Direct Comparison of Patch and Needle Electromyography in the Evaluation of Urinary Sphincter Function

Needle electromyography (EMG) is the gold standard for studying striated muscle innervation. Despite this, surface patch EMGs are widely adapted to evaluate pelvic floor function and detrusor-sphincter coordination. However, it is unknown whether the 2 modalities produce concordant results when assessing external urinary sphincter function. The objective is to compare patch and needle EMG signals recorded during a urodynamic study to characterize differences in children during bladder filling and emptying.

We prospectively enrolled children scheduled for urodynamic study from March to December 2023 at our institution. Patients underwent simultaneous patch and concentric needle EMG evaluation. Primary outcomes were defined as the ability to characterize sphincter muscle motor unit potentials, sacral reflex reactivity, and detrusor sphincter coordination during bladder filling and emptying.

Among the 47 patients, the median age was 7 (IQR 2-12.5) years and 51.1% were male. Among 37 patients who voided, 18 patients were synergic on needle EMG. In these same 18 patients, 9 patch EMGs demonstrated synergy, while 9 exhibited dyssynergy. The sensitivity and specificity for patch EMG to detect dyssynergy were 73.3% and 50.0%, respectively. Complex repetitive discharges were observed on needle EMG in 2 patients but were not discernable on patch EMG. Sacral reflexes were weaker in 60.0% of patients using patch compared with needle EMG.

Surface patch EMG results were highly inconsistent compared with needle EMG, risking inaccurate diagnoses of detrusor sphincter dyssynergy and management. Needle EMG should be considered when critical data are needed to determine urologic and neurosurgical support.