Gamma Knife Radiosurgery — How It Works, Benefits & Recovery — Procedure Guide, Recovery & Risks | MyMedicPlus

Gamma Knife radiosurgery (GKS), trademarked by Elekta, is a form of stereotactic radiosurgery (SRS) that delivers precisely focused beams of gamma radiation from one hundred and ninety-two to two hundred and one cobalt-60 radioactive sources arranged in a hemispheric array around the patient's head. Each individual beam carries a low dose of radiation harmless to the tissues it traverses, but all beams converge simultaneously at a precisely defined target point within the brain — producing an ablative dose of fifteen to twenty-five gray (Gy) at the isocenter while sparing surrounding brain tissue. The steep dose gradient at the field edge — dropping by fifty percent within approximately one to three millimetres of the target boundary — allows treatment of eloquent brain regions that would be inaccessible by conventional neurosurgery. The system achieves sub-millimetre targeting accuracy (approximately 0.3–0.5 mm), enabled by rigid fixation of a stereotactic frame to the skull under local anaesthesia (or a relocatable frameless mask for fractionated treatments) and high-resolution MRI, CT, and angiography for target localisation. Despite the name, Gamma Knife does not involve surgical incision — it is entirely non-invasive. Treatment is delivered in one or more sessions (fractions) and is performed in dedicated radiosurgery units by a multidisciplinary team of neurosurgeons, radiation oncologists, and medical physicists.

Gamma Knife radiosurgery is appropriate for a defined set of intracranial lesions where the target is small enough (typically below three to four centimetres in maximum diameter), located in an eloquent or surgically inaccessible region, or where the patient's general health or personal choice makes open neurosurgery undesirable. Primary intracranial indications include: vestibular schwannoma (acoustic neuroma) — the most common benign brain tumour treated with GKS, where it provides excellent tumour control without the morbidity of microsurgery; brain metastases from systemic cancer, particularly one to four lesions (limited metastatic disease) in good performance status patients where whole brain radiotherapy carries higher neurocognitive toxicity; cerebral arteriovenous malformations (AVMs) — vascular tangles not amenable to safe microsurgical resection due to location in the brainstem, thalamus, or other eloquent areas; meningiomas as primary treatment for small lesions or after incomplete surgical resection; trigeminal neuralgia refractory to carbamazepine and other medications; pituitary adenomas as adjuvant therapy after surgery or as primary treatment for small functioning tumours; and cavernous malformations with recurrent haemorrhage in eloquent locations. Functional indications such as essential tremor and refractory epilepsy (using Gamma Knife thalamotomy or hippocampal radiosurgery) are performed at select specialist centres.

Treatment begins on the day of the procedure. The stereotactic Leksell frame — four pins attached to the outer skull table under local anaesthesia (bupivacaine) — establishes a fixed reference coordinate system relative to the brain. Alternatively, frameless Gamma Knife ICON with cone-beam CT and optical surface guidance is used for fractionated treatments spanning multiple days, avoiding repeated frame application. High-resolution imaging is obtained with the frame in situ: gadolinium-enhanced MRI (one millimetre slice thickness), CT angiography or digital subtraction angiography (DSA) for AVM treatment, and CT for bone anatomy. Images are fused and uploaded to the Leksell Gamma Plan software. The multidisciplinary team — neurosurgeon, radiation oncologist, and physicist — delineates the target volume (GTV), defines organs at risk (optic nerves, chiasm, brainstem, cochlea), and creates a treatment plan specifying the prescription isodose, dose to organs at risk, and number and diameter of isocentres (collimator shots). The patient is positioned in the Gamma Knife unit with the frame attached to a robotic patient positioning system. Treatment delivery proceeds automatically, with each isocentre treated sequentially. Total radiation delivery time ranges from fifteen minutes to several hours depending on target complexity, source activity, and number of isocentres. The frame is removed and the patient discharged with dexamethasone to manage post-treatment oedema.

Gamma Knife radiosurgery achieves tumour control and vascular obliteration outcomes that rival open surgery for appropriately selected targets, without surgical incision, general anaesthesia, or prolonged hospitalisation. For vestibular schwannoma (acoustic neuroma), GKS achieves tumour control rates exceeding ninety-five percent at ten years (tumour stable or reduced in size), with hearing preservation in fifty to sixty percent of patients with serviceable hearing at treatment — superior to the hearing outcomes of microsurgery. Facial nerve function is preserved in over ninety-five percent of GKS cases compared to seventy to ninety percent after microsurgery. For brain metastases, local tumour control at twelve months is eighty to ninety percent per lesion, and SRS for one to four metastases extends median survival and preserves neurocognitive function compared to whole-brain radiotherapy alone. AVM obliteration — the definitive endpoint of AVM radiosurgery — occurs in seventy to eighty-five percent of AVMs less than three centimetres in maximum diameter at three-year angiography, eliminating the haemorrhage risk. For trigeminal neuralgia, initial pain relief (BNI score I–IIIa) is achieved in seventy to ninety percent of patients within weeks to six months. Meningioma five-year control rates for Grade I tumours exceed ninety percent after GKS. Treatment is outpatient, completed in one session, and patients return to normal activities within one to two days.

Gamma Knife radiosurgery is a generally well-tolerated procedure with significantly lower procedural morbidity than open neurosurgery for the same targets. Acute side effects on the day of treatment include headache from frame placement (managed with paracetamol), nausea, and scalp tenderness at pin sites. A short course of dexamethasone two to four milligrams twice daily for three to five days is prescribed to prevent or manage post-treatment cerebral oedema. Symptomatic radiation oedema causing temporary neurological deterioration (headache, focal deficits) occurs in five to ten percent of patients, usually at three to eight months, and responds to a corticosteroid course. Radiation necrosis — irreversible necrosis of treated and surrounding brain tissue — is the most serious late complication, occurring in one to three percent of patients. It may require surgical debulking in refractory cases. Specific target-related risks include hearing deterioration over two to five years in acoustic neuroma patients (occurring in fifteen to thirty percent who had serviceable pre-treatment hearing), facial numbness after trigeminal neuralgia radiosurgery (ten to twenty percent), and facial nerve palsy (less than one percent). AVM radiosurgery carries a latency period of two to three years before obliteration during which the AVM remains at risk of haemorrhage, and the annual bleeding rate in this period (three percent per year) must be weighed against the long-term obliteration benefit. The risk of secondary radiation-induced malignancy is extremely rare (below one in one thousand over twenty years) based on long-term follow-up data.

Gamma Knife patients are typically discharged home two to four hours after treatment completion. Pin site wounds from the stereotactic frame are cleaned and covered with small plasters; they heal within three to five days. Mild headache on the day of treatment is managed with paracetamol. Dexamethasone is prescribed for three to five days to prevent oedema, with a proton pump inhibitor for gastric protection. Patients may drive and return to work the following day in most cases. Restrictions on driving are not standard unless neurological symptoms are present. The treating team provides specific follow-up plans according to the indication: brain metastases are reassessed with contrast-enhanced MRI at six to eight weeks (to confirm early response), then every three months; acoustic neuromas require MRI at six months and annually thereafter; AVMs require contrast MRI at twelve and twenty-four months and catheter angiography at thirty-six months to confirm obliteration; meningiomas are followed annually with MRI. Trigeminal neuralgia patients are followed clinically with pain diary assessments. Patients should report any new or worsening neurological symptoms, severe headache, visual changes, or fever promptly, as these may indicate radiation oedema or treatment-unrelated pathology requiring assessment.