【Learning Key Points】

1. Indications for Gamma Knife stereotactic radiosurgery (SRS) include intracranial arteriovenous malformations (AVMs), meningiomas, pituitary tumors, metastatic brain tumors, and other selected intracranial lesions.
2. Gamma Knife stereotactic radiosurgery is generally not recommended for lesions larger than 4 cm.
3. After treatment, if you experience sudden severe headache, vomiting, seizures, altered consciousness, or other acute neurological symptoms, seek emergency medical attention immediately.

I. Introduction

Gamma Knife stereotactic radiosurgery is a highly precise, minimally invasive treatment that uses a stereotactic head frame together with brain magnetic resonance imaging (MRI) or computed tomography (CT) for three-dimensional localization of the target lesion.

Gamma Knife treatment uses multiple beams of gamma radiation generated by cobalt-60 sources. The beams are directed from multiple angles and converge precisely on the target at the center of the hemispherical unit, delivering radiation to the brain lesion while minimizing radiation exposure to surrounding normal brain tissue.

Gamma Knife stereotactic radiosurgery is generally not recommended for lesions larger than 4 cm.

II. Indications

Gamma Knife stereotactic radiosurgery may be used for selected patients with:

• Intracranial arteriovenous malformations (AVMs)
• Meningiomas
• Pituitary tumors
• Metastatic brain tumors
• Trigeminal neuralgia and other selected conditions that are not suitable for conventional surgery or other standard treatment options.

The final treatment decision depends on the patient's condition, lesion characteristics, and physician's assessment.

III. Preoperative Precautions

1. Complete and sign the surgical consent form and the consent form for brain MRI or CT. Patients who require cerebral angiography must also complete and sign the angiography consent form.
2. Undergo preoperative examinations as indicated by the physician, such as an electrocardiogram (ECG), chest X-ray, and blood tests, including biochemical tests, complete blood count, or coagulation studies.
3. Women of childbearing potential are advised to undergo a urine pregnancy test to confirm that they are not pregnant.
4. The procedure is performed under local anesthesia, so a routine pre-anesthesia evaluation is generally not required.
5. For patients undergoing cerebral angiography, the perineal hair may be shaved by the nursing staff as instructed by the physician.
6. Wash your hair one day before the procedure and keep it clean. Do not apply hair oil, hair gel, or other hair products.
7. Follow the physician's instructions regarding whether fasting and fluid restriction for 6–8 hours are required.
8. MRI is performed in a strong magnetic field. For your safety, inform the healthcare team in advance if you have any implanted metallic devices, metal objects, or a cardiac pacemaker.
9. On the day of the procedure, the nurse will assist with insertion of a peripheral intravenous (IV) catheter. Change into a hospital gown. Do not wear clothing or accessories containing underwire, metal fasteners, zippers, or metal hair accessories. Remove removable dentures if present. You may be transported to the Gamma Knife treatment room by wheelchair at the scheduled time.
10. If cerebral angiography is required, the peripheral IV catheter will be inserted in the left arm, and you should remove your underwear on the day of the procedure.

IV. Intraoperative Procedures

You will generally remain awake during the procedure. The treatment process basically consists of four steps:

1. Placement and fixation of the stereotactic head frameThe stereotactic head frame is securely fixed to the patient's head to provide precise three-dimensional localization, which helps ensure the accuracy and safety of the procedure.
2.  Brain imaging and target localization MRI, CT, and/or cerebral angiography may be performed to determine the exact location and size of the lesion.
3. Three-dimensional computerized treatment planning A computer is used to perform three-dimensional treatment planning and dose calculations so that the prescribed radiation dose can be precisely focused on the target lesion.
4. Gamma Knife radiosurgery During gamma radiation treatment, you generally will not feel pain from the radiation itself. The treatment may take approximately several tens of minutes to several hours, depending on the lesion and the prescribed radiation dose.

V. Postoperative Care

1. After returning to the ward, the head-frame pin sites will be covered with sterile adhesive strips, gauze, and an elastic bandage to provide compression and help control bleeding. Observe the sites for bleeding and notify the healthcare staff immediately if abnormal bleeding occurs.
2. If the gauze or elastic bandage becomes loose due to movement but there is no bleeding, re-covering the area with additional gauze may not be necessary unless otherwise instructed.
3. Observe for nausea, vomiting, pain at the pin sites, bleeding, or other discomfort. Notify the healthcare staff if any symptoms occur.
4. For patients who also undergo cerebral angiography:
   1. A sandbag may be placed over the groin puncture site for compression and hemostasis. According to the physician's instructions, patients generally need to remain supine with compression for approximately 6 hours and rest in bed for approximately 12 hours. Observe the puncture site for bleeding.
   2. Monitor your ability to urinate. Notify the healthcare staff if you have difficulty urinating.
5. If there are no complications and you are considered suitable for discharge, the physician may prescribe pain medication for use at home. If the head-frame pin sites become painful, take the medication according to the prescription instructions.
6. Do not wash your hair immediately after returning home. Apply antibiotic ointment to the head-frame pin sites as instructed by the healthcare team. After approximately 2–3 days, once the skin has healed, you may wash your hair as instructed.
7. Return for regular follow-up appointments and imaging examinations according to the physician's instructions.
8. If you develop sudden severe headache, vomiting, seizures, altered consciousness, or other significant neurological symptoms, seek emergency medical attention immediately.

VI. Conclusion

Gamma Knife stereotactic radiosurgery is a precise, minimally invasive treatment option for selected intracranial lesions. It may be used for various conditions, including intracranial arteriovenous malformations, meningiomas, pituitary tumors, and metastatic brain tumors. It is generally not recommended for lesions larger than 4 cm.

Patients should follow instructions regarding preoperative examinations, stereotactic localization, postoperative wound care, activity restrictions, and regular follow-up to support treatment effectiveness and reduce the risk of complications.

After returning home, if you develop sudden severe headache, vomiting, seizures, altered consciousness, or other acute neurological symptoms, seek emergency medical attention immediately to ensure timely evaluation and treatment.

VII. Reference

Bin Sumaida, A., Shanbhag, N. M., & Balaraj, K. (2024). Evaluating the efficacy and safety of CyberKnife for meningiomas: A systematic review. Cureus, 16(3), e56848. https://doi.org/10.7759/cureus.56848