An ever-increasing number of indications have been treated using the Gamma Knife. Published reports indicate a tumor control rate of 90% and total obliteration rates of approximately 80% for AVMs over a period of two years. Outstanding results have made Gamma Knife the premier choice for an increasing number of patients. With the Gamma Knife, surgeons can treat lesions near critical structures that may be otherwise contraindicated for conventional surgical procedures.

Arteriovenous Malformations
Numerous studies show that Gamma Knife surgery has high clinical efficacy and a significantly reduced morbidity rate compared with microsurgical techniques in the treatment of arteriovenous malfunctions.

This is a non-invasive and effective strategy for grades I and II AVM patients. It is often the treatment of choice for those medically unable or emotionally unwilling to undergo conventional surgery. Gamma Knife surgery has also demonstrated its usefulness in treating AVMs close to critical brain structures, such as the brain stem.

Cavernous Malformations
(CMs) should be differentiated from arteriovenous malformations (AVMs) While with an AVM, a high pressure artery can be seen directly "feeding" a low pressure vein, in a CM, no such "feeding" supply can be identified. As such, CMs are "angiographically occult" or cannot be seen via an arterial angiogram. While most CMs are not clinically apparent, occasionally they cause a seizure or bleed. Once a CM has bled, the risk of a second bleed into the brain goes up substantially.

The first line therapy for CMs requiring treatment is micro surgery. Reports describing the use of Gamma Knife radiosurgery are conflicting both with regard to efficacy and toxicity. As such, Gamma Knife radiosurgery is not a standard treatment, but may be considered on a case-by-case basis.

Trigeminal Neuralgia
Trigeminal neuralgia was one of the first conditions successfully treated by the Gamma Knife. Initially the treatment target was the gasserian ganglion, however with the advancement of MRI and CT the treatment target is now the trigeminal root entry zone. The success rate has been very high and Gamma Knife SRS is now the leading form of non-medical treatment.

Acoustic Neuromas
Gamma Knife surgery combined with a multiple isocenter technique has proved highly effective in managing progressive acoustic neuromas while preserving cranial nerve functions. A major study shows tumor stabilization or reduction rates of 94% while other studies have shown favorable preservation rates of auditory, facial and trigeminal nerve functions.

Meningiomas
Gamma Knife surgery has demonstrated its value as an adjunct to sub-total microsurgical removal. The post-microsurgical use of the Gamma Knife can allow for a less aggressive intracavernous surgical resection with very successful results.

Metastases
Excellent results have been reported for the reduction or disappearance of these tumors with Gamma Knife surgery, even in traditionally radio-resistant tumors such as melanomas. Gamma Knife surgery has proved to be an effective management strategy for both solitary and multiple cerebral metastases.

Essential Tremor
Essential tremor, or movement disorder, typically involves a tremor of the arms, hands or fingers but sometimes involves the head or other body parts during voluntary movements such as eating and writing. Essential tremor is commonly described as an action tremor (it intensifies when one tries to use the affected muscles) rather than a resting tremor. Rigidity, such as is seen in Parkinsonís, is usually not included among its symptoms. Tremors on the left side of the body are caused by overactive brain cells in the right thalamus and vice versa. Only a small part of the thalamus, called the ventral intermediate nucleus (VIM) is the cause of the tremor. The Gamma Knife targets the cells of the ventral intermediate nucleus (VIM) in the thalamus with such precision that it minimizes the risk of radiation to nearby normal parts of the brain.

Expanding Indications
The range of vascular malformations and tumors currently treated with the Gamma Knife continues to grow. As the ability to better visualize brain anomalies and functional disorders improves through advances in diagnostic imaging and functional mapping of the brain, applications for the Gamma Knife will continue to expand. The uniformity and specificity of the Gamma Knife coupled with its unique non-invasive approach makes it particularly appropriate for an increasing role in neurosurgery.