Jitter patterns in conventional concentric needle electromyography recordings of regenerating motor units

Background: The time interval between two potential components of the same motor unit potential (MUP) is measured for jitter analysis. Enhanced jitter is generally thought to result from impaired neuromuscular transmission as occurs in myasthenia gravis or during reinnervation.

Methods: Within a database of conventional video-electromyography (EMG) recordings 4 MUP with peculiar jitter patterns were identified. In 1 spontaneously discharging MUP, massive and chaotic jitter was seen with a mean consecutive difference (MCD) of 9.3 ms. In 2 spontaneously discharging MUP a certain potential subgroup jittered relative to the other part(s) of the MUP (MCD 2.0 and 3.3 ms). A jittering satellite was detected in a fourth voluntarily recruited MUP (MCD 0.6 ms).

Results: These different jitter patterns recorded with conventional EMG technique may mainly result from dysmyelination.

Conclusions: A new look at the contribution of dysmyelination to abnormal jitter is also warranted in single fiber EMG recordings.