Semi-quantitative electromyography as a predictor of nerve transfer outcome.

OBJECTIVES: Evaluate correlation between donor nerve semi-quantitative electromyography (sqEMG) and strength outcome in nerve transfer surgery. METHODS: Retrospective review of pre-operative donor nerve semi-quantitative neurophysiology and post-operative recipient muscle force after at least one-year follow-up. The semi-quantitative technique is the average motor unit number estimate associated with needle recorded interference patterns in the donor muscle (IP-AMUNE), which was correlated with hand-held manometry, standardized as a percent of the contralateral arm, using multivariable linear regression with backward selection. RESULTS: Twenty-eight nerve transfer cases were included. The correlation between the donor nerve IP-AMUNE and the recipient muscle strength was moderate to strong and highly significant (r = 0.67, p < 0.001). Medical Research Council (MRC) grading did not predict strength (p > 0.54). CONCLUSIONS: IP-AMUNE is a good predictor of strength after nerve transfer surgery and should be considered in the evaluation and planning of patients undergoing nerve transfer to aid in donor nerve selection. SIGNIFICANCE: IP-AMUNE may significantly benefit those undergoing nerve transfer surgery for the restoration of movement.

A neurophysiological approach to nerve transfer to restore upper limb function in cervical spinal cord injury.

A successful nerve transfer surgery can provide a wealth of benefits to a patient with cervical spinal cord injury. The process of surgical decision making ideally uses all pertinent information to produce the best functional outcome. Reliance on clinical examination and imaging studies alone can miss valuable information on the state of spinal cord health. In this regard, neurophysiological evaluation has the potential to effectively gauge the neurological status of even select pools of anterior horn cells and their axons to small nerve branches in question to determine the potential efficacy of their use in a transfer. If available preoperatively, knowledge gained from such an evaluation could significantly alter the reconstructive surgical plan and avoid poor results. The authors describe their institution's approach to the assessment of patients with cervical spinal cord injury who are being considered for nerve transfer surgery in both the acute and chronic setting and broadly review the neurophysiological techniques used.

Anesthesia considerations for monitoring TCMEPs in adults diagnosed with poliomyelitis as children: a case report.

UNLABELLED: The use of transcranial motor evoked potentials (TCMEPs) to detect and hopefully prevent injury to the brain, spinal cord, and peripheral nerves intraoperatively has increased greatly in recent years. It is well established that in addition to certain anesthetic agents, patient factors such as advanced age, obesity, diabetes, hypertension, and a collection of neurological and neuromuscular diseases and disorders can greatly reduce or completely eliminate the ability to monitor TCMEPs effectively. One such disease, poliomyelitis (polio), is a highly contagious viral disease that has been mostly forgotten since its near-eradication through vaccination. Over the past three decades there has been increasing recognition of late onset neurological deterioration in individuals who were afflicted by, and apparently recovered from, paralytic poliomyelitis much earlier in life. This condition is known as post-poliomyelitis syndrome (PPS). Patients that appear to have fully recovered from polio, and those with PPS, may require special anesthetic considerations to facilitate effective TCMEP monitoring. CASE REPORT: We report the rapid loss of only lower extremity TCMEPs bilaterally during a C6-C7, C7-T1 ACDF in a 67-year-old female to treat left-sided C7-C8 radiculopathy and C6-T1 foraminal stenosis. The general anesthetic maintenance regimen of 0.3 MAC sevoflurane and 100 microg/kg/min propofol was paused, and a wake-up test was initiated. Full upper and lower extremity motor function was observed. A thorough review of the patient's medical history revealed the potential risk factor of full recovery from poliomyelitis as a child. The sevoflurane was removed from the anesthetic regimen, and the lower extremity TCMEPs returned and were present for the remainder of the surgery.

The clinical practice of reconstructive neurosurgery.

Surgical interventions to improve function following nervous system injury have been in development since the early 1900s. Only recently these have been assimilated into a coherent approach which can be applied to injuries of the brain, spinal cord and peripheral nerves. In addition to pharmacological and stimulation based interventions, surgical manipulation of the peripheral nerves and muscles of the extremity can offer functional enhancement for a variety of limb impairments. In order to plan an effective surgical intervention, neurophysiological assessment of the injury and residual motor control is essential. Effective implementation of these surgical interventions can enhance function and quality of life for many individuals whose activity has been limited as a result of nervous system injury.

A self-referential outlier detection method for quantitative motor unit action potential analysis.

Quantitative MUAP analysis is often based on outlier detection, in the case of neurogenic conditions, the finding of MUAPs that are larger than the limit determined from a reference normal population. Such reference data is available from only a few sources and for only a few muscles. It would be desirable if muscles could serve as their own controls. The Henneman size principle determines the order of recruitment, following an exponential distribution of twitch force, motor neurone, motor unit, and MUAP size. Therefore, an outlier could be detected by being too large for the level of recruitment, as judged by its size relative to the other MUAPs. This would improve the sensitivity of detecting neurogenic muscles and obviate the need for external reference data.

Quantification of motor unit action potential energy.

OBJECTIVE: Motor unit action potentials (MUAPs) recorded by needle electrode reflect the functional state of the motor unit and its force-generating capacity, and are usually described morphologically (e.g. amplitude, duration). However, since the purpose of motor unit activation is force generation, MUAP energy seems a more physically meaningful measurement. METHODS: MUAPs were obtained by multi-MUAP decomposition of real interference patterns taken from human patients with neurological diseases. The energy content of each MUAP was measured from a time-frequency representation (TFR), specifically the Choi-Williams distribution, and compared with the standard MUAP morphological measure, the Size Index. The sample included normal, neurogenic, and myopathic MUAPs, from 11 patients. RESULTS: There is an exponential distribution of energy within a sample of MUAPs and a strong exponential relationship between the Size Index and MUAP energy was observed. CONCLUSIONS: The energy content of a MUAP can be quantified and corresponds very well with the current quantitative standard. Energy is a possible addition to MUAP quantification. SIGNIFICANCE: MUAPs could be classified as having normal, large (neurogenic), or low (myopathic) energy. MUAP energy has direct physical and physiological meaning that reflects the force-generating capacity of the motor unit. Time-frequency analysis could also be used to study the specific frequency content of MUAPs and the energy of MUAPs within an interference pattern, without the need for decomposition.

Application of time-varying analysis to diagnostic needle electromyography.

Quantification in clinical, diagnostic electromyography (EMG) currently includes motor unit action potential (MUAP) analysis and interference pattern analysis. Early efforts to examine the frequency/power spectra of the interference pattern showed modest value but the technique was not developed further. This paper re-examines spectral analysis, extending it into the time-varying domain, which has never been studied in diagnostic needle EMG. Time-frequency and time-scale analysis employing wavelet and non-wavelet techniques were applied to short trains of MUAPs. The results show that time-varying analysis produces clear visual representations of the energy content of individual MUAPs within an interference pattern. The time frequency representations allow easy, qualitative distinction between normal and neurogenic MUAPs. Furthermore, the quantified MUAP energy correlates well with the current morphological standard and the quantification process is substantially faster. Time-varying analysis links classical power spectral analysis in the realm of interference patterns with quantitative MUAP analysis. In addition to morphological classification, MUAPs might also be classified by energy content, which more closely reflects the physical and physiological consequences of neuromuscular pathology on the motor unit.

Efficacy and safety of botulinum type A toxin (Dysport) in cervical dystonia: results of the first US randomized, double-blind, placebo-controlled study.

Botulinum toxin type A (Dysport) has been shown in European studies to be a safe and effective treatment for cervical dystonia. This multicenter, double-blind, randomized, controlled trial assessed the safety and efficacy of Dysport in cervical dystonia patients in the United States. Eighty patients were randomly assigned to receive one treatment with Dysport (500 units) or placebo. Participants were followed up for 4 to 20 weeks, until they needed further treatment. They were assessed at baseline and weeks 2, 4, 8, 12, 16, and 20 after treatment. Dysport was significantly more efficacious than placebo at weeks 4, 8, and 12 as assessed by the Toronto Western Spasmodic Torticollis Rating Scale (10-point vs. 3.8-point reduction in total score, respectively, at week 4; P < or = 0.013). Of participants in the Dysport group, 38% showed positive treatment response, compared to 16% in the placebo group (95% confidence interval, 0.02-0.41). The median duration of response to Dysport was 18.5 weeks. Side effects were generally similar in the two treatment groups; only blurred vision and weakness occurred significantly more often with Dysport. No participants in the Dysport group converted from negative to positive antibodies after treatment. These results confirm previous reports that Dysport (500 units) is safe, effective, and well-tolerated in patients with cervical dystonia.