Gamma Knife stereotactic radiosurgery: an in-depth look into treatment for trigeminal neuralgia

Gamma Knife stereotactic radiosurgery is a revolutionary treatment for patients with trigeminal neuralgia. In this insightful article, highly esteemed consultant neurosurgeon Mr Jonathan Hyam shares his expertise on the procedure. The London-based neurosurgeon explains what Gamma Knife entails, who can benefit from it, and what side effects to be aware of. 

What is Gamma Knife stereotactic radiosurgery?

Gamma refers to the Gamma rays which are used in this treatment and stereotactic refers to the three-dimensional manoeuvring of radiational instruments in space.

Stereotactic brain surgery was developed by Victor Horsley in the 1800s. He was the first to devise a frame which is a three-dimensional map of the head and it has x, y, and z coordinates so every bit of the brain can be mapped against this frame. Although his original one wasn't designed for humans, a few years afterward it was adapted by Lars Leksell in Sweden, who was the inventor of Gamma Knife. He used this technology for his own stereotactic frame and pioneered the use of radiation instead of instruments to determine coordinates in the brain. 

He experimented with different types of radiation delivery and found that sending doses of radiation in multiple different directions so they cross at the target points delivered radiation at the target but it dramatically lowered the radiation exposure to the surrounding parts of the brain. 

Leksell was limited quite extensively by the sophistication of the imaging available but since then CT scans and MRI scans were invented. We now have much more sophisticated imaging so that we can deliver treatments exactly where we want them.

With this technology, he could reach lesions within the brain without opening the head and without causing significant collateral radiation injury to precious structures. This technology has advanced even further since then, we now have the icon and Queen Squares Hospital has built up quite an expertise in using this newest platform. Each year there’s an exponential growth in the number of patients undergoing Gamma Knife radius surgery. 

What is involved in the procedure? Can it be repeated?

It's a day case or outpatient procedure. When the patient comes in in the morning, we apply a frame that is pinned to the head under local anaesthetic. That's the uncomfortable part of the procedure but most patients tolerate it and by the time they go for the MRI, they're very used to the frame and are much more relaxed. During treatment, you don't feel any sensation of the Gamma rays and it is painless itself. The patient can lie in the gantry while listening to the radio or dozing off during the treatment. After the frame is taken off, the patient can go home almost immediately.

The treatment certainly can be repeated. There are a small number of patients whose lesions are quite large and delivering a one-off dose could expose the surrounding brain to too much radiation. We often break it up into what we call fractions for those patients. The vast majority, however, will have a one-off one-day visit and treatment can be repeated again in the future. 

If patients with brain secondaries, for example, develop other little secondaries in other places in the brain, then certainly it can be repeated. In trigeminal neuralgia, if there's a recurrence, then we can also repeat treatment too.

What are the risks and complications that may happen?

Whenever you treat the brain, there are risks to the surrounding tissue. The brain receives radiation through this treatment and it can cause irritation, occasionally swelling, or even seizures. That's in the minority of patients. The target you're treating, for example, a tumour, it can swell but it will settle down usually spontaneously. We always warn patients of such risks prior to the procedure.

The incidence is very low and if you compare that to surgery the chance of stroke or healing problems is dramatically reduced.  According to the DVLA guidelines, if you have open surgery, you are restricted from driving for much longer than if you've had Gamma Knife. Although the risks of Gamma Knife are not zero, they're less in their magnitude than open head surgery.

Who is a good candidate for the Gamma Knife stereotactic radiosurgery procedure?

It depends on the diagnostic group. For example, a patient who has quite classic trigeminal neuralgia meaning they have paroxysmal pain, attacks of severe pain that then settle down and can flare up again. They can benefit greatly from Gamma Knife treatments. If they have more of a complex neuropathy, it tends to respond less. It's very important that you work with a neurologist and that a diagnosis of trigeminal neuralgia has been made, otherwise you might have disappointing results.

I treat patients with meningioma. This is a brain tumour that is benign in approximately 96% of cases and grows on the inside of the skull. They can continue to grow, causing swelling to the local brain or squashing the brain. When these tumours are reasonably small and, certainly, when they have started to grow, we treat them. This avoids the need for an open head surgery and often when given the option, patients are very keen to have the incisionless treatment, Gamma Knife. 

What can be expected during recovery from the procedure and how long is recovery time?

We always warn patients that for two or three days they may have a headache or feel a bit under the weather, but it is unusual for them to have any severe adverse effects. When the side effects of Gamma Knife occur, they can be further down the line, anywhere from three to six to nine months later. It's a gentle treatment but its effects can be delayed. In trigeminal neuralgia, for instance, we're very careful with patients who already have facial numbness because we can make that worse. Occasionally, in a small number of patients, we can trigger a condition called anaesthesia dolorosa, a painful numbness, which some patients say is more unpleasant than the neuralgia itself. Thankfully, this hasn’t happened at the Queen Square Amethyst Gamma Knife but we have to be cautious. 

How successful is it for the treatment of trigeminal neuralgia?

We tell patients they will experience the benefits for about three years.  There'll be patients who have just a few months of benefits and others who have many years of benefits, but the average tends to be three years. Of course, trigeminal neuralgia during the course of one's lifetime varies anyway. In terms of adverse effects, it's a small chance of causing a severe adverse effect but it is much less likely than the chance associated with open surgeries. 

If you are interested in finding out more about Gamma Knife and would like to book a consultation with Mr Jonathan Hyam, you can do so directly via his Top Doctors profile.