Motor cortex evaluation by nTMS after surgery of central region tumors: a feasibility study.
BACKGROUND
Largely discussed during the past decade, motor cortex reorganization in brain tumor surgery has been investigated only by few studies. We therefore aimed to investigate cortical motor representation after resection of perirolandic WHO grade II and III gliomas using navigated transcranial magnetic stimulation (nTMS).


METHODS
Five patients were examined before neurosurgery and after a follow-up period of 17.7 ± 6.8 months. As a control, five healthy age-matched subjects were equally studied by nTMS in two sessions spaced 12.6 (range 2-35) days apart. Resting motor thresholds (RMT), hotspots and centers of gravity (CoG) were identified for the first dorsal interosseous (FDI), abductor pollicis brevis (APB), extensor digitorum (EXT), tibialis anterior (TA) and abductor hallucis (AH) muscles. Euclidian distances, coefficients of variance and intraclass correlation coefficients (ICC) were calculated.


RESULTS
Healthy subjects showed moderate to excellent reliability measurement of RMT (ICC = 0.69-0.94). Average displacement of CoGs across sessions was 0.68 ± 0.34 cm in the dominant and 0.76 ± 0.38 cm in the non-dominant hemisphere; hotspots moved 0.87 ± 0.51 cm and 0.83 ± 0.45 cm, respectively.                         In one patient these parameters differed significantly from the control group (p < 0.05 for both CoGs and hotspots). Overall, all patients' CoGs moved 1.12 ± 0.93 cm, and hotspots were 1.06 ± 0.7 cm apart. In both patients and healthy subjects, movement of assessed parameters was more important along the X- than the Y-axis.


CONCLUSIONS
nTMS allows evaluating cortical reorganization after brain tumor surgery. It may contribute to the understanding of neurofunctional dynamics, thus influencing therapeutic strategy.
Department of Neurosurgery, Goethe University Hospital, Schleusenweg 2-16, 60528, Frankfurt am Main, Germany. Marie-Therese.Forster@med.uni-frankfurt.de
Marie-Thérèse
MT
Forster
Christian
C
Senft
Elke
E
Hattingen
Mario
M
Lorei
Volker
V
Seifert
Andrea
A
Szelényi
D000328:Adult; D001931:Brain Mapping; D001932:Brain Neoplasms / Q000503:physiopathology* / Q000601:surgery; D005240:Feasibility Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology* / Q000601:surgery; D018482:Muscle, Skeletal / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology; D019635:Neurosurgical Procedures; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D016896:Treatment Outcome; D055815:Young Adult