TABLE 11-1 Spinal Dysraphism: Classification and Characteristics
Spina Bifida/Neurogenic Bladder
Spina Bifida/Neurogenic Bladder
Ronald S. Sutherland
Neurogenic bladder dysfunction occurs as a result of developmental anomalies, injuries, and disease of the nervous system. Maldevelopment of the spinal cord, broadly termed as spinal dysraphism and commonly known as spina bifida, leads to myelodysplasia. The most common form is myelomeningocele; other forms are listed in Table 11-1. Myelodysplasia is the most common primary cause of neurogenic bladder dysfunction in children, affecting approximately 1 in 1,000 in the United States. About 95% of children with myelodysplasia have abnormal innervation of the bladder and sphincter. Other causes of neurogenic bladder dysfunction include spinal cord and brain injury and diseases of the central nervous system (CNS) such as Guillain-Barre and CNS tumors. As a consequence of bladder dysfunction these patients are at risk for urinary incontinence, and, more importantly, damage to their kidneys because of increased bladder pressure, vesicoureteral reflux, obstruction, and infection. Early recognition of neurovesical abnormalities enables prompt intervention and usually prevents kidney damage.
Spinal dysraphism arises from a defect in the formation of the neural tube. The etiology is uncertain, but various teratogens such as alcohol and zinc as well as some medications such as valproic acid have been implicated. Deficient maternal intake of folic acid is well established as a factor leading to development of myelodysplasia, and supplementation reduces the chances of acquiring such birth defects sevenfold.
Injury to and diseases of the CNS cause different forms of bladder dysfunction depending on the location and degree of injury/disease. Two main regions of the CNS are essential for normal bladder function: (1) the pontine micturition complex (upper voiding reflex center); and (2) the sacral spinal cord (lower, or spinal, voiding reflex center). Injuries to the brain (above the pons), to the spinal cord between the pons and the sacral cord, and to the sacral cord and below, produce very different forms of bladder dysfunction. Consequently the management to prevent risks of further complications is different depending on the region injured.
Urologic goals to consider in the care of children with neurogenic bladder dysfunction are: (1) to preserve renal function; (2) to achieve urinary and fecal continence (defined as “out of diapers” at a developmentally appropriate age); and (3) to promote the development of healthy sexual function when age appropriate. By attaining these goals, these patients are much more likely to develop a sense of autonomy and remain healthy.
II. DIAGNOSIS OF MYELODYSPLASIA
A. Prenatal Assessment
1. Serum α-fetoprotein (AFP): Open spina bifida or anencephaly should be suspected if maternal serum α-fetoprotein is elevated more than 3 standard deviations from the norm before 24 weeks’ gestation.
2. Fetal sonography: Fetal sonography and elevated serum AFP combined are highly sensitive (80%) and specific (99%) in diagnosing myelodysplasia.
3. Method of birth: Although vaginal delivery is safe, some recent studies have suggested that cesarean section may limit neurologic injury.
B. Newborn Assessment
After delivery it is important to have a well-trained support staff consisting of, but not limited to, a neonatologist, pediatrician, neurosurgeon, pediatric urologist, orthopedic surgeon, experienced nurses, physical therapists, and social services personnel.
1. Neurosurgical intervention: For open defects such as myelomeningocele where neural elements are exposed, neurosurgical intervention is performed as soon as possible. Abdominal ultrasound (US) is obtained to assess the kidneys. A functional evaluation of the bladder (urodynamic study or UDS) is not usually done before neonatal back closure. If the closure is delayed, however, the UDS can provide useful information. Most children undergoing spinal surgery develop “spinal shock” accompanied by urinary retention for several weeks, so urologic intervention (such as clean intermittent catheterization or CIC) is often necessary before the UDS is done.
2. Evaluate for “occult” spinal dysraphisms: Although open spinal dysraphism is the most common type observed, closed spinal defects (Table 11-1) also occur frequently. Suggestive signs include a sacral “pit” or dimple, a hairy patch, hemangiomas, deformed gluteal cleft, lipoma, and laxity of anal sphincteric tone. Spinal defects are also associated with other conditions including anorectal anomalies, cloacal anomaly, and cloacal exstrophy.
III. CARE OF THE NEWBORN
1. Urodynamic studies: The goal of UDS is to characterize the compliance and contractility of the bladder and the function of the outlet (the bladder neck and external sphincter). These tests evaluate bladder pressure during filling (storage) and emptying (cystometry), sphincter activity (electromyography), and radiographic appearance of the lower urinary tract (fluoroscopic cystourethrography). In addition, vesicoureteral reflux may be detected on fluoroscopy during urodynamic assessment. Urodynamic testing is done when the infant can safely be placed in the supine position once the spinal shock phase has passed. Some centers may prefer “watchful waiting” and follow the infant with sonography alone, deferring urodynamic evaluation until hydronephrosis is detected or continence is desired.
2. Sonography: Ultrasound (US) is performed to detect hydronephrosis, which may be the result of vesicoureteral reflux or a “hostile,” noncompliant bladder, and to monitor renal growth.
3. Urinalysis and culture: Urinalysis and urine culture should be performed only if the child is symptomatic for a urinary tract infection.
B. Treatment of the Newborn
1. Treatment is based upon the urodynamic findings.
a. Weak sphincter, normal bladder: observation.
b. Flaccid (arreflexic) bladder: clean intermittent catheterization (CIC).
c. Hyperreflexic and/or noncompliant bladder: CIC plus anticholinergic medication.
2. Clean intermittent catheterization (CIC): Some centers start all babies on CIC immediately at birth regardless of the UDS findings, although UDS are abnormal in the majority. Eventually most children will require CIC to gain continence or to protect the kidneys, and it is our experience that older children who were started on CIC as infants better tolerate and are more compliant with the CIC than children who begin CIC at a later age. For example, if a baby has a weak sphincter in infancy, there may no medical reason to catheterize the baby (although one must be certain that the bladder can completely empty). However, later, this same baby will be incontinent and the urologist may operate to “tighten” the sphincter, after which the child will have to do CIC in order to empty the bladder. This type of surgery is usually done close to the age of normal potty training or prior to entry to kindergarten. Unfortunately, the timing of the surgery is at one of the worst stages of development to start a CIC program. The best approach is to educate the parents about the UDS findings, the need for future catheterization, and potential problems they will encounter if they choose to delay CIC so that the parents can make an informed choice.
Early institution of CIC every 3 hours is preferred over the Credé maneuver (suprapubic compression to express urine), which is not physiologic, causes markedly increased bladder pressures, and is not appropriate for long-term management.
3. The addition of anticholinergic medication (see below) in the neonatal period is safe and well tolerated. In the infant who has progressive urinary tract deterioration despite maximal medical therapy, a temporary vesicostomy (surgical diversion of the bladder to the lower abdominal wall) will prove effective.