gms | German Medical Science

Objective: Conducting neurosurgical interventions directly within the primary motor cortex is controversially discussed. In particular, the risks of permanent deficits may hamper the long-term profit for such patient. To reduce risks of a postoperative motor decline after surgery within or adjacent to this area, a detailed preoperative functional mapping of these areas may be beneficial.

Method: Out of 337 patients operated on with the aid of FMRI motor mapping, there were 16 patients with surgery within the precentral gyrus. For fMRI we used a 1.5T MR scanner with echo planar imaging (Sonata, Siemens Medical Solutions) and a block paradigm with 120 measurements in 6 blocks (rest alternating with activation, 16 slices, 3 mm thickness & resolution TR=1580, TE=60). During the activation intervals patients had to perform movements. For pyramidal tract maps, DTI was used with 1.9 mm slices and 6 directions. Intraoperative MRI was used and registered to the functional images to verify the extent of resection and to correct brain shift.

Results: Out of 16 patients, 9 obtained surgery in the area of leg (7 glioma,1 metastasis), 4 in the area of arm/ fingers (3 glioma, 1 metastasis) and 5 in the area of the mouth motor cortical representation (3 glioma, 1 metastasis, 1 cavernoma). Additionally, there were 7 patients with surgery touching the pyramidal tract. Permanent plegia occurred in none of the cases. Only in one patient (6.25%) there was a permanent worsening of foot movement. In another patient, there was a clear improvement of movement after surgery compared to the motor function before surgery. In another patient, who had surgery without functional mapping and subsequently developed postoperative plegia of the leg, this deficit resolved within one year and was subsequently found to have a cortical motor representation on the contralateral hemisphere in a follow-up fMRI study. Obviously, no postoperative worsening occurred in this patient after another surgery in the same area.

Conclusions: Neurosurgical resection close and even within the precentral gyrus is possible without permanent movement deficit. This demands a detailed mapping of active motor areas preoperatively and an ongoing update using neuronavigation and intraoperative MR imaging during surgery.