Clinic Electromyography
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[[|Italian]]Clinic Electromyography
Clinical electromyography is a cornerstone in evaluating neuromuscular function, comprising three sequential phases: 1. Spontaneous activity examination. 2. Motor unit potential (MUP) analysis. 3. Interference pattern (IP) analysis during muscle contraction.
A motor unit (MU) includes a motor neuron, its axon, and the innervated muscle fibers. MU activity can be recorded using various electrode types: - **Single Fiber Electrode (SF-EMG):** Records one or two muscle fibers with a recording area of ~300 μm. Ideal for high-precision applications. Macro-EMG Needle Electrode:** Covers a large area (~15 mm) to record entire motor units. Concentric Electrode:** Balances recording precision and noise reduction with a 0.07 mm² area. - **Monopolar Electrode:** Larger recording area (~0.5-0.8 mm²), suitable for broader applications. MUPs represent the summation of action potentials from fibers within an MU. Key parameters include: Duration: Reflects MU size and fiber diameter. Amplitude:Indicates the number and proximity of fibers. Jiggle: Variability in MUP shape, indicative of reinnervation or pathology.
MUPs are evaluated using both manual and computerized methods: Template Matching: Identifies MUPs by comparing shapes.Signal Decomposition:Separates overlapping signals for detailed analysis.
The interference pattern reflects muscle contraction, analyzed through recruitment and frequency modulation mechanisms: - **Recruitment:** Progressive activation of MUs, starting with smaller, fatigue-resistant units.Frequency Modulation:Increase in MU firing frequency correlates with contraction strength.
Advanced methods like **Cloud analysis** plot IP parameters to distinguish myopathic from neuropathic conditions. In myopathy, points cluster below the "normal cloud," whereas in neuropathy, they fall above.
EMG provides invaluable insights into neuromuscular disorders: In 'myopathy', IP activity increases rapidly with reduced strength, reflecting smaller muscle fibers. In 'neuropathy', fewer MUs are activated, but reinnervation may increase MUP amplitude.
Conclusion: Clinical electromyography, with its advanced techniques and objective methodologies, remains an indispensable tool in neurology. Innovations like multiMUP and Cloud analysis enhance diagnostic precision, offering significant contributions to patient care.
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