gms | German Medical Science

Objective: Besides gross total resection of the tumour, preservation of important functions such as motor control is the major goal in glioma surgery. Brain mapping techniques such as navigated transcranial magnetic stimulation (nTMS) have facilitated the preoperative risk evaluation and resection planning for rolandic brain tumours. However, the clinical course after the resection of brain tumours located within the premotor area is often associated at least transient deterioration of motor functions.

Method: A consecutive case series of 10 patients (7M/3F, mean age 57.8 yrs) with brain tumours located within the premotor area was collected within a prospective clinical trial between 2012-2014. All of them underwent preoperative nTMS mapping of the tumour-adjacent M1 areas (Nexstim eXimia 4.2). Tumour volume, oedema volume, the minimal distance between tumour / oedema and the adjacent primary motor (M1) representation (hot spot, margin of map; iPlanNet) and the resting motor threshold (RMT) were compared to the neurological outcome which was evaluated before surgery, immediately after surgery (ICU), at discharge and 3-6 months later (follow-up).

Results: 7/10 of the patients deteriorated immediately after surgery (ICU). At discharge, 5/10 patients showed an improved motor status compared to admission. In 4 of these patients, the neurological symptoms were totally reversible. 3/10 patients still had neurological deficit at discharge. Of these, one patient continued with slightly deteriorated motor function 3 months after surgery. The preliminary analysis suggests a weak correlation (p < 0.2) of the postoperative neurological deterioration / improvement with the distance between contrast-enhancing tumour parts and the M1 hot spot (11.6 ± 4.6 mm) as well as with the relative RMT (ipsi-/contralateral: 0.96 ± 0.33).

Conclusions: Aiming at the total resection of premotor brain tumours, a transient motor deficit should be expected in a high percentage (70% in this study). However, the deficit usually recovers well during the first week after surgery. Mapping techniques for the supplementary and premotor area may improve the predictability of transient motor deficits and, thus, facilitate diagnostic decisions and presurgical consultation. A novel protocol for SMA-mapping by repetitive nTMS is currently under pre-clinical investigation.