Clinical neurophysiological assessment in children with faecal incontinence and related disorders
EMG sphincter mapping is a standard investigation for faecal incontinence but is restricted in children by limited cooperation and tolerance. In adult studies, trans-rectal pudendal nerve stimulation and trans-cutaneous cauda equina stimulation have permitted more precise localisation of pelvic floor neuropathic lesions. However, the use of these new non-invasive techniques has not been assessed in children. In this study, clinical neurophysiological assessment was undertaken in 124 children. EMG examination (109 cases) with analysis of individual motor unit potentials (isolated under low frequency attenuation) was combined with attempted pudendal nerve (44 cases) and/or spinal stimulation (21 cases). In 80 children with various ano-rectal malformations, a substantial external anal sphincter could be demonstrated with EMG mapping (often under anaesthesia) in the great majority, even in those with high anomalies, and this was found to be useful for surgical correction. The presence and position of an external anal sphincter could be checked by pudendal nerve stimulation in the post-operative group. Unexpected evidence of abnormal external anal sphincter function in Hirschprung's disease was found in 5 children with persisting incontinence following surgical correction. Eight children with chronic constipation and 6 with encopresis did not show the high incidence of neurogenic lesions reported in adult series. The neurophysiological features in 10 children with possible cauda equina lesions (including sacral dysplasia) correlated well with radiological findings. The established clinical value of EMG sphincter mapping in perineal trauma was confirmed in 3 children. These studies suggest that clinical neurophysiological assessment of children with faecal incontinence contributes to the management of these difficult clinical problems. In addition it may help to improve our understanding of some of the mechanisms underlying both normal and abnormal function in the development and maintenance of continence in childhood.