Surgical removal of the glioma at the precentral gyrus

A 15-year-old female presented with a 10-month history of generalized epileptic activity. Neurological and neuropsychological examination revealed no abnormalities. Magnetic resonance imaging (MRI) demonstrated a slightly enhanced round expansive tumor, which appeared identical on both T1- and T2-weighted imaging, in the left precentral gyrus medial to the precentral knob. Magnetoencephalography, functional MRI, surface anatomy scan with venography, and fiber mapping using diffusion-weighted MRI disclosed that the tumor was located just before the leg motor cortex and had displaced the corticospinal tract posterolaterally. Surgery was performed with the patient under general anesthesia. Stimulation mapping techniques for localization of the motor cortex and the descending motor pathway was applied under guidance from a neuronavigation system. Direct cortical stimulation of the anterior half of the precentral gyrus overlying the tumor did not evoke leg motor movements. Thus, the cortex was resected up to the location of the leg motor cortex confirmed by the direct cortical stimulation technique. The tumor was completely resected with preservation of the descending motor pathway. The histological diagnosis was ganglioglioma. Postoperatively, the patient only had transient weakness of the right leg, and was discharged home 11 days after the operation without neurological deficit. The whole of the precentral gyrus does not correspond to primary motor area (area 4). If the patient has no neurological deficit and the tumor has an expansive nature, as evaluated by MR imaging, gliomas at the anterior side of the precentral gyrus can be resected without permanent motor deficit.