The electromyographic pattern (EMG) in two perineal muscles, the external anal sphincter muscle and the puborectalis muscle, was examined in 30 normal subjects consisting of women aged 24-77 years, using a concentric needle electrode. The interference pattern in the two muscles was recorded at rest and at maximal voluntary activation and analyzed with a computerized technique. The number of turns and the mean amplitudes in the interference pattern were measured and the recorded differences between the two investigated muscles as well as the differences compared to other striated extremity muscles are discussed. This technique (T/A analysis) has been shown to differentiate between neurogenic and myopathic changes in a weak muscle, and it is proposed that the technique could be useful in characterizing disturbances in perineal muscles in patients with micturition or defaecation dysfunctions.

Quantitative analysis of the interference pattern and fiber density in the perineal muscles in incontinent women showed a denser interference pattern at rest and increased fiber density. Both observations indicate a peripheral nerve lesion. Furthermore, the interference pattern showed signs of reduced central activation in the incontinent women during cystometry.

Quantitative analysis of the interference pattern and fiber density in the perineal muscles in incontinent women showed a denser interference pattern at rest and increased fiber density. Both observations indicate a peripheral nerve lesion. Furthermore, the interference pattern showed signs of reduced central activation in the incontinent women during cystometry.

The numerical reduction of turns during rest can be explained by disturbed feedback, indicating that not only efferent, but also sensory afferent nerve fibres can be involved in an iatrogen lesion during prostatic surgery. The increased mean amplitude at maximal activation was probably due to reinnervated motor units with increased amplitudes.

No abstract