Role of Functional Imaging Techniques to Assess Motor and Language Cortical Plasticity in Glioma Patients: A Systematic Review

Abstract

Cerebral plasticity is the ability of the central nervous system to reorganize itself in response to different injuries. The reshaping of functional areas is a crucial mechanism to compensate for damaged function. It is acknowledged that functional remodeling of cortical areas may occur also in glioma patients. Principal limits of previous investigations on cortical plasticity of motor and language functions included scarce reports of longitudinal evaluations and limited sample sizes. This systematic review is aimed at elucidating cortical brain plasticity for motor and language functions, in adult glioma patients, by means of preoperative and intraoperative mapping techniques. We systematically reviewed the literature for prospective studies, assessing cortical plasticity of motor and language functions in low-grade and high-grade gliomas. Eight longitudinal studies investigated cortical plasticity, evaluated by motor and language task-based functional MRI (fMRI), motor navigated transcranial magnetic stimulation (n-TMS), and intraoperative mapping with cortical direct electrocortical stimulation (DES) of language and motor function. Motor function reorganization appeared relatively limited and mostly characterized by intrahemispheric functional changes, including secondary motor cortices. On the other hand, a high level of functional reshaping was found for language function in DES studies. Occurrence of cortical functional reorganization of language function was described focusing on the intrahemispheric recruitment of perilesional areas. However, the association between these functional patterns and recovery of motor and language deficits still remains partially clear. A number of relevant methodological issues possibly affecting the finding generalization emerged, such as the complexity of plasticity outcome measures and the lack of large longitudinal studies. Future studies are required to further confirm these evidences on cortical plasticity in larger samples, combining both functional imaging and intraoperative mapping techniques in longitudinally evaluations.

Clinical Management of Diffuse Low-Grade Gliomas

“…Resting-state fMRI functional connectivity as well as new advanced HARDI (high angular resolution diffusion imaging) tractography methods are improving and reshaping the role of these advanced functional MRI techniques for surgery of gliomas [ 53 ], although larger studies are still warranted to encourage their wide clinical implementation in the near future. A promising application of functional imaging techniques in the assessment of cortical plasticity of motor and language functions in gliomas is currently a matter of investigation, especially to define how cognitive functional recovery or impairment is mirrored by specific imaging modifications, and to understand the association between longitudinal functional changes and progression of disease [ 55 ].…”

Functional Mapping before and after Low-Grade Glioma Surgery: A New Way to Decipher Various Spatiotemporal Patterns of Individual Neuroplastic Potential in Brain Tumor Patients

“…Presurgical task-based/rsfMRI [ 46 ] and TMS [ 47 , 48 ] in glioma patients have first supported a local rearrangement of cortical motor representations, made possible thanks to a more complex and dynamic organization of the primary motor cortex than previously thought [ 49 ]. However, such a potential of local reshaping has limitations, since the motor system serves as a unimodal output, and then belongs to the “minimal common brain” (the neural structures with a low plastic potential) [ 50 ].…”

What do we know about pre- and postoperative plasticity in patients with glioma? A review of neuroimaging and intraoperative mapping studies

“…A recent systematic review of eight studies comparing post- and preoperative brain activations in these two networks ( Cirillo et al, 2019 ) concluded that the motor function tends to reorganize mainly intrahemispherically, whereas language showed a wider reorganization potential. Results from the present review also suggest that the sensorimotor network reorganization may extend to the healthy hemisphere.…”

“…The current review aimed to provide a comprehensive overview of neuroplasticity in patients with glioma. With respect to previous reviews on the topic (e.g., Cirillo et al, 2019 ; Duffau, 2014 ), this review aimed to explore the extent of plasticity not only associated with glioma growth but also with surgery, the latter being more poorly explored. The studies we reviewed investigated plasticity under different aspects and by different methodologies.…”