f-wave & h-reflex

    
      Re: f-wave & h-reflex
    


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Posted by CCF NEURO MD on May 13, 1997 at 21:28:13:

In Reply to: f-wave & h-reflex posted by julie on May 06, 1997 at 15:52:57:

: Very curious...
  What are f-wave and h-reflex waveforms? Origin?  
  Do the "f" and "h" stand for something?  
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H-reflex and F-waves are obtained on nerve conduction studies which use electrical impulses to assess the integrity of nerves.  Thes responses gives us information on how the proximal part (nearest to the spinal cord) of the nerve conducts impulses.  H- reflex was named after a physician named Hoffman, who discovered it.  The reflex is based on activation ( by a submaximal response) of spindle afferent fibers after which it travels up the sensory fibers into the spinal cord down the motor nerve fibers to the muscle.  This is also what happens when a physician taps on your knee to check your reflexes.  This reflex may be abnormal if one has back pain from a nerve impingement at the first sacral root.  It may also be absent or reduced in generalized neuropathies and in older individuals (>60).  People who have lost their ankle reflexes usually have absent H reflexes.  
F- wave is named because it was initially found in the feet.  It is elicited by using a supramaximal stimulus to stimulate the nerves.  Their is the stimulation of motor fibers which travels up to the spinal cord synapses and travels back down the motor nerve which is then recorded in the muscle.  It is not abnormal in diseases that mainly affect the sensory nerves because it does not test them.  It's usefullness depends on the findings of the rest of the nerve conduction study.  Again it can be absent in normal subjects over the age of 60.
If you would like more detailed information or drawings of what I have described I would recommend any neurology textbook.  However, they hold little clinical significance other than assisting in diagnosis.