Meningomyelocele/Spina Bifida

By Philip E. Gleason, MD

 

Meningomyelocele may also be called myelomeningocele, lipomeningocele and spina bifida. It is also related to sacral agenesis. These are all spinal cord abnormalities affecting the nerves to the bladder, bowel and lower extremities. The most common presentation of myelomeningocele is as an opening along the lower back and spinal cord at birth. Sometimes the skin is covered and the child may present with a hidden, or occult, spinal dysraphism. This section topic will provide introductory information regarding these diagnoses and their subsequent neurogenic bladder and neurogenic bowel.

 

Meningomyelocele lesions are thought to occur about once is five thousand births. They can occur in both boys and girls. They can occur by themselves, but are also sometimes related to other congenital abnormalities, often considered other midline abnormalities, such as anus, heart, tracheo-esophageal fistulas, kidneys, arms and limbs.

 

During development, the spinal cord and vertebral bodies form as a neural tube. The spinal column closes over the spinal cord and protects the nerves which run along the back to the abdominal and pelvic organs, and the legs. If the neural tube does not close or form correctly, this results in a neural tube defect such as an open myelomeningocele, or other occult spinal dysraphism abnormalities. All of these may affect the spinal cord nerves which include the nerves to the bladder, bowels and lower extremities. The spinal cord lesions can occur anywhere along the back from the chest down to the pelvis, but most often occur along the lower back affecting the lumbar and sacral spinal cord. The nerves can be normal, or may be balled up or disorganized, and function poorly, or not at all. Thus, there is a wide variety of nerve function to the bladder, bowels, and legs depending on the level of the spinal cord lesion and the amount of related nerve involvement. Some children may have fairly normal bladders, bowels and legs. Others can have fairly severely affected bladders, bowels and legs.

 

At birth, if the spinal cord lesion is an open meningomyelocele, it is closed by a pediatric neurosurgeon to protect against infection. There may also be related hydrocephalus, or excess spinal fluid around the brain and this may need to be shunted to the abdomen with a ventriculo-peritoneal shunt.

 

Further assessment of the bladder, bowels and lower extremities is also made. Urologically, this often includes a kidney renal ultrasound to assess the kidneys and bladder. A bladder VCUG x-ray is also done to assess bladder size, the ability of the bladder to squeeze, contract and empty during voiding, and to look for possible reflux of urine going backward up to the kidneys.

 

Children with meningomyelocele may have neurogenic bladders. These can range from very mild to fairly severe. If the nerves to the bladder are fairly well preserved, the bladder may function normally, relaxing to hold and store urine, maintaining continence and protecting the kidneys, and then squeezing to void, and empty the bladder well. The urinary sphincter muscles are also coordinated with the bladder and function normally to help hold urine and prevent incontinence or urine leaking and accidents, but also relax and allow the bladder to empty completely, helping prevent any hold over of urine and protect against urinary stasis and urinary tract infections.

 

In other situations the nerves to the bladder may be more involved and function abnormally. This can range along a broad spectrum of neurogenic bladders. Sometimes the nerves to the bladder are hyper-sensitive and hyper-active. This may produce a hyperactive bladder which does not hold urine well, and tends to be small and produce urinary incontinence and leaking of urine. The bladder pressure may also be higher than safe and cause back-pressure back up to the kidneys which can cause kidney dilation and hydronephrosis and kidney damage if left unchecked over periods of time.

 

At the other end of the spectrum, there is a hypotonic neurogenic bladder. In these children, the nerves to the bladder are weak or do not function at all, and the bladder may be a very large, relaxed bladder. However, the bladder muscle may not be able to squeeze well to void and empty the bladder. These children tend to have a full bladder all of the time and may be prone to urinary tract infections. In addition, if the bladder gets too full, they will not be able to hold urine and may have overflow incontinence and leaking.

 

Last, there are many combinations of bladder and urinary sphincter function in the middle. In some children, the bladder may function reasonably well, but the urinary sphincters may be weak, sometimes called intrinsic sphincter dysfunction, and they may not be able to hold urine and leak urine even when their bladder is relatively empty with incontinence. Others may have hyperactive urinary sphincters. In these children, the bladder may squeeze and empty fairly well, but the urinary sphincters do not relax properly, and when they void the bladder will not empty completely and they may be prone to urinary tract infections.

 

Thus, children with meningomyelocele and neurogenic bladders can have any number of combinations of bladder and urinary sphincter abnormalities. These can range from problems with both holding urine as well as emptying urine. Each child will need to be assessed and managed individually. In addition, neurogenic bladders can change over time. Thus these children will need to be followed urologically their whole lives

 

The goals of management and treatment of neurogenic bladders are to store urine in the bladder at a low, safe pressure to protect the kidneys from damage; and to empty the bladder completely to prevent urinary tract infections, prevent urine leaking and incontinence, and to manage any associated vesicoureteral reflux. If a child can do these on their own, they may not need any intervention. However, most children with neurogenic bladders will have some difficulties and need some management and treatment.

 

A mainstay of treatment for children who can not empty their bladders well, and may be having urinary tract infections or incontinence, is to perform Intermittent Clean Catheterization (ICC). This is considered a relative landmark observation in Pediatric Urology and was described by Dr. Lapides at the University of Michigan many years ago. ICC involves passing a small, soft catheter through the urethra into the bladder to empty the bladder and prevent infections and incontinence. While this can seem very foreign and invasive, once families have the hang of it, it can go very well and be very helpful and important. Catheters are made of a soft silastic plastic material to prevent exposure to latex and development of latex allergies. In addition, newer catheters are coated with hydrophilic coatings which make the catheters very slippery and allow them to pass through the urethra and penis very easily, without much friction or irritation or discomfort. While there is always concern over passing a catheter into the bladder and causing infections, and while this can occur, the exact opposite observation is actually true in neurogenic bladders. Most urinary tract infections in children with neurogenic bladders are caused by hold over of urine and urinary stasis. If bacteria get back into the bladder, which is not that uncommon, they can then produce an infection of the urinary tract. However, if the urine is drained and emptied completely, this will help prevent infection. Thus, although it seem counter-intuitive, the best treatment to prevent infections and incontinence in children with neurogenic bladders is to empty the bladder with ICC. To further protect infections, some catheters are now impregnated with antibiotic coatings as well. If catheterization through the urethra and penis is difficult, althernative catheterizable channels using the appendix and bowel have now been described respectively by Dr. Mitrofanoff in France, Dr. Monti in Brazil, and others.

 

If the bladder is hyperactive, or a high pressure bladder, you can use anticholinergic medications to help relax the bladder muscle and decrease bladder pressure and incontinence. Anticholinergic mediations include Ditropan, Levsin and Detrol. Some families have concern that relaxing the bladder may cause incontinence, however, these medications do not relax the urinary sphincters, but rather relax the bladder muscle itself to decrease bladder pressure and incontinence.

 

Most children with neurogenic bladders can be successfully managed with ICC and medications. However, some children with more severe neurogenic bladders will continue to have high pressure bladders. These children may be at risk for renal and kidney damage, or have severe or refractory incontinence. In these children, a surgery to enlarge the bladder and decrease bladder pressure and muscle tone may be considered. This is called bladder augmentation and uses a piece of intestine to augment, or enlarge, the bladder. If necessary, procedures to correct vesicoureteral reflux and narrow the bladder neck may also be performed. There are various forms of bladder neck reconstruction to try to increase bladder outlet resistance and correct weak urinary sphincters and correct urinary incontinence from intrinsic sphincter deficiency.

 

In the distant past, children with meningomyelocele and neurogenic bladders often had significant bladder, and subsequently kidney problems, sometimes including kidney failure. At this time, with careful urologic management and follow-up, they typically do well with safe kidneys, few urinary tract infections and good bladder continence. However, each child will need to be assessed and managed individually. In addition, neurogenic bladders can change over time. Thus these children will need to be followed urologically their whole lives.

 

Children with meningomyelocele often also have nerve problems and dysfunction of the bowels, known as neurogenic bowels . They will often have poor or weak bowel peristalsis and motility. This will often cause constipation and difficulties with bowel movements and evacuating the bowels. They may also have bowel accidents and encopresis . While this often seems like they are having diarrhea and accidents, they are most often actually having severe constipation, obstipation and leaking stool from impacted bowels. Thus, the management of neurogenic bowels involves stool softeners and help emptying and evacuating the bowels with medications or enemas, etc. An Antegrade Colonic Enema (ACE) program has been described by Malone (MACE) in which the appendix is used to create a catheterizable channel to the colon to allow enema flushing and evacuation of the bowel. Cecostomy tubes have also been used. Thus these children may also be followed by pediatric gastroenterologists.

 

The spine and lower extremities are followed and managed by neurosurgeons and orthopedic surgeons.

 

Another important consideration in children with meningomyelocele is the possibility of developing latex allergies . Latex is a rubber material found in a lot of materials including red rubber catheters, medical gloves and medical equipment. These children may be performing intermittent clean catheterization and may over their lives have several surgeries. Thus they are at a high risk of developing latex allergies which can be quite severe and life threatening. Therefore, attempts to avoid latex exposure and sensitization are warranted to help protect against latex allergies.

 

One last consideration when discussing meningomyelocele is the importance of folic acid to prevent meningomyelocele. Folic acid appears to be required for normal neural tube formation and to have a protective effect against meningomyelocele abnormalities. Meningomyelocele can, in fact, almost entirely be prevented by supplying folic acid as a dietary or vitamin supplement to women of child bearing age. Thus, there are general recommendations for women trying to become pregnant to use vitamins with folic acid, although keep in mind that these need to be used before becoming pregnant rather than afterwards. As such, some have advocated adding folic acid to basic food groups as a dietary supplement.

 

 

© 2005-2010, Dr. Philip E. Gleason, MD