Increased H-reflex response induced by intramuscular electrical stimulation of latent myofascial trigger points.
BACKGROUND
Myofascial trigger points (MTrPs) present with mechanical hyperalgesia and allodynia. No electrophysiological evidence exists as to the excitability of muscle spindle afferents at myofascial trigger points MTrPs. The purpose of this current study was to explore whether an H-reflex response could be elicited from intramuscular electrical stimulation. If so, to assess the possibility of increased reflex response at MTrPs.


METHODS
The H-reflex latency and the conduction velocity were first determined from electrical stimulation of the tibial nerve in 13 healthy subjects. Then an intramuscular monopolar needle electrode was inserted randomly into a latent MTrP or a non-MTrP in the gastrocnemius muscle. Electrical stimuli at different intensities were delivered via the intramuscular recording electrode to the MTrP or non-MTrP.


RESULTS
The average conduction velocity (44.3 +/- 1.5 m/s) of the electrical stimulation of tibial nerve was similar (p>0.05) with the conduction velocity (43.9 +/- 1.4 m/s) of intramuscular electrical stimulation. The intramuscular H-reflex at MTrPs was higher in amplitude than non-MTrPs (p<0.001). The reflex threshold was lower for MTrPs than non-MTrPs (p<0.001).


CONCLUSIONS
The current study provides first electrophysiological evidence that intramuscular electrical stimulation can evoke H-reflex, and that higher H-reflex amplitude and lower H-reflex threshold exist at MTrPs than non-MTrPs respectively, suggesting that muscle spindle afferents may be involved in the pathophysiology of MTrPs.
Ge
Hong-You
HY
Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7 D-3, Aalborg, Denmark. ghy@hst.aau.dk
Serrao
Mariano
M
Andersen
Ole K
OK
Graven-Nielsen
Thomas
T
Arendt-Nielsen
Lars
L
D000328:Adult; D004558:Electric Stimulation / Q000379:methods*; D004599:Electric Stimulation Therapy / Q000379:methods*; D004576:Electromyography / Q000379:methods; D005260:Female; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D007273:Injections, Intramuscular; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D026201:Musculoskeletal Manipulations; D009209:Myofascial Pain Syndromes / Q000503:physiopathology; D017288:Pain Threshold / Q000502:physiology*; D012016:Reference Values