Gamma Knife radiosurgery for obsessive compulsive disorder.

Gamma Knife radiosurgical capsulotomy has been performed for over 40 years as a rarely used surgical intervention for the treatment of obsessive-compulsive disorder. Over time, the procedure has evolved in many ways with most significant modifications being made in target location, number of isocenters and prescribed dose, subsequently producing changes in lesion size and geometry. Long-term clinical response data and adverse outcomes to the earlier empiric treatment parameters have resulted in shifting the target from its initial location within the midpoint of the anterior limb of internal capsule to a currently used point that includes its most ventral portion as well as the ventral striatum. This led to the contemporary Gamma Knife ventral capsulotomy procedure that focuses on ventral capsule/ventral striatum. Many of the early studies, despite demonstrating efficacy in some patients, were complicated by clinically relevant radiation-induced adverse effects. More recent studies have demonstrated strong efficacy with diminished adverse effects with well-placed lesions created at lower radiation doses. Advances in neuroimaging technology such as diffusion tensor imaging (DTI) based fiber tracking may provide further insight into precisely targeting of the ventral capsule/striatum based on patient-specific variations in white matter connectivity.