Elsevier

Clinical Neurophysiology

Volume 110, Issue 11, 1 November 1999, Pages 1900-1908
Clinical Neurophysiology

Comparison between concentric needle EMG and macro EMG in patients with a history of polio

https://doi.org/10.1016/S1388-2457(99)00150-9Get rights and content

Abstract

Objectives: Acute poliomyelitis causes degeneration of anterior horn cells, followed by denervation. Reinnervation and muscle fibre hypertrophy are mechanisms that compensate this loss of neurones. Concentric needle EMG (CNEMG) and macro EMG are two methods to assess the magnitude of initial involvement and the compensatory reinnervation. The aim of this study is to explore the difference between CNEMG and macro EMG describing the status of the motor unit in patients previously affected by polio.

Methods: Macro and concentric needle EMG investigations were performed in 261 muscles in 121 patients with a remote history of polio.

Results: CNEMG was abnormal in 211 muscles, macro EMG was abnormal in 246 muscles. The macro amplitude was 3–4 times ‘more abnormal’ than CNEMG amplitude relative to the reference values. CNEMG duration was less abnormal and showed only weak correlation with macro amplitudes. The most likely explanation for the difference in magnitude of deviation from reference values for CNEMG and macro EMG, is a more pronounced ‘phase cancellation’ between single fibre action potentials in CNEMG. This is supported by simulation studies reported here.

Conclusions: In conclusion macro EMG better reflects the size of the motor unit than the CNEMG. For detection of concomitant disorders, CNEMG is the method of choice.

Introduction

Acute poliomyelitis causes degeneration of groups of ventral horn cells, with subsequent acute denervation of muscle fibres in corresponding motor units. This is followed by reinnervation by the mechanism of collateral sprouting. The result may be a complete functional compensation or, in cases of pronounced acute denervation, an incomplete compensation. Muscle fibre hypertrophy is another type of compensatory phenomenon occurring in most of these cases. (Dalakas, 1988, Grimby et al., 1998) The clinical situation will thus show various degree of remaining weakness.

With normal ageing there is a physiologic progressive loss of ventral horn cells. Therefore in patients with old polio, a slow process of ageing-dependent denervation-reinnervation is superimposed, with a possible acceleration after decades (Grimby et al., 1998). In old polio there is a reduced number of ventral horn cells, each supporting a manifold increase in the number of muscle fibres compared to normal. Here, further loss of each ventral horn cell e.g. due to the ageing mechanisms, will cause denervation of a much higher number of muscle fibres than in the normal muscle because of previous reinnervation generating large motor units. The remaining reinnervated motor units will continuously become even larger (Grimby and Stålberg, 1994, Grimby et al., 1998).

One way to investigate the degree of involvement and reinnervation in a given muscle is by means of EMG techniques, aiming at the estimation of the average size of motor units and the description of the organization of muscle fibres in the motor unit (Cruz-Martinez et al., 1984, Trojan et al., 1991).Together with clinical information such as force and muscle atrophy, this will give an impression of the severity of the involvement and the dynamics of the process.

Usually, the EMG investigation is performed with concentric or monopolar needle electrodes. Amplitude, duration, area, shape, stability on repeated discharges and activity at full effort are parameters conventionally used to quantitate the EMG (Stålberg et al., 1996).

From experience and experimental studies it is known that these parameters are indirect indicators of the number of muscle fibres and their concentration within the uptake area of the electrode. EMG may also assess the present activity of the denervation-reinnervation process.

Another method to assess the motor unit is the so-called macro EMG (Stålberg, 1980, Stålberg and Fawcett, 1982). This recording provides information from a larger area of the muscle than other needle EMG methods. The recorded signal is determined by most of the fibres in a motor unit and reflects number and size of muscle fibres in the entire motor unit. This method has been used in some studies of patients with old polio to follow the degree of reinnervation (Lange et al., 1989, Ivanyi et al., 1994).

The aim of the present study is to compare concentric needle EMG with macro EMG in muscles from patients with old polio with varying degrees of reinnervation. The first method is widely used for quantitative EMG analysis in routine. The second method requires a special electrode and analysis procedure. It is therefore of interest to know whether or not the methods differ in describing the status of the motor unit in the muscles of patients with a history of polio?

Section snippets

Methods

Most EMG recordings are performed on Keypoint EMG equipment (Medtronic Dantec, Copenhagen). In a few cases, Counterpoint (Dantec, Copenhagen) is used.

Statistics

Linear regression is used for statistical analysis. All analysis is made with commercial available standard software (SPSS®, Chicago, IL).

The Pearson's correlation coefficient is used to study the interrelations between parameters.

The significance of correlation coefficients is two-tailed tested.

The results is considered significant when P<0.05.

Patient material

One hundred and twenty one patients with old polio referred to the department for EMG investigations were included. Inclusion criteria for a patient to be included were: a history of acute polio >20 years ago and no other major neurological disorders. Two patients were excluded, one patient suffering from L5 radiculopathy and one patient with HMSN 1. The inclusion criteria for muscles to be included in the study was that quantitative analysis had been made with data from at least 15 MUPs with

Results

The concentric needle EMG showed classic neurogenic findings in some muscles in all patients but not necessarily in those included in this study, supporting the history of earlier polio. Fibrillation potentials were present in a small proportion of the muscles investigated. The general conclusion of the entire investigation is summarised in Table 2.

Of the 3 muscles studied here, CNEMG showed most pronounced changes in VL and least in BB, corresponding to the clinical involvement. The reduction

Discussion

EMG in patients with old polio show typical signs of loss of motor units and of reinnervation. This is due to the initial acute attack to the neurones followed by reinnervation. In addition, there is an ongoing process with reinnervation probably due to age related changes (Grimby et al., 1998). In the case of reinnervation by the mechanism of collateral sprouting, a surviving motor unit seems to innervate only those denervated muscle fibres that are situated within its original territory (

Acknowledgements

This work was supported by the Swedish Medical council; ES grant 135. The authors thanks M. Grindlund for technical assistance and B. Falck for participation in the sampling of data.

References (24)

  • S.D. Nandedkar et al.

    Simulation of macro EMG motor unit potentials

    Electroenceph clin Neurophysiol

    (1983)
  • E. Stålberg et al.

    Scanning EMG in normal muscle and in neuromuscular disorders

    Electroenceph clin Neurophysiol

    (1991)
  • C. Bischoff et al.

    Outliers-a way to detect abnormality in quantitative EMG

    Muscle Nerve

    (1994)
  • M.H. Brooke et al.

    The histographic analysis of human muscle biopsies with regard to fiber types

    Neurology

    (1969)
  • A. Cruz-Martinez et al.

    Electrophysiological features in patients with non-progressive and late progressive weakness after paralytic poliomyelitis. Conventional EMG automatic analysis of the electromyogram and single fiber electromyography study

    Neurology

    (1984)
  • M. Dalakas

    Morphologic changes in the muscles of patients with postpoliomyelitis neuromuscular symptoms

    Neurology

    (1988)
  • M. Ertas et al.

    Can the size principle be detected in conventional EMG recordings?

    Muscle Nerve

    (1995)
  • I. Gath et al.

    Techniques for improving the selectivity of electromyographic recordings

    IEEE Trans Biomed Eng

    (1976)
  • G. Grimby et al.

    Dynamic changes in muscle structure and electrophysiology in late polio with aspects on muscular trainability

    Scand J Rehab Med

    (1994)
  • G. Grimby et al.

    An 8-year longitudinal study of muscle strength, muscle fiber size, and dynamic electromyogram in individuals with late polio

    Muscle Nerve

    (1998)
  • L.S. Halstead et al.

    Post-polio syndrome: clinical experience with 132 consecutive outpatients

    Birth Defects Orig Series

    (1987)
  • B. Ivanyi et al.

    Macro EMG follow-up study in post-poliomyelitis patients

    J Neurol

    (1994)
  • Cited by (15)

    • Motor unit properties do not correlate between MUNIX and needle EMG in remote polio in the biceps brachii muscle

      2023, Clinical Neurophysiology Practice
      Citation Excerpt :

      The location of the surface EMG electrodes over the skin may also cause the measurements to suffer from suppression of the higher frequency content from the filtering effect from the subcutis (Petrofsky, 2008). EMG signals with higher frequency content compared to EMG signals with lower frequency content from densely collaterally reinnervated MUs may be at a greater risk of the effects of phase cancellation which results in lower amplitude EMG signals than expected for the MUs with the higher frequency content (Nandedkar et al., 1988, Sandberg et al., 1999). This may be a reason for the missing correlation between CNEMG and MUNIX since MUNIX may depend on the filtering effect from the subcutis.

    • Motor unit and muscle fiber type grouping after peripheral nerve injury in the rat

      2016, Experimental Neurology
      Citation Excerpt :

      However, unlike the documentation of branching patterns of intact nerve fibers (Lu et al., 2009), the pattern of branching of regenerating motor nerve fibers has not been investigated. Clinical findings of muscle fiber type clumping rather than the normal mosaic distribution of muscle fiber types, and electrophysiological evidence of enlarged MU action potentials in skeletal muscles are commonly interpreted to reflect nerve injury and muscle reinnervation (Bertorini et al., 1994; Buchthal and Schmalbruch, 1980; Einarsson et al., 1990; Ermino et al., 1959; McComas et al., 1971; Sandberg et al., 1999; Stalberg, 1986, 1990, 2011) Reported clumping of glycogen-depleted MU muscle fibers that paralleled fiber type clumping in a reinnervated rat muscle was consistent with the conclusion that the muscle fiber type clumping reflects the clumping of reinnervated MU muscle fibers (Kugelberg et al., 1970). However, later spatial analysis of several glycogen-depleted MUs in cat hindlimb muscles revealed that neither MU muscle fiber clumping nor muscle fiber type clumping are obligatory consequences of nerve injury and muscle reinnervation (Rafuse and Gordon, 1996; Unguez et al., 1996) and, that this clumping in these larger muscles becomes evident only when the number of reinnervating nerve fibers is experimentally reduced (Rafuse and Gordon, 1996).

    • Single fiber EMG Fiber density and its relationship to Macro EMG amplitude in reinnervation

      2014, Journal of Electromyography and Kinesiology
      Citation Excerpt :

      EMG is a sensitive measurement of presence of collateral sprouting in reinnervation as a sign of previous denervation. In some situations the degree of changes is of special interest and the Macro EMG motor unit potential amplitude (MUP) has been shown to be a robust measurement for the degree of collateral reinnervation, at least in ALS (Sartucci et al., 2011) and prior polio (Sandberg et al., 1999). The Macro EMG measures the electrical activity from the whole motor unit (MU), compared to more selective EMG techniques as single fiber EMG (SFEMG) or concentric needle EMG (CNEMG) which only measure a fraction of the electrical activity from the MU under study.

    • The standard concentric needle cannula cannot replace the Macro EMG electrode

      2014, Clinical Neurophysiology
      Citation Excerpt :

      The Macro EMG is a single fiber EMG triggered averaging technique which uses in this context a large recording surface electrode approximately covering the activity from the whole motor unit (MU) under study. It had been shown for instance that the method shows a higher degree of pathology in a condition that commonly shows a great degree of collateral sprouting (e.g. prior polio) than concentric needle EMG (CNEMG) (Sandberg et al., 1999) and the new motor unit estimation technique of motor unit number index (MUNIX) (Sandberg et al., 2011). These differences between the techniques were in the case of the Macro/CNEMG comparison due to technical reasons, different degree of so called phase cancellation in the MUP for these two electrodes.

    • Whither needle EMG?

      2010, Clinical Neurophysiology
    View all citing articles on Scopus
    View full text