Functional neurosurgery in the treatment of severe obsessive compulsive disorder and major depression: overview of disease circuits and therapeutic targeting for the clinician.

Over the past 20 years, there has been a concerted effort to expand our understanding of the neural circuitry involved in the pathogenesis of psychiatric disorders. Distinct neuronal circuits and networks have been implicated in obsessive compulsive disorder (OCD) and major depressive disorder (MDD) involving feedback loops between the cortex, striatum, and thalamus. When neurosurgery is used as a therapeutic tool in severe OCD and MDD, the goal is to modulate specific targets or nodes within these networks in an effort to produce symptom relief.Currently, four lesioning neurosurgical procedures are utilized for treatment refractory OCD and MDD: cingulotomy, capsulotomy, subcaudate tractotomy, and limbic leucotomy. Deep brain stimulation (DBS) is a novel neurosurgical approach that has some distinct advantages over lesioning procedures. With DBS, the desired clinical effect can be achieved by reversible, high frequency stimulation in a nucleus or at a node in the circuit without the need to produce an irreversible lesion. Recent trials of deep brain stimulation in both OCD and MDD at several neuroanatomical targets have reported promising early results in highly refractory patients and with a good safety profile. Future definitive trials in MDD and OCD are envisaged.