Tuesday, February 26, 2008

Deep brain stimulation for treatment-resistant depression

Mayberg et al. (March 3, 2005). Deep brain stimulation for treatment-resistant depression. Neuron, Vol. 45, 651-660.

This experiment exposed a small sample of six people with treatment-resistant depression to deep brain stimulation (DBS) in the subgenual cingulate region (BA25), known to be a critical region for modulating negative mood states, and showing elevated activity in these refractory patients.

Acute effects of stimulation included sudden mood change (reduced negative and increased positive scores), as well as improvements in interest and activity level. Upon continued use, sleep patterns were among the first of the normalized symptoms, followed by increased energy, interest and pleasure in social activity, decreased apathy and anhedonia, and improved planning abilities. Upon discontinuation of chronic treatment, mood improvements tended to persist, whereas cognitive aspects of depression (e.g. poor concentration, apathy) did not, perhaps indicating differential effects on different connected systems.

These results, showing a sustained remission of depression in four out of six patients who previously failed to respond to medications, psychotherapy, and ECT, still warrant further investigation (for starters, a larger sample size) but do favor a positive interpretation of the efficacy of DBS for people with refractory depression. With its connections to brainstem, hypothalamus, and insula (read: sleep, appetite, libido, and neuroendocrine effects) and reciprocal pathways to the orbitofrontal/medial prefrontal cortices and the anterior and posterior cingulate cortices (read: influences on learning, memory, reward, and motivation), this study also sheds light on the subgenual cingulate region as a critical node of a distributed mood-regulatory network involved in major depression.

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