Statistical Technique for Classification of MUAPs for Neuromuscular disease

Abstract

Electromyograph (EMG) is useful to know the state of a patient under medical diagnosis and treatment. As the number of neuromuscular patients is increasing, it is not possible to take care of all the neuromuscular patients by carrying out manual investigations under all the conditions. Therefore it is required to design a computer aided expert system which can analyze and interpret the EMG signal. The EMG data acquisition and preprocessing, detection of MUAPs, classification of EMGs into similar groups, feature extraction of these groups and their usage in disease classification and diagnostics are the important stages in computer aided EMG analysis and interpretation. The objective of the present work is to detection of MUAPs, classification of EMGs into similar groups for computer aided analysis and interpretation of EMG signals for disease diagnosis. In the work real time recordings of myopathy, motor neuron disease and normal cases have been considered for MUAP segmentation and classification by statistical technique. EMG signal recorded by the needle electrode has been used. 1. INTRODUCTIONbody is composed of various systems and sub-systems. All human body functions are carried out by coordinated and controlled activities of the subsystems. The structural support is provided by bones while the functional support is provided by neuromuscular system. As such, the human body works under the influence of inputs from external environment and from within the body itself. Electromyography is used for the classification of various neuromuscular disorders .The word is made up of three parts: electro- + - myo- + -graphy. -Myo- is from the Greek mys, meaning muscle and graphy comes from the Greek grapho meaning to write. So electromyography literally is the writing (recording) of muscle electricity. The bioelectric potentials associated with the muscle activity constitute the electromyogram .EMG stands for electromyography. It is the study of muscle electrical signals EMGs can be used to detect abnormal muscle electrical activity that can occur in many diseases and conditions. Electromyogram (EMG) is a test that is used to record the electrical activity of muscles. When muscles are active, they produce an electrical current. This current is usually proportional to the level of the muscle activity. The electric current may be produced due to voluntary or involuntary muscle contraction. The EMG activity of voluntary muscle contractions is related to tension. The functional unit of the muscle contraction is a motor unit, which is comprised of a single alpha motor neuron and all the fibers it enervates. This muscle fiber contracts when the action potentials (impulse) of the motor nerve which supplies it reaches a depolarization threshold. The depolarization generates an electromagnetic field and the potential is measured as a voltage. The depolarization, which spreads along the membrane of the muscle, is a muscle action potential. The motor unit action potential is the spatial and temporal summation of the individual muscle action potentials for all the fibers of a single motor unit. Therefore, the EMG signal is the algebraic summation of the motor unit action potentials within the pick-up area of the electrode being used. The electrical signals produced by the muscles and nerves are analyzed to assess the state of neuromuscular functions in subjects with suspected neuromuscular disorders. The repetitive activation of several individual motor units results in superposed pulse train and constitutes the electromyogam signal. The potentials from individual motor units are characterized by unpredictable shapes depending upon the motor unit structure, electrode shapes and sizes, electrode placement, intervening tissues, and the state of neuromusculature. The analysis the EMG is based on its constitute i.e. motor unit action potential (MUAPs). The motor unit is the smallest functional unit of a muscle, which can be activated voluntarily. It consists of a group of muscle fibers, which are innervated from the same motor nerve. The shape of MUAP reflects the pathological and functional states of the motor unit. With increasing muscle force, the EMG signal shows an increase in the number of activated MUAPs recruited at increasing firing rate, making it difficult for the neurophysiologist to distinguish individual MUAP waveforms. In most of the clinical EMG examinations, it is the shape of the action potential that is analyzed for diagnostics. For this purpose, clinical examinations are carried out with the EMG signal recorded at low contraction level of the muscle, usually such that individual motor unit action potentials are distinguishable. This single motor unit activity is the summation of electrical activity of each muscle fiber within a motor unit. Figure1 shows the steps for the preprocessing and classification of MUAP into similar Classes.