Arteriovenous Malformations
Gamma Knife surgery has proven highly effective in the treatment of AVMs. More than 15,000 patients have been treated since 1971.  The complete obliteration rate for AVMs (most of which were considered unsuitable for microsurgery) is over 80% with zero treatment mortality and minimal morbidity. This success rate underscores the importance of Gamma knife treatment as an alternative to microsurgery.

Multiple studies show that the clinical efficacy and the non-invasive procedure makes it advantageous for patients medically unable or unwilling to undergo conventional  open surgery.The non-invasive nature of the Gamma Knife treatment also helps when treating centrally located lesions and those close to critical structures such as the brain stem.

Acoustic Neuromas
 

Acoustic Neuroma Before and after 18 months

Significant success has been achieved in the treatment of acoustic neuromas with Gamma Knife since the first statement in 1969 by the late Professor Lars Leksell in Sweden.  Several published studies indicate effective management of acoustic neuromas while still preserving cranial nerve function. According to a recent study, a permanent growth control rate after Gamma Knife surgery 80% was achieved with facial nerve function preservation of nearly 100% and preservation of serviceable hearing of approximately 70%.

With enhanced diagnostic imaging techniques, a growing number of previously undetected acoustic neuromas are being identified.In addition, noteworthy studies indicate that most of these tumours enlarge within 1 to 2 years.

The challenge is to treat these tumors totally while preserving full cranial nerve function and hearing.  Results in a study by the University of Pittsburgh, comparing microsurgery with Gamma knife surgery, indicate the open microsurgery is associated with a greater incidence of pre-operative or delayed facial dysfunction and a decreased rate of preservation of the preoperative level of serviceable hearing compared to Gamma Knife. This further indicates the importance of Gamma Knife surgery for acoustic neuroma patients.

Metastases
It is currently estimated that around 20-30% of all patients harbouring malignant disease develop metastases to the brain.The established treatment modality for cerebral metastases has been craniotomy and whole brain radiation therapy.The convenience and efficacy of Gamma Knife procedures, however, has given rise to an increasing use of this treatment for both single and multiple metastases.Excellent results have been achieved with the Gamma Knife, even for such traditionally radioresistant tumours as melanoma.

Meningiomas
Although the accepted first line of treatment for meningiomas is microsurgical removal, Gamma Knife surgery is being increasingly used as a valuable adjunct, particularly in cases of subtotal tumours removal.

For example, morbidity from intracavernous surgery may be markedly decreased by planning in advance for a less aggressive intracavernous surgical resection followed by delayed radiosurgery to the intracavernous tumour residua.
Additionally, Gamma Knife surgery can result in a significant reduction in recurrence rates and prevents reoperation in up to 67% of patients with relatively low complication rates.This includes tumours close to important structures such as the brain stem and cranial nerves.

Functional Disorders
Success of area of treatment of Trigeminal Neuralgia, Parkinson's disease has been noteworthy.Patient Childhood Disintegrative Psychosis with marked Akathesia & Obsessive Compulsive disorder have also been effectively treated.

Expanding Indications The array of vascular malformations and tumors currently treated with Gamma Knife surgery is continuing to grow.As the ability to better visualize brain abnormalities and functional disorders increases through advances in diagnostic imaging and functional mapping of the brain, applicable 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 expanding role in neurosurgery. Treatment for Parkinson's disease, trigeminal neuralgia, epilepsy, uveal melanomas and intractable pain are just a few of the ongoing research areas.