A measure of peripheral nerve stimulation efficacy applicable to H-reflex studies.
BACKGROUND
When H-reflexes are recorded during movement in human subjects, the stimulator current output is not a good indicator of sensory stimulation efficacy because of unavoidable nerve movement relative to the stimulus electrodes. Therefore, the M-wave amplitude has been used by researchers as an indicator of the efficacy of the stimulus. In this study we have examined the general validity of the hypothesis that the M-wave amplitude is directly proportional to the group I sensory afferent volley evoked by the stimulus.


METHODS
A nerve recording cuff, stimulating electrodes, and EMG recording electrodes were implanted in cats. Nerve cuff recordings of centrally propagating volleys evoked by electrical stimuli were directly compared to M-waves produced by the same stimuli. Compound action potentials (CAPs) recorded in the sciatic nerve were compared with soleus M-waves during either tibial nerve or soleus muscle nerve stimulation. CAPs in the ulnar nerve were correlated with flexor carpi ulnaris M-waves during ulnar nerve stimulation.


CONCLUSIONS
Our findings indicate that for mixed nerve stimulation (e.g., tibial or ulnar nerve) the M-wave can be a reliable indicator of the centrally propagating sensory volley. Due to the high correlation between CAP and M-wave amplitude in these nerves, a small number of M-waves can give a good estimate of the size of the group I sensory volley. On the other hand, when nerves with only partially overlapping fibre diameter populations are stimulated (e.g., the soleus muscle nerve), the M-wave is not well correlated with the group I sensory volley and thus may not be used as a measure of the size of the input volley for H-reflex studies.
Boorman
G I
GI
Department of Clinical Neurosciences, University of Calgary, Alberta.
Hoffer
J A
JA
Kallesoe
K
K
Viberg
D
D
Mah
C
C
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002415:Cats; D004558:Electric Stimulation; D004576:Electromyography; D006181:H-Reflex / Q000502:physiology*; D006614:Hindlimb / Q000502:physiology*; D006801:Humans; D008297:Male; D010525:Peripheral Nerves / Q000502:physiology*; D012584:Sciatic Nerve / Q000502:physiology; D014459:Ulnar Nerve / Q000502:physiology