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. 2013 Jan 14:2:221-8.
doi: 10.1016/j.nicl.2013.01.002. eCollection 2013.

Primary motor cortex activation and lateralization in patients with tumors of the central region

Magdalini Tozakidou  1 , Holger Wenz, Julia Reinhardt, Ernst Nennig, Katharina Riffel, Maria Blatow, Christoph Stippich
Affiliations

Primary motor cortex activation and lateralization in patients with tumors of the central region

Magdalini Tozakidou et al. Neuroimage Clin. .

Abstract

Hemispheric lateralization is a frequently encountered phenomenon of cortical function. It describes the functional specialization of a region on one side of the brain for a given task. It is well characterized in motor and sensory, as well as language systems and becomes more and more known for various cognitive domains. While in the adult healthy brain hemispheric lateralization is mostly set, pathological processes may lead to cortical reorganization. In these cases neuroplasticity of the corresponding region in the non-dominant hemisphere seems to play an important role. In a previous study we investigated language associated regions in right-handed patients with frontal and temporal tumors of the left hemisphere. We observed a marked change of language lateralization in these patients towards the non-dominant hemisphere as measured by functional MRI (Partovi et al., 2012). In the present study we evaluated activation and lateralization of cortical motor areas in patients with tumors of the central region. BOLD fMRI was performed during unilateral voluntary movements of the contralesional hand in 87 patients. Individual correlations of measured BOLD-signals with the model hemodynamic reference function were determined on a ROI basis in single subjects and compared to those of 16 healthy volunteers. In volunteers the strongest activation is usually found in the M1 hand representation contralateral to the movement, while a weaker homotopic co-activation is observed in ipsilateral M1 (Stippich et al., 2007a). In the patient group our results show significant changes of motor activations, ranging from a reduction of M1 lateralization to equalization of M1 activations or even inversion of M1 lateralization during contralesional movements. This study corroborates in a large patient group the idea that lesions affecting M1 may lead to functional reorganization of cortical motor systems and in particular equalize hemispheric lateralization. However, it is not yet clear whether these changes are only an epiphenomenon or indeed reflect an attempt of recovery of brain function.

Keywords: Functional MRI; Functional reorganization; Ipsilateral coactivation; M1; Plasticity.

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Figures

Supplementary Fig. 1
Supplementary Fig. 1
Exemplary fMRI analysis in a patient with an astrocytoma (WHO grade II) during movement of the right (contralesional) fingers. Activation in M1 contralateral to the performed movement is circled in green, SMA activation is seen in the midline. Measured hemodynamic response function is presented in the left, lower row.
Fig. 1
Fig. 1
Analysis of activation of the motor cortical network in healthy volunteers and patients with tumors of the central region using BOLD fMRI. (A) Schematic drawing of activations in M1, PMA, SMA, IPL and SPL and (B) example of normal motor network activation in a healthy volunteer during movement of the right hand. Volunteers: (C) Comparison of right and left hand activation showed no difference. Mean r-values of activations in M1 contralateral to the performed movement or in ipsilateral M1i, SMAi/PMAi or SPLi/IPLi during movement of the left (n = 16) or right (n = 16) hand. Comparisons of volunteers and patients: (D) Pooled mean r-values in volunteers (n = 32, left panel) compared to patients (n = 87, right panel). (E) Occurrence probabilities of the different cortical activations in volunteers (n = 32, left panel) and patients (n = 87, right panel).
Fig. 2
Fig. 2
M1 lateralization in volunteers and patients based on the analysis of r-values. (A) r-Values of activation in ipsilateral M1 are presented as fraction of r-value in contralateral M1 (rrel-values); volunteers pooled data of right and left hand (n = 22, out of 32 measurements), patient movement of the contralesional hand (n = 79, in 87 patients). (B) Three degrees of M1 lateralization could be identified. The 75% percentile of healthy volunteers (rrel = 0.94) and the inversion of lateralization (rrel = 1) were used as criteria for group separation.
Fig. 3
Fig. 3
Examples of fMR images demonstrating different types of M1 lateralization in patients. (A) Schematic drawings and (B) example fMRI of different degrees of M1 lateralization: Type 1 (left column) “Normal M1 lateralization” represented by Case 11 showing robust M1 activation contralateral to the performed movement. Type 2 (middle column): Moderately changed M1 lateralization represented by Case 64. r-Value of M1 activation is still higher in M1c but pronounced ipsilateral M1i activation is present. Type 3 (right column): Inversion of M1 lateralization represented by Case 85. r-Value in M1i is higher than in M1c.
Fig. 4
Fig. 4
Lesion type, lesion localization and motor deficits. (A) Lesion type: Distribution of lesion type within different groups of M1 lateralization. Strongest effect on M1 lateralization is found in high grade tumors and metastasis (B) Lesion localization: Percentage of patients in which the pre/postcentral or the parietal lobe was affected. Effect on M1 lateralization increases with parietal lobe involvement. Note that in various patients more than one gyrus could be affected. (C) Motor deficit: Percentage of patients without (black) or with (white) motor deficits in each group of M1 lateralization. Atypical M1 lateralization is more pronounced in patients with motor deficits.
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