Skull base tumours are essentially tumours that grow in the brain, but really around the base
of the brain. So you can split brain tumours into those that grow within the brain substance itself
and those that grow around the brain, and skull base tumours tend to be the ones that grow
at the base of the brain and around the brain. The reason why we consider them as a separate category
is because well, firstly they cross boundaries between the brain and other parts of the body so
for example the nose or the ear. So often they're managed between specialties like neurosurgery and
also ear, nose and throat surgery. And secondly because there are lots of nerves that go to your
your special senses, like your eyes or your nose or your ears, and also blood vessels that are that
are mixed in with these tumours, so they often require quite specific management because of that.
Well, the majority of skull base tumours are benign, but the reason that they are important
is because they they grow slowly but they push those critical nerves and blood vessels
out of the way, and cause symptoms as a result. The cause is usually not known,
so in medicine we say that they're idiopathic, and for whatever reason
certain patients suffer from them, but we usually don't know why. There are certain genetic
conditions that can be associated with skull base tumours, like something called neurofibromatosis,
which can be associated with meningiomas or vestibular schwannomas. But the majority of these
tumours, they appear with age and we don't really know why certain people end up getting them.
Yes, for example, vestibular scwannoma is a very common, skull base tumour that I deal with on a
regular basis. And the key sign with a vestibular schwannoma is unilateral hearing loss ,which
usually is unusual because it presents on one side and also is associated with ringing in the ears
and sometimes other symptoms like balance problems. So a simple hearing test will pick
that up and the majority of those tumours are caught via otologists and audiologists who have
who have identified the tumour from hearing tests and then an MRI scan. Any symptom,
it's not usually vague symptoms that cause, or are associated with these tumours. Usually it's
something quite specific, because a specific nerve is compressed. So as I say, hearing loss,
for example, or you might find double vision or a drooping of the face or drooping of the eyelid,
it's often something quite specific that you might notice that would then stimulate an MRI scan, so
most doctors or general practitioners would pick up on those specific signs.
Yes, there are many different kinds of skull base tumour. The the most common two categories are
something called meningiomas and something called and the vestibular scwannomas, I've talked about.
The meningiomas, they grow on the meninges of the brain which is the covering of the brain,
but they particularly happen to occur around the base of the skull because there's quite a lot of
meningeal tissue in that area. And because they cause symptoms quite early because of the nerves
and the blood vessels in that area, the behavior of a meningioma is quite typical. In some ways
they're like a it's like a wart on your skin, but it's growing inside the cranial cavity so
because it's persistently growing eventually it starts to get symptoms and needs treatment,
but the growth is very slow, it's usually about one to two millimeters a year.
But as they grow slowly they can get to quite big sizes and then they do really need intervention
to stop them growing any further. The vestibular schwannoma, and it's called that because it grows
on the hearing and balance nerves specifically. So that tumour actually grows in the same region
pretty consistently but they are also quite common. And again, those tumours grow about
one to two millimeters a year classically, and the treatment options are also quite similar so
it's usually either monitoring or surgery, or some sort of radiation treatment.
There are a complex of other skull base tumours so it's not just those two categories,
but those would be two of the most common.
Well, yes so as I say, there's the three main options for treatment. And the first thing that
we always do for these tumours is a repeat MRI scan usually, unless it's extremely large or very
symptomatic. Ordinarily we would like to get an idea of the behavior of the tumour first of all,
and you will find actually a proportion of these tumours do not grow at all. So you can do an MRI
scan at six months, and if there's no growth at all you might do an MRI scan at one year, and
then monitor the tumour and you may never require any treatment for it, which is the best scenario.
You may find that the tumour is growing slowly and is small, and there is a particular treatment we
have called stereotactic radiosurgery. One kind of stereotactic radiosurgery that we will do at Queen
Square is called Gamma Knife radiosurgery, and that's a very focused form of radiation treatment,
which is given over the course of one day. So it's done as a day case, and it requires
a frame to be fitted onto the skull under local anaesthetic and that means that we can focus the
radiation very specifically at the tumour and avoid radiation going to the rest of the brain,
particularly in these sort of sensitive locations where the skull base tumours grow.
And that's extremely effective but doesn't remove the tumour it controls the growth. So that's good
for the small tumours that you don't want to get any bigger, but as I say if you've got a large
tumour, and that's compressing structures, giving significant symptoms or is a risk,
if there was further swelling for example, than you are really talking about surgery. So I would
estimate maybe 10 or 20 percent of the tumours will end up having an operation to remove them,
and typically speaking we aim to do the maximum safe resection that we can do.
So often with skull base tumours you can't necessarily remove
100% of the tumour tissue because it's so applied to the these critical nerves and blood vessels,
that you might cause a stroke or you might cause a permanent injury to, for example, the nerve that
gives you movement to your face. So we often will aim to do what's called a maximum safe debulking,
and take out maybe 80 or 90 percent of the tumour, relieve the pressure on the
surrounding brain structures, and then monitor the residual. And if the residual does grow then
that may be treated with, for example, gamma knife radiosurgery afterwards.
In terms of how we remove the tumours there are lots of different methods of removal of tumour
depending on where it is. So often these tumours grow in and around the brainstem
and you have to pick the appropriate approach depending on exactly where it is,
and that might be through the side of the skull here, it might be from behind, it might be
through the ear structures with ENT surgeons for example. Also skull base tumours are removed
up the nose if they're quite far forwards. So there's lots of different ways to remove them, and
you really need the right set of expertise and the multi-disciplinary team to assess
each tumour on its location and size and the patient to decide exactly what is best really