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

OBJECTIVE: Although 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.

METHODS: Eighteen right-handed antidepressant-free unipolar treatment resistant depressed (TRD) patients participated in this sham-controlled accelerated high frequency (aHF)-rTMS (1)H 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).

RESULTS: Compared 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.

CONCLUSIONS: Accelerated 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.

SIGNIFICANCE: Although more statistical power is needed for reaching firm conclusions, aHF-rTMS does not appear to negatively influence neural integrity.