Objective Assessment of Cortical Activity Changes in Stroke Patients before and after Hand Rehabilitation with and without Botulinum Toxin Injection

Abstract

Summary erebrovascular stroke is considered the leading cause of adults‟ long term disability. Post-stroke upper limb spasticity can be disabling and can result in several functional limitations; it impairs movement, self-care, and hygiene; causes pain; alters body image; and as a result, the patient may develop poor self-esteem and poor social participation (Francisco & McGuire, 2012). There is some evidence which suggests that the occurrence of post-stroke spasticity is paralleled by reorganization of the central nervous system structures. Spasticity is one example of the maladaptive plasticity (Pundik et al., 2014). Botulinum toxin-A injection is considered to the 1st line of treatment of focal spasticity. Although the main action of botulinum toxin is peripheral inhibition of presynaptic releases of acetyl-choline at the neuromuscular junction, somatosensory evoked potentials and fMRI studies have suggested a possible central effect of the peripherally injected botulinum toxin (Palomar & Mir, 2012). The present study was carried out to assess the functional, electrophysiological, and cortical activation outcome of two anti-spastic protocols for stroke hand and wrist, and to detect the possible central role of botulinum C  Summary 214 toxin in an attempt to implement a regimen for its regular injection to maintain the best functional activity of the hand and wrist. This study was conducted on 30 patients with poststroke upper limb spasticity. Our patients were randomly assigned into two groups (group A & B), based on the treatment received, each group included 15 patients. The study also included 15 healthy volunteers, to determine the reference values of electrophysiological and fMRI parameters. Clinical assessment of our patients included; assessment of muscle tone using Modified Ashworth scale (MAS), assessment of hand grip strength using hand held dynamometer and sphygmomanometer, and assessment of upper limb function using Action Research Arm Test and Nine Hole peg test. Electrophysiological assessment of spasticity included H max/M max ratio and F max/M max ratio, while cortical activity was studied using somatosensory evoked potential (N20 latency and N20-P25 amplitude), and fMRI. Patients were assessed at baseline and at 8 weeks post-treatment. Both patient groups (A&B) received the same rehabilitation program for one hour, three times per week for 8 weeks while group B received additional botulinum toxin- A injection in the spastic muscles of hand and wrist.  Summary 215 At baseline there was no significant difference in any of clinical, functional, electrophysiological, and fMRI data between the two patient groups. While the Fmax/Mmax ratio, Hmax/Mmax ratio, N20 latency were higher in both patient groups in comparison to that of the control. On other hand, the N20-P25 amplitude was significant lower in our patient groups compared to that of the control. Also the cortical activity measured by the fMRI in the following areas; bilateral primary motor area, supplementary motor area, basal ganglia, thalamus, cerebellum, and ipsilateral somatosensory area was higher in our two patient groups in comparison to that of the control, while the activity of the contralateral somatosensory cortex was lower in our patients than that of the control group. When the 8-weeks post-treatment assessment was compared to the baseline assessment, group A showed significant reduction of MAS of fingers long flexors and pronators; improvement of hand grip strength, functional scores, as well as reduction of Hmax/Mmax ratio. Group A also showed reduction of N20 latency in response to treatment. While the fMRI cortical activity showed significant reduction in the contralateral; primary motor area, supplementary motor area, basal ganglia, thalamus, cerebellum, and ipsilateral somatosensory cortex. On the other hand, group B showed significant reduction of MAS of wrist flexors, fingers long flexors and pronators; hand grip strength; functional scores, as well as  Summary 216 reduction of Fmax/Mmax ratio, and Hmax/Mmax ratio posttreatment. Group B also showed reduction in N20 latency and increase in N20-P25 amplitude post-treatment. While the fMRI cortical activity in group B showed significant reduction in the following areas bilateral; primary motor area, supplementary motor area, basal ganglia, thalamus, cerebellum, and ipsilateral somatosensory cortex, while the activity increased in the contralateral somatosensory cortex post-treatment in comparison to baseline.