Other median neuropathies

Median mononeuropathy is common, with carpal tunnel syndrome the most frequently encountered acquired mononeuropathy in clinical practice. However, other disorders of the median nerve and many known anatomical variants can lead to misdiagnosis and unexpected surgical complications if their presence is not correctly identified. A number of inherited and acquired disorders can affect the median nerve proximal to the wrist, alone or accompanied by other affected peripheral nerves. Recognizing other disorders that can masquerade as median mononeuropathies can avoid misdiagnosis and misguided management. This chapter explores median nerve anatomical variants, disorders, and lesions, emphasizing the need for careful examination and electrodiagnostic study in the localization of median neuropathy.

Guidelines for Qualifications of Neurodiagnostic Personnel: A Joint Position Statement of the American Clinical Neurophysiology Society, the American Association of Neuromuscular & Electrodiagnostic Medicine, the American Society of Neurophysiological Monitoring, and ASET The Neurodiagnostic Society

The Guidelines for Qualifications of Neurodiagnostic Personnel (QNP) document has been created through the collaboration of the American Clinical Neurophysiology Society (ACNS), the American Society of Neurophysiological Monitoring (ASNM), the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM), and ASET The Neurodiagnostic Society (ASET). The quality of patient care is optimized when neurophysiological procedures are performed and interpreted by appropriately trained and qualified practitioners at every level. These societies recognize that neurodiagnostics is a large field with practitioners who have entered the field through a variety of training paths. This document suggests job titles, associated job responsibilities, and the recommended levels of education, certification, experience, and ongoing education appropriate for each job. This is important because of the growth and development of standardized training programs, board certifications, and continuing education in recent years. This document matches training, education, and credentials to the various tasks required for performing and interpreting neurodiagnostic procedures. This document does not intend to restrict the practice of those already working in neurodiagnostics. It represents recommendations of these societies with the understanding that federal, state, and local regulations, as well as individual hospital bylaws, supersede these recommendations. Because neurodiagnostics is a growing and dynamic field, the authors fully intend this document to change over time.

Neuromuscular electrodiagnosis

The electrodiagnostic (EDX) study is an extension of the clinical examination, which means that the clinical features dictate the initial nerve conduction studies (NCS) performed. However, once the EDX study is started, it continues in an independent manner, meaning that the initial NCS findings dictate the subsequent studies performed. Because competent EDX study performance requires considerable knowledge (and special training), it is not possible to convey all of the basic and advanced concepts in a single chapter. Nonetheless, the most important concepts are easily conveyed by a discussion limited to EDX-pertinent anatomical, physiological, pathological, pathophysiological, and basic electrical concepts. The focus of this chapter will be on the standard NCS and needle EMG measurements made during EDX studies and their significance with regard to lesion localization and characterization. Because the most challenging portion of EDX study is motor unit action potential analysis, this topic is more extensively reviewed. The utility of the sensory NCS for identifying focal axon loss, the utility of the motor NCS for screening long nerve segments for focal demyelination and for determining lesion severity, and the utility of the needle EMG for confirming the NCS findings, better defining lesion localization, and identifying the temporal features (e.g., chronicity) and rate of progression of the lesion are also reviewed.

Sensory Neuropathy in Parkinson Disease: Electrodiagnostic Evaluation

The relationship between Parkinson Disease (PD) and peripheral neuropathy (PN) has gained attention in recent years. There is increasing evidence of a-synuclein deposition and pointing to a form of small fiber neuropathy intrinsic to PD, medium-large fiber PN is also a relatively frequent and potentially severe complication in advanced levodopa-treated PD, but degenerative factors and vitamin deficiency were related. Objective: To determine the neurophysiological characteristics of patients with PD and the clinical manifestations of suspected PN. Methods: We performed a cross-sectional study between January 2014 and December 2017, of 36 patients diagnosed with PD who were referred for electrodiagnostic studies (EDX) with suspected clinical PN. We performed electromyography of five muscle or more (brachial biceps, first dorsal interosseous, thumb abductor, anterior tibial, medial gastrocnemius and short finger extensor), and nerve conduction/velocity studies on fibular and tibial nerves (motor) sural and superficial fibular nerves (sensory) and median and ulnar, (both motor and sensory). Results: Twenty-one females (58.3%) with an average age of 69.6 years and fifteen males (41.7%) with an average age of 68.0 years who were submitted for EDX were included in this study. All had a tremor and the average evolution of PD was 5 years. Thirty-two patients were receiving oral levodopa treatment. EDX of twenty-two patients demonstrated neuropathy abnormalities, and in 90.9% of these patients, sensory neuropathy was confirmed. The most common nerve found to be compromised was the superficial fibular nerve (55.0%), followed by the sural (50.0%). Conclusions: Sensory neuropathy was the main finding. Diagnosing PN based on symptom prevalence assessed by checklists and questionnaire has a risk of overestimating the prevalence of PN. The age and the time of disease evolution were factors related to neuropathy. In our study we found that 39% of the patients did not have neuropathic alterations despite clinical suspicion, which opens up new questions about the mechanisms of PD neuropathy and the possibility of fine fiber neuropathy in these patients, motivating further research.

Comparison of nerve conduction parameters in canine studies using recording needle and surface electrodes

Surface electrodes have been used in electromyography and nerve conduction studies in human and veterinary medicine, but comparisons have not been made between surface and needle electrode recordings in dogs. Our aim in this method comparison study was to determine whether surface electrodes captured larger compound motor action potentials (CMAP) than needle electrodes. Tibial nerve CMAP from 25 dogs with normal limb function was acquired using both surface and needle recording electrodes; the stimulus was elicited with monopolar concentric needles. Paired Wilcoxon signed rank test (if data was not normally distributed) or a paired two tailed t-test was used if data were normally distributed; significance was set at P<0.05. Mean CMAP amplitude (P=0.009), area (P=0.045) and latency (P=0.02) recorded with needle electrodes were larger compared with surface recording. CMAP duration was not significantly longer when recorded with surface electrodes (P=0.898). Needle electrode recordings are suitable for canine studies, although surface electrodes could also be considered. Low CMAP amplitudes recorded with surface electrodes should be verified with needle electrodes.

Tibial motor and sural electrophysiological relationship in subjects without and patients with mild axonal peripheral neuropathy

The distal motor fibers of the tibial and sural nerves are predominantly derived from the S1 root. We aimed to describe the electrophysiological relationship of these two nerves. Clinical, radiological and neurophysiological data of patients with mild, length-dependent, peripheral neuropathy (PN) and subjects without PN were retrospectively collected and analyzed. Eighty-eight individuals without PN and 24 patients with mild axonal PN who had no evidence of lumbosacral radiculopathy were included for analysis. Significant positive correlations were observed for the tibial CMAP and the sural SNAP for both controls and patients. Multivariate linear regression analyses showed that the predicted tibial CMAP can be calculated using the following equations: for male subjects without PN, tibial CMAP = 20.7 - 0.21 × age; for female subjects without PN, tibial CMAP = 23.3 - 0.21 × age and for patients with mild PN, tibial CMAP = 2.7 + sural SNAP. This study demonstrates the high correlation between the tibial CMAP and the sural SNAP in subjects without PN and patients with mild axonal peripheral neuropathy, and provides mathematical equations for the calculation of the predicted tibial CMAP for such individuals.

Guiding Treatment for Foot Pain

In the electrodiagnostic (EDX) approach of the patient who presents with foot pain, numbness, and/or tingling, it is important to consider a broad differential diagnosis of both neuropathic and nonneuropathic conditions, including focal and systemic causes. This article assists the electromyographer in the selection and utilization of the most appropriate EDX studies for evaluation. The EDX findings and impression can then help guide potential treatment options for the patient with foot pain and other symptoms. Moreover, this discussion demonstrates the added value that EDX evaluation of the foot provides to the comprehensive assessment of foot pain.

Electrodiagnostic studies in presumptive primary hypothyroidism and polyneuropathy in dogs with reevaluation during hormone replacement therapy

Background

Peripheral neuropathy is the most common neurological manifestation of canine hypothyroidism. Data concerning electrodiagnostic studies in hypothyroid associated polyneuropathy in dogs are very limited and usually lack a reevaluation after hormone replacement therapy. The objective of this study was to perform a detailed, retrospective analysis of electromyographic (EMG), motor nerve conduction velocity (MNCV), F-wave and brainstem auditory evoked response (BAER) findings in 24 dogs with presumptive primary hypothyroidism and polyneuropathy with a comparison of the results before and after initiation of levothyroxine treatment with the assessment of the clinical outcome.

Results

The results obtained from hypothyroid dogs showed a significant reduction in MNCV at a proximal–distal and middle–distal stimulation, decreased amplitudes of compound muscle action potentials (CMAP), an increased CMAP duration and a prolonged distal latency prior to treatment. Fifty percent of the dogs had an increased F-wave latency. A normal BAER recording was found in 78 % of the hypothyroid patients without vestibular impairment. Bilaterally increased peak V latencies and increased interpeak I–V latencies were found in the remaining individuals. Dogs with concurrent vestibular impairment had ipsilaterally increased peak latencies with normal interpeak latencies and decreased amplitudes of wave I and II. A comparison of the findings before and after 2 months of treatment revealed a decrease in the pathological activity on EMG, an improvement of proximal, middle and distal CMAP amplitudes and an increase in the proximal–distal conduction velocity in all dogs. F-wave latency improved in 38 % of dogs. The BAER reexamination revealed a persistent prolongation of peak I, II, III and V latencies and decreased wave I amplitude on the affected side in all dogs manifesting vestibular signs. Conversely, in dogs without vestibular signs, the peak V and interpeak I–V latencies decreased to normal values after a given time of the treatment.

Conclusions

The results indicate a demyelinating and axonal pattern of polyneuropathy in dogs with suspected hypothyroidism. Most of the patients without vestibular signs showed neither peripheral nor central auditory pathway impairment, concurrent to the generalized neuropathy. The follow-up examination showed a very good clinical outcome and only partial improvement in electrophysiological assessment.

Electrodiagnostic approach in entrapment neuropathies of the median and ulnar nerves

OBJECTIVE

The present study's aim was to analyze the late responses' parameters in order to determine the utility of each one.

METHODS

The study, conducted on a total of 325 patients with entrapment neuropathy of the median nerve and 36 with entrapment neuropathy of the ulnar nerve, included the bilateral evaluation of the median and the ulnar nerve and analysis of 20 F-wave and 4 A-wave parameters.

RESULTS

The authors emphasize the necessity of bilateral examination and that of examining the ipsilateral ulnar/median nerve, such as to calculate the difference in F-wave average latency of the median/ulnar and the ipsilateral ulnar/median nerve. This was the most sensitive parameter studied, altered in more than 70% of cases, significantly in more cases than when using only the M-wave distal latency. Also there was a statistically significant correlation between patient age and F-wave latency.

CONCLUSIONS

The completed research yielded the recommendation for F-wave parameter studies to include the difference in F-wave average latency of the median/ulnar and the ipsilateral ulnar/median nerve. This parameter was also included in the composite score, along with the recommendations of the American Academy of Emergency Medicine (AAEM).