Language mapping with navigated repetitive TMS: proof of technique and validation

Area of Science:

• Neuroscience
• Neurosurgery
• Neurology

Background:

• Direct cortical stimulation (DCS) is the gold standard for invasive, lesion-based speech pathway mapping during neurosurgery.
• Noninvasive methods like navigated transcranial magnetic stimulation (nTMS) and magnetoencephalographic imaging (MEGI) offer potential alternatives for language mapping.

Purpose of the Study:

• To compare the accuracy of noninvasive nTMS and MEGI with invasive DCS for lesion-based language pathway mapping.
• To evaluate the potential of nTMS as a noninvasive tool for managing patients with peri-eloquent lesions.

Main Methods:

• Preoperative nTMS and MEGI language mapping were performed on 12 subjects with lesions near cortical language areas.
• nTMS utilized repetitive TMS during a picture naming task; MEGI used adaptive spatial filtering of beta-band power decreases.
• Intraoperative DCS was used for awake language mapping, with all resulting maps compared.

Main Results:

• nTMS showed high accuracy compared to DCS: 90% sensitivity, 98% specificity, 99% negative predictive value.
• MEGI identified numerous activation sites but showed less consistent correlation with DCS compared to nTMS.
• Both nTMS and DCS most frequently identified positive language sites in the pars opercularis.

Conclusions:

• nTMS-generated language maps demonstrate strong correlation with DCS, supporting its use for noninvasive, lesion-based mapping.
• Negative nTMS mapping also correlates well with negative DCS findings.
• While MEGI provides supplementary information, nTMS emerges as a promising noninvasive method for pre-surgical language pathway assessment.