Low frequency rTMS as an add-on antidepressive strategy: heterogeneous impact on Tc-99m-HMPAO and F-18-FDG uptake as measured simultaneously with thedouble isotope SPECT technique. Pilot study

Single photon emission computed tomography (SPELT) and positron emission to mography (PET) are examination procedures that have shown that repetitive t ranscranial magnetic stimulation (rTMS) is biologically active. The aim of the present study was to investigate the patterns of regional cerebral F-18 -fluorodeoxyglucose (F-18-FDG) uptake and regional Tc-99m-hexamethylpropyle neamine oxime (Tc-99m-HMPAO) uptake simultaneously during a series of thera peutic rTMS at low frequency. Four drug-resistant depressed patients underw ent 10 rTMS as an add-on measure over 14 days. One day before and one day a fter TMS, simultaneous measurements of F-18-FDG, representing regional cere bral metabolic rate (rCMR),. and Tc-99m-HMPAO, representing regional cerebr al blood flow (rCBF), were carried out. A conventional double head SPELT ca mera with 511 keV collimators was used. Statistically significant simultane ous overall changes of rCBF and rCMR were found in the upper prefrontal reg ions bilaterally in terms of increased uptake rates and in the left gyrus f rontalis inferior in terms of decreased uptake rates of both isotopes compa red to controls. Although this method improves our understanding of rTMS me chanism, there are limitations due to the lower resolution provided. Therap eutic rTMS seems to influence distinct, cortical regions affecting rCBF and rCMR. ((C) 2001 Lippincott Williams & Wilkins).