Multimodal and Repeated Localization of Primary Hand Motor Function to the Lateral Postcentral Gyrus in a Case of Frontal Motor Area Brain Metastasis.

Abstract

Background and importance: The human motor homunculus is a well-known topographical map of the functional-anatomical relationships of the precentral gyrus. Within this homunculus, the primary hand motor area is considered one of the least plastic functional-anatomical relationships. Only a few cases in the literature describe relocation of functional hand representation away from the classical anatomical location. These cases have been reported in the context of children, primary gliomas, or arteriovenous malformations.

Clinical presentation: Here, we describe a unique case where the area of lowest hand motor stimulation threshold (ie, hand motor representation) was found in the postcentral gyrus in an older adult with a metastasis in the premotor area of the brain. This localization was based on intraoperative cortical stimulation-evoked motor potentials and confirmed with electrophysiological phase reversal and MRI-based neuronavigation. This mapping was repeated and consistent 2 months later during a reoperation for recurrence. In addition, the remapped anatomical location was found in an area that was active during finger tapping on preoperative functional MRI.

Conclusion: These findings suggest that neuroplastic remapping of hand motor cortex to the postcentral gyrus can occur in brain metastases even in adults. This has implications for planning tumor resections and interventional neurorehabilitation strategies, and it suggests that the motor homunculus may have more plastic potential in adulthood than previously recognized.