Sphincter behaviour in myelomeningocele

Four hundred and two videourodynamic studies were performed on 207 children with neuropathic vesicourethral dysfunction due to myelomeningocele. The children were divided into three groups (contractile, intermediate and acontractile) according to the urodynamic behaviour of their bladders, and the behaviour of the bladder neck and distal sphincter mechanism was assessed in each group. The bladder neck may be competent or incompetent in children with contractile bladders but is never obstructive, and is always incompetent in children with either intermediate or acontractile bladders at their usual bladder volumes. The distal sphincter mechanism is nearly always dynamically obstructive (detrusor-sphincter dyssynergia) in children with contractile bladders but is rarely if ever incompetent, whereas in children with intermediate or acontractile bladders, both (static) distal sphincter obstruction and sphincter weakness incontinence exist to some degree, although the predominance of one of these may mask the existence of the other unless it is specifically looked for or some therapeutic manoeuvre unmasks it. The main conclusion from this study is that, with the possible exception of those few children with more minor partial cord lesions, dysfunction of one or both sphincter mechanisms is the rule in congenital cord lesions.