Paraspinal electromyography: Age-correlated normative values in asymptomatic subjects

Study Design. Cross-sectional study. Objectives. To determine if the amount of lumbar paraspinal denervation increases with age and present normative data on the amount of denervation present in asymptomatic subjects. Summary of Background Data. To our knowledge, there are no data on the relationship of paraspinal denervation with age or normative data on the amount of denervation expected in asymptomatic older adults. Methods. We combined the data from our current study of asymptomatic adults, age 55 - 79 years, and a previous study of asymptomatic adults, age 18 - 58 years, who underwent lumbar paraspinal muscle needle electromyography using a validated needle electromyography (MiniPM) technique. We then compared the results of the age group 55 - 79 to that of the age group 18 - 54. Results. The older group scored significantly higher than the younger group by 1.7 ( P = 0.008, 95% confidence interval 0.5 - 3.0). Linear regression showed that age was a significant predictor of the MiniPM score (beta = 0.04, and P = 0.04). For subjects 55 years and older, mean MiniPM score on one side was 2.3 ( standard deviation 3.6). The upper range of the 95th percentile was 10. Conclusions. The amount of lumbar paraspinal muscle denervation does increase with age. Understanding the range of findings in asymptomatic subjects will help us interpret lumbar paraspinal needle electromyography findings in patients with spinal disorders.