Demonstration of Cerebral Plasticity by Intra-Operative Neurophysiological Monitoring: Report of an Uncommon Case

Abstract

It has been postulated long ago that "eloquent" areas shift their location in patients with arteriovenous malformations (AVM). Obviously the "motor region" in not located in the precentral gyrus in a patient with an AVM in the "motor region". We report on the case of a 15-year old boy with an AVM in the left sensorimotor cortex, in whom intra-operative mapping showed an inexcitability of the precentral gyrus, while stimulation of the cortex anterior to the primary motor cortex elicited motor responses. This indicates that motor function was translocated from the primary to the supplementary motor cortex. Surgery was performed under general anaesthesia. Neurophysiological monitoring was performed throughout surgery. The central sulcus was identified by phase reversal of the somatosensory evoked potentials. The motor cortex was mapped by direct high-frequency (500 Hz) monopolar anodal stimulation. In the patient herein reported, stimulation of the "anatomically" defined primary motor cortex induced no motor response, as expected. Motor response was elicited only by stimulation of the cortex anterior to the precentral gyrus. There was no postoperative deterioration of motor function. These observations indicate that the precentral gyrus was functionally "useless". The motor region was relocated into more rostral areas in the supplementary motor cortex. This translocation of function in the presence of an AVM indicates cerebral plasticity.

Neuromuscular Plasticity: Disentangling Stable and Variable Motor Maps in the Human Sensorimotor Cortex

“…The present study confirmed earlier animal experiments [58–61] and human studies [14, 39, 62–64], which indicated that corticospinal connections are not limited to the primary motor cortex but extend to different regions of the sensorimotor system. Approximately half of the primate brain's pyramidal tract neurons are located in postcentral areas, for example, the primary somatosensory cortex, sharing functional properties with regard to movement-related activity and discharge patterns as a function of muscle strength with precentral pyramidal tract neurons [31, 65–67].…”

Functional reorganization of the corticospinal tract in a pediatric patient with an arteriovenous malformation

“…Although reorganization of the motor cortex [13] and plasticity characterized by abnormal branching of the CSTs [14] have previously been reported, this study is to our knowledge the first description of the functional reorganization of an existing tract to serve as a CST in children.…”