title: Correlation of EMG, CMAP and SNAP amplitude decrease in mononeuropathies with axonal loss.
abstract: We retrospectively reviewed electrodiagnostic studies from 1983 to 1994 and found 48 patients who met our criteria for mononeuropathy with axonal loss (40 ulnar, 4 peroneal, 4 radial). Appropriate diagnostic criteria required bilateral studies with a normal contralateral, sensory nerve action potential (SNAP) amplitude decrease of > 50% compared to contralateral, and/or distal compound muscle action potential (CMAP) amplitude decrease of > 40% compared to contralateral, and/or presence of denervation potentials; and sufficient electrodiagnostic investigation to rule out peripheral polyneuropathy. We conclude that in the electrodiagnosis of mononeuropathy with axonal loss: 1) a significant quantitative correlation between CMAP and SNAP amplitude percentage decrease does not exist (r = 0.274, p = 0.06), 2) SNAP amplitude percentage decrease [75.3 +/- 31.8%] is greater than CMAP amplitude percentage decrease [43.9 +/- 31.3%] (paired t-test, p = 0.0001), and 3) CMAP amplitude decrease is positively correlated with the presence of denervation potentials (Xtrend2 = 6.22, p = 0.013).
authors.affiliation: Department of Functional Restoration, Stanford University Medical Center, USA.
authors.forename: P B
authors.initials: PB
authors.lastname: Wu
authors.forename: C G
authors.initials: CG
authors.lastname: Gussner
authors.forename: E S
authors.initials: ES
authors.lastname: Date
mesh_terms: D000200:Action Potentials; D000328:Adult; D000368:Aged; D001369:Axons; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction; D010523:Peripheral Nervous System Diseases / Q000503:physiopathology*; D012677:Sensation