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A Prospective Evaluation of Leak Point Pressure, Bladder Compliance and Clinical Status in Myelodysplasia Patients with Tethered Spinal Cords
0022-534 7/94/1511-0177$03.00/0 THE JOURNAL OF UROLOGY Copyright© 1994 by AMERICAN UROLOGICAL ASSOCIATION, INC.
Vol. 151, 177-181, January 1994
Printed in U.S.A.
A PROSPECTIVE EVALUATION OF LEAK POINT PRESSURE, BLADDER COMPLIANCE AND CLINICAL STATUS IN MYELODYSPLASIA PATIENTS WITH TETHERED SPINAL CORDS ELIZABETH E, HOUSER, THOMAS H. BARTHOLOMEW, MICHAEL S. COOKSON, ARTHUR E. MARLIN AND NANCY A. LITTLE* From the Departments of Pediatrics and Surgery, Division of Urology, The University of Texas Health Science Center, San Antonio, Texas
ABSTRACT
We evaluated prospectively 26 patients with myelodysplasia and a tethered spinal cord to determine whether surgical release of the tethered cord positively influenced leak point pressure, bladder compliance, upper tract status and/or clinical management. Urodynamics were performed immediately before and after the neurosurgical procedure, and at 3 and 6 months postoperatively. Mean patient age was 7.8 years (range 2 days to 34 years) and median interval from onset of symptoms to surgery was 60 days (range 2 days to 4 years). Patient presentation included a combination of orthopedic, neurological and urological symptoms. Of 26 patients 9 (35%) had new hydronephrosis, urinary tract infections or urinary incontinence. Leak point pressure and bladder compliance did not change significantly by 6 months postoperatively. Of the 4 patients who presented with hydronephrosis 1 worsened in status, 2 stabilized and 1 improved. Clinical status was unchanged in 16 patients, improved in 4 and worsened in 6. There was no significant relationship between patient age and urodynamic or clinical outcome. Among patients followed for at least 6 months radiographic and clinical improvement occurred in 25% and 15%, respectively. Urodynamic improvements were transient. Surgical release of a tethered cord improved the urological status in less than a quarter of the patients in this series. KEY WORDS:
neural tube defects, myelodysplastic syndromes, spinal cord, urodynamics
It is well known that patients with spinal dysraphism have neurogenic bladder dysfunction. Preservation of the upper urinary tracts in these patients is dependent upon low filling pressures, high bladder compliance and a pressure at the time of urinary leakage of less than 40 cm. water. 1- 4 The role of urodynamics in assessing the exact degree of voiding dysfunction has become increasingly important with the realization that bladder and outlet behavior cannot be predicted solely on the level of the neurological lesion. Recognition of these factors and the advent of clean intermittent catheterization have revolutionized care of the patient with a neurogenic bladder due to spinal dysraphism but the urologist must be continually aware of potential for change in the neurourological status. 5 The tethered spinal cord syndrome is a potential cause of deterioration of the urinary tract. 6 Recent advances in radiographic imaging and increased awareness have resulted in more frequent diagnosis of the tethered spinal cord syndrome. Improvements in surgical treatment, including microscopic optical magnification, laser and electromyography, have decreased morbidity and improved surgical outcome. The urological literature suggests that patients with a tethered spinal cord undergo prompt surgical release to prevent further deterioration and relieve urological symptomatology. 7-lo Inconsistent clinical outcomes after surgical release of the tethered cord at our institution led us to investigate urodynamic and clinical parameters in 26 consecutive patients undergoing release of a tethered cord. MATERIALS AND METHODS
On the basis of diverse orthopedic, urological and neurological symptoms, 26 of 260 myelodysplastic patients followed at Santa Rosa Children's Hospital were diagnosed with a tethered spinal cord between December 1989 and December 1990. After Accepted for publication May 28, 1993. * Requests for reprints: Division of Urology, University of Texas, Health Science Center, 7703 Floyd Curl Dr., San Antonio, Texas 782847845.
urological and neurosurgical evaluation, all patients underwent radiographic confirmation of tethering by loss of spinal cord pulsations on sonography, magnetic resonance imaging or computerized tomography and myelography of the spine. The 10 male and 16 female patients ranged from 2 days to 34 years old (mean age 7.8 years). Nine patients had primary tethering associated with an unrepaired back defect, 16 had undergone 1 prior operation and 1 had undergone 4 previous operations. All patients underwent simple preoperative bedside cystometry and a determination of leak point pressure. A water column manometer was used to monitor pressure as the bladder was filled at a standardized rate (10% calculated bladder capacity per minute) with room temperature normal saline. A 7F Bard double lumen urodynamics catheter and standard intravenous tubing were used for infusion. Initial resting bladder pressure, end filling or leak point pressure and bladder capacity were recorded. Bladder compliance was calculated as the change in volume divided by the change in pressure. 1 Leak point pressure-to-compliance ratio, a value considered by some to be another parameter of upper tract risk, was calculated. 11 Studies were terminated at the point of leakage or capacity in those without leakage. Neurosurgical release of a tethered cord was performed by 1 neurosurgeon (A. E. M.) using optical magnification, a carbon dioxide laser and electromyography. All patients were reevaluated 3 to 7 days postoperatively, 16 were studied 3 months later and 15 were studied 6 months postoperatively. A total of 20 patients underwent preoperative, 24 postoperative, and 16 preoperative and postoperative upper tract studies. Statistical analysis was performed on variables of leak point pressure, compliance, leak point pressure-to-compliance ratio, patient age and interval from diagnosis to treatment using the McNemar test of significance of change and unbalanced repeated measures of variance. A p value of <0.05 was considered significant.
177
178
URODYNAMICS IN MYELODYSPLASTIC PATIENTS WITH TETHERED SPINAL CORD RESULTS
Table 1 lists individual patient data. Values with asterisks indicate end filling pressures in patients without leakage. Table 2 lists mean values of leak point pressure, compliance and the leak point pressure-to-compliance ratio. Figure 1 depicts the changes in mean leak point pressure with time and figure 2 shows the mean compliance with time. Initially the mean leak point pressure decreased and the compliance increased but these values reverted to near preoperative values by 6 months. Of the 20 preoperative studies 16 were normal, while 4 patients had hydronephrosis (table 3). Of these 4 patients 3 had a leak point pressure of more than 40 cm. water preoperatively. Patient 25, a 5-year-old girl, was dry and had rare infections on clean intermittent catheterization and antibiotic suppression before the spinal cord became tethered. She had leak point pressures of 45 before and 40 immediately after the operation. The leak point pressure 3 months later was 45 and at 6 months it was 42. Progressive hydronephrosis developed and she improved on clean intermittent catheterization after bladder augmentation and bilateral ureteral reimplantation. Patient 3, a 31-month-old boy in diapers, had high leak point pressures of more than 55 preoperatively and 3 months postoperatively. He had frequent urinary tract infections postoperatively, and responded to antibiotic suppression and clean intermittent catheterization. The hydronephrosis stabilized on this regimen. Patient 24, a 3-year-old girl, had new hydronephrosis and high leak point pressures of greater than 55 preoperatively and postoperatively. She did well on clean intermittent catheterization alone before and after untethering, and she had no further radiographic or clinical deterioration. Patient 22, a 10-year-old boy, had leak point pressures of 28, 44, 27 and 22 before, immediately after, and 3 and 6 months after the operation. He was dry on clean intermittent catheterization and anticholinergics before untethering, and became continually incontinent postoperatively. The hydronephrosis resolved TABLE 1.
Pt. No.-Age 1-12 yrs. 2-4days 3-31 mos. 4 -6 yrs. 5-6yrs. 6-5mos. 7-5 yrs. 8-11 yrs. 9-9yrs. 10-34 yrs. 11-6 days 12-6wks. 13-30 mos. 14-2 mos. 15 - 12 yrs. 16-9 yrs. 17- 32 yrs. 18-2 days 19-23 mos. 20-18 yrs. 21-3 mos. 22 - 10.5 yrs. 23-10 yrs. 24-3 yrs. 25-5 yrs. 26-13 yrs.
postoperatively. Therefore, of the 3 patients with high leak point pressures preoperatively, 1 worsened in status and 2 stabilized after spinal cord surgery. The patient who had complete resolution of hydronephrosis had a low leak point pressure preoperatively and was continually incontinent postoperatively. Table 3 lists the ages of the patients with preoperative hydronephrosis that deteriorated or improved after untethering. The 4 patients who had hydronephrosis were 2.6, 3, 5 and 10.5 years old (mean age 5.3 years) when diagnosed with the tethered cord syndrome. The 6 patients who worsened clinically were 2.6 to 18 years old (mean age 9.5 years). Four patients improved and the ages were 2.5, 5, 6 and 34 years (mean age 11.8 years). There was no significant relationship between patient age at diagnosis and outcome. The interval from diagnosis of a tethered spinal cord to treatment is also listed for these patients in table 3. In the group who deteriorated the intervals to treatment were longer (mean 428.3 days) than in those who improved (mean 63.5 days). This difference approached statistical significance at p = 0.09. Overall, 16 of 26 patients had no change in the incontinence or infection rate and they required no change in the catheterization and medication regimen. DISCUSSION
Neuropathic bladder dysfunction in myelodysplastic patients is not reliably predicted by the anatomical spinal cord lesion or the neurological examination, and radiographic evidence of upper tract deterioration is a late sign of lower tract decompensation.2· 12 Urodynamic assessment assists the urologist in determining urinary tract behavior and there is a high incidence of change in the pattern of bladder dysfunction in these patients. Therefore, periodical urodynamic testing, and radiographic and clinical examination are required for appropriate management of the upper and lower urinary tracts. 5 Spinal cord tethering is a clinical syndrome that occurs when the
Individual data Leak Point Pressure/Compliance
Presentation Ventriculoperitoneal shunt malfunction Lumbar mass New hydronephrosis Lower back pain, foot inversion Lower back pain Lumbar mass New urinary incontinence and infections, low back pain New urinary incontinence New fecal incontinence Lower extremity weakness, new urinary infections and incontinence Lumbar mass Skin tag lumbar spine Lower extremity weakness Lumbar mass Lower extremity weakness, lower back pain Lower back pain Lower back pain, lower extremity weakness Lower extremity pain Recurrent urinary infections Lower extremity pain Thoracic mass New hydronephrosis Urinary urgency, lower back pain New hydronephrosis New hydronephrosis Lower extremity
• No leakage, number given is end filling pressure.
Preop.
Postop.
3Mos.
42*/12.85
43/13.51
25/17.50
37/1.82 55/2.71 21/17.14
30/0.52 32/2.69 15/1.25
55/2.00 55/2.67 28/15.00
50/5.00 16/1.50 14/3.75
50/6,90 10/2.00 26*/16.67
28/7.50
38*/13.33 33/8.85 17/15.00
38/14.10 22/5.00 21/30.77
25/0.56 48/0.49 11/18.00 42/1.35 21*/46.67
16/1 11/6.67 21/4.38 8/35,00 14*/121.42
27/7.73 32* /31.82
23/11.18 26*/41.67
28/6.52
30*/26.67 31/30.35
35/1.48 8/30.00 14* /50.00 38/1.21 28/2.56 55/5.53
32/2.69 42/1.36 14*/66.67 35/0.93 44/8.72 8/200,00
38/1.36 17/8.33
42/2.22
27* /26.47
22/31.67 55/2.67
55/2.20 45/2.56 26*/37.50
55/1.700 40/3.17 14*/187.50
28/13.64
6Mos.
25/13.33 45/#
32/21.15
34*/20.83 22/1.66 37/12.50
16/2.78
25/1.58
41 /1.43
32/8.85 38/1.82
55/1.43 45/4.86 32*/30.77
42/2.78 17*/54.54
179
URODYNAMICS IN MYELODYSPLASTIC PATIENTS WITH TETHERED SPINAL CORD TABLE 2.
lvfean values of leak point pressure, compliance and /,eak point pressure-to-compliance ratio Leak Point Pressure (cm. water)
Preop. Postop. 3 mos. 6mos.
Compliance (mL/cm. water)
Leak Point Pressure: Compliance Ratio
12.36 30.28 10.21 15.10
14.54 10.09 11.07 8.41
32 26
34 33
Relationship among new hydronephrosis, clinical deterioration or improvement, age and delay to treatment
TABLE 3.
Pt. No.
Age at Diagnosis (yrs.)
Delay to Treatment (days)
New Hydronephrosis
3 22 24 25 Means
36
2.6 10.5 3 5 5]
60 90 90 90 82.5
Clinical deterioration
34
3
2.6
9
9
15 20 22 25 Means
32
12 18 10.5 9.5
9.5
60 150 720 1460 90 90 428.3
Clinical improvement
26
2 4 ' - - ' ~ ~ - ~ ' - - ' ~ - ~ ~ . . _ . ~ ~ ~ ~.......~ - ~ ~ " - - ' ~ 0
1
12
Pre Post
Time (weeks)
FIG. 1. Mean leak point pressure versus time 35
.
30
i:l
25
%
~
g
20
II)
'-' C: .!ll C.
E 0
15 10
(.)
5 0
1
12
6 5 34 2.5 11.8
14 60 90 90 63.5
24
Operative
.:2
4 7 10 13 Means
24
Pre Post Operative
Time (weeks)
Fm. 2. Mean compliance versus time
conus medullaris is prevented from its usual ascent during growth. It frequently occurs during times of rapid axial skeletal growth and can be primary (related to a bony spicule, spinal lipoma or myelomeningocele) or secondary (as a result of scarring at a previous surgical site. 9 Lower extremity paresthesias or palsies, low back pain or a change in urinary tract status frequently alerts the clinician to this condition. The neurosurgical and urological literature supports early surgical release of tethered spinal cord elements. Yamada et al demonstrated mitochondrial deterioration in tethered spinal cords in animal models and human examples, with improved oxidative metabolism after untethering. 13 Hypoxemia of the tethered neuronal elements led to axonal degeneration and nerve cell death. They concluded that surgical release of tethered elements could facilitate repair of injured neurons. Of the 6 patients with genitourinary symptoms 5 improved clinically. No urodynamic parameters were reported. Others have similarly concluded that any neural trauma, such as transection, compression, tension or hypoxemia, results in metabolic and functional changes in neuronal activity. 14- 15 Several reports in the literature indicate that urinary tract
status may be improved by spinal cord untethering. Kaplan et al reported a 60% improvement in 20 patients after surgical release of a tethered spinal cord. 8 Improvement was defined as a shift to the right on the pressure volume curve of the cystometrogram and decreased uninhibited contractions. Flanigan et al evaluated 8 patients urodynamically before and after untethering. 10 Urodynamic studies were performed between 3 days and 3 years postoperatively. Clinical improvement was reported in 2 patients and urodynamic parameter improvement was noted in 5. Fukui et al studied 46 tethered spinal cord patients preoperatively and postoperatively with multichannel urodynamics. 16 Their initial postoperative report indicated a 50% improvement overall and a 25% decrease in detrusor sphincter dyssynergia. However, at 6 months and 1 year postoperatively there was no real difference in clinical or urodynamic parameters. 7 Leak point pressure was not measured and these data were not subjected to statistical analysis. Urodynamics. The optimal situation for the patient with a neurogenic bladder allows for ease of management, and protection of the upper and lower urinary tracts. A leak point pressure of less than 40 cm. water appears to be related to upper tract protection, and although there is no ideal value for bladder compliance it is generally believed that high compliance equates with low risk. 2 • 3 • 17 In our series the initial postoperative leak point pressure or end filling pressure decreased in 62% of the patients, while compliance increased immediately in 69%. These changes were transient and reverted to near preoperative values 6 months postoperatively. These findings could reflect a period of spinal shock, since they resolved by 6 months. Leak point pressures of more than 40 cm. water were observed in 3 of 4 patients who had hydronephrosis at diagnosis. Of these patients 2 deteriorated in status clinically, and 2 stabilized and are being followed closely. Our data support the relationship of a leak point pressure of more than 40 cm. water and upper tract deterioration. Patient variables. Others have suggested that patient age, interval from diagnosis to treatment and density of adhesions at the tethered site may relate to urological outcome after untethering. 7 In our series patient age did not significantly impact' on outcome. The patients who improved had shorter intervals from diagnosis to treatment than the 6 who deteriorated but this difference was not statistically significant. Patient 20, who deteriorated in status, failed to return promptly for followup and, therefore, had a delay in treatment of 1,460 days. If this patient is omitted, this difference is even less
180
URODYNAMICS IN MYELODYSPLASTIC PATIENTS WITH TETHERED SPINAL CORD
significant. In our series, adhesion density was not assessed prospectively. Our review of operative reports was not adequate to provide conclusions. Clinical management. Clinical management did not change in 16 patients. Four patients with a preoperative leak point pressure of less than 40 cm. water had clinical improvement. Patients 4 and 7, who voided with Crede's maneuver preoperatively, no longer required this maneuver, and patients 10 and 13 were converted from wet to dry on intermittent catheterization and anticholinergic medication. Of 6 patients who required changes in the regimen 2 had preoperative and postoperative leak point pressures of more than 40 cm. water. Patient 22 was converted from dry to wet despite intermittent catheterization and anticholinergic medications. Patient 25, who had a high leak point pressure preoperatively and postoperatively, required augmentation cystoplasty and bilateral ureteral reimplantation. Patient 3, who also had high leak point pressures before and after surgery, suffered febrile urinary tract infections. Patients 15 and 20 did not have leakage preoperatively. Both patients voided normally preoperatively and patient 15 required catheterization postoperatively, while patient 20 became totally incontinent and was lost to followup. Patient 9 had preoperative and postoperative leak point pressures of less than 40 cm. water, became totally incontinent postoperatively and is awaiting placement of an artificial urinary sphincter. Therefore, in this series only 4 of 26 patients (15%) improved in terms of clinical management. Patients 3, 22 and 25, who presented with new hydronephrosis, worsened clinically and patients 3 and 25 had a leak point pressure of more than 40 cm. water preoperatively. This finding supports a relationship among high leak point pressure, upper tract damage and clinical deterioration. CONCLUSION
At latest followup, radiographic and clinical parameters improved in 25% and 15% of the patients, respectively. The changes that occurred immediately postoperatively were probably related to a period of spinal shock since they reversed by 6 months postoperatively. Patient age at diagnosis and the interval from diagnosis to release of tethered elements were not significantly related to urodynamic, radiographic or clinical outcome. To determine if spinal cord untethering truly is of urological benefit a control group of patients to be observed without surgical intervention would be necessary. We would suggest that this control group may be represented by all patients who have undergone spinal cord surgery. Bedside urodynamic evaluation is simple, cost-effective and informative. In this series there was a period of spinal shock during which urodynamic parameters improved. However, these changes were transient. Radiographic and clinical improvement occurred in a small number of patients. Based on our data we conclude that spinal cord release in patients with a tethered spinal cord is of benefit to the urinary tract in only a small percentage of patients. REFERENCES
1. Ghoneim, G. M., Roach, M. B., Lewis, V. H. and Harmon, E. P.: The value of leak pressure and bladder compliance in the urodynamic evaluation of meningomyelocele patients. J. Urol., 144: 1440, 1990. 2. McGuire, E. J., Woodside, J. R., Borden, T. A. and Weiss, R. M.: Prognostic value of urodynamic testing in myelodysplastic patients. J. Urol., 126: 205, 1981. 3. McGuire, E. J., Woodside, J. R. and Borden, T. A.: Upper urinary tract deterioration in patients with myelodysplasia and·detrusor hypertonia: a followup study. J. Urol., 129: 823, 1983. 4. Sidi, A. A., Dykstra, D. D. and Gonzalez, R.: The value of urodynamic testing in the management of neonates with myelodysplasia: a prospective study. J. Urol., 135: 90, 1986. 5. Spindel, M. R., Bauer, S. B., Dyro, F. M., Krarup, C., Khoshbin, S., Winston, K. R., Lebowitz, R. L., Colodny, A. H. and Retik,
6. 7. 8. 9.
10. 11. 12.
13. 14. 15. 16.
17.
A. B.: The changing neurologic lesion in myelodysplasia. J.A.M.A., 258: 1630, 1987. Al-Mefty, 0., Kandzari, S. and Fox, J. L.: Neurogenic bladder and the tethered spinal cord syndrome. J. Urol., 122: 112, 1979. Fukui, J. and Kakizaki, T.: Urodynamic evaluation of tethered cord syndrome including tight filum terminale. Prolonged follow-up observation after intraspinal operation. Urology, 16: 539, 1980. Kaplan, W. E., McLone, D. G. and Richards, I.: The urological manifestations of the tethered spinal cord. J. Urol., 140: 1285, 1988. Keating, M. A., Rink, R. C., Bauer, S. B., Krarup, C., Dyro, F. M., Winston, K. R., Shillito, J., Fischer, E. G. and Retik, A. B.: Neurourological implications of the changing approach in management of occult spinal lesions. J. Urol., part 2, 140: 1299, 1988. Flanigan, R. C., Russell, D. P. and Walsh, J. W.: Urologic aspects of tethered cord. Urology, 33: 80, 1989. Bloom, D. A., Knechtel, J.M. and McGuire, E. J.: Urethral dilation improves bladder compliance in children with myelomeningocele and high leak point pressures. J. Urol., part 2, 144: 430, 1990. Wyndaele, J. J. and De Sy, W. A.: Correlation between the findings of a clinical neurological examination and the urodynamic dysfunction in children with myelodysplasia. J. Urol., 133: 638, 1985. Yamada, S., Zinke, D. E. and Sanders, D.: Pathophysiology of "tethered cord syndrome." J. Neurosurg., 54: 494, 1981. Kobrine, A. I., Doyle, T. F. and Martins, A. N.: Local spinal cord blood flow in experimental traumatic myelopathy. J. Neurosurg., 42: 144, 1975. Senter, H.J. and Venes, J. L.: Loss of autoregulation andposttraumatic ischemia following experimental spinal cord trauma. J. Neurosurg., 50: 198, 1979. Fukui, J., Kodaira, K., Watanabe, S., Takezaki, T. and Shiba, N.: Diagnosis, treatment and prognosis of congenital neurogenic bladder caused by traction of lower spinal cord segment with spina bifida occulta. Jap. J. Urol., 68: 569, 1977. Ghoneim, G. M., Bloom, D. A., McGuire, E. J. and Stewart, K. L.: Bladder compliance in meningomyelocele children. J. Urol., 141: 1404, 1989.
EDITORIAL COMMENT There is no question that it is important to have continuous neurourological surveillance of the lower urinary tract in patients with myelodysplasia because of the high incidence of documented secondary tethering of the spinal cord, with its tendency to worsen the neurological condition further. How best to conduct this surveillance is another matter. The idea is to measure those parameters that are likely to detect a change early so that a second neurosurgical procedure has a high likelihood of achieving a beneficial effect. It is not appropriate to group together patients who did and did not undergo prior back surgery. In addition, I am not sure whether the authors chose the correct parameters for determining an early change in lower urinary tract function-hydronephrosis may not occur for 6 to 12 months after a neurological change has affected detrusor compliance, so this late discovery may be a reason why only 15% of the study population improved and why 2 even had progression. It is not stated whether the measurement of compliance used was initial, terminal or an average throughout bladder filling, so the reader does not know exactly what to measure if he is to conduct his own surveillance. The authors also state that a leak point pressure of greater than 40 cm. leads to hydronephrosis. However, only 3 of 7 patients with a leak point pressure of greater than 40 cm. and 1 of 19 with a low leak point pressure had hydronephrosis. Of 10 patients with a compliance of less than 10 cm., 4 had hydronephrosis. Thus, both of these parameters are not great indicators of upper urinary tract deterioration. When the 2 parameters are considered together they are more meaningful: 4 of 5 patients with a leak point pressure of greater than 40 cm. and a compliance of less than 10 cm. had hydronephrosis preoperatively. Finally, 5 patients (19%) had no studies done more than 3 to 7 days postoperatively. Including them in the analysis slants the findings and does not add credence to the conclusions. Stuart B. Bauer Division of Urology Children's Hospital Medical Center Boston, Massachusetts
Vol. 151, 177-181, January 1994
Printed in U.S.A.
A PROSPECTIVE EVALUATION OF LEAK POINT PRESSURE, BLADDER COMPLIANCE AND CLINICAL STATUS IN MYELODYSPLASIA PATIENTS WITH TETHERED SPINAL CORDS ELIZABETH E, HOUSER, THOMAS H. BARTHOLOMEW, MICHAEL S. COOKSON, ARTHUR E. MARLIN AND NANCY A. LITTLE* From the Departments of Pediatrics and Surgery, Division of Urology, The University of Texas Health Science Center, San Antonio, Texas
ABSTRACT
We evaluated prospectively 26 patients with myelodysplasia and a tethered spinal cord to determine whether surgical release of the tethered cord positively influenced leak point pressure, bladder compliance, upper tract status and/or clinical management. Urodynamics were performed immediately before and after the neurosurgical procedure, and at 3 and 6 months postoperatively. Mean patient age was 7.8 years (range 2 days to 34 years) and median interval from onset of symptoms to surgery was 60 days (range 2 days to 4 years). Patient presentation included a combination of orthopedic, neurological and urological symptoms. Of 26 patients 9 (35%) had new hydronephrosis, urinary tract infections or urinary incontinence. Leak point pressure and bladder compliance did not change significantly by 6 months postoperatively. Of the 4 patients who presented with hydronephrosis 1 worsened in status, 2 stabilized and 1 improved. Clinical status was unchanged in 16 patients, improved in 4 and worsened in 6. There was no significant relationship between patient age and urodynamic or clinical outcome. Among patients followed for at least 6 months radiographic and clinical improvement occurred in 25% and 15%, respectively. Urodynamic improvements were transient. Surgical release of a tethered cord improved the urological status in less than a quarter of the patients in this series. KEY WORDS:
neural tube defects, myelodysplastic syndromes, spinal cord, urodynamics
It is well known that patients with spinal dysraphism have neurogenic bladder dysfunction. Preservation of the upper urinary tracts in these patients is dependent upon low filling pressures, high bladder compliance and a pressure at the time of urinary leakage of less than 40 cm. water. 1- 4 The role of urodynamics in assessing the exact degree of voiding dysfunction has become increasingly important with the realization that bladder and outlet behavior cannot be predicted solely on the level of the neurological lesion. Recognition of these factors and the advent of clean intermittent catheterization have revolutionized care of the patient with a neurogenic bladder due to spinal dysraphism but the urologist must be continually aware of potential for change in the neurourological status. 5 The tethered spinal cord syndrome is a potential cause of deterioration of the urinary tract. 6 Recent advances in radiographic imaging and increased awareness have resulted in more frequent diagnosis of the tethered spinal cord syndrome. Improvements in surgical treatment, including microscopic optical magnification, laser and electromyography, have decreased morbidity and improved surgical outcome. The urological literature suggests that patients with a tethered spinal cord undergo prompt surgical release to prevent further deterioration and relieve urological symptomatology. 7-lo Inconsistent clinical outcomes after surgical release of the tethered cord at our institution led us to investigate urodynamic and clinical parameters in 26 consecutive patients undergoing release of a tethered cord. MATERIALS AND METHODS
On the basis of diverse orthopedic, urological and neurological symptoms, 26 of 260 myelodysplastic patients followed at Santa Rosa Children's Hospital were diagnosed with a tethered spinal cord between December 1989 and December 1990. After Accepted for publication May 28, 1993. * Requests for reprints: Division of Urology, University of Texas, Health Science Center, 7703 Floyd Curl Dr., San Antonio, Texas 782847845.
urological and neurosurgical evaluation, all patients underwent radiographic confirmation of tethering by loss of spinal cord pulsations on sonography, magnetic resonance imaging or computerized tomography and myelography of the spine. The 10 male and 16 female patients ranged from 2 days to 34 years old (mean age 7.8 years). Nine patients had primary tethering associated with an unrepaired back defect, 16 had undergone 1 prior operation and 1 had undergone 4 previous operations. All patients underwent simple preoperative bedside cystometry and a determination of leak point pressure. A water column manometer was used to monitor pressure as the bladder was filled at a standardized rate (10% calculated bladder capacity per minute) with room temperature normal saline. A 7F Bard double lumen urodynamics catheter and standard intravenous tubing were used for infusion. Initial resting bladder pressure, end filling or leak point pressure and bladder capacity were recorded. Bladder compliance was calculated as the change in volume divided by the change in pressure. 1 Leak point pressure-to-compliance ratio, a value considered by some to be another parameter of upper tract risk, was calculated. 11 Studies were terminated at the point of leakage or capacity in those without leakage. Neurosurgical release of a tethered cord was performed by 1 neurosurgeon (A. E. M.) using optical magnification, a carbon dioxide laser and electromyography. All patients were reevaluated 3 to 7 days postoperatively, 16 were studied 3 months later and 15 were studied 6 months postoperatively. A total of 20 patients underwent preoperative, 24 postoperative, and 16 preoperative and postoperative upper tract studies. Statistical analysis was performed on variables of leak point pressure, compliance, leak point pressure-to-compliance ratio, patient age and interval from diagnosis to treatment using the McNemar test of significance of change and unbalanced repeated measures of variance. A p value of <0.05 was considered significant.
177
178
URODYNAMICS IN MYELODYSPLASTIC PATIENTS WITH TETHERED SPINAL CORD RESULTS
Table 1 lists individual patient data. Values with asterisks indicate end filling pressures in patients without leakage. Table 2 lists mean values of leak point pressure, compliance and the leak point pressure-to-compliance ratio. Figure 1 depicts the changes in mean leak point pressure with time and figure 2 shows the mean compliance with time. Initially the mean leak point pressure decreased and the compliance increased but these values reverted to near preoperative values by 6 months. Of the 20 preoperative studies 16 were normal, while 4 patients had hydronephrosis (table 3). Of these 4 patients 3 had a leak point pressure of more than 40 cm. water preoperatively. Patient 25, a 5-year-old girl, was dry and had rare infections on clean intermittent catheterization and antibiotic suppression before the spinal cord became tethered. She had leak point pressures of 45 before and 40 immediately after the operation. The leak point pressure 3 months later was 45 and at 6 months it was 42. Progressive hydronephrosis developed and she improved on clean intermittent catheterization after bladder augmentation and bilateral ureteral reimplantation. Patient 3, a 31-month-old boy in diapers, had high leak point pressures of more than 55 preoperatively and 3 months postoperatively. He had frequent urinary tract infections postoperatively, and responded to antibiotic suppression and clean intermittent catheterization. The hydronephrosis stabilized on this regimen. Patient 24, a 3-year-old girl, had new hydronephrosis and high leak point pressures of greater than 55 preoperatively and postoperatively. She did well on clean intermittent catheterization alone before and after untethering, and she had no further radiographic or clinical deterioration. Patient 22, a 10-year-old boy, had leak point pressures of 28, 44, 27 and 22 before, immediately after, and 3 and 6 months after the operation. He was dry on clean intermittent catheterization and anticholinergics before untethering, and became continually incontinent postoperatively. The hydronephrosis resolved TABLE 1.
Pt. No.-Age 1-12 yrs. 2-4days 3-31 mos. 4 -6 yrs. 5-6yrs. 6-5mos. 7-5 yrs. 8-11 yrs. 9-9yrs. 10-34 yrs. 11-6 days 12-6wks. 13-30 mos. 14-2 mos. 15 - 12 yrs. 16-9 yrs. 17- 32 yrs. 18-2 days 19-23 mos. 20-18 yrs. 21-3 mos. 22 - 10.5 yrs. 23-10 yrs. 24-3 yrs. 25-5 yrs. 26-13 yrs.
postoperatively. Therefore, of the 3 patients with high leak point pressures preoperatively, 1 worsened in status and 2 stabilized after spinal cord surgery. The patient who had complete resolution of hydronephrosis had a low leak point pressure preoperatively and was continually incontinent postoperatively. Table 3 lists the ages of the patients with preoperative hydronephrosis that deteriorated or improved after untethering. The 4 patients who had hydronephrosis were 2.6, 3, 5 and 10.5 years old (mean age 5.3 years) when diagnosed with the tethered cord syndrome. The 6 patients who worsened clinically were 2.6 to 18 years old (mean age 9.5 years). Four patients improved and the ages were 2.5, 5, 6 and 34 years (mean age 11.8 years). There was no significant relationship between patient age at diagnosis and outcome. The interval from diagnosis of a tethered spinal cord to treatment is also listed for these patients in table 3. In the group who deteriorated the intervals to treatment were longer (mean 428.3 days) than in those who improved (mean 63.5 days). This difference approached statistical significance at p = 0.09. Overall, 16 of 26 patients had no change in the incontinence or infection rate and they required no change in the catheterization and medication regimen. DISCUSSION
Neuropathic bladder dysfunction in myelodysplastic patients is not reliably predicted by the anatomical spinal cord lesion or the neurological examination, and radiographic evidence of upper tract deterioration is a late sign of lower tract decompensation.2· 12 Urodynamic assessment assists the urologist in determining urinary tract behavior and there is a high incidence of change in the pattern of bladder dysfunction in these patients. Therefore, periodical urodynamic testing, and radiographic and clinical examination are required for appropriate management of the upper and lower urinary tracts. 5 Spinal cord tethering is a clinical syndrome that occurs when the
Individual data Leak Point Pressure/Compliance
Presentation Ventriculoperitoneal shunt malfunction Lumbar mass New hydronephrosis Lower back pain, foot inversion Lower back pain Lumbar mass New urinary incontinence and infections, low back pain New urinary incontinence New fecal incontinence Lower extremity weakness, new urinary infections and incontinence Lumbar mass Skin tag lumbar spine Lower extremity weakness Lumbar mass Lower extremity weakness, lower back pain Lower back pain Lower back pain, lower extremity weakness Lower extremity pain Recurrent urinary infections Lower extremity pain Thoracic mass New hydronephrosis Urinary urgency, lower back pain New hydronephrosis New hydronephrosis Lower extremity
• No leakage, number given is end filling pressure.
Preop.
Postop.
3Mos.
42*/12.85
43/13.51
25/17.50
37/1.82 55/2.71 21/17.14
30/0.52 32/2.69 15/1.25
55/2.00 55/2.67 28/15.00
50/5.00 16/1.50 14/3.75
50/6,90 10/2.00 26*/16.67
28/7.50
38*/13.33 33/8.85 17/15.00
38/14.10 22/5.00 21/30.77
25/0.56 48/0.49 11/18.00 42/1.35 21*/46.67
16/1 11/6.67 21/4.38 8/35,00 14*/121.42
27/7.73 32* /31.82
23/11.18 26*/41.67
28/6.52
30*/26.67 31/30.35
35/1.48 8/30.00 14* /50.00 38/1.21 28/2.56 55/5.53
32/2.69 42/1.36 14*/66.67 35/0.93 44/8.72 8/200,00
38/1.36 17/8.33
42/2.22
27* /26.47
22/31.67 55/2.67
55/2.20 45/2.56 26*/37.50
55/1.700 40/3.17 14*/187.50
28/13.64
6Mos.
25/13.33 45/#
32/21.15
34*/20.83 22/1.66 37/12.50
16/2.78
25/1.58
41 /1.43
32/8.85 38/1.82
55/1.43 45/4.86 32*/30.77
42/2.78 17*/54.54
179
URODYNAMICS IN MYELODYSPLASTIC PATIENTS WITH TETHERED SPINAL CORD TABLE 2.
lvfean values of leak point pressure, compliance and /,eak point pressure-to-compliance ratio Leak Point Pressure (cm. water)
Preop. Postop. 3 mos. 6mos.
Compliance (mL/cm. water)
Leak Point Pressure: Compliance Ratio
12.36 30.28 10.21 15.10
14.54 10.09 11.07 8.41
32 26
34 33
Relationship among new hydronephrosis, clinical deterioration or improvement, age and delay to treatment
TABLE 3.
Pt. No.
Age at Diagnosis (yrs.)
Delay to Treatment (days)
New Hydronephrosis
3 22 24 25 Means
36
2.6 10.5 3 5 5]
60 90 90 90 82.5
Clinical deterioration
34
3
2.6
9
9
15 20 22 25 Means
32
12 18 10.5 9.5
9.5
60 150 720 1460 90 90 428.3
Clinical improvement
26
2 4 ' - - ' ~ ~ - ~ ' - - ' ~ - ~ ~ . . _ . ~ ~ ~ ~.......~ - ~ ~ " - - ' ~ 0
1
12
Pre Post
Time (weeks)
FIG. 1. Mean leak point pressure versus time 35
.
30
i:l
25
%
~
g
20
II)
'-' C: .!ll C.
E 0
15 10
(.)
5 0
1
12
6 5 34 2.5 11.8
14 60 90 90 63.5
24
Operative
.:2
4 7 10 13 Means
24
Pre Post Operative
Time (weeks)
Fm. 2. Mean compliance versus time
conus medullaris is prevented from its usual ascent during growth. It frequently occurs during times of rapid axial skeletal growth and can be primary (related to a bony spicule, spinal lipoma or myelomeningocele) or secondary (as a result of scarring at a previous surgical site. 9 Lower extremity paresthesias or palsies, low back pain or a change in urinary tract status frequently alerts the clinician to this condition. The neurosurgical and urological literature supports early surgical release of tethered spinal cord elements. Yamada et al demonstrated mitochondrial deterioration in tethered spinal cords in animal models and human examples, with improved oxidative metabolism after untethering. 13 Hypoxemia of the tethered neuronal elements led to axonal degeneration and nerve cell death. They concluded that surgical release of tethered elements could facilitate repair of injured neurons. Of the 6 patients with genitourinary symptoms 5 improved clinically. No urodynamic parameters were reported. Others have similarly concluded that any neural trauma, such as transection, compression, tension or hypoxemia, results in metabolic and functional changes in neuronal activity. 14- 15 Several reports in the literature indicate that urinary tract
status may be improved by spinal cord untethering. Kaplan et al reported a 60% improvement in 20 patients after surgical release of a tethered spinal cord. 8 Improvement was defined as a shift to the right on the pressure volume curve of the cystometrogram and decreased uninhibited contractions. Flanigan et al evaluated 8 patients urodynamically before and after untethering. 10 Urodynamic studies were performed between 3 days and 3 years postoperatively. Clinical improvement was reported in 2 patients and urodynamic parameter improvement was noted in 5. Fukui et al studied 46 tethered spinal cord patients preoperatively and postoperatively with multichannel urodynamics. 16 Their initial postoperative report indicated a 50% improvement overall and a 25% decrease in detrusor sphincter dyssynergia. However, at 6 months and 1 year postoperatively there was no real difference in clinical or urodynamic parameters. 7 Leak point pressure was not measured and these data were not subjected to statistical analysis. Urodynamics. The optimal situation for the patient with a neurogenic bladder allows for ease of management, and protection of the upper and lower urinary tracts. A leak point pressure of less than 40 cm. water appears to be related to upper tract protection, and although there is no ideal value for bladder compliance it is generally believed that high compliance equates with low risk. 2 • 3 • 17 In our series the initial postoperative leak point pressure or end filling pressure decreased in 62% of the patients, while compliance increased immediately in 69%. These changes were transient and reverted to near preoperative values 6 months postoperatively. These findings could reflect a period of spinal shock, since they resolved by 6 months. Leak point pressures of more than 40 cm. water were observed in 3 of 4 patients who had hydronephrosis at diagnosis. Of these patients 2 deteriorated in status clinically, and 2 stabilized and are being followed closely. Our data support the relationship of a leak point pressure of more than 40 cm. water and upper tract deterioration. Patient variables. Others have suggested that patient age, interval from diagnosis to treatment and density of adhesions at the tethered site may relate to urological outcome after untethering. 7 In our series patient age did not significantly impact' on outcome. The patients who improved had shorter intervals from diagnosis to treatment than the 6 who deteriorated but this difference was not statistically significant. Patient 20, who deteriorated in status, failed to return promptly for followup and, therefore, had a delay in treatment of 1,460 days. If this patient is omitted, this difference is even less
180
URODYNAMICS IN MYELODYSPLASTIC PATIENTS WITH TETHERED SPINAL CORD
significant. In our series, adhesion density was not assessed prospectively. Our review of operative reports was not adequate to provide conclusions. Clinical management. Clinical management did not change in 16 patients. Four patients with a preoperative leak point pressure of less than 40 cm. water had clinical improvement. Patients 4 and 7, who voided with Crede's maneuver preoperatively, no longer required this maneuver, and patients 10 and 13 were converted from wet to dry on intermittent catheterization and anticholinergic medication. Of 6 patients who required changes in the regimen 2 had preoperative and postoperative leak point pressures of more than 40 cm. water. Patient 22 was converted from dry to wet despite intermittent catheterization and anticholinergic medications. Patient 25, who had a high leak point pressure preoperatively and postoperatively, required augmentation cystoplasty and bilateral ureteral reimplantation. Patient 3, who also had high leak point pressures before and after surgery, suffered febrile urinary tract infections. Patients 15 and 20 did not have leakage preoperatively. Both patients voided normally preoperatively and patient 15 required catheterization postoperatively, while patient 20 became totally incontinent and was lost to followup. Patient 9 had preoperative and postoperative leak point pressures of less than 40 cm. water, became totally incontinent postoperatively and is awaiting placement of an artificial urinary sphincter. Therefore, in this series only 4 of 26 patients (15%) improved in terms of clinical management. Patients 3, 22 and 25, who presented with new hydronephrosis, worsened clinically and patients 3 and 25 had a leak point pressure of more than 40 cm. water preoperatively. This finding supports a relationship among high leak point pressure, upper tract damage and clinical deterioration. CONCLUSION
At latest followup, radiographic and clinical parameters improved in 25% and 15% of the patients, respectively. The changes that occurred immediately postoperatively were probably related to a period of spinal shock since they reversed by 6 months postoperatively. Patient age at diagnosis and the interval from diagnosis to release of tethered elements were not significantly related to urodynamic, radiographic or clinical outcome. To determine if spinal cord untethering truly is of urological benefit a control group of patients to be observed without surgical intervention would be necessary. We would suggest that this control group may be represented by all patients who have undergone spinal cord surgery. Bedside urodynamic evaluation is simple, cost-effective and informative. In this series there was a period of spinal shock during which urodynamic parameters improved. However, these changes were transient. Radiographic and clinical improvement occurred in a small number of patients. Based on our data we conclude that spinal cord release in patients with a tethered spinal cord is of benefit to the urinary tract in only a small percentage of patients. REFERENCES
1. Ghoneim, G. M., Roach, M. B., Lewis, V. H. and Harmon, E. P.: The value of leak pressure and bladder compliance in the urodynamic evaluation of meningomyelocele patients. J. Urol., 144: 1440, 1990. 2. McGuire, E. J., Woodside, J. R., Borden, T. A. and Weiss, R. M.: Prognostic value of urodynamic testing in myelodysplastic patients. J. Urol., 126: 205, 1981. 3. McGuire, E. J., Woodside, J. R. and Borden, T. A.: Upper urinary tract deterioration in patients with myelodysplasia and·detrusor hypertonia: a followup study. J. Urol., 129: 823, 1983. 4. Sidi, A. A., Dykstra, D. D. and Gonzalez, R.: The value of urodynamic testing in the management of neonates with myelodysplasia: a prospective study. J. Urol., 135: 90, 1986. 5. Spindel, M. R., Bauer, S. B., Dyro, F. M., Krarup, C., Khoshbin, S., Winston, K. R., Lebowitz, R. L., Colodny, A. H. and Retik,
6. 7. 8. 9.
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17.
A. B.: The changing neurologic lesion in myelodysplasia. J.A.M.A., 258: 1630, 1987. Al-Mefty, 0., Kandzari, S. and Fox, J. L.: Neurogenic bladder and the tethered spinal cord syndrome. J. Urol., 122: 112, 1979. Fukui, J. and Kakizaki, T.: Urodynamic evaluation of tethered cord syndrome including tight filum terminale. Prolonged follow-up observation after intraspinal operation. Urology, 16: 539, 1980. Kaplan, W. E., McLone, D. G. and Richards, I.: The urological manifestations of the tethered spinal cord. J. Urol., 140: 1285, 1988. Keating, M. A., Rink, R. C., Bauer, S. B., Krarup, C., Dyro, F. M., Winston, K. R., Shillito, J., Fischer, E. G. and Retik, A. B.: Neurourological implications of the changing approach in management of occult spinal lesions. J. Urol., part 2, 140: 1299, 1988. Flanigan, R. C., Russell, D. P. and Walsh, J. W.: Urologic aspects of tethered cord. Urology, 33: 80, 1989. Bloom, D. A., Knechtel, J.M. and McGuire, E. J.: Urethral dilation improves bladder compliance in children with myelomeningocele and high leak point pressures. J. Urol., part 2, 144: 430, 1990. Wyndaele, J. J. and De Sy, W. A.: Correlation between the findings of a clinical neurological examination and the urodynamic dysfunction in children with myelodysplasia. J. Urol., 133: 638, 1985. Yamada, S., Zinke, D. E. and Sanders, D.: Pathophysiology of "tethered cord syndrome." J. Neurosurg., 54: 494, 1981. Kobrine, A. I., Doyle, T. F. and Martins, A. N.: Local spinal cord blood flow in experimental traumatic myelopathy. J. Neurosurg., 42: 144, 1975. Senter, H.J. and Venes, J. L.: Loss of autoregulation andposttraumatic ischemia following experimental spinal cord trauma. J. Neurosurg., 50: 198, 1979. Fukui, J., Kodaira, K., Watanabe, S., Takezaki, T. and Shiba, N.: Diagnosis, treatment and prognosis of congenital neurogenic bladder caused by traction of lower spinal cord segment with spina bifida occulta. Jap. J. Urol., 68: 569, 1977. Ghoneim, G. M., Bloom, D. A., McGuire, E. J. and Stewart, K. L.: Bladder compliance in meningomyelocele children. J. Urol., 141: 1404, 1989.
EDITORIAL COMMENT There is no question that it is important to have continuous neurourological surveillance of the lower urinary tract in patients with myelodysplasia because of the high incidence of documented secondary tethering of the spinal cord, with its tendency to worsen the neurological condition further. How best to conduct this surveillance is another matter. The idea is to measure those parameters that are likely to detect a change early so that a second neurosurgical procedure has a high likelihood of achieving a beneficial effect. It is not appropriate to group together patients who did and did not undergo prior back surgery. In addition, I am not sure whether the authors chose the correct parameters for determining an early change in lower urinary tract function-hydronephrosis may not occur for 6 to 12 months after a neurological change has affected detrusor compliance, so this late discovery may be a reason why only 15% of the study population improved and why 2 even had progression. It is not stated whether the measurement of compliance used was initial, terminal or an average throughout bladder filling, so the reader does not know exactly what to measure if he is to conduct his own surveillance. The authors also state that a leak point pressure of greater than 40 cm. leads to hydronephrosis. However, only 3 of 7 patients with a leak point pressure of greater than 40 cm. and 1 of 19 with a low leak point pressure had hydronephrosis. Of 10 patients with a compliance of less than 10 cm., 4 had hydronephrosis. Thus, both of these parameters are not great indicators of upper urinary tract deterioration. When the 2 parameters are considered together they are more meaningful: 4 of 5 patients with a leak point pressure of greater than 40 cm. and a compliance of less than 10 cm. had hydronephrosis preoperatively. Finally, 5 patients (19%) had no studies done more than 3 to 7 days postoperatively. Including them in the analysis slants the findings and does not add credence to the conclusions. Stuart B. Bauer Division of Urology Children's Hospital Medical Center Boston, Massachusetts