EE 4BD4 Lecture 10 Electromyography. Goals of Electromyography Diagnosis (Identify Neuromuscular...
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Transcript of EE 4BD4 Lecture 10 Electromyography. Goals of Electromyography Diagnosis (Identify Neuromuscular...
EE 4BD4 Lecture 10
Electromyography
Goals of Electromyography
• Diagnosis (Identify Neuromuscular Disease, e.g. ALS, muscular dystrophy)
• Determine extent of disease and monitor progress
• Study control of muscles during movement• Measure dysfunction and propose solutions• Study normal anatomy and physiology
Surface Diagnostic Techniques(Motor and Sensory Conduction)
Patient Instrumentation(Sensory and Motor Conduction Velocity)
Stimulation at Wrist
Stimulation at the Elbow
Pathological Findings
Some Lossof AxonsDemyelinatingConditionComplete Loss of Axons
Motor Unit Electrical and Mechanical Responses
Invasive Techniques
• Measure motor unit action potentials (MUAPs)• Recorded from voluntary contractions• Information is in shape, duration and
amplitude of MUAPs• Considered “gold standard” by physicians• Pattern recognition is subjective except for
fibrillation and fasiculation potentials• MUAPs from low threshold units only
Selectivity of Recording
Needle Recorded EMG
Extracting Motor Unit Action Potentialsfrom Higher Level Recordings
Needle Recorded Signal – InterferencePattern (20 Hz – 5 KHz)
High Pass Filtered400 Hz – 5 KHz
Extracted MUAPs by“Spike Triggered Averaging”
Central Nervous System Identification
• Diagnose and monitor diseases of the central nervous system (Parkinsonism)
• Assess dysfunction following trauma
• Assess effects of intervention (drugs, physiotherapy, surgery)
• Study normal muscle control
• Prosthesis Control
Modeling the Electromyographic Signal
Measuring Control of Individual Motor UnitsRecorded with Single Fibre 25 micron Needle
Compressed Single Fibre MUAPs(one to several contributing fibres)
Motor Unit Firing Rates
Surface Recorded EMG
RAW EMG DURING GAIT
LEFT FOOT
RIGHT QUAD
RIGHTHAM
RIGHTTIB ANT
Right GAST.
RIGHT FOOT
0 TIME 5 SEC
LEFT HEMIPLGIC GAIT NO AIDS WALKING SPEED .87 m/sec
50 μvolt Div
EMG PROCESSINGFull –Wave Rectification plus LPF
EFFECTS OF INCREASING SMOOTHING
LEFTFOOT
LEFTTIB ANTFULL WAVERECTIFIED
10 HZ
5 HZ
2 HZ
0 TIME 4.5 sec
50 μvolt Div
EMG Profiles for Light HemiplegiaMean Profile plus 1 Std Dev
0% 100%
EMG Profiles for Severe HemiplegiaMean Profile plus 1 Std Dev
EMG Profiles for Severe HemiplegiaMean Profile plus 1 Std Dev