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To assess whether patients with acute inflammatory demyelinating polyneuropathy (AIDP) associated with SARS-CoV-2 show characteristic electrophysiological features. Clinical and electrophysiological findings of 24 patients with SARS-CoV-2 infection and AIDP (S-AIDP) and of 48 control AIDP (C-AIDP) without SARS-CoV-2 infection were compared. S-AIDP patients more frequently developed respiratory failure (83.3% vs. 25%, P = 0.000) and required intensive care unit (ICU) hospitalization (58.3% vs. 31.3%, P = 0.000). In C-AIDP, distal motor latencies (DMLs) were more frequently prolonged (70.9% vs. 26.2%, P = 0.000) whereas in S-AIDP distal compound muscle action potential (dCMAP) durations were more frequently increased (49.5% vs. 32.4%, P = 0.002) and F waves were more often absent (45.6% vs. 31.8%, P = 0.011). Presence of nerves with increased dCMAP duration and normal or slightly prolonged DML was elevenfold higher in S-AIDP (31.1% vs. 2.8%, P = 0.000);11 S-AIDP patients showed this pattern in 2 nerves. Increased dCMAP duration, thought to be a marker of acquired demyelination, can also be oserved in critical illness myopathy. In S-AIDP patients, an increased dCMAP duration dissociated from prolonged DML, suggests additional muscle fiber conduction slowing, possibly due to a COVID-19-related hyperinflammatory state. Absent F waves, at least in some S-AIDP patients, may reflect α-motor neuron hypoexcitability because of immobilization during the ICU stay. These features should be considered in the electrodiagnosis of SARS-CoV-2 patients with weakness, to avoid misdiagnosis. [ABSTRACT FROM AUTHOR]

Zusammenfassung Die Untersuchung der distal motorischen Latenz ist Standard zur Diagnose der Karpaltunnelsyndroms. Obwohl einfach auszuführen birgt sie einige Fehler. Die gilt es zu erkennen und zu vermeiden. Dazu dienen Standard Operating Procedures (SOPs), die die Untersuchung sehr detailliert beschreiben und damit deren Sicherheit erhöhen. Summary The examination of the distal motor latency is standard for the diagnosis of carpal tunnel syndrome. Although simple to run, it contains some errors. They must be recognized and avoided. Standard Operating Procedures (SOPs) are used to describe the investigation in a very detailed manner and thus increase their safety. [ABSTRACT FROM AUTHOR]

Highlights: [•] Polyneuropathy associated with IgM monoclonal gammopathy is an immune-mediated polyneuropathy clinically characterized by symmetrical, distal polyneuropathy with predominant sensory ataxia. [•] Many cases of IgM-related neuropathy with a clinical phenotype not fitting the classic sensory-ataxic form have been described in literature. [•] Present findings suggest that demyelinating abnormalities in nerve conduction studies are more often associated with classical forms while axonal impairment occurs more often in atypical phenotypes. [ABSTRACT FROM AUTHOR]

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Summary: Objective: This paper describes a new electrode placement for recording compound muscle action potentials (CMAPs) of the first dorsal interosseous muscle (FDI) to determine the distal motor latency (DML) and study nerve conduction of the ulnar nerve across the wrist. Methods: The DML to the FDI was evaluated bilaterally in 90 subjects after stimulation 1cm proximal to the distal wrist crease and at the palm. The CMAP was recorded with a pair of disposable surface electrodes fixed over the FDI and wrist. Results: The CMAP never exhibited a positive initial deflection, with a gain of 0.5mV per division. DML to the FDI was 2.65±0.26ms (mean±SD), and CMAP amplitude was 14.7±3.3mV. A prolonged DML was taken as 3.4ms (mean+3standard deviation [SD]). Conclusions: This new electrode placement offers more reproducible results for determining the DML to the FDI as it provides the shortest DML, and the tightest SD values. Significance: This result is obtained through the respect of fundamental rules for CMAP recording, as it shows no positive wave at the onset of the CMAP of the FDI. Its use should improve the diagnosis of ulnar nerve lesions at the wrist and more especially of the deep motor branch. [ABSTRACT FROM AUTHOR]

Abstract: Nerve conduction slowing in amyotrophic lateral sclerosis (ALS) is usually caused by loss of fast motor axons. We studied the frequency, extent, and distribution of prominently prolonged distal motor latencies in ALS. We reviewed results of median, ulnar, and tibial nerve conduction studies in 91 patients with ALS, 24 with lower motor neuron disorders, and 36 with axonal neuropathy. Coincidental carpal tunnel syndrome was found for 4 (4.4%) of the ALS patients who were excluded from analyses. Markedly prolonged distal latencies (>125% of the upper limit of normal) were found only in the median nerve of ALS patients (9%), and in none of the disease controls. Excitability studies suggested membrane depolarization in some ALS patients. Our results show that approximately 10% of ALS patients shows prominently prolonged median distal latency, which cannot be explained by axonal loss and carpal tunnel lesion. The distal nerve conduction slowing may partly be caused by membrane depolarization possibly due to motor neuronal degeneration in ALS. We suggest that recognition of the pattern of distal motor axonal dysfunction predominant in the median nerve is clinically important, and could provide additional insights into the pathophysiology of ALS. [Copyright &y& Elsevier]

Abstract: Objective: To evaluate the diagnostic value of second lumbrical and interossei distal motor latency difference (2LIDMLD) in diagnosing CTS of different electro-physiological grades of CTS. Methods: 2LIDMLD was standardized in 120 hands of healthy controls. Subjects with clinically diagnosed CTS and CTS with incidental polyneuropathy were prospectively evaluated with 2LIDMLD in addition to other standard diagnostic tests. Sensitivities of these tests were compared in patients with CTS of varying grades of severity and CTS associated with polyneuropathy. Results: Two hundred and fifty hands of 130 patients met the clinical criteria for CTS. Sensitivity and specificity of 2LIDMLD, palm–wrist distal sensory latency difference (PWDSLD), and median distal motor latency (MDML) were 85.60% and 96.67%, 68.80% and 96.10%, 60.80% and 97%, respectively. Sensitivity of 2LIDMLD in mild CTS was similar to that of PWDSLD. In severe CTS, and CTS with polyneuropathy, 2LIDMLD was the most sensitive test. It was the only test of localizing value in 16% of hands with severe CTS, when all other methods failed due to absent median motor and sensory responses. Conclusions: 2LIDMLD is a sensitive, specific for diagnosis of all grades of CTS. It is an accurate and reliable method that helps especially in diagnosis of severe CTS and CTS associated with polyneuropathy, when other standard localized tests fail. Significance: The second lumbrical is relatively less affected in severe carpal tunnel syndrome and median to ulnar comparison, using 2LIDMLD, appears to be a reliable and a valuable technique in the localization of severe CTS and CTS associated with polyneuropathy, especially when the median sensory or motor responses are absent on routine conduction studies. [Copyright &y& Elsevier]

Abstract: Objective: Median nerve entrapment neuropathy at the wrist can be accompanied by slowed motor conduction within the forearm. Existing studies conflict regarding a correlation between the severity of the entrapment neuropathy in carpal tunnel syndrome (CTS) and slowing of median motor nerve conduction velocity (MNCV) in the forearm. Here, it was asked if there is a correlation between markers of CTS severity and median forearm MNCV, and if there is an explanation for the preceding conflicting results. Methods: Median MNCV in the forearm was correlated with neurophysiologic markers of severity of a median neuropathy at the wrist in 91 hands from 64 patients with clinical and electrodiagnostic evidence of CTS. Results: Median MNCV within the forearm segment was negatively correlated with the median nerve distal motor latency (r =−0.64, P <0.001, n =91) and positively correlated with the CMAP amplitude of the abductor pollicis brevis muscle (r =0.45, P <0.001, n =91). These correlations only occurred in patients with a prolonged median distal motor latency. Previous investigations that failed to find such correlations used variable or non-standardized methods or analyzed smaller numbers of patients. Conclusions: Slowing of median MNCV in the forearm is related to the severity of the entrapment of median motor fibers at the wrist. Significance: Slowed forearm median MNCV can be a marker of motor nerve injury at the wrist. [Copyright &y& Elsevier]

Abstract: Objective: Distal motor latency (DML) is shortened when the anode is held distally instead of the cathode by increasing the stimulus intensity. The objective of this study was to clarify the mechanism responsible for this shortening. Methods: In seven healthy subjects, compound muscle action potential (CMAP) was obtained from the thenar muscle by bipolar stimulation of the median nerve at the wrist, and the intensity at which the first motor units were stimulated was defined as the threshold. Bipolar stimulation with extended interpole distance was employed to identify the generating site of the CMAP and F-wave. Results: The shortening of DML was dependent on the stimulus intensity and threshold. For the low threshold condition, the CMAP generating site was replaced from the proximal cathodal pole to the distal anodal pole by increasing the stimulus intensity. The generating site of the F-wave remained at the proximal cathodal pole irrespective of stimulus intensity. Conclusions: Replacement of the generating site results in the shortening of DML. When the F-wave is recorded after being induced by anode distal stimulation, CMAP should not be simultaneously evaluated. Significance: This study clarified the generation sites of CMAP and the F-wave when induced by anode distal stimulation. [Copyright &y& Elsevier]

Abstract: Background: With increase in type 2 diabetes mellitus patients the complications of diabetes are being seen more frequently. Patients with diabetic neuropathy often present with distressing symptoms such as pain and burning sensation in the feet. Tarsal tunnel syndrome with electrophysiological changes may be a causative or contributing factor. The present study was designed to assess the presence and features of tarsal tunnel syndrome in diabetes mellitus patients. Method: In this study a group of 10 normal volunteers were selected who had no neurological complaints or foot trauma. Another group of 33 patients having longstanding diabetes mellitus with complaints of pain, burning sensation and paraesthesia in the feet were selected for electrophysiological tests and median plantar nerve was studied. Results: In the present study we observed that 15 (45%) of diabetic cases showed abnormal findings e.g., prolonged distal motor latency, decreased amplitude of M-response, low or absent sensory response suggesting tarsal tunnel syndrome. Conclusion: This study shows that the tarsal tunnel syndrome may be present in a significant number of diabetic patients with subjective neuropathic symptoms in the feet. The tarsal tunnel syndrome should be kept in mind during the diagnostic workup and management of diabetes mellitus. [Copyright &y& Elsevier]