潜在性二分脊椎を有し,脊髄下部の牽引により生じた先天性神経因性膀胱(いわゆるTethered Cord Syndrome)の尿水力学的,電気生理学的検査法による術前および牽引除去後の評価

Abstract

Congenital neurogenic bladder associated with spina bifida occulta, or the so-called tethered cord syndrome, is one of the rare conditions that may be completely cured by surgery among other varieties of the disease. We make it a rule to make the diagnosis and follow-up of cases of the syndrome principally on the basis of findings in the urodynamic and electrophysiologic examinations. The urodynamic examination consisted of Lewis' cystometry and urethral pressure profiles during filling, whereas during voiding, the intra-abdominal, vesical and urethral pressures, tone and EMG of the anal sphincters and urinary flow rate were recorded simultaneously on a 6 channel polygraph (VUD). The patient was also tested for sacral reflex activity by means of bilateral electromyograms recorded from the anal sphincters to estimate the degree of sacral cord injury. A total of 46 patients, 21 males and 25 females, were studied in the recent five years. Subjects between II and 15 years of age, at the height of growth in stature in life-time, were most frequent, accounting for 35% of all patients (Table 1). Intraspinal surgery was performed on 15 of the 46 patients (Table 2). In the urodynamic examination of the syndrome, measurements were made chiefly of thirty-five voiding urodynamic (VUD) parameters (Fig. 1) to characterize the disease states before and after intraspinal surgery. Statistical data analyses were made by the t-test on preoperative values in comparison with values obtained in a normal control group and on postoperative values compared with the preoperative values. Table 3 shows the results of the t-test for comparison between the preoperative values for voiding urodynamic parameters in patients with tethered cord syndrome and the values obtained in the normal control group. The data indicate that, in this syndrome, voiding is accomplished by abdominal straining where the vesical neck is the main site of urethral resistance (detrusor-vesical neck dyssynergia), involving vesical neck constriction and dysectasia. External urethral sphincter dysectasia was also evident during voiding (detrusor-external urethral sphincter dyssynergia). Consequently, a high voiding pressure is required to initiate and maintain micturition by overcoming the urethral resistance of the vesical neck and external urethral sphincter. This can be assumed from the fact that all the voiding urodynamic parameters concerned with intravesical pressure showed high values. In contrast, low values were obtained for the parameters depicting contractility of the detrusor muscle, i.e. intrinsic detrusor contraction rate" ((19) Pb.max-Pabd.max/Pb.max) and "intrinsic voiding pressure" ((20) Pb.max-Pb.rest/Pb.max). These findings suggested disturbance in the micturition center in the sacral cord of the patient with this syndrome. The study also revealed diminution of urinary flow rate due to lowered detrusor muscle contractility and increased urethral resistance. Following surgery, the increased urethral resistance declined and the patient became able to micturate even under a lower vesical pressure during micturition. The postoperative urodynamic study demonstrating a decrease in the intra-abdominal pressure during voiding with a decrease of the ratio of intra-abdominal pressure to the total vesical voiding pressure, suggested recovery of the detrusor muscle contractility (Tables 5, 6, 7-A-a, b, 7-B, 7-C, 7-D, 7-E-a and 7-E-b and Figs. 2-Aa, 2-Ab, 2-B, 2-C, 2-D, 2-Ea and 2-Eb). A wide variety of abnormal patterns were observed in VUD curves depending upon the degree of sacral cord injury (Figs. 3 to 7). A case with the most pronounced sacral cord injury in this syndrome presented abnormal patterns closely resembling those in neurogenic bladder associated with meningomyelocele. It was frequently the case that the anal sphincter EMG, recorded bilaterally, disclosed abnormal patterns for either side in the test for sacral reflex activity. The urethral pressure profile disclosed lowered pressure in the mid-urethral segment in some of the cases studied. The degree of improvement in voiding urodynamic patterns obtained by surgical treatment varried considerably among the cases, from marked (Figs. 14 and 15) to practically nil (Fig. 13), though, generally, a trend to improvement in voiding patterns was obvious after surgery in most cases (Figs. 8 to 12). The results of the urodynamic and electrophysiologic studies indicate that the voiding condition of the surgically treated patients is in the course of normalization, thus demonstrating effectiveness of the surgical treatment.