Mark G. Bowden

Step Activity Monitor: Accuracy and test-retest reliability in persons with incomplete spinal cord injury

Recovery of walking after incomplete spinal cord injury (iSCI) is a common focus of rehabilitation, but few measurement tools capture walking performance outside the clinic or laboratory. This study determined the accuracy and test-retest reliability of the Step Activity Monitor (SAM), a microprocessor-driven accelerometer that measures walking activity. We evaluated 11 individuals with iSCI during replicate 6-minute walk tests (6MWTs) and 10-meter walk tests (10mWTs) scheduled <1 week apart. The SAM was 97% accurate compared with hand-tallied step counts. SAM values were stable across repeated walking performances (intraclass correlation coefficient = 0.97-0.99). Standard error of measurement values were 6.0 steps and 0.8 steps for the 6MWT and 10mWT, respectively. Ninety-five percent confidence intervals were 203.7 to 177.0 steps for the 6MWT and 16.1 to 12.7 steps for the 10mWT. The SAM is an accurate and reliable device for capturing walking activity in individuals with iSCI.

Lower extremity skeletal muscle function in persons with incomplete spinal cord injury

Study design:A cross-sectional study design.Objectives:To characterize and specifically quantify impairments in muscle function after chronic incomplete spinal cord injury (SCI).Setting:University of Florida, Gainesville, FL, USA.Methods:Voluntary and electrically elicited contractile measurements were performed and voluntary activation deficits were quantitatively determined in the knee extensor and ankle plantar flexor muscle groups in 10 individuals with chronic incomplete SCI (C5-T8, ASIA C or D) and age-, gender-, height- and body weight matched healthy controls.Results:Persons with incomplete-SCI were able to produce only 36 and 24% of the knee extensor torque and 38 and 26% of the plantar flexor torque generated by noninjured controls in the self-reported less-involved and more-involved limbs, respectively (P<0.05). In addition, both indices of explosive or instantaneous muscle strength, torque200 (absolute torque reached at 200u2009ms) and the average rate of torque development (ARTD) were dramatically reduced in the ankle plantar flexor and knee extensor muscle groups in persons with incomplete-SCI. However, the deficit in instantaneous muscle strength was most pronounced in the ankle plantar flexor muscles, with an 11.7-fold difference between the torque200 measured in the self-reported more involved limb and a 5-fold difference in the less-involved limb compared to control muscles. Voluntary activation deficits ranged between 42 and 66% in both muscle groups. Interestingly, electrically elicited contractile properties did not differ between the groups.Conclusion:The resultant impact of incomplete-SCI is that affected muscles not only become weak, but slow to develop voluntary torque. We speculate that the large deficit in torque200 and ARTD in the ankle plantar flexors muscles of persons with incomplete-SCI may limit locomotor function. The results presented in this study provide a quantitative and sensitive assessment of muscle function upon which future research examining rehabilitation programs aimed at restoring muscle function and promoting functional recovery after incomplete-SCI may be based.

Locomotor Training and Muscle Function After Incomplete Spinal Cord Injury: Case Series

Abstract Background/Objective: To determine whether 9 weeks of locomotor training (LT) results in changes in muscle strength and alterations in muscle size and activation after chronic incomplete spinal cord injury (SCI). Study Design: Longitudinal prospective case series. Methods: Five individuals with chronic incomplete SCI completed 9 weeks of LT. Peak isometric torque, torque developed within the initial 200 milliseconds of contraction (Torque200), average rate of torque development (ARTD), and voluntary activation deficits were determined using isokinetic dynamometry for the knee-extensor (KE) and plantar-flexor (PF) muscle groups before and after LT. Maximum muscle crosssectional area (CSA) was measured prior to and after LT. Results: Locomotor training resulted in improved peak torque production in all participants, with the largest increases in the more-involved PF (43.9% ± 20.0%), followed by the more-involved KE (21.1% ± 12.3%). Even larger improvements were realized in Torque200 and ARTD (indices of explosive torque), after LT. In particular, the largest improvements were realized in the Torque200 measures of the PF muscle group. Improvements in torque production were associated with enhanced voluntary activation in both the KE and ankle PF muscles and an increase in the maximal CSA of the ankle PF muscles. Conclusion: Nine weeks of LT resulted in positive alterations in the KE and PF muscle groups that included an increase in muscle size, improved voluntary activation, and an improved ability to generate both peak and explosive torque about the knee and ankle joints.

Soleus H-Reflex Modulation After Motor Incomplete Spinal Cord Injury: Effects of Body Position and Walking Speed

Abstract Objective: To examine position-dependent (semireclined to standing) and walking speed-dependent soleus H-reflex modulation after motor incomplete spinal cord injury (SCI). Participants: Twenty-six patients with motor incomplete SCI (mean: 45 ± 15 years) and 16 noninjured people (mean: 38 ± 14 years). Methods: Soleus H-reflexes were evoked by tibial nerve stimulation. Patients were tested in semireclined and standing positions (experiment 1) and in midstance and midswing positions (experiment 2). Results: H-reflexes were significantly greater after SCI in all positions compared with noninjured people (P < 0.05). Position-dependent modulation from semireclined to standing (normally observed in noninjured people) was absent after SCI. In SCI patients, H-reflex modulation was not significantly different at 1.2 m/s compared with 0.6 m/s treadmill walking speed; in noninjured people, H-reflex modulation was significantly greater at 1.2 m/s compared with 0.6 m/s treadmill walking speed. There was a significant positive correlation between modified Ashworth scores, a clinical measure of spasticity and soleus H-reflex amplitudes tested in all positions. A significant negative correlation was also found between H-reflexes in standing and midstance positions and the amount of assistance patients required to walk. Conclusions: An improvement in position-dependent and walking speed-dependent reflex modulation after SCI may indicate functional recovery. Future studies will use H-reflex testing to track changes as a result of therapeutic interventions.

Clinical and neurophysiologic assessment of strength and spasticity during intrathecal baclofen titration in incomplete spinal cord injury: single-subject design.

Abstract Background/Objective: Spasticity after spinal cord injury (SCI) is commonly managed with oral and intrathecal baclofen (ITB), with less attention to the effects on voluntary motor control. Studies combining clinical and neurophysiologic assessments during dose optimization are rare. Study aims (a) systematically evaluate effects of varied doses of oral and ITB on clinical and neurophysiologic measures of strength and spasticity and (b) relate clinical and neurophysiologic findings. Methods: A 41-year-old man with an incomplete T11-ASIA D SCI was studied during ITB titration. Spasticity and strength in the lower extremities were assessed clinically and neurophysiologically at 5 different daily dosages of baclofen: (a) 80 mg oral, (b) 80 mg oral/50 jig ITB, (c) 80 mg oral/125 jug ITB, (d) 30 mg oral/125 jig ITB, and (e) 125 μg ITB only. Results: A dose-dependent change in the Ashworth score and lower limb motor score was observed during titration of oral and ITB. Whereas the Hoffman (H)-reflex was abolished after the introduction of ITB, the flexion withdrawal reflex approximated a dose-dependent pattern. Changes in the motor score and EMG during voluntary muscle activation were proportionally smaller than the corresponding changes in clinical and neurophysiologic measures of spasticity. Neurophysiologic assessment largely paralleled clinical findings. Conclusions: This single-subject study shows that the control of spasticity can be achieved without detrimental effects on strength in incomplete SCI and suggests the need for including strength testing in comprehensive clinical assessment of spasticity. The study shows convergent validity between clinical and neurophysiologic assessments during ITB dose titration. Adding neurophysiologic assessment to clinical assessment may provide objectivity and sensitivity and facilitate decision-making during ITB titration.

Clinical trials in neurorehabilitation.

The clinical trial is essential to testing efficacy and effectiveness of therapeutic interventions. Neurorehabilitation presents unique challenges in the execution of clinical trials due to the complexity of both human interface with complex interventions and clinical/research staff interaction. Attention to key elements, recruitment, retention, treatment fidelity, and control intervention selection, contributes to successful conduct of a trial. Alternatives to the randomized controlled trial and outcome measure selection are important considerations contributing to the merit of the trial. While clinical trial outcomes contribute to the scientific evidence, their true value and impact comes in the next step, translation to clinical practice and the improvement of patient outcomes and qualify of life. Translation of evidence into practice may best be achieved via partnerships of scientists, clinicians, and administrators resulting in a dynamic interface between science and practice, the laboratory, and the clinic.