assessment by a neurologist
and there is a firm diagnosis of typical neuralgia trigeminal neuralgia.
That's very important if this is not typical trigeminal neuralgia, or if it's another one
of the autonomic conditions such as cluster headache, then these don't tend to respond
to Gamma Knife.
So, it's very important.
that there has been a neurologist headache review
at some stage in the process to refine that
diagnosis.
So, we make sure we're treating patients with typical trigeminal neuralgia because those
are the
ones where we know we can help.
So in that way, a neurologist is a very important part of the multidisciplinary
process.
that a patient goes to before having a treatment.
Certainly, I'd recommend all patients to have a review by a neurologist,
and of course they can be referred to us,
if you haven't already had a neurology assessment, and we can organise that as part
of the workup for treatment, if necessary.
What's important is that the patient
has firstly tried a range of medications.
Pharmacological management is the preferable
treatment rather than neurosurgical procedures.
So, we want to know that you've tried a host of medications and either the medications
are
not controlling the pain, or they're causing too many adverse effects that are intrusive
into your quality of life.
Those are the two important indications for considering any of the brain treatments.
There are three brain treatments that we consider:
one is a percutaneous procedure through the front of the face.
That's sometimes called glycerol or radiofrequency lysis.
Another is an open procedure behind the ear.
So, this is open brain surgery called microvascular decompression, that teases the blood vessel
away
from the nerve.
so it's no longer pounding against it.
That provides the longest duration of reduction in severity and reduction in
frequency of pain.
It's the closest to a cure that we get in trigeminal neuralgia, but many patients
are not
surgically suitable due to the general anesthetic requirements, or they
don't have blood vessel contact to actually target for the operation.
There's a small risk of bleeding, stroke, and a small risk to life with the open-head
brain surgery.
The third option is stereotactic radio surgery, of which Gamma Knife is the one that we practise
here at Queen Square.
It's one of the stereotactic radiosurgeries, and this is a closed-head procedure.
We don't need to make any incisions in the head.
We don't need to make any incisions in the skull, nor into the brain.
It works by applying innocuous radiation doses at different angles through the head,
but where they cross over, they sum up to give a toxic dose.
We aim that to injure the nerve just as it's about to enter the brain.
The aim of that is to reduce the frequency and the severity, and also the triggers of
the neuralgia.
The advantage is that this is a closed-head procedure.
For the procedure itself, we use
a frame that we must pin to the head, so that can feel like a tight fitting hat.
And we do that under local anesthetic, and that's the only uncomfortable part of the
procedure.
And that's very important.
It's a three dimensional map, which we use to plot the exact location down to sub-millimeter
accuracy of where we're going to give the treatment dose.
We call it a day-case or even an outpatient procedure, because you don't even need
to change into hospital gowns.
You can go through the day from frame fitting to MRI, to treatment, and then
home, usually in the space of a morning or into the early afternoon.