SUPERIORITY OF SINGLE FIBRE ELECTROMYOGRAPHY TO CONVENTIONAL EMG IN EARLY DIAGNOSIS OF ALCOHOLIC POLYNEUROPATHY

by KOUNTOURIS, D.

Neurologische Abteilung Knappschaftskrankenhaus 4 630 Bochum-Largendreer Universitatsklinik

Abstract

In 16 patients (4 female, 12 male), with chronic alcoholism the m. tibialis anterior was examined both by means of conventional EMG and Single Fibre Electromyography.

In all patients the fibre density was estimated. The results were compared to 16 sex and age matched control subjects. In the patients the fibre density was considerably increased as a sign of reinnervation. It was increased in those muscles where the conventional EMG did not demonstrate any abnormality.

The results showed that the estimation of the fibre density is a far more sensitive method than conventional EMG in the early diagnosis of alcoholic polyneuropathy.

Introduction

It is known that the electromyographic findings in alcoholic polyneuropathy are mainly the fibrillation potentials, the positive sharp waves (PSW), increased mean motor unit potential duration (MUPD), reduced interference pattern and decreased nerve and motor action potentials (NAP), (MAP) by determination of sensory and motor conduction velocity (NCV), and frequency repititive discharges (FRD). Sometimes the sensory and nerve conduction velocity of the conventional electromyographic measurements (NCVC) and of the F-wave latency (NCVF), are delayed. (1, 2, 7, 5, 8, 10, 14).

The electrophysiological changes and the nerve biopsy findings are com-patible with axonal involvement and with signs of reinnervation (1). The process of reinnervation, particularly in young patients with alcoholic polyneuropathy, was reported by Thiele and Stalberg when determining the fibre density (FD) in the extensor digitorum communis muscie by means of single fibre electromyography (SFEMG) (13).

In recent studies, the diagnostic sensibility of this method has proved useful in the diagnosis of alcoholic polyneuropathy, (6-7). The FD appeared increased in muscles, which were clinically intact and did not show signs of reinnervation even in the conventional EMG (6) Thus, it can be expected that deinnervation and reinnervation might occur in patients with chronic alcoholism before any symptoms of polyneuropathy appear.

The purpose of this report is to examine the FD in patients with chronic alcoholism without or with minimal symptoms of polyneuropathy.

Material and method

Control subjects and patients

16 patients, (4 female, 12 male) with chronic alcoholism but without signs of polyneuropathy were examined. Age ranged between 28 and 47 years with a mean age of 38,7 ± 6,7 years. All of them were neurologically examined and in addition to that, conventional EMG of the m. tibialis anterior was performed. The FD of the same muscle was determined. Besides, the MAP, the motor NCVC, the NCVF of the median and peroneal nerve and the NAP and sensory NCV of the median and sural nerve were estimated. The results were compared to 16 sex and age matched control subjects.

Determination of FD

For the recordings of the conventional and of the single fibre EMG, a myo-graph DA II R Tonnis was used.

The FD was determined by means of SFEMG. An electrode with a leading off surface of 25/pm in diameter and an amplifier with a low frequency limit of 500Hz were used (12).

The single fibre action potential, obtained during minimal voluntary con-traction was made maximal by slight adjustment of the electrode The action potential triggered the oscilloscope. The number of synchronous spike components with an amplitude exceeding to 200/pV, a rise time less than 300/ìsec and a constant shape, belong to the same motor unit (Fig 1-2) The mean number of the single fibre potentials from the motor units in 20 different recording sites of the same muscle recorded with the above criteria is the fibre density (11-12).

Results

All pathological findings of the performed neurophysiological examinations are shown on table 1. The conventional EMG was pathological in 5 patients. In the rest 11 patients, no evidence of peripheral neuropathy was found

Failure of cooperation in 3 patients prevented us from estimating the sensory NLC of the sural nerve and in one of them the motor NCVF of the peroneal nerve.

Polyphasic and fibrillation potentials were found in detail in 5 patients. Positive sharp waves and high frequency repititive discharges were observed four times. The motor unit potential duration was increased three times. In the same patients with the above reported pathological results in EMG, the neurographic examinations showed the following findings: the motor NCVF was decreased once in the median and twice in the peroneal nerve. The sensory NLG was delayed twice in the median and twice in the sural nerve. Decreased NAP was found four times in the median and three times in the sural nerve. The motor NCVF was decreased, once in the median and three times in the peroneal nerve.

The FD proved itself as the most sensitive method among the other per-formed neurophysiological methods.

In particular, the mean FD was considerably increased in the alcoholic patients with 1,82 ± 0,17 in comparison to the mean FD in the control subjects with 1,32 ± 0,15 (Wilcoxon matched pairs signed rank test, p < 0,001 (Fig. 3). In 15 patients the FD was increased above two SD of the normal value. Five alcoholic patients with pathological findings in the conv.

EMG had also the most increased values in the FD. This finding confirms our results in this group of patients. In the rest 10 patients, 4 had a light and 6 a clear increase of the FD.

The determination of FD by means of SFEMG has been presented in many recent studies by various authors as a particularly sensitive method for detecting deinnervation-reinnervation processes in muscies (3, 13, 6, 7) Disorders, like general muscle atrophy, selective motor unit loss or peripheral nerve sprouting, lead to increased FD (1 1).

In polyneuropathies with primary axonal involvement where intensive reinnervation by collateral nerve sprouting (4) take place, the FD is in-creased FD may also be considered as indicator of the reinnervation grade.

When increased, is a point in differential diagnosis between axonal and demyelinating types of polyneuropathy (13). It is noteworthy that the FD method has proved to be more sensitive than conventional EMG in alcoholic polyneuropathy (7) and radiculopathy caused by herniation of the intervertebral disk (6). In radiculopathy, increased FD has been found even in muscles that did not show abnormal results in conv. EMG t6).

Thereafter rises the question whether something similar happens to patients with chronic alcoholism without any clinical signs of polyneuropathy, i.e. if a reinnervation process can be proved by measuring the FD earlier than measuring it by conv. EMG. Our results confirmed this assumption. The FD was found considerably increased in our patients. Besides, conv. EMG results were abnormal in 5 out of 16 patients.

Even the sensory NCV estimation. which is considered as a particularly sensitive method, showed abnormal results in only 4 cases.

Concluding, measurement of FD by SFEMG may be a superior tool in the diagnosis of alcoholic and other polyneuropathies of the axonal type. Furthermore, it could be shown that measurement of FD is more sensitive than conventional EMG and it reveals abnormalities even in patients without clinically manifest polyneuropathy.

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paper published in journal of Electromyography and clinical Neurophysiology,

International monthly review, The EMG Journal, March-April,1986;26(2)

Key words: Alcoholic neuropathy, single fibre electromyography (EMG)