Depression and neurosurgery: past, present, and future.

Neurosurgery has been used to treat depression since 1935, when open surgery was first used to isolate relatively large areas of the limbic system from the rest of the brain. Soon thereafter, more selective leucotomies were performed based on a growing knowledge of the role played by brain limbic circuitry in processing the emotions. Subsequent discovery of the effectiveness in depression of both electroconvulsive therapy and various pharmacotherapies raised serious doubts about "psychosurgical" treatments, but the introduction of stereotactic techniques revived interest in the selective-lesion, neurobiology-based approach. However, neurosurgery has only come to be regarded as an appropriate treatment of severe depression since Benabid introduced the frequency-dependent chronic electric stimulation technique. Because of its nondestructive nature, this procedure will undoubtedly be favored in the future. One can anticipate that, eventually, frequency-dependent chronic electric stimulation will be complemented by newer techniques such as microdialysis and reverse dialysis, with concomitant functional magnetic resonance imaging and/or positron emission tomography scanning, and the use of chemodes for microinfusion or for in situ insertion of reactivated-stem cells. To optimize success, these modern methods will require a new taxonomy of "depressions" based on up-to-date neurobiological criteria.