Functional Neurosurgery - A Future for the Gamma Knife?

Abstract

The Gamma Knife is currently the only radiosurgical device which has been used in functional neurosurgery. This mode of utilization is possible because the instrument can make lesions in normal brains with a volume as small as 50 mm³. The experience of functional radiosurgery accumulated at the Karolinska Institute over 21 years is reviewed, and the possible implications of the new developments in imaging techniques for the future of functional radiosurgery are considered. The review Covers gamma thalamotomy for pain and tremor, radiosurgery for trigeminal neuralgia, gamma capsulotomy for severe anxiety and obsessive-compulsive neurosis, and Gamma Knife surgery for focal epilepsy. The important role of stereotactic MRI localization in functional radiosurgery is pointed out, and a preliminary report of the recent experience with stereotactic magnetoencephalography combined with stereotactic MRI for physiological and anatomic target localization is given. It is concluded that functional radiosurgery should only be performed with radiation of very small volumes of brain, as the very high doses required would be devastating if delivered to even small volumes.

A successful case of multiple stereotactic radiosurgeries for ipsilateral recurrent trigeminal neuralgia

“…Previously, studies utilizing targeting of the trigeminal ganglion had very poor rates of pain relief and mild success rates. 5,16,28 The belief behind targeting the root entry zone is that this area involves a transition zone in the axons from peripheral to central myelin, which in theory is believed to be more susceptible to radiation. 33 Several articles have documented histopathological evidence of axonal degeneration and fibrosis after GKRS.…”

Stereotactic radiosurgery for functional disorders

“…The first reports of using GKS in the treatment of tremor were published in the early 1990s, when Rand et al 51 in the United States, Lindquist and colleagues 35 in Europe, and Ohye et al 44 in Japan described their experiences. The positive findings of these groups have since been duplicated at numerous treatment centers around the world.…”

“…The estimated target doses were 16.5-22 Gy. Several years later, Lindquist et al 35 and Rand et al 52 reported on their patients with tic doloreux treated with radiosurgery to the Gasserian ganglion. Because the results were inconsistent, the authors concluded that other targets should be considered.…”

“…34 After 7 years' follow-up, 5 patients reported long-term benefits. 35 Further treatments were performed at the Karolinska Institute in Stockholm starting in 1988, first by using the 8-mm collimator and later-because of excessive lesion sizes-with the 4-mm collimator. 25 Long-term follow-up 17 years after treatment of OCD with bilateral radiosurgical anterior capsulotomy at maximum doses of 120-180 Gy has been reported.…”

“…Radiosurgery as a possible tool to treat OCD was introduced in the 1990s, encouraged by some positive reports from the Karolinska Institute. 24,35,39 Because there are significant ethical concerns and organizational issues associated with the treatment of such patients, 19 we have offered this treatment exclusively to an extremely treatment-refractory group of patients who were selected by a team of psychiatrists as part of a strict research protocol. At our own institution we continue to provide radiosurgical treatment for OCD to a small group of very treatment-resistant patients as part of an ongoing open-label research study.…”