Ina M. Tarkka

Effects of intensive therapy using gait trainer or floor walking exercises early after stroke.

OBJECTIVE To analyse the effects of gait therapy for patients after acute stroke in a randomized controlled trial. METHODS Fifty-six patients with a mean of 8 days post-stroke participated in: (i) gait trainer exercise; (ii) walking training over ground; or (iii) conventional treatment. Patients in the gait trainer exercise and walking groups practiced gait for 15 sessions over 3 weeks and received additional physiotherapy. Functional Ambulatory Category and several secondary outcome measures assessing gait and mobility were administered before and after rehabilitation and at 6-month follow-up. Patients also evaluated their own effort. RESULTS Walking ability improved more with intensive walk training compared with conventional treatment; median Functional Ambulatory Category was zero in all patients at the start of the study, but it was 3 in both walk-training groups and 0.5 in the conventional treatment group at the end of the therapy. Median Functional Ambulatory Category was 4 in both walk-training groups and 2.5 in conventional treatment group at 6-month follow-up. Mean accomplished walking distance was not different between the gait trainer exercise and over ground walking groups. Borg scale indicated more effort in over ground walking. Secondary outcomes also indicated improvements. CONCLUSION Exercise therapy with walking training improved gait function irrespective of the method used, but the time and effort required to achieve the results favour the gait trainer exercise. Early intensive gait training resulted in better walking ability than did conventional treatment.

Cortical excitability changes following grasping exercise augmented with electrical stimulation

Rehabilitation with augmented electrical stimulation can enhance functional recovery after stroke, and cortical plasticity may play a role in this process. The purpose of this study was to compare the effects of three training paradigms on cortical excitability in healthy subjects. Cortical excitability was evaluated by analysing the input–output relationship between transcranial magnetic stimulation intensity and motor evoked potentials (MEPs) from the flexor muscles of the fingers. The study was performed with 25 healthy volunteers who underwent 20-min simulated therapy sessions of: (1) functional electrical stimulation (FES) of the finger flexors and extensors, (2) voluntary movement (VOL) with sensory stimulation, and (3) therapeutic FES (TFES) where the electrical stimulation augmented voluntary activation. TFES training produced a significant increase in MEP magnitude throughout the stimulation range, suggesting an increase in cortical excitability. In contrast, neither the FES nor voluntary movement alone had such an effect. These results suggest that the combination of voluntary effort and FES has greater potential to induce plasticity in the motor cortex and that TFES might be a more effective approach in rehabilitation after stroke than FES or repetitive voluntary training alone.

Gait characteristics and functional ambulation profile in patients with chronic unilateral stroke

Titianova EB, Pitkänen K, Pääkkönen A, Sivenius J, Tarkka IM: Gait characteristics and functional ambulation profile in patients with chronic unilateral stroke. Am J Phys Med Rehabil 2003;82:778–786. Objective Recent technical progress in gait analysis has resulted in portable walkways with embedded pressure-sensitive sensors. Often claims are made in connection with new equipment of their straightforward clinical use. The purpose of the present study was to assess whether the functional ambulation profile (FAP), calculated from walkway data, is a sensitive measure in the characterization of dissimilar patients with chronic hemiparesis due to stroke. Design We investigated the relationships between FAP and the type of stroke, patients’ functional disability, and spatial and temporal variables of gait obtained with the pressure sensor system walkway. Gait variables and FAP scores were compared in 25 patients with residual hemiparesis due to stroke and in 31 healthy subjects. Results A prolonged swing phase in the affected side and a prolonged stance phase in the nonaffected side were found in patients. Footprint pressure data revealed reduced peak pressure of the affected-side metatarsal area in patients, probably reflecting foot paresis. Higher Barthel Index score and lower Rankin Scale score were reflected in FAP scores. Conclusions The FAP scores of patients reflected well their characteristic spatio-temporal gait variations; however, the FAP score seemed a reliable measure of gait normality/abnormality only in rather unhurried gait. Thus, it is useful when a single number is needed.

Augmentation of Auditory N1 in Children with Fragile X Syndrome

We compared the N1 responses of the auditory event-related brain potentials (ERPs) in school-aged children with fragile X syndrome to age-matched controls in order to assess auditory processing. Event-related potentials to non-attended standard and deviant tone stimuli were recorded with EEG electrodes and here the standard tones were analysed. The amplitude of the N1 component to standard tones was significantly larger in children with fragile X syndrome than in control children. In addition, the global field power maximum of ERP corresponding to the N2 component was significantly (p<0.05) larger in fragile X children than in controls. The N2 scalp distribution in children with fragile X syndrome appeared more frontal than that in controls. Furthermore, the fragile X children exhibited no habituation of N1 and an absence of N2 sensitization for repeated tones. Increased responsiveness observed in the N1 evoked potential together with abnormal habituation of auditory responses in childhood may indicate increased sensory sensitivity for auditory stimuli in fragile X syndrome. The data, though very limited, suggest that stimulus processing in the auditory afferent pathways and/or in the corresponding cortical receiving areas is abnormal in children with fragile X syndrome.

Footprint analysis of gait using a pressure sensor system.

The purpose of this study was to investigate if the detailed pressure data of the footprints of normal gait add essential information to the spatio-temporal variables of gait. The gait of 62 healthy adult subjects was investigated using GAITRite pressure sensor system. Each footprint was divided into 12 equal trapezoids and after that the hindfoot, midfoot and forefoot analysis was developed. A typical activation pattern of the sensors with two peaks of active area and peak pressure distribution during normal walking was obtained. The first peak reflected the heel strike, and the second peak reflected push-off at the end of the stance phase. The lowest pressure values were in the midfoot, where the lateral part of the foot activated sensors more than the medial part. The footprint patterns of right and left legs were symmetrical and corresponded with the symmetry found in the spatio-temporal variables of gait. The variability for the active area and the peak pressure were more pronounced for the lateral part of the midfoot and a smaller variation was seen in areas with concentrated observations (e.g. 1st, 2nd and 5th lateral trapezoids). Increasing active area in the forefoot was associated with decreasing pressure sensor activity in the midfoot. The footprint patterns identified the symmetry between the legs and at the same time revealed the velocity performance.

Surface EMG and acceleration signals in Parkinson’s disease: feature extraction and cluster analysis

We present an advanced method for feature extraction and cluster analysis of surface electromyograms (EMG) and acceleration signals in Parkinson’s disease (PD). In the method, 12 different EMG and acceleration signal features are extracted and used to form high-dimensional feature vectors. The dimensionality of these vectors is then reduced by using the principal component approach. Finally, the cluster analysis of feature vectors is performed in a low-dimensional eigenspace. The method was tested with EMG and acceleration data of 42 patients with PD and 59 healthy controls. The obtained discrimination between patients and controls was promising. According to clustering results, one cluster contained 90% of the healthy controls and two other clusters 76% of the patients. Seven patients with severe motor dysfunctions were distinguished in one of the patient clusters. In the future, the clinical value of the method should be further evaluated.

Alterations in cortical excitability in chronic stroke after constraint-induced movement therapy.

Abstract Objective: Cerebral stroke is a major cause for long-term disability in the elderly and it is often manifested in hemiparesis of the upper extremity. Constraint-induced movement therapy (CIMT), an intensive 2 week rehabilitation program, improves affected upper limb motor abilities in subjects with stroke. Intensive training has also been suggested to modify neural function. We wanted to find out if there are changes in cortical excitability in subjects with chronic stroke after CIMT. Methods: Participants were 13 subjects with stroke who fulfilled the entry criteria for the CIMT program. The motor function of the affected arm and hand was assessed using a structured motor behavior test (WMFT). The cortical excitability changes were assessed in regard to involuntary and voluntary motor control, former with transcranial magnetic stimulation (TMS) and latter with movement-related cortical potentials (MRCP). Results: The motor abilities of the affected arm improved after 2 week rehabilitation (total time in WMFT shortened 36%). The motor-evoked potential (MEP) amplitudes were unchanged following the stimulation of the non-affected hemisphere; however, the MEP amplitudes of lateral stimulation locations increased significantly in the affected side after the intervention. The power spectra of MRCPs revealed reduced peak frequency over the supplementary motor area when the affected hand was moved. However, no changes occurred when the healthy hand was moved. Discussion: We show changes in cortical electrical excitability while performing both involuntary and voluntary movements after 2 weeks of CIMT in subjects with chronic stroke. These changes may be seen as a sign of neural reorganization instigated by the intervention.

Analysis of surface EMG signal morphology in Parkinson's disease.

A novel approach is presented for the analysis of surface electromyogram (EMG) morphology in Parkinsons disease (PD). The method is based on histogram and crossing rate (CR) analysis of the EMG signal. In the method, histograms and CR values are used as high-dimensional feature vectors. The dimensionality of them is then reduced using the Karhunen-Loève transform (KLT). Finally, the discriminant analysis of feature vectors is performed in low-dimensional eigenspace. Histograms and CR values were chosen for analysis, because Parkinsonian EMG signals typically involve patterns of EMG bursts. Traditional methods of EMG amplitude and spectral analysis are not effective in analyzing impulse-like signals. The method, which was tested with EMG signals measured from 25 patients with PD and 22 healthy controls, was promising for discriminating between these two groups of subjects. The ratio of correct discrimination by augmented KLT was 86% for the control group and 72% for the patient group. On the basis of these results, further studies are suggested in order to evaluate the usability of this method in early stage diagnostics of PD.

Increased Perfusion in Motor Areas after Constraint-Induced Movement Therapy in Chronic Stroke: A Single-Photon Emission Computerized Tomography Study

Hemiparesis is the most common deficit after cerebral stroke. Constraint-induced movement therapy (CIMT) is a new neurorehabilitation method that emphasizes task-relevant repetitive training for the stroke hand. Twelve chronic stroke patients were studied with single-photon emission computerized tomography at rest before and after the two-week CIMT period. Increased perfusion was found in motor control related areas. The specific areas with an increase in perfusion in the affected hemisphere were in the precentral gyrus, premotor cortex (Brodmanns area 6 (BA6)), frontal cortex, and superior frontal gyrus (BA10). In the nonaffected hemisphere, perfusion was increased in the superior frontal gyrus (BA6) and cingulate gyrus (BA31). In the cerebellum increased perfusion was seen bilaterally. The brain areas with increased perfusion receive and integrate the information from different sensory systems and plan the movement execution. Regional cerebral perfusion decreased in the lingual gyrus (BA18) in the affected hemisphere. In the nonaffected frontal cortex, two areas with decreased perfusion were found in the middle frontal gyrus (BA8/10). Also, the fusiform gyrus (BA20) and inferior temporal gyrus (BA37) in the non-affected hemisphere showed decreased perfusion. Intensive movement therapy appears to change local cerebral perfusion in areas known to participate in movement planning and execution. These changes might be a sign of active reorganization processes after CIMT in the chronic state of stroke.

Functional MRI and motor behavioral changes obtained with constraint-induced movement therapy in chronic stroke

Background:  The clinical benefits of intensive stroke rehabilitation vary individually. We used multimodal functional imaging to assess the relationship of clinical gain and imaging changes in patients with chronic stroke whose voluntary motor control improved after constraint‐induced movement therapy (CIMT).