Parietofrontal motor pathways and their association with motor function after stroke

Abstract

Corticocortical interactions between the primary motor cortex, the ventral premotor cortex and posterior parietal motor areas, such as the anterior and caudal intraparietal sulcus, are relevant for skilled voluntary hand function. It remains unclear to what extent these brain regions and their interactions also contribute to basic motor functions after stroke. We hypothesized that white matter integrity of the underlying parietofrontal motor pathways between these brain regions might relate to residual motor function after stroke. Twenty-five chronic stroke patients were recruited (aged 64 ± 8.8 years, range 46-75, 17 males, one left-handed) and evaluated 34 months after stroke (range 12-169 months) by means of grip force, pinch force and the Fugl-Meyer assessment of the upper extremity. Based on these measures, motor function was estimated applying a factor analysis with principal component extraction. Using diffusion tensor imaging and probabilistic tractography we reconstructed probable intrahemispheric trajectories between the primary motor cortex, the ventral premotor cortex and the anterior and caudal intraparietal sulcus in each patient. White matter integrity was estimated for each individual tract by means of fractional anisotropy. Generalized linear modelling was used to relate tract-related fractional anisotropy to the motor function. We found that the white matter integrity of the fibre tracts connecting the ventral premotor cortex and the primary motor cortex (P < 0.001) and the anterior intraparietal sulcus and the ventral premotor cortex (P < 0.01) positively correlated with motor function. The other tracts investigated did not show a similar structure-behaviour association. Providing first structural connectivity data for parietofrontal connections in chronic stroke patients, the present results indicate that both the ventral premotor cortex and the posterior parietal cortex might play a relevant role in generating basic residual motor output after stroke.

Synergistic but independent: The role of corticospinal and alternate motor fibers for residual motor output after stroke

“…The present data is well in line with a variety of reports showing that a stroke leads to the disruption of the CST a and that its residual structural state critically influences residual motor output (Lindenberg et al, 2010, Rüber et al, 2012, Schaechter et al, 2009, Schulz et al, 2015b), for a comprehensive review please see Koch and colleagues (Koch et al, 2016). It has already been suggested that these remote lesion effects might also lower white matter integrity of aMF a comprising cortico-rubro-spinal and cortico-reticulo-spinal fibers due to Wallerian degeneration (Lindenberg et al, 2012, Schaechter et al, 2009), particularly originating from M1 (Rüber et al, 2012).…”

“…They were evaluated by means of grip force (calculated as the ratio between the affected and unaffected hand, mean value 0.2 ± 0.3, range 0–1.2) and the upper limb score of the Fugl-Meyer assessment (mean value 40.1 ± 19.3, range 4–66). In order to calculate a more general motor score including distal and proximal motor components, both measures were combined to one composite motor output score (MO) by principal component analysis (1st principal component explaining 75% of variance in both measures) as applied in previous trials (Schulz et al, 2015b). Table 1 summarizes the clinical data for all patients.…”

“…Multiple linear regression models were fitted using R's lm for the absolute CST and aMF FA values and residual motor output in the stroke patients (MO, log-transformed after data translation to a minimum of 1, for the sake of a normal distribution). Age and the information whether the dominant or non-dominant hemisphere was lesioned ( Dom ) were included as additional variables to adjust the target effects in agreement with recent reports (Schulz et al, 2015a, Schulz et al, 2015b). Estimated coefficients are given with 95% CI.…”

“…Structural brain imaging has significantly enhanced our understanding of how brain networks react to focal lesions caused by e.g., an ischemic stroke (Lindenberg et al, 2010, Rüber et al, 2012, Schaechter et al, 2009, Schulz et al, 2015b). For a comprehensive review see Koch and colleagues (Koch et al, 2016).…”

The functional role of beta‐oscillations in the supplementary motor area during reaching and grasping after stroke: A question of structural damage to the corticospinal tract

“…As for the structural changes, the lesion volume has little explanatory value of motor function after stroke (Puig et al, ; Schiemanck, Kwakkel, Post, Kappelle, & Prevo, ), whereas the lesion location (Crafton, ; Shelton & Reding, ) and the microstructural white matter integrity has been shown to strongly determine motor function (Koch & Hummel, ). In particular, better integrity of the lesioned corticospinal tract (CST) is positivity correlated with better motor function (Lindenberg et al, ; Schulz et al, ; Schulz et al, ). Disconnection from descending pathways results in neuroplastic changes toward alternative motor network activation patterns.…”