Effect of chronic repetitive transcranial magnetic stimulation on regional cerebral blood flow and regional cerebral glucose uptake in drug treatment-resistant depressives. A brief report.

Brain imaging studies have shown that repetitive transcranial magnetic stimulation (rTMS) is biologically active. The aim of the present study was to investigate the patterns of the regional cerebral glucose uptake rate (rCMRGlu) and regional (99m)Tc HMPAO uptake rate (regional cerebral blood flow; rCBF) during a series of therapeutic rTMS sessions at low frequency. Four drug-resistant depressed patients underwent 10 rTMS sessions as an add-on measure over 14 days. One day before and 1 day after the TMS series, 511-keV SPECT with simultaneous (18)F-fluorodeoxyglucose and (99m)Tc HMPAO measurements were carried out. All patients showed a good clinical outcome. Statistically significant common changes in rCBF and rCMRGlu patterns were found in the upper frontal regions bilaterally in terms of increased uptake rates and in the left orbitofrontal cortex in terms of decreased uptake rates of both isotopes compared to controls. However, the lateralization patterns of rCBF and rCMRGlu after rTMS treatment revealed marked differences. Thus, although no relevant changes in lateralization of the glucose uptake were observed, a clear right-sided preponderance of rCBF also in areas remote from the stimulation site was described. Therapeutic rTMS seems to influence distinct cortical regions, affecting rCBF and rCMRGlu in a homogeneous manner as well as in different ways, which are probably region dependent and illness related. The role of the stimulation coil placement site should be taken into account.