Towards development of a nonhuman primate model of carpal tunnel syndrome: performance of a voluntary, repetitive pinching task induces median mononeuropathy in Macaca fascicularis.

This study investigated changes in median sensory nerve conduction velocity (SNCV) over several weeks of exposure to a voluntary, moderately forceful, repetitive pinching task performed for food rewards by a small sample of young adult female monkeys (Macaca fascicularis). SNCV, derived from peak latency, decreased significantly in the working hands of three of the four subjects. The overall decline in NCV was 25%-31% from baseline. There was no decrease in SNCV in the contralateral, nonworking hands. Several weeks after being removed from the task, SNCV returned to within 87%-100% of baseline. MRI showed enlargement of the affected nerves near the proximal end of the carpal tunnel, at the time of maximal SNCV slowing. This new animal model demonstrates a temporally unambiguous relationship between exposure to a moderately forceful, repetitive manual task and development of median mononeuropathy at the wrist, and recovery of SNCV following termination of task exposure. This study contributes to the pattern of evidence of a causal relationship between manual work, median mononeuropathy, and carpal tunnel syndrome in humans. In the future, this new animal model could be used to characterize dose-response relationships between risk factors and carpal tunnel syndrome.

Long-Term Follow-up to a Randomized Controlled Trial Comparing Peroneal Nerve Functional Electrical Stimulation to an Ankle Foot Orthosis for Patients With Chronic Stroke.

BACKGROUND: Evidence supports peroneal nerve functional electrical stimulation (FES) as an effective alternative to ankle foot orthoses (AFO) for treatment of foot drop poststroke, but few long-term, randomized controlled comparisons exist. OBJECTIVE: Compare changes in gait quality and function between FES and AFOs in individuals with foot drop poststroke over a 12-month period. METHODS: Follow-up analysis of an unblinded randomized controlled trial (ClinicalTrials.gov #NCT01087957) conducted at 30 rehabilitation centers comparing FES to AFOs over 6 months. Subjects continued to wear their randomized device for another 6 months to final 12-month assessments. Subjects used study devices for all home and community ambulation. Multiply imputed intention-to-treat analyses were utilized; primary endpoints were tested for noninferiority and secondary endpoints for superiority. Primary endpoints: 10 Meter Walk Test (10MWT) and device-related serious adverse event rate. Secondary endpoints: 6-Minute Walk Test (6MWT), GaitRite Functional Ambulation Profile, and Modified Emory Functional Ambulation Profile (mEFAP). RESULTS: A total of 495 subjects were randomized, and 384 completed the 12-month follow-up. FES proved noninferior to AFOs for all primary endpoints. Both FES and AFO groups showed statistically and clinically significant improvement for 10MWT compared with initial measurement. No statistically significant between-group differences were found for primary or secondary endpoints. The FES group demonstrated statistically significant improvements for 6MWT and mEFAP Stair-time subscore. CONCLUSIONS: At 12 months, both FES and AFOs continue to demonstrate equivalent gains in gait speed. Results suggest that long-term FES use may lead to additional improvements in walking endurance and functional ambulation; further research is needed to confirm these findings.

Surface and wire electromyographic. Recording during fatiguing exercise.

Electromyographic (EMG) signals are routinely recorded during assessments of biomechanic activity for ergonomic and medical purposes. Surface and intramuscular electrodes (i.m.) are employed by different researchers and there is a continuing need to understand the indications for each. This research evaluated the reproducibility of the shift of the frequency content of the EMG signals during fatiguing exercise using simultaneous recording with these two electrode types. Using healthy adult volunteers, EMG recordings from the vastus lateralis (VL) and anterior tibial (AT) were made during repeated isokinetic exertions causing fatigue. The median power frequency (MPF) was calculated for a 0.5 sec sample of data taken during each concentric contraction. Test-retest, and multiple day repeat testing were performed to exclude the effects of training and fatigue upon the data. Surface electrode recordings demonstrated better reliability testing with values of 0.54 for VL and 0.68 for AT, while simultaneous i.m. recordings were -0.90 and 0.47, respectively. This finding of greater reliability, combined with the ease of use of surface electrodes suggest that they should be preferred for most studies of EMG analysis of muscle fatigue.

The effects of peroneal nerve functional electrical stimulation versus ankle-foot orthosis in patients with chronic stroke: a randomized controlled trial.

BACKGROUND: Evidence supports peroneal nerve functional electrical stimulation (FES) as an effective alternative to ankle-foot orthoses (AFO) for treatment of foot drop poststroke, but few randomized controlled comparisons exist. OBJECTIVE: To compare changes in gait and quality of life (QoL) between FES and an AFO in individuals with foot drop poststroke. METHODS: In a multicenter randomized controlled trial (ClinicalTrials.gov #NCT01087957) with unblinded outcome assessments, 495 Medicare-eligible individuals at least 6 months poststroke wore FES or an AFO for 6 months. Primary endpoints: 10-Meter Walk Test (10MWT), a composite of the Mobility, Activities of Daily Living/Instrumental Activities of Daily Living, and Social Participation subscores on the Stroke Impact Scale (SIS), and device-related serious adverse event rate. Secondary endpoints: 6-Minute Walk Test, GaitRite Functional Ambulation Profile (FAP), Modified Emory Functional Ambulation Profile (mEFAP), Berg Balance Scale (BBS), Timed Up and Go, individual SIS domains, and Stroke-Specific Quality of Life measures. Multiply imputed intention-to-treat analyses were used with primary endpoints tested for noninferiority and secondary endpoints tested for superiority. RESULTS: A total of 399 subjects completed the study. FES proved noninferior to the AFO for all primary endpoints. Both the FES and AFO groups improved significantly on the 10MWT. Within the FES group, significant improvements were found for SIS composite score, total mFEAP score, individual Floor and Obstacle course time scores of the mEFAP, FAP, and BBS, but again, no between-group differences were found. CONCLUSIONS: Use of FES is equivalent to the AFO. Further studies should examine whether FES enables better performance in tasks involving functional mobility, activities of daily living, and balance.

Electrical safety in electrodiagnostic medicine.

Enhancing safety during procedures is one of our primary professional obligations to our patients. The vigilant application of basic principles allows electrodiagnostic medicine consultants to maintain a safe environment for both patients and office staff. Use of a nerve stimulator in close proximity to the path of wires or catheters that enter the heart or great vessels should be avoided; a separation of at least 15 cm (6 in) is recommended. Other testing of nerves in the limbs can be performed safely, particularly in patients with modern bipolar pacemakers and even with cardiac defibrillation devices in place. Current must never have a path to flow through the torso. Proper grounding of electrodiagnostic equipment should be ensured, and both the instruments and the wall plugs should be tested periodically. In addition, adherence to the proper stimulation intensity and avoidance of overstimulation is important not only for safety but also because it improves measurement accuracy and patient comfort.

Score reliability and construct validity of the Flinn Performance Screening Tool for adults with symptoms of carpal tunnel syndrome.

OBJECTIVE: We investigated the psychometric properties of the Flinn Performance Screening Tool (FPST) for people referred with symptoms of carpal tunnel syndrome (CTS). METHOD: An occupational therapist collected data from 46 participants who completed the Functional Status Scale (FSS) and FPST after the participants' nerve conduction velocity study to test convergent and contrasted-group validity. RESULTS: Seventy-four percent of the participants had abnormal nerve conduction studies. Cronbach's α coefficients for subscale and total scores of the FPST ranged from .96 to .98. Intrarater reliability for six shared items of the FSS and the FPST was supported by high agreement (71%) and a fair κ statistic (.36). Strong to moderate positive relationships were found between the FSS and FPST scores. Functional status differed significantly among severe, mild, and negative CTS severity groups. CONCLUSION: The FPST shows adequate psychometric properties as a client-centered screening tool for occupational performance of people referred for symptoms of CTS.

Phrenic nerve stimulation in the evaluation of ventilator-dependent individuals with C4- and C5-level spinal cord injury.

Three individuals with C4 or C5 spinal cord injuries (SCI) were seen in follow-up for management of their late complications, which included impaired ventilation. Electrodiagnostic studies were performed on all three as part of the assessment of the function of their phrenic nerves and diaphragm muscles in relation to their need for mechanical ventilator support. Each patient had evidence of lower-motor neuron injury to the phrenic nerves. Two of the patients who initially displayed small-amplitude (<0.1 mV) compound muscle action potentials (CMAP) bilaterally were later reevaluated during the course of their observation in the outpatient rehabilitation clinic. The CMAP amplitude of the diaphragm increased in these two cases during the 3-11 mos after SCI. Evidence of nerve recovery occurred in parallel with improvements in pulmonary function testing and was followed by successful weaning from the ventilator. These individuals both gained ventilator independence after the CMAP amplitude of least one hemidiaphragm was >0.4 mV. In the third case, early failure of ventilator weaning was reported to the patient as a poor prognostic sign. At the time of our first evaluation 11 mos after injury, a CMAP of 1.0 mV was seen on the right, with an absent response on the left. In case 3, the needle electromyogram demonstrated voluntary active motor unit action potentials that provided additional electrophysiologic support for phrenic nerve function. Phrenic nerve-conduction studies can provide useful measures in assessing the recovery of lower-motor neuron diaphragm function in relation to impaired ventilation in individuals with C4- or C5-level SCI.

A novel technique for recording from the serratus anterior.

OBJECTIVE: To design an electrodiagnostic technique by which to accurately record the serratus anterior compound muscle action potential (CMAP). DESIGN: Observational study. SETTING: Academic electromyography laboratory. PARTICIPANTS: Fifteen healthy volunteers. INTERVENTIONS: The long thoracic nerve was stimulated by using a standard bipolar surface electrode in the axilla, just anterior to the midaxillary line. The serratus anterior CMAP was recorded by using a self-adhesive, 8.0 x 0.5 cm, ring electrode as the E1 placed across the serratus anterior interdigitations starting at the nipple level. A self-adhesive, motor (1 x 1 cm) electrode was used as E2 and placed over the seventh rib. A standard self-adhesive ground electrode was placed over the inferior region of the latissimus dorsi. MAIN OUTCOME MEASURES: Distal motor latency (DML), and CMAP amplitude and duration. RESULTS: After removing 2 outliers, the results are reported as the mean +/- 1.96 standard deviations. Right long thoracic DML was 2.2+/-1.0ms and the left was 2.3+/-0.9ms, with a side-to-side mean difference of 0.3+/-0.4ms. The right serratus CMAP amplitude was 3.8+/-3.9mV and the left was 3.9+/-3.7mV, with a side-to-side mean difference of 0.6+/-1.2mV. Statistical analysis did not reveal a significant side-to-side difference for DML or CMAP amplitude. Both sides were combined to form a single set of trials for DML and CMAP amplitude. The mean DML became 2.2+/-0.7ms, and the CMAP amplitude was 3.5+/-1.9mV. The CMAP duration was 14.5+/-4.3ms on the right and 14.5+/-4.1ms on the left. A significant, positive correlation existed between height and DML ( P <.02). The 95% confidence intervals for DML and CMAP amplitudes were 2.1 to 2.5ms and 1.5 to 3.1mV, respectively. CONCLUSIONS: Our latency, side-to-side comparisons and amplitude data were consistent with other motor nerve conduction findings in the literature. Stimulating the long thoracic nerve in the axilla will provide a reliable technique to aid in the diagnosis and treatment of long thoracic neuropathy.

Large-array surface electromyography in low back pain: a pilot study.

STUDY DESIGN: A large-array surface electromyography device was used to collect data from healthy pain-free persons and from those with acute or chronic low back pain. Images of regional muscle electromyographic activity were assessed visually, and maximum root mean square values were compared statistically. OBJECTIVE: To determine whether data differs by patient type. SUMMARY OF BACKGROUND DATA: Whereas there is a good understanding of the anatomy and psychosocial aspects of low back pain, there is a need to understand better the physiology of low back pain. METHODS: Large-array surface electromyography data were collected from the low back muscles of 201 participants over a 3-month period using a 63-electrode fixed array and a standardized protocol. Color images representing the voltage root mean square difference of each electrode pair were created. Three images from each of three positions (standing upright, standing in 20 degrees of trunk flexion, standing holding weights) were collected from each participant. Serial studies were performed on the acute population over a 6-week follow-up period. RESULTS: Images of regional muscle activity from 92.7% of normal controls (n = 163) showed symmetrical activity. Patients with acute (n = 13) or chronic (n = 25) low back pain had multifocal and/or asymmetrical patterns. Symmetrical patterns returned in the three patients whose acute pain resolved during the study. Maximum root mean square values were higher among patients with acute (P = 0.03) and chronic (P = 0.04) pain than among control subjects. CONCLUSIONS: Large-array surface electromyography produced data from patients with back pain that differed from data on subjects without back pain. This method may be useful in evaluating patients with low back pain.