A novel interleaved TMS-MRS approach with standard MRI hardware

Area of Science:

• Neuroscience
• Neuroimaging
• Psychiatry

Background:

• Interleaved transcranial magnetic stimulation-functional magnetic resonance imaging (TMS-fMRI) advanced network modulation understanding but was limited to hemodynamic measures.
• Assessing real-time neurochemical changes during TMS requires novel methodologies.

Purpose of the Study:

• Introduce and demonstrate the feasibility of an interleaved TMS-MRS platform using standard MRI hardware.
• Assess real-time neurochemical changes during TMS in patients with treatment-resistant depression (TRD).

Main Methods:

• Nine TRD participants underwent interleaved TMS-MRS on a 3T Siemens Prisma.
• A 20 mm³ voxel targeted the left dorsolateral prefrontal cortex (dlPFC).
• ¹H-MRS spectra were acquired at baseline and during 10 Hz burst stimulation, comparing spectral quality and metabolite concentrations.

Main Results:

• Spectral quality and signal-to-noise ratio remained stable during stimulation.
• Alanine levels increased (p=0.031) and NAA+NAAG levels decreased (p=0.031) during TMS.
• Exploratory analyses indicated associations between baseline/stimulated metabolites and clinical improvement.

Conclusions:

• Interleaved TMS-MRS is feasible in TRD patients using standard MRI hardware.
• This method enables in-vivo detection of acute neurochemical changes during TMS.
• It provides a new tool for investigating excitatory/inhibitory balance, neuronal metabolism, and treatment mechanisms.