SPECT mapping of cerebral activity changes induced by repetitive transcranial magnetic stimulation in depressed patients. A pilot study

Repetitive transcranial magnetic stimulation (rTMS) is being investigated a s an alternative treatment for depression. However, little is known about t he clinical role and the neurophysiological mechanisms of the action of rTM S in these patients. In this study, Tc-99m-HMPAO single photon emission com puted tomography (SPECT) was used to map the effects of left dorsolateral p refrontal rTMS on prefrontal activity in seven patients who met DSM-IV crit eria for major depression resistant to pharmacological treatment. rTMS cons isted of 30 trains of 2-s duration stimuli (20 Hz, 90% of motor threshold), separated by 30-s pauses. Each patient underwent three SPECTs: at baseline ; during the first rTMS; and 1 week after 10 daily sessions of rTMS. Region al cerebral blood flow (rCBF) of each cerebral region was normalized to the rCBF value in the cerebellum and relative changes in normalized rCBF were addressed using a region-of-interest analysis. The Hamilton Depression Rati ng Scale (HDRS) was used for clinical evaluation before and after rTMS. A s ignificant rCBF increase after the 10 sessions of rTMS was found in the lef t prefrontal region (MANOVA F = 5.29, d.f. = 2,10, P = 0.027), but no signi ficant rCBF changes were found during the first rTMS session,The remaining cerebral regions showed no significant rCBF changes at any time. Only two p atients showed a clinic;ll improvement after rTMS, with 50% reduction of th e initial HDRS score. The study was repeated under placebo conditions (iden tical design but addressing coil discharges to the air) in these two patien ts, who failed to show any rCBF increase during sham-rTMS. No relationship was found between the percentage of left prefrontal rCBF change and the cli nical findings. In conclusion, rTMS of the left prefrontal cortex induces a significant rCBF increase in this region, despite the limited clinical eff ect in our sample: of depressed patients. Cerebral perfusion SPECT is a use ful tool to map cerebral activity changes induced by rTMS. (C) 2001 Elsevie r Science Ireland Ltd. All rights reserved.