The impact of accelerated high frequency rTMS on brain neurochemicals in treatment-resistant depression: Insights from 1H MR spectroscopy

- Treatment-resistant depression (TRD) is characterized by lower glutamatergic concentrations in the left dorsolateral prefrontal cortex (DLPFC).
- Accelerated high-frequency rTMS (aHF-rTMS) does not seem to affect neural integrity in TRD patients.
- aHF-rTMS could be related to increased left DLPFC GABAergic neurotransmission.

ObjectiveAlthough accelerated repetitive transcranial magnetic stimulation (rTMS) designs seem to be able to alleviate mood over a relatively short period of time, no studies yet examined the cellular effects on neurochemicals with regard to working mechanisms, safety and neural integrity.MethodsEighteen right-handed antidepressant-free unipolar treatment resistant depressed (TRD) patients participated in this sham-controlled accelerated high frequency (aHF)-rTMS 1H MR spectroscopy study applied to the left dorsolateral prefrontal cortex (DLPFC). Baseline measurements were compared to eighteen age- and gender-matched healthy controls. We explicitly focused on neurochemical concentrations in the bilateral DLPFC and rostral anterior cingulate cortex (rACC).ResultsCompared to healthy individuals, TRD patients displayed significantly lower baseline glutamatergic (sum absolute concentrations glutamate and glutamine) concentrations in the left DLPFC. aHF-rTMS does not significantly alter neurochemical concentrations in the three predefined brain regions. Clinical improvement was related to significant GABA concentration increases in the left DLPFC.ConclusionsAccelerated HF-rTMS treatment did not affect neural integrity in the examined regions. The observed GABA concentration increases suggest that the immediate therapeutic effects of aHF-rTMS could be mediated through a locally increased GABAergic inhibitory neurotransmission.SignificanceAlthough more statistical power is needed for reaching firm conclusions, aHF-rTMS does not appear to negatively influence neural integrity.