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electrodiagnosis 3, EVOKED POTENTIALS, Strength-Duration curves, Nerve…

- - - - graph
      - Partial Denervation
        
        graph
        
        kink
  - - - It is quick and easy to perform.
        
        It requires minimal training.
        
        It is economical in comparison to other clinical tests.
      - Disadvantages of the Strength-
        Duration Curve
        
        It only provides qualitative data in relation to the degree of denervation.
        
        it cannot locate the site of the lesion
        
        in large ms, only few fibers can be studied due to the limits of the method.
        
        Rheobase and Chronaxie
        
        Rheobase
        
        is the smallest current that will produce a
        muscle contraction if the stimulus is of infinite duration.
        
        in practice an impule of 100ms is used
        
        in denervation the rheobase may be less than that of innervated ms
        
        Chronaxie
        
        the chronaxie is the duration of the shortest impulse that will produce a response with a current of double the rheobase.
        
        the chronaxie of the innervated ms is appreciably less than that of denervated ms
        
        graph
- - - - for sensory nerves,
      - compound nerve action potentials (CNAPs)
        
        for mixed
        (sensory & motor)
        nerves
        
        late responses
        
        (primarily F-waves and H-reflexes).
        
        diagrams
        
        Conduction Velocity
        
        is how fast the nerve is propagating an action
        potential. It can be calculated by the formula:
        
        velocity = distance/time
        
        Since motor nerves do conduct across a myoneural junction,
        the conduction velocity cannot be measured directly.
        Therefore, we use the formula:
        
        velocity = change in distance/change in time
        
        1 more item...
        
        NCS
        
        Active (surface electrode – this is also referred to as the pickup electrode)
        
        Reference (surface electrode)
        
        Ground (surface electrode)
        
        graph
        
        H-reflex
        
        2 more items...