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TITLE:
[Are convulsions necessary for the antidepressive
effect of electroconvulsive therapy: outcome of repeated transcranial magnetic
stimulation]
AUTHOR:
Post RM; Kimbrell TA; McCann U; Dunn RT; George
MS; Weiss SR
AUTHOR AFFILIATION:
NIMH, Bethesda MD 20892-1272, USA.
SOURCE:
Encephale 1997 Jun;23 Spec No 3:27-35
NLM CIT. ID:
97406677
ABSTRACT:
Sismotherapy (ST) brings about numerous
neurobiological changes, particularly changes in neuromediators and their receptors,
second messengers, neuropeptides and neurotropic factors, a number of which are
hypothesized to play a role in the pathophysiology or therapeutics of affective disorders
(M. Fink). What is not yet known is which of these mechanisms is crucial for the
psychotropic and anticonvulsant effects of ST. However, it is clear that the effects of ST
tend to be relatively acute, and do not attack the deep-seated abnormalities that are the
underlying causes of recurrences of affective disorders. This is corroborated by the fact
that in animals, most of the effects of ECS on catecholamines and their receptors (and on
receptors for benzodiazepines or neuropeptides such as TRH) tend to be relatively
transient, and in most cases have been found to represent compensatory adaptations to the
induced motor convulsions. However, recent preclinical data using attenuation, and
clinical findings using reiterated transcranial magnetic stimulation (rTMS), suggest that
it may not be necessary to provoke a clonic convulsion in order to achieve the beneficial
psychotropic and anticonvulsant effects of ST. In rodents receiving stimulation to the
cerebellar tonsil, seven daily subacute low-frequency sessions (stimulation at 1 Hz for 15
minutes) produced clear improvement in clonic convulsions and in post-discharge
thresholds, together with durable inhibition of convulsions when stimulation was resumed
(Weiss et al., 1995). Stimulation at 1 Hz for 15 minutes was more effective than
stimulation at 10 or 20 Hz in attenuating convulsions. Although reiterated ECS also
induced an anti-triggering effect, this dissipated rapidly over five days (Post et al.,
1984). It is of great interest that recent publications have shown that rTMS at 10 or 20
Hz to the left frontal cortex, administered to patients suffering from refractory
depression (George et al., 1995) or to patients (hospitalised or not) with milder degrees
of depression (Pasquale-Leon et al., 1996), had a moderate or marked antidepressant
effect. In these studies, rTMS showed few unwanted effects (other than mild pain in some
patients, due to contraction of the temporal muscles); it did not induce motor
convulsions, and did not, as such, appear to be associated with the memory loss described
in subjective accounts or in preliminary neuropsychological tests (Little and Kimbrell et
al., 1996). The optimal frequencies, durations and positions for rTMS to maximise its
antidepressant effect still remain to be determined. However, the first controlled and
open studies have tended to show that (because of the capacity of rapid magnetic fluxes to
produce sub-convulsant electrical discharges that are relatively localised in the brain),
rTMS may be found to be a clinically useful antidepressant model. This would suggest the
possibility that some of the neurochemical changes induced by the clonic convulsions of
ECS could be directly induced by stimulation at the very edge of the threshold (but still
below it); this would open up the hope that one day these endogenous neurochemical
processes could be identified and exploited in an optimal way for therapeutic purposes.
Brain/PHYSIOPATHOLOGY
Brain Mapping
English Abstract
Human
Treatment Outcome
PUBLICATION TYPES:
JOURNAL ARTICLE
REVIEW
REVIEW, TUTORIAL
LANGUAGE:
Fre
On Sabbatical!
When my office
lease expired at the end of 2004, I decided to turn it into a
"sabbatical" from my private practice. Many years ago, in my
grandfather's 89th year of life, he told me, "John, it is important
to smell the roses while you can still smell them." His life
gave living a very good reputation. It is also true that the
pursuit of that philosophy required my grandfather to to re-open his
assay office/ore market in Wickenburg, Arizona as a 75-year-old because
he had run a little short of retirement money. Thus, if blessed with his
luck and health, I'll be back.. --jjh
