Chris Oake

Background: Low-grade gliomas (LGGs) frequently arise near eloquent motor regions such as the primary motor cortex (M1) and supplementary motor area (SMA), where even subtle postoperative weakness can significantly impair independence and quality of life¹. Conventional structural imaging may underestimate the functional impact of these tumors because network-level disruption can extend beyond visible lesion margins and because gradual tumor growth allows substantial cortical reorganization^1,2. Resting-state functional MRI (rs-fMRI), which measures spontaneous blood oxygen level-dependent (BOLD) signal correlations between regions at rest, enables noninvasive mapping of motor network connectivity without requiring task performance^3,4. However, it remains unclear whether rs-fMRI reliably captures perioperative changes in motor connectivity after resection of LGGs involving M1 or SMA and whether such changes parallel motor recovery^1,5.

Objective: This review aims to evaluate the role of rs-fMRI in mapping perioperative motor network connectivity following resection of LGGs near M1/SMA and its relationship to postoperative motor outcomes.

Methods: A focused PubMed literature review was conducted using predefined search terms from 2012-2026 including “low-grade glioma,” “brain tumor,” “resting-state fMRI,” “functional connectivity,” “motor network,” “primary motor cortex,” “supplementary motor area,” “corticospinal tract,” and “resection.”

Results: Patients with motor weakness had reduced resting-state motor network connectivity, particularly in interhemispheric motor links. Interhemispheric connectivity within the sensorimotor network significantly decreased immediately post‑op compared with pre‑op, then increased again by 3 months, approaching or exceeding baseline values. Connectivity between the lesioned‑side motor cortex and contralateral SMA rose to higher than pre‑operative levels during recovery, suggesting compensatory strengthening². Longitudinal data suggest that motor network connectivity decreases immediately postoperatively and may recover over time in patients with clinical improvement, while remaining impaired in those with persistent weakness deficits at approximately 5 months¹.

Conclusions: Current evidence suggests that rs-fMRI can detect measurable perioperative changes in motor network connectivity after resection of gliomas involving M1 or SMA and that medium-term recovery of connectivity may parallel clinical motor recovery^1,4. Nonetheless, the direct longitudinal data are limited by small sample sizes, heterogeneous tumor grades, and follow-up closer to 5 months than 6 months, and rs-fMRI signal changes may be confounded by altered hemodynamics or neurovascular uncoupling^3,5. Currently, rs-fMRI is best viewed as a promising complementary tool for assessing motor-system reorganization rather than a standalone determinant of outcome, and larger prospective longitudinal studies focused on LGGs are needed to clarify its prognostic and clinical utility⁶.

Works Cited:

1. Kokkonen SM, Nair VA, La C, et al. Motor deficits correlate with resting state motor network connectivity in patients with brain tumours. Brain. 2012;135(4):1017-1026. doi:10.1093/brain/aws041
2. Vassal M, Charroud C, Deverdun J, et al. Recovery of functional connectivity of the sensorimotor network after surgery for diffuse low-grade gliomas involving the supplementary motor area. Journal of Neurosurgery. 2017;126:1181-1190. doi: 10.3171/2016.4.JNS152484
3. Willemse RB, Hillebrand A, Ronner HE, Vandertop WP, Stam CJ. Magnetoencephalographic study of hand and foot sensorimotor organization in 325 consecutive patients evaluated for tumor or epilepsy surgery. Neuroimage Clin. 2020;27:102326. doi:10.1016/j.nicl.2020.102326
4. Liu H, Song M, Wang Z, et al. Altered resting-state functional connectivity in the hand motor network in glioma patients. Front Hum Neurosci. 2016;10:555. doi:10.3389/fnhum.2016.00555
5. Jütten K, Machetanz K, Grittner U, et al. Decreased hand motor resting-state functional connectivity in patients with brain tumors in the primary motor cortex. Front Neurol. 2020;11:9. doi:10.3389/fneur.2020.00009
6. Niu C, Zou Q, Peng Y, et al. Resting state functional connectivity of the supplementary motor area in brain tumor patients. Front Neurol. 2019;10:706. doi:10.3389/fneur.2019.00706
7. van Dellen E, de Witt Hamer PC, Douw L, et al. Structural brain network disturbances in the temporal lobe of glioma patients. Brain. 2014;137(7):179-188. doi:10.1093/brain/awu055
8. De Baene W, Rutten GJ, Siero JC. Functional connectivity in adult brain tumor patients. Brain Connect. 2019;9(4):251-263. doi:10.1089/brain.2018.0623
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