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Standardization of anal sphincter electromyography: Quantification of continuous activity during relaxation
Author(s) -
Podnar Simon,
Mrkaić Mićo,
Vodušek David B.
Publication year - 2002
Publication title -
neurourology and urodynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 90
eISSN - 1520-6777
pISSN - 0733-2467
DOI - 10.1002/nau.10058
Subject(s) - medicine , electromyography , external anal sphincter , motor unit , conus medullaris , motor unit recruitment , sphincter , muscle relaxation , anatomy , urology , physical medicine and rehabilitation , anal canal , anesthesia , magnetic resonance imaging , rectum , radiology
Aim. Sphincter motor units (MUs) are continuously firing during relaxation. The quantification of this activity is a potentially useful electromyographic (EMG) parameter related to the number of MUs innervating the muscle and the level of motor neuron excitation. The aim of the present study was to develop a reliable, quantitative measure of continuous sphincter muscle activity during relaxation. Methods. EMG activity was analyzed during relaxation, 1 minute after insertion of the concentric needle electrode into four sites in the external anal sphincter (EAS) muscle. In 10 control subjects, 8 interference pattern samples were obtained by “turn/amplitude” analysis. In 35 control subjects, a multi‐MUP count of continuously firing motor unit potentials (MUPs) was used, quadruplets with scores of 0–6 obtained, and the lower reference limits (95th percentile) calculated. This approach was then evaluated in 57 patients (182 muscles) with cauda equina or conus medullaris lesion (CECML) and 7 patients (13 muscles) with “idiopathic fecal incontinence.” Results. The lower reference (“outlier”) limits for MUP count were 0 0 6 6 and 0 1 2 2 for the subcutaneous, and 0 0 0 6 and 0 0 1 1 for the deeper EAS muscles. Both patient groups had a significantly diminished number of continuously firing MUPs, which was below the reference range in 43% of the EAS muscles from CECM patients and in 85% of muscles from patients with idiopathic fecal incontinence. In patients with CECML, the decrease in MUP count correlated with the severity of the lesion, as defined by the sensory deficit. Conclusions. MUP count in sphincter muscles during relaxation is technically feasible, and it is a promising tool, particularly in patients with idiopathic fecal incontinence. Neurourol. Urodynam. 21:540–545, 2002. © 2002 Wiley‐Liss, Inc.