Affiliations: Department of Neurology, Charité Campus Mitte
(CCM), Berlin, Germany | Epilepsy Center Berlin-Brandenburg, Ev. Krankenhaus
Königin-Elisabeth-Herzberge, Berlin, Germany
Note: [] Corresponding author: Department of Neurology, Charité
Campus Mitte (CCM), Charitéplatz 1, 10117, Berlin, Germany. Tel.: +49 30
450660111; Fax: +49 30 450560955; E-mail: stephan.brandt@charite.de
Abstract: Purpose: The quality of presurgical evaluation in focal
extratemporal epilepsy surgery is highly dependent on precise structural and
functional identification of the epileptic focus. Navigated transcranial
magnetic stimulation (nTMS) is a tool that combines the spatial information of
high-resolution magnetic resonance imaging (MRI) with the functionality of
non-invasive cortical stimulation. The non-invasive character of nTMS suggests
that it could be a promising tool for presurgical evaluation of cortical
excitability. Methods: Presurgical nTMS evaluation was performed on an 8-year-old
boy with left-sided intractable focal epilepsy, somatosensory auras and
epilepsia partialis continua. In line with standardized procedures, motor
evoked potentials were sought in both hemispheres over perirolandic cortex
during simultaneous belly-tendon surface recordings of the first dorsal
interosseus muscles. Results: One singular motor-evoked potential (MEP) could be elicited
in the unaffected hemisphere. In contrast, in the affected hemisphere MEPs
could be elicited over a large area of the cortex even after the stimulation
strength was reduced by at least 44%. Latency stratification in the affected
hemisphere differentiated a motor from a sensory region of interest.
Stimulation over the sensory region induced a sensory aura. The sensory site
was concordant with a previous transient diffusion restriction found in an MRI
two years prior to nTMS. Conclusions: NTMS can locate pathological excitability with high
spatial precision. Future studies should compare nTMS with direct cortex
stimulation, as well as the combination of nTMS with electroencephalography
(EEG) in a larger patient-collective.
Keywords: Focal epilepsy, preoperative evaluation, navigated brain stimulation, cortical excitability, motor evoked potential, transcranial magnetic stimulation
