New Somatic Treatments
Coincident with the considerable advances in clinical research aimed at optimizing the use of ECT, the past decade has also witnessed renewed interest in the development of new somatic, nonpharmacologic interventions for mental disorders, particularly depression. Ongoing research supports the antidepressant efficacy of repetitive transcranial magnetic stimulation (rTMS) (Holtzheimer et al., 2001). These and other related interventions stimulate the brain in manners less direct but more focused than does ECT. In contrast to the application of an electrical stimulus to the scalp, as in ECT, a more precisely localized electrical current can be produced within the brain by pulsing a magnetic wave (generated through a coil on the head), which passes undistorted through the skull. A train of TMS pulses, delivered to the left prefrontal cortex repeatedly but at a subconvulsive rate up to 20 minutes/day to an awake and alert patient, has demonstrated antidepressant efficacy in several small open and sham-controlled trials. To date, antidepressant effects have been relatively modest, and few patients have been medication free or followed systematically beyond a 1- or 2-week rTMS treatment trial.
Vagus nerve stimulation (VNS) has been used as an effective treatment of refractory seizure disorders, and now is showing promise as an antidepressant intervention. VNS is now approved by the US Food and Drug Administration for selected cases of depression. The afferent connections of the left vagus nerve with locus coeruleus, dorsal raphe and limbic structures have been im-plicated in the putative antidepressant effect of this intervention.
An initial surgical procedure is required for implanta-tion of a small pacemaker-like stimulus generator beneath the clavicle, with an attached lead wrapped around the left vagus nerve in the neck. The generator can be programmed automati-cally to deliver a fixed duration of vagus nerve stimulation, for example 30 seconds of stimulation every 5 minutes. Many pa-tients notice physical concomitants of vagal stimulation, such as coughing or hoarseness (Sackeim et al., 2001b). While this may defeat the masking of no-stimulation programming as a control condition in research studies, the intervention otherwise appears well tolerated. In the event of disturbing adverse effects, a magnet held over the stimulus generator will abort a stimula-tion. Safety experience thus far with seizure disorder patients has been satisfactory; stimulation of the left vagus nerve has no cardiac effects.