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Abstract: We report clinical and detailed nerve conduction findings in case of polyneuropathy associated with kappa light chains monoclonal gammopathy of undetermined significance with progression to lymphoproliferative disorder. A 55-year-old man had a predominantly distal, chronic (5 years duration), slowly progressive, symmetric, predominantly sensory impairment with sensory ataxia, and mild weakness. M protein was identified by serum protein electrophoresis. The kappa/lambda ratio of free light chains was significantly elevated to 11.96. The cerebrospinal fluid protein level was elevated at 3.5 g/L. This case study has revealed 2 unusual electrophysiological phenomena-a very unusual prolongation of distal motor latencies of compound muscle action potentials (CMAP) up to 86.5 ms and impaired excitability of the distal segments of the peripheral nerves. The distal CMAP areas were considerably lower compared with the proximal CMAP areas. Radiography of the skull revealed osteolytic lesions., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Introduction: The main goal of this study was to determine the contribution of the anterior forearm muscles to the compound muscle action potential (CMAP) recorded from the extensor digitorum (ED) after proximal stimulation., Methods: Twenty-one healthy volunteers and 114 patients with compressive and traumatic radial neuropathies were examined. Stimulation was carried out at six different points: distal third of the upper arm; Erb's point; axilla; medial upper arm; antecubital fossa; and ulnar groove., Results: In the control group, Erb's CMAP area was significantly greater than the distal CMAP area. In compressive neuropathy, there was conduction block, but no change in conduction velocity. There were no differences in Erb's CMAP latencies between the control group and the neuropathies group., Discussion: CMAPs recorded over the ED with stimulation at the brachial plexus represent the sum of the motor unit action potentials of the posterior and anterior forearm muscles., (© 2020 Wiley Periodicals, Inc.)

The electroneuromyographic study of the posterior interosseous nerve (PIN) with determination of conduction block (CB) at the level of the upper third of the forearm using the surface electrodes has been carried out. Seven healthy volunteers, 22 patients with compressive-ischemic neuropathy (CIN) at the level of the supinator, 14 patients with the total affection of the radical nerve, aged from 21 to 64 years, have been studied. The M-response has been recorded from the extensor digitorum communis. Stimulation has been performed at: (1) the middle of the forearm; (2) the lateral brachium; (3) the axillary crease; (4) the Erb's point; (5) the sulcus of ulnar nerve; (6) the cubital flexion; (7) the inner part of the shoulder. A method of stepwise stimulation has been used in the segment "a middle third of the forearm--a middle third of the shoulder". The M-responses of similar shape and amplitude have been recorded by stimulation of the first and second points in the controls. The M-responses recorded by stimulation of the brachial plexus were higher by average of 44,2% compared to the radical nerve in the shoulder area. The focal CB was found between two stimulation points in 86,4% of patients with PIN CIN that was confirmed by the method of stepwise nerve stimulation as well. The correlation between CB and the data of the global electromyogram was revealed. In patients with the total affection of the radical nerve, the M-responses during stimulation of distal and proximal PIN points were absent and the similar M-responses were recorded by stimulation of the brachial plexus (the Erb's point and the axillary crease) as well as the inner part of the shoulder.

A study aims to design an electroneuromyographic technique of radial nerve investigation and conduction block (CB) definition at the spiral groove level using surface electrodes. Eight healthy volunteers, 17 patients with focal radial nerve neuropathy in the spiral groove, 4 patients with a complete injury of the radial nerve aged from 22 to 54 years have been studied. The M-response was recorded from the extensor digitorum communis. Stimulation was performed at (1) the lateral brachium; (2) the Erb's point; (3) the medical brachium (stimulation of the median and ulnar nerves). Normal values have been determined. CB was calculated as follows: 100-A2/(A1+A3)*100%, where A1--a value of the M-response area amplitude at first point stimulation, A2--the second one, A3--the third one. The proximal M-response is the sum of motor unit action potentials of posterior and anterior groups of forearm muscles. Proximal M-response in patients with a complete injury of the radial nerve did not differ from the third one. The correlation between CB and the paresis degree as well as surface EMG were revealed in patients with radial neuropathy. Besides, there was correlation between CB and the percentage contribution of the third M-response in proximal one in this group.

Motor fibers of the median nerve innervating the anterior forearm muscles during stimulation of the brachial plexus have been studied. A role of forearm muscles innervated by the cubital and radial nerves in the formation of the M-response recorded from the anterior forearm muscles has been determined. Surface stimulating and recording electrodes have been used, with the active recording electrode being placed on the border between the upper and the middle one third of the anterior forearm surface and the reference electrode--in the area of the lower one third of the forearm. Nerve stimulation was conducted at 5 points: in the region of elbow flexion (median nerve); in the border between the middle and the lower one third of the inner side of the shoulder (median and cubital nerves); in the Erb's point or in the axillary space (brachial plexus); in the sulcus of ulnar nerve (cubital nerve); on the border between the middle and the lower one third of the outer shoulder surface (radial nerve). During stimulation of the brachial plexus, the M-response recorded from the anterior forearm muscles is caused mostly by the median nerve. The radial nerve also exerts a significant influence on development of the M-response. A role of the cubital nerve is minimal (p>0.05). The M-response recorded from the anterior forearm surface during brachial plexus stimulation is a result of summed potentials of motor units both of the anterior forearm muscles innervated by the median and cubital nerves and of the lateral and posterior groups innervated by the radial nerve.

The results of subclinical brain damage study of 20 patients with inflammatory demyelinating polyneuropathy, aged 46.5 +/- 3.7 years, are presented. Eleven patients were diagnosed to have Guillain--Barre syndrome and 9--chronic inflammatory demyelinating polyneuropathy. No clinical systems for central nervous system damage were found. Magnetic resonance tomography defected demyelination foci in periventricular and sub-cortical brain regions in 35% of the patients and diffuse atrophic process--in 55%. Registration of brainstem acoustic-evoked potentials showed bilateral latency increase and a change of a signal shape in 60% of the patients. Possible mechanisms of combined damage of central and peripheral nervous system in this pathology are discussed.

The aim of the investigation was to determine electroneuromyographic diagnostic criteria of conduction block (CB) and temporal dispersion on the basis of 78 healthy volunteers and 82 patients with alcoholic polyneuropathy examination. We investigated motor fiber ulnar, median, peroneal and tibial nerves on distal segments of extremities at the level of forearm and leg, respectively. We determined a percentage of the maximal degree of negative peak (NP) and "peak to peak" amplitude reduction, the NP area and the total M-response as well as the degree of NP duration increase and the total M-response obtained from proximal nerve stimulation point versus to distal one. The area of M-response was shown to be the less changeable index, while the degree of amplitude, area and M-response duration changes depended on the nerve studied. The greatest changes of these parameters were revealed during a tibial nerve study in the controls and in the patients with alcohol polyneuropathy. The CB presence proves being identified when the proximal NP area reduction and the total M-response is over than 30 and 35%, respectively. The temporal dispersion can be confirmed if NP duration increase is over than 30%. CB is likely suspected when the proximal NP area and the total M-response reduction is greater than 20 and 25% for the peroneal, ulnar and median nerves.

The aim of the study was to identity main types of alterations in the form of M-responses in patients with primary axonal and demyelinating polyneuropathies (PNP). Clinical and electroneuromyographic examination was performed in 227 patients aged 15-72 years with alcoholic (axonal) and inflammatory demyelinating PNP. M-response was registered from the abductor pollicis brevis, abductor digitus minimum, short extensor of the hallux, and abductor hallucis during stimulation of the motor fibers of median, ulnar, tibial, peroneal nerves using superficial registration electrodes. The basis for selection of altered types of M-responses was the analysis of the following criteria: a spatial correlation of the positive and negative picks; presence of the additional crooks, turns and phases on M-responses; location of these changes on the curve. 5 types of M-response alterations were singled out. The first three types were revealed in patients with alcoholic PNP and two other types--in patients with inflammatory demyelinating PNP. These 5 types of the changes in M-responses reflect the degree of desynchronization in coming of the impulses to muscular fibers. Classification proposed allows to improve a quality of both diagnosis and control of therapy in patients with PNP of different genesis.

The aim of the work was determination of the pattern of electroneuromyographic disorders (ENMG) with determination of the character, degree and peculiarities of the damages in peripheral nerves of upper and lower, extremities in 82 patients aged 25-65 years with alcoholic polyneuropathy. By means of standard ENMG methods the study was made of motor fibrae of median, tibia, fibular and sensory fibrae of median and sural nerves. Generalized symmetric sensomotor distal axonopathy was revealed. The most pronounced ENMG-signs were: a considerable decrease of the amplitude or the absence of the action potentials from the sensory fibrae of sural nerve as well as a decrease of the amplitude of M-component of muscle action potential from the short extensor of the fingers during study of fibular nerve. There was a prevalent decrease of the amplitude of positive peak of M-response. The index of the amplitude of the positive peak is proposed which more objectively reflects an alteration of its amplitude on the early stage of the disease. The degree of a damage of different peripheral nerves was also determined.