Electromyographic Examination of External Sohincter Muscle in Ano-Rectal Malformations

Abstract

We evaluated the external sphincter muscle by the application of electromyography in 52 preoperative patients of ano-rectal malformation and 10 patients of them had been sequentially examined to check the development of the muscle. Insertions of needle electrode within 5mm in depth were made at twenty five different points in 1 cm square at the perineum which had been determined to be the center of anus from the skin findings. EMG score was calculated by the summation of the points from which action potentials were picked up. The distribution map of the external sphincter was made by connecting those points. The EMG score was 18.1 ± 4.7 / 25 in low-type malformations. Otherwise, it was 11.0 ± 5.2 and 11.9 ± 4.1 in intermediate and high-type malformations respectively. In low-type malformations, the external sphincter was abundantly present in the area of 5 to 10mm in width and 10mm in length. Otherwise, intermediate and high malformations showec remarkably narrower distribution of the muscle than that of low-type malformations. In 15 patients (29%), the deviated distribution of the muscle from the dimple was demonstrated indicating the technical difficulty to preserve the muscle around the newly-constructed anus without preperrative electromyographic examination. The development of the muscle was shown even in high-type malformation and the increase of EMG score was +3.7 and +5 in the patient of intermediate and high-type malformation respectively. These results of electromyographic examination lead us to stress that preoperative electromyographic examination is extremely valuable technique to know the precise locality and volume of the external sphincter muscle which should be preserved to get the satisfactory sphincteric function.