IMPORTANCE Select cases of intractable obsessive-compulsive disorder (OCD) have undergone neurosurgical ablation for more than half a century. However, to our knowledge, there have been no randomized clinical trials of such procedures for the treatment of any psychiatric disorder.OBJECTIVE To determine the efficacy and safety of a radiosurgery (gamma ventral capsulotomy [GVC]) for intractable OCD. DESIGN, SETTING, AND PARTICIPANTSIn a double-blind, placebo-controlled, randomized clinical trial, 16 patients with intractable OCD were randomized to active (n = 8) or sham (n = 8) GVC. Blinding was maintained for 12 months. After unblinding, sham-group patients were offered active GVC.INTERVENTIONS Patients randomized to active GVC had 2 distinct isocenters on each side irradiated at the ventral border of the anterior limb of the internal capsule. The patients randomized to sham GVC received simulated radiosurgery using the same equipment. MAIN OUTCOMES AND MEASURESScores on the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) and the Clinical Global Impression-Improvement (CGI-I) Scale at 1 year. Response was defined as a 35% or greater reduction in Y-BOCS severity and "improved" or "much improved" CGI-I ratings.RESULTS Two of 8 patients randomized to active treatment responded at 12 months, and none of the 8 sham-GVC group patients responded (the absolute difference was not statistically significant: 0.25; 95% CI, Ϫ0.05 to 0.55; P = .11). At 12 months, median Y-BOCS scores were 23.5 in the active group vs 31 in the sham patients (P = .01). The median Y-BOCS scores decreased 28.6% in the active treatment group and 5.8% in the sham group (P = .04988). The median CGI-I scores were 3 and 4 in the active and sham treatment groups, respectively. At 54 months, 3 additional patients in the active group had become responders. Of the 4 sham-GVC patients who later received active GVC, 2 responded by post-GVC month 12. The most serious adverse event was an asymptomatic radiation-induced cyst in 1 patient. CONCLUSIONS AND RELEVANCEIn this preliminary trial, patients with intractable OCD who underwent GVC may have benefitted more than those who underwent sham surgery although the difference did not reach statistical significance. Additional research is necessary to determine if GVC is better than deep-brain stimulation.TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01004302

Gamma Knife ventral capsulotomy is an effective radiosurgical procedure for many treatment-refractory OCD patients. A minority of patients developed cysts at long-term follow-up, 1 of whom had permanent neurological sequelae.