Meta M. Dimitrijevic

Modification of motor control of wrist extension by mesh-glove electrical afferent stimulation in stroke patients

OBJECTIVE To study the effect of mesh-glove afferent stimulation on motor control of voluntary wrist movement in stroke patients who have chronic neurological deficits. DESIGN Case series. Motor control was evaluated by surface EMG of the arm muscles and kinematics of voluntary wrist movements on 3 occasions: before and immediately after the initial session of mesh-glove stimulation, and then after a daily mesh-glove stimulation program conducted over several months. SETTING Tertiary care center. PATIENTS The inclusion criteria were: a history of stroke lasting longer than 6 months; completion of a rehabilitation program during early recovery; and preserved cognitive and communicative ability. Fourteen referred patients (age 63 +/- 9yr; time since stroke 31 +/- 22mo) fulfilled the criteria and completed the daily stimulation program. INTERVENTION A single initial and then daily mesh-glove electrical afferent stimulation was applied to the hand of the involved upper limb for 20 to 30min. MAIN OUTCOME MEASURES Surface EMGs from the affected biceps brachii and wrist extensor muscles and amplitudes of wrist movements were analyzed. RESULTS The single, initial mesh-glove application had no effect on outcome measures. Following a daily mesh-glove stimulation program, however, both the amplitude of wrist extension movement and wrist extensor integrated EMG were significantly increased while coactivation of biceps brachii decreased. These findings were most prominent in subjects with partially preserved voluntary wrist movements. CONCLUSION We conclude that daily mesh-glove stimulation can modify altered motor control and improve voluntary wrist extension movement in stroke subjects with chronic neurological deficits.

Omental transposition in chronic spinal cord injury

The results of omental transposition in chronic spinal cord injury have been reported in 160 patients operated upon in the United States, Great Britain, China, Japan, India and Mexico, with detailed outcomes reported in few studies. Recovery of function to a greater degree than expected by natural history has been reported. In this series, 15 patients with chronic traumatic spinal cord injury (>1.5 years from injury) underwent transposition of pedicled omentum to the area of spinal cord injury. Of the first series of four patients who were operated upon in 1988, one died, one was lost to follow-up and two were followed with sequential neurological examinations and Magnetic Resonance Imaging (MRI) scans preoperatively, at 1 year post injury and 4½ years post injury. Another 11 patients were operated in 1992 and underwent detailed neurological and neurophysiological examinations and had MRI scans preoperatively and every 4 months for at least 1 year after surgery. All patients completed a detailed self-report form. Of the total of 13 operated patients in both series followed for 1-4½ years, six reported some enhanced function at 1 year and five of these felt the changes justified surgery primarily because of improved truncal control and decreased spasticity. MRI scans showed enlargement of the spinal cord as compared to preoperative scans in seven patients. Increased T2 signal intensity of the spinal cord was found by 1 year after surgery in eight of 13 operated patients. Neurophysiological examinations of 11 patients in the second series agreed with self-reports of increases or decreases in spasticity (r = 0.65, P0.03). Somatosensory evoked potentials and motor evoked potentials at 4 month intervals up to 1 year in these patients showed no change after surgery. Neurological testing, using the American Spinal Injury Association (ASIA) and International Medical Society of Paraplegia (IMSOP) international scoring standards, failed to show any significant changes when the 1-year post operative examination was compared to the first preoperative examination except for decreased sensory function after surgery which approached statistical significance. When the 11 patients in the second series were compared to eight non-operated matched patients, followed for a similar length of time, no significant differences were found. Complications encountered in the operated patients from both series included one postoperative death from a pulmonary embolus, one postoperative pneumonia, three chronic subcutaneous cerebrospinal fluid (CSF) fistulae requiring wound revision, and one patient who developed biceps and wrist extensor weakness bilaterally requiring graft removal. We conclude that the omental graft remains viable over time and this operation can induce anatomical changes in the spinal cord as judged by MRI. Some patients reported subjective improvement but this was not supported by objective testing. We, therefore, find no justification for further clinical trials of this procedure in patients who have complete or sensory incomplete lesions. Further testing in motor incomplete patients would seem appropriate only with compelling supportive data.

Reflex effects of vibration in patients with spinal cord lesions.

The vibration reflex was studied in 49 patients with traumatic spinal cord lesions. It was elicited in all patients, even after presumably complete division of the cord. The vibration reflex consisted of a short-latency, brief outburst of phasic activity of motor units, followed by rapidly decreasing phasic component and a later slowly declining tonic component. When periods of vibration were repeated at short intervals of 2 to 10 seconds, the responses showed an approximately exponential decline, although the beginning of each subsequent response was always larger than the end of the preceding response. A large part of this decline can be characterized as a habituation of the vibration reflex. In comparison with the vibration reflex in normal subjects, the phasic component was increased and the tonic one reduced. The tonic component was especially susceptible to potentiation and dishabituation by voluntary effort to contract the vibrated muscle, even in some patients with no other evidence that the lesion was incomplete. We suggest that the tonic component of the human vibration reflex depends, at least in part, on segmental interneurons and their descending spinal pathways, while the phasic component depends mainly on the excitability level of spinal motoneurons.

Modulation of Stimulation Frequency of Spinal Cord Afferents with Constant Electrode Site and Stimulus Intensity Can Induce a Variety of Movements

With methodological development for external control of afferents in order to evoke functional movements - afferent functional electrical stimulation (aFES) - we have noticed that frequency of delivered stimuli can have specific influence on motor control.