Recently hailed by some sections of the media as the, ‘brain pacemaker for depression', deep brain stimulation continues to show promising results in people with depression who are otherwise treatment-resistive. Such patients will almost inevitably have tried a variety of medications, alone or in combination, and electroconvulsive therapy with little or no therapeutic effect. It is estimated that up to 20 percent of people with depression fail to respond to standard treatments.
The search for a single brain region or neurological system to explain depression has not been fruitful. Research has instead focused more on depression as a disorder that involves different areas of the brain and different neurotransmitters. Functional neuroimaging studies have had an important role in identifying pathways that may be involved in depression. Studies have shown one area of the brain known as the subgenual cingulate region (Brodmann area 25) as having an active role in acute sadness, depression and the antidepressant treatment effects.
It is estimated that over 40,000 people worldwide achieve symptom relief from Parkinson's disease as a direct result of deep brain stimulation. Parkinson's sufferers have an electrode positioned in an area of the brain known as the thalamus. A tiny electrical pulse that can be varied according to need is then sent down a cable usually located just beneath the clavicle (collar bone). This results in a disruption of overactive cells that would normally result in tremors.
In one study into the effects of the surgical procedure on depression, Helen S. Mayberg, M.D., professor of psychiatry neurology of the University of Toronto, reports patients spontaneously experiencing, "sudden calmness or lightness," "disappearance of the void," a sense of "connectedness" and sudden brightening of the room, including a description of the sharpening of visual details and intensification of colors (p.652).
Not all patients respond to deep brain stimulation and so far the technique remains in a very experimental stage. Dr Helen Mayberg of Emory University has implanted approximately 50 depression patients. She estimates that four out every six show sufficient improvement to be regarded as responsive to treatment.
The mechanisms and action of deep brain stimulation remain something of a mystery. However, what is known is that stimulation produces a positive and often marked clinical effect in terms of depression relief. More investigation is needed to establish whether all people with treatment-resistive depression are candidates for deep brain stimulation.
The technique itself is invasive and not without the associated risks of internal bleeding or infection. Furthermore, as not all patients respond positively, it may mean that screening needs to be established as to which patients should undertake the risk of surgery, or it may mean that other areas of the brain need targeting.