What Gamma Knife Treats: The Conditions Radiosurgery Is Used For

Gamma Knife treats a defined set of targets inside the skull: acoustic neuromas, meningiomas, brain metastases, arteriovenous malformations, trigeminal neuralgia and pituitary tumours. It suits targets that are small enough, generally 3 to 3.5 cm or less, and clearly seen on a scan, and the decision to use it is made by a team looking at your imaging rather than by preference¹.

When I was first told my acoustic neuroma could be treated this way, my next question was the obvious one: what else does it treat, and does that tell me anything about how well it might work for me? This is the overview I put together. For the full picture of the treatment itself, start with Gamma Knife radiosurgery, and for how suitability is judged, see am I a candidate for Gamma Knife.

Benign tumours

Gamma Knife is a mainstay for small benign tumours, where control rates are high but the tumour changes slowly over years. These are the conditions where radiosurgery most often replaces or delays open surgery:

• Acoustic neuroma (vestibular schwannoma): a benign tumour on the balance and hearing nerve, controlled in roughly 90 to 99% of cases at 5 years with a margin dose of about 12 to 13 Gy. See Gamma Knife for acoustic neuroma and hearing after Gamma Knife.
• Meningioma (benign, grade I): a tumour of the lining of the brain, with 5-year local control of roughly 85 to 100% at 12 to 16 Gy. Control is much lower for the rarer grade II and III forms. See Gamma Knife for meningioma.
• Pituitary adenoma: a tumour of the pituitary gland, with tumour control over 90%; for hormone-producing types, bringing the hormone levels back to normal is slower. See Gamma Knife for pituitary adenoma.

For how these fit into the wider tumour picture, benign and malignant, see Gamma Knife for brain tumours.

Cancer that has spread to the brain

Brain metastases are one of the biggest uses of Gamma Knife, with 1-year local control of roughly 70 to 90% depending on the dose. For a limited number of metastases, focused radiosurgery is often chosen over whole-brain radiotherapy because it treats each deposit while sparing the rest of the brain, which protects memory and thinking². See Gamma Knife for brain metastases and, where there are several, Gamma Knife for multiple brain metastases. The choice between the two approaches is set out in Gamma Knife versus whole-brain radiotherapy.

Blood-vessel malformations

Gamma Knife treats arteriovenous malformations (AVMs) by gradually closing the abnormal vessels, with obliteration of roughly 65 to 90% over a latency of 2 to 3 years. An AVM is a tangle of arteries and veins that carries a risk of bleeding, and radiosurgery is one way to seal it without opening the skull. The catch is the wait: the malformation closes slowly, and the bleed risk falls over that time rather than at once³. See Gamma Knife for AVM and the latency period after AVM radiosurgery.

Facial pain: trigeminal neuralgia

For trigeminal neuralgia, Gamma Knife targets the trigeminal nerve and eases the severe facial pain in roughly 70 to 90% of people, over a median of about 2 months. It is the only trigeminal treatment with a built-in wait before relief, and the pain can return over the years, so it is one option among several. See Gamma Knife for trigeminal neuralgia.

What Gamma Knife is not used for

Gamma Knife is not the answer for large targets, for tumours causing pressure that must be relieved quickly, or where a tissue diagnosis is needed. Much above 3 to 3.5 cm, a single session cannot dose the target safely, so surgery or a course split over several sessions is preferred. If the target is pressing dangerously on the brain, or the team needs a sample to know exactly what it is, surgery does what radiation cannot. The trade-offs are compared in Gamma Knife versus surgery and, for slow-growing tumours that may not need treating yet, watch and wait versus Gamma Knife.