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Friday, March 24, 2023
Dr. Brown: Progress in treating brain tumours and berry aneurysms
Dr. William Brown Supplied

One of the most common benign brain tumours involves the vestibular nerve.

During my training and early practice years, these were major challenges for neurosurgeons because there were no CT and MRI scans, and most of these tumours were discovered late when they were large and hard to deal with. 

In their late stages, some of those large tumours were big enough to cause deafness, loss of sensation in the face, facial paralysis and clumsy movement in the limbs, all on the same side as the tumour – plus loss of balance walking. 

Located in the space between the back of the temporal bone, brainstem and cerebellum, those large tumours were hard to take out without further damaging the cochlear (hearing) division of the same nerve, injuring neighbouring cranial nerves or even the brainstem, sometimes with severe disabling or even fatal consequences.

The crowded nature of the surgical field made them challenging for the best of neurosurgeons.

Fast-forward 40 years to today – most vestibular schwannomas are much smaller and often picked up incidentally by CT and MRI examinations carried out for other reasons.

These days when small vestibular schwannomas are found unassociated with symptoms or perhaps only a little deafness on the affected side, the question is often whether surgery is necessary.

The wiser course would be to wait, following the patient and repeating MRI studies to see whether the tumour grows and begins to produce significant symptoms.

Roughly half such small tumours increase a little in size. Even with somewhat larger tumours, especially in older patients, many surgeons and physicians take a wait-and-see attitude because many grow slowly enough that they probably won’t present much of a problem in the patient’s lifetime.

There is another option – radiosurgery, one version of which is aptly called the “gamma knife.”

As the name implies, these techniques involve focusing radiation on the tumour with as little spillover into healthy tissue as possible. As you might guess, radiosurgery works best for smallish tumours – less than three centimetres in diameter.

These days surgery is usually a team effort, which involves specialists in ENT (ear, nose and throat) and neurosurgery, with a special expertise in excising these tumours, especially the bigger, more challenging ones.

Surgery is often carried out with monitoring of the nearby cranial nerves to minimize injury to hearing and facial movement, as well as monitoring the integrity of the brainstem. 

The larger the tumour, the greater the surgical risk to all neighbouring structures. Sometimes it’s impossible to avoid injuring the facial nerve and/or vestibular nerves because these are often buried in the tumour and hard to tease out.

Most of the time with the bigger tumours, complete removal is impossible – there’s too much risk, which means the tumour may regrow, usually slowly.

Despite the challenges posed by the bigger tumours, the outcomes are much better than even the best neurosurgeons were able to accomplish years ago. That’s progress.

The evolution of the assessment and management of these tumours is similar to other changes in neurosurgery and more broadly in medicine over my career. 

One example involves the treatment of berry aneurysms at the base of the brain. Rupture of a berry aneurysm can be devastating for patients depending on its location and the extent of the hemorrhaging that occurs.

Forty-years ago, once the acute situation settled down, surgeons usually clipped the base of the aneurysm, a manoeuvre that was tricky because at any moment the aneurysm might rupture, creating a nightmare for the less skilful.

That was bad enough, but clipping aneurysms at the base of the brain was especially tricky because the view was often limited and it was all too easy to fail to see tiny arterial branches feeding the brainstem. If they were clipped by mistake, it was usually disastrous because of the ensuing brainstem stroke. 

In London, Ont., we had one of the best surgeons in the world at carrying out such high-risk surgery – Dr. Charles Drake. He was a hero of mine because of his excellent judgment, skill and lovely manner with his patients 

The field changed in the late 1980s when surgery from within the artery became possible by threading a catheter into an artery in the groin all the way up to the site of the aneurysm and fixing it from within by releasing a coil.

It was transformational and has become the standard way of treating most berry aneurysms and vascular malformations involving the brain.

Two examples of revolutions in neurosurgery in my time that transformed care – with more to come. 

Dr. William Brown is a professor of neurology at McMaster University and co-founder of the InfoHealth series at the Niagara-on-the-Lake Public Library.  

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