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.
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