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Updated: Aug 14, 2026
Dynamic Quantitative Sensory Testing to Characterize Central Pain Processing
Published on: February 16, 2017
Quantitative motor unit action potentials (QMUAP) in whiplash patients with neck and upper-limb pain
1Department of Physical Medicine and Rehabilitation, Hospital of the University of PA, Philadelphia 19104, USA. jechu@comcast.net
Introduction:
Needle EMG studies in patients with whiplash symptoms to document presence of neural injury, such as cervical radiculopathy, are not available.
Objective:
To document presence of motor unit action potential (MUAP) parameter changes compatible with neurogenic involvement in symptomatic-limb muscles in whiplash induced acute and chronic pain states.
Design:
Retrospective review.
Setting:
Out patient quantitative electromyography (QEMG) laboratory.
Participants:
72 consecutive patients (mean age 43.6 years) who underwent QEMG between 1/2001 - 12/2004 for electrodiagnosis of neck and upper-limb pain related to auto-accidents (mean symptom duration 15.3 months).
Interventions:
QEMG with MUAP parameter analysis.
Main Outcome Measures:
Amplitude, duration, size-index (SI), percentage of polyphasic units and firing rate analysis in chosen bilateral muscles representing C3-C8 myotomes.
Results:
No spontaneous activity noted in muscles examined. Without subsetting symptom duration, symptomatic-side: asymptomatic-side MUAP parameter comparison showed significant increase in MUAP frequency on the symptomatic-side C6-muscle (10.4 +/- 1.3 vs. 9.7 +/- 1.4, p = < 0.05), and C7 muscle (10.0 +/- 1.2 vs. 9.1 +/- 1.1, p < or = 0.01). The symptomatic-side C6-muscle also showed increased percentage of polyphasic-MUAPs (23.7 +/- 13.1 vs. 15.9 +/- 12.7, p < 0.001). Patients with acute symptom duration (< 6 months, mean duration 3.4 +/- 1.4 months, N=26), showed increased percentage of polyphasic MUAPs in the symptomatic-side C6-muscle (27.0 +/- 12.3% vs. asymptomatic 22.2 +/- 17.6%, p < or = 0.05). In patients with chronic symptom duration (> or =6 months, mean duration 22.0 +/- 17.9 months, N=46), symptomatic-side C6-muscle showed increased polyphasic MUAPs (22.2 +/- 13.2%) vs. asymptomatic (15.5 +/- 11.6%), p < or = 0.02, and higher firing rates (10.3 +/- 1.7 vs. 9.6 +/- 1.3 respectively, p < or = 0.003).
Conclusions:
QEMG changes suggest neural injury in symptomatic side C6 and C7 innervated muscles, even in the absence of spontaneous activity. In acute and chronic pain patients a higher percentage of polyphasic MUAPs is noted in the symptomatic side C6 muscle. In chronic pain patients higher MUAP frequencies are noted in the symptomatic side C6 muscle.
