Abstracts

RATIONALE: When planning lesional surgery in sensorimotor cortex, the following questions may arise: (1) Has functional cortical anatomy been reorganized by the lesion? (2) Is there evidence for redundant cortical representations, and if so, should this evidence be used to guide the resection? Reorganization has been demonstrated by functional imaging (e.g. Wunderlich et al. Neurosurgery 42.1:18-26, 1998), and by cortical stimulation mapping during surgery (e.g. Burchiel et al. Neurosurgery 24.3:322-7,1989). Multiple redundant sensorimotor representations for the arm have been identified by intraoperative corticalstimulation before and after resection of chronic Rolandic lesions (Duffau J Neurol Neurosurg Psychiatry 70:506-513, 2000; Duffau et al. Ann Neurol 47.1:132-5, 2000). To further investigate these issues we used preoperative fMRI, cortical stimulation, and somatosensory evoked potentials (SEPs) to study the functional anatomy of sensorimotor cortex in an 18-year-old man with multiple cavernous angiomas and intractable simple partial seizures of the right upper extremity.
METHODS: Preoperative fMRI was performed during a complex finger-tapping task. Both scalp EEG and subdural electrocorticography (ECoG) were used to identify seizure onset. Extraoperative cortical stimulation mapping of sensorimotor functions was performed, and median nerve SEPs were recorded with ECoG.
RESULTS: The patient[ssquote]s typical recorded seizures were simple partial seizures at the right wrist and elbow with variable involvement of the fingers and shoulder. EEG and ECoG ictal discharges originated in and around a single angioma on the anterior lip of a left frontoparietal sulcus. Phase reversal of the N1 and P1 of the SEP occurred ~0.5 cm posterior to the angioma. With preoperative fMRI right complex finger-tapping activated a similar area posterior to the angioma. Cortical stimulation over the angioma produced deficits in right arm and finger movements. However, there were areas inferior and posterior to this where stimulation also produced deficits in fine finger, hand, and arm movements. The angioma and adjacent cortex were resected. Postoperatively, the patient had transient, mild proximal weakness of the right arm, but fine finger movements were unaffected. At the time of follow-up a week later, his strength and dexterity were at baseline.
CONCLUSIONS: Sensorimotor cortex may contain multiple, potentially redundant, representations of the same body part. In addition, chronic lesions may induce remodelling of sensorimotor functional anatomy. In either case, redundant sensorimotor representations may be capable of assuming the function of resected perirolandic cortex.
Support: This project was supported in part through a grant from the National Epifellows Foundation.