Cerebellar hemispheric activation ipsilateral to the paretic hand correlates with functional recovery after stroke

Abstract

An experimental lesion in the primary motor or sensory cortices in monkeys leads to functional reorganization in areas surrounding the lesion or in contralateral homologous regions. In humans, task-dependent brain activation after motor stroke seems to be multifocal and bilateral. Although many active structures are seen after stroke, their roles are unclear. For instance, the uninjured primary motor cortex may play a significant role in recovery or may be associated with mirror movements. Other motor areas, particularly those outside the affected middle cerebral artery distribution, have also been thought to play such a role, including the medial pre-motor areas and both cerebellar hemispheres. The lateral pre-motor areas might also contribute but the demarcation of primary motor and pre-motor cortices is not trivial. It is not known from existing studies how brain activation relates to behavioural change over the time course of recovery. We used functional MRI (fMRI) to study 12 patients longitudinally over the first 6 months of stroke recovery. All subjects had acute stroke causing unilateral arm weakness and had some ability to move the impaired hand within 1 month. Each patient had both motor testing and fMRI during finger and wrist movements at four points during the observed period. Six of these patients showed good motor recovery, whereas the other six did not. The imaging results support a role for the cerebellum in mediating functional recovery from stroke. The data suggest that patients with good recovery have clear changes in the activation of the cerebellar hemisphere opposite the injured corticospinal tract. Patients with poor recovery do not show such changes in cerebellar activation. No other brain region had a significant correlation with recovery. Interestingly, activation in the cerebellum ipsilateral to the injury increases transiently after stroke, independently of the success of recovery. The present work suggests a possible link between cerebellar activation and behavioural recovery from hand weakness from stroke. The underlying mechanism is not known, but it could relate to haemodynamic changes such as diaschisis or to the postulated role of the cerebellum in motor skill learning.

Sensorimotor Cortex Activation during Mirror Therapy in Healthy Right-Handed Subjects: A Study with Near-Infrared Spectroscopy

“…Although the mechanism is not clear enough, changes in cerebral activation induced by MT may play an important role in inducing neural plasticity. Previous functional imaging studies have suggested that several motor related areas (premotor cortex, supplementary motor areas, and cerebellum) as well as SMC contribute to motor recovery after stroke [22][23][24][25] . Therefore, it would be interesting to consider the effect of MT on these motor related areas in future studies.…”

Mental Practice With Motor Imagery: Evidence for Motor Recovery and Cortical Reorganization After Stroke

“…47 Furthermore, evidence to support our data comes from a study in which hemiparetic patients with good recovery showed changes in the activation of the cerebellar hemisphere opposite the injured corticospinal tract, whereas patients with poor recovery did not show such changes in cerebellar activation. 74 The appearance of cerebellar activation after mental practice may reflect unmasking of pre-existing connections 75 or mechanisms of longterm potentiation, because certain forms of learning lead to an enhancement of synaptic responses in a variety of brain structures. 76-78 Recently, long-term potentiation has been shown to be involved in learning new motor skills 79 and provides compelling evidence for long-term potentiation to be a mechanism involved in natural learning.…”

Nogo Receptor Antagonism Promotes Stroke Recovery by Enhancing Axonal Plasticity

“…To the extent that recovery occurs, function appears to be redistributed to parallel pathways or to new alternate pathways, or both. For example, partial recovery from the contralateral hemiparesis associated with a stroke involving the primary motor cortex sometimes involves activation of regions in the opposite, undamaged hemisphere (Pineiro et al, 2001;Feydy et al, 2002;Schaechter et al, 2002;Small et al, 2002;Foltys et al, 2003;Fujii and Nakada, 2003;Zemke et al, 2003). In other cases, activation of regions ipsilateral to the stroke occurs as new neurons are recruited to perform specific tasks (Pineiro et al, 2001;Feydy et al, 2002;Small et al, 2002;Foltys et al, 2003;Fujii and Nakada, 2003;Werhahn et al, 2003;Zemke et al, 2003).…”