Risk Factors for Neurological Deficits Following Brain Tumor Resection in the Supplementary Motor Area (SMA): A 66-Case Double-Center Study.

BACKGROUND

Resection or damage of the supplementary motor area (SMA) is associated with the development of a transient negative motor response defined as SMA syndrome. The risk of neurological deficits after resection in the SMA has been reported to vary widely from 23% to 100%. Various influencing factors can be involved. However, since tumors in the SMA are relatively infrequent, most of the evidence for surgical treatment of these lesions is based on small, retrospective, single-center case series. Furthermore, previous studies focused only on a few variables, and our knowledge regarding the outcome of these patients is still limited.

OBJECTIVE

To better define the risk of neurological deficits after brain tumor resection in the SMA.

METHODS

We retrospectively reviewed 66 surgeries that involved the SMA for gliomas and metastasis in 53 patients from two separate centers. Out of those, 13 cases were recurrence of the disease. We carefully evaluated various clinical factors, preoperative neuroimaging, intraoperative neurophysiology monitoring, and anatomical factors. By using Fisher's exact probability test, we examined the relationship between these factors and the occurrence of postoperative neurological deficits. Statistical significance was considered at a -value of less than 0.05.

RESULTS

In 28 cases, patients experienced neurological deficits after surgery. Among those cases, 26 experienced partial SMA syndrome, one experienced complete SMA syndrome, and one experienced a permanent neurological deficit. The research found that the patient's past medical history ( = 0.005), lack of intraoperative language mapping ( = 0.044), and extent of resection ( = 0.040) significantly influenced the occurrence of language deficits. Additionally, the proximity between the corticospinal tract and the tumor ( = 0.005) and fMRI activation of the SMA in response to motor tasks ( = 0.044) were found to correlate with the development of motor deficits. However, there was no correlation found between the lack of intraoperative monitoring of motor-evoked potentials (MEPs) and the development of motor deficits ( > 0.05).

CONCLUSIONS

Certain pre-existing medical conditions may increase the risk of postoperative language deficits. Intraoperative language mapping can help prevent these deficits. The extent of resection, along with the anatomical characteristics of the resection cavity, correlates with postoperative outcomes. Tractography and fMRI can assist in predicting the risk of motor deficits. Although intraoperative MEP monitoring can help prevent permanent motor deficits, it does not appear to prevent the transient deficits characteristic of SMA syndrome. Further intraoperative studies are needed to refine mapping and monitoring strategies for tumors involving the SMA and pre-SMA.