Deep Brain Stimulation (DBS)
Intro ECT TMS MST VNS Neurosurgery
Deep brain stimulation has been used to treat Parkinson’s disease since 1987. In psychiatry, it is still in an investigational stage; but has been approved in the USA to treat obsessive-compulsive disorder. It is a refined alternative to psychosurgery and involves the use of an electrical stimulus on a specific target in the brain[1]. It’s superiority to psychosurgery remains to be scientifically proven.
The structures targeted in DBS vary- depending on the psychiatric condition to be treated. An area of the brain called the subgenual cingulate cortex is believed to be overactive in depression. DBS to this area can reduce the elevated activity [2]. Additional targets are continuously being developed and the optimum site for stimulation remains unclear.
DBS is invasive but reversible (Unlike psychosurgery that is permanent). Under local anaesthetic, holes are drilled in the skull. The brain itself has no pain receptors and so the patient does not feel pain. A special framework is placed on the head. Guided by the framework and using MRI scanning, the electrodes are surgically implanted in the brain. The patient is awake and can provide feedback to the surgeon. Once the electrodes are implanted, the patient is given a general anaesthetic. A stimulator (similar to the ones used for VNS) is then implanted in the chest and this is connected by leads to the electrodes in the brain. The stimulator has a life span of up to 4-5 years. The stimulation parameters are customised to the patient- adjusted by a clinician using a hand- held device. Stimulation is constant.
The patient must be capable of giving informed consent for DBS to be carried out. A multidisciplinary team is essential, as is long term follow up. Although the mechanism of action of DBS is unclear- it is believed that electric pulses reset the area of the brain that is malfunctioning. Various chemicals (neurotransmitters) are released, and DBS alters the blood flow to the brain.
Surgical side effects [3] include: infection, bleeding in the brain, stroke and electrode damage. Stimulation side effects include movement disorders, numbness, and tingling sensations in parts of the body, difficulty with speech, visual disturbances, fear, agitation, over-elated mood and the risk of suicide. More studies are needed to determine if personality and cognitive function are affected. If the side effects become severe- the electrodes can be blocked to cease treatment and the hardware can be removed.
Several small-scale studies on DBS have been carried out. Only a few have been of a high quality including a treatment group and a control group which did not receive DBS. Two randomised control trials in depression have failed [4, 5]. More trials and further research are essential.