Other neurosurgical interventions for treatment-resistant depression

Introduction

The use of somatic interventions to control or treat mental symptoms dates back to ancient times ( ; ; ). Evidence for burr holes drilled into the skull to “cure the demons” goes back to the Neolithic age. The notions that convulsions and fever may help mental disorders have been known since Hippocrates, while in medieval times, make-believe surgeries were performed to extract the “stone of madness.”

In the 17th century, Descartes hypothesized that the ventricles were the reservoir of vital fluids and basis for the rational mind. This deemphasized the brain’s role. Conversely, modern somatic treatments for mental illness are rooted in the conceptualization that neural tissue is responsible for behavior. This started in 1796, when Gall proposed that different brain regions were responsible for different functions, a system he called phrenology. Although this notion was revolutionary and would prove essential to our current understanding of brain function, he and his followers were later involved in pseudoscience and contributed little to the functional neuroanatomy of the mind ( ).

Almost a decade later, modern scientific conceptualization of brain functions and localizations began to emerge from animal experiments, cadaver dissections, and clinical observations conducted by , , and others. Also, the notion of neuronal transmission based on electrochemical signals replaced the 19th century hydraulic neuronal transmission model ( ). These ideas of regional brain functional localization and electrochemical neuronal transmission would later evolve into the contemporary neuronal network models that guide and inform much of the current applications of somatic treatments in disorders such as obsessive compulsive disorder and depression. As the biological underpinnings of the complexity of the mind are still being worked out, current somatic interventions are being used both for understanding the neurobiology of mental illness as well as for treating disease ( ).

Treatment-resistant depression (TRD) patients have long lasting depressive episodes, are prone to frequent relapses and have limited treatment options ( ). They are unable to effectively situate themselves in relation to others, to control negative emotions and divert attention from negative experiences to cope with daily life. They present us with major clinical and socioeconomic challenges with cost estimates exceeding $44 billion ( ). A better understanding of the functional neuroanatomy of mood regulation and socialization will lead to optimal and effective treatments. The success rate with pharmacological treatments for TRD is low ( ). Even after achieving relief from depressive symptoms, 35%–70% will relapse often precipitated by medication poor compliance or discontinuation of therapy. These patients become more vulnerable to stress ( ) and the course of their illness worsens leading to longer episode durations and shorter interepisodes periods in between. Brain stimulation therapies (BSTs) directly modulate brain function and regulate mood. Each presents with unique characteristics that define its role in the TRD therapeutic landscape. These various therapies have been discussed in more details in previous chapters (ADD number for chapters on ECT, MST, rTMS, tDCS, VNS, and DBS respectively). This chapter will discuss the current applications of other neurosurgical procedures not otherwise discussed, focusing on prefrontal cortical stimulation (PCS) and neurosurgery for psychiatric conditions.

PCS: The over simplification of the functional neuroanatomy of mood regulation may lead to missed opportunities in treatment development