Common Disorders

Spina Bifida (Myelodysplasia)

What is spina bifida?

Spina bifida is a neonatal condition in which a region of the spinal column, usually in the lower spine, undergoes abnormal growth during fetal development, creating a defect in the protective bony encasement that normally surrounds the spinal cord.   As a result, children born with this condition incur varying degrees of damage to the spinal cord, causing neurological abnormalities that affect the growth and function of the lower extremities.   Spina bifida is one of the most common birth defects today and may be called by a number of other clinical names, such as spina bifida cystica and myelodysplasia , both of which are synonyms of ?spina bifida' ( meningocele , myelocele , and myelomeningocele , are names that denote the different variations of severity of the condition, but orthopaedic surgeons may use the name myelomeningocele synonymously with spina bifida because these are the patients they most often see).   In the past, spina bifida was fatal for the majority of infants born with the condition.   However, as a result of earlier, antenatal detection (while in the womb) and improved medical technology and practices in recent decades, most myelodysplasia patients live into adolescence and adulthood.   This development has caused medical and surgical management of the condition to advance at a rapid pace in recent years and orthopaedic surgeons have taken on a critical role in the general care and treatment of spina bifida patients.

A range of clinical effects, or symptoms, may result from spina bifida, but among the children being seen by orthopaedic surgeons, symptoms most often include lower extremity paralysis, spasticity, or some degree of both.   Although these symptoms occur in varying severity in different patients, the effects are generally progressive in all patients, meaning that they worsen as the child grows.   These symptoms may lead to problems or deformities in almost any portion of the lower extremities, including the hip joints, knee joints, legs and feet.   While some of these problems are managed by a pediatric orthopaedic surgeon, general care of children with spina bifida should be provided by a team of doctors that work together and may include a neurologist, physical therapist, pediatrician, and other specialists that may be needed to address the physical and emotional problems and challenges that affected children face.

Some basic facts about spina bifida

  • Spina bifida occurs in approximately 1 out of every 1,000 live births; over 2500 infants in the U.S. and over 400,000 worldwide are born with the condition each year.
  • The incidence (i.e. number of new cases over a period time) of spina bifida cases in the world and the U.S. is decreasing today.
  • The ingestion of folate, or folic acid, by pregnant mothers and women trying to become pregnant has been shown to significantly decrease the risk of spina bifida in newborn children.   The incorporation of this practice into standard, recommended prenatal care by primary care physicians and obstetrician/gynecologists has contributed to the recent decreases in the incidence of this condition.
  • Valproic acid, an anticonvulsant medication, has been shown to have an association with spina bifida.   Women of child-bearing age who are taking valproic acid or suffer from epilepsy should consult their gynecologist or primary care physician about the risks of medications related to pregnancy.
  • There are a number of different classifications of spina bifida, all derived from similar problems in the normal development of the spine, but with different anatomical and clinical manifestations:
  • Spina bifida occulta ? In this mildest form of spina bifida, a defect exists in a single vertebra, or segment of the spinal column, but the spinal cord develops normally and does not protrude from its normal place within the bony spine. In some cases of this condition, the vertebra ends up forming appropriately during infancy and does not lead to significant symptoms.
  • Meningocele ? Involves a larger defect, in which the tissues surrounding the spinal cord (the meninges) protrude out of the vertebral canal, increasing the chance of damage to delicate nervous tissue of the spinal cord.
  • Myelomeningocele ? The most common and most severe defect, involves the protrusion of the spinal cord itself, creating the greatest chance of motor and sensory deficiencies of the lower extremities.   The vast majority of spina bifida patients managed by orthopaedic surgeons have myelomeningocele.
  • Hydrocephalus , a condition marked by the presence of excess accumulation of cerebrospinal fluid (CSF) in the brain, occurs in close to 80% of children with spina bifida and is usually treated with a shunting procedure by a neurosurgeon, which allows the excess fluid to be drained, thereby preventing increased pressure on the brain tissue.
  • Problems of the genitourinary system are also quite common in children with spina bifida.   These problems may cause both urinary and fecal incontinence and may require specialized management or education for self-care of these problems.
  • Obesity is more common among children with spina bifida, partially because of the relative inactivity associated with later stages of the condition.   Obesity represents a particularly debilitating health hazard in such patients, chiefly because it decreases ambulation and increases the chances that surgery will be indicated, not to mention the hazards related to cardiovascular health, diabetes, and other conditions.   Emphasizing and facilitating adherence to a dietary regimen provided by a primary care physician or orthopaedist is an important part of managing spina bifida in growing children.
  • Because most patients have at least some regions of their legs that lack sensation (from paralysis), skin sores and ulcers can arise due to pressure on the skin that goes undetected.   Prevention of such ulcers involves educating children at a young age about the causes, proper hygiene, and how to perform daily skin inspections.  
  • Fractures are more common than normal in spina bifida patients because the bones become weaker from inactivity and may lead to a condition called osteopenia , in which there is decreased storage of calcium in the bones.   Because fractures are most common following surgical operations, early weight-bearing activity in the post-operative period and the use of braces, rather than casts, whenever possible, are usually quite beneficial for fracture prevention.  

Normal spine development

The spine, or vertebral column, as it is also called, is a complex structure made up of 33 vertebrae, or bony segments, arranged vertically in succession from just below the skull to the tailbone.  The spine has two main functions -- to support the weight of the skull and upper body, and to provide a protective encasement for the spinal cord, the long cylindrical nervous structure that sends messages to and from the brain and the rest of the body.  The vertebrae are attached to other vertebrae above and below them by a number of ligaments, thick fibrous structures found throughtout the musculoskeletal system that attach bones to other bones.  The connection points between the vertebrae are called joints, in which small areas of smooth cartilage lined with lubricating material, known as synovial fluid, allow the bony vertebrae to slide past each other with minimal friction, allowing movement.  Unlike joints, such as the knee or elbow, which allow for considerable movement, each joint of the spinal column allows for very little movement becauase of the number of tightly attached ligaments, thereby ensuring the strength and stability of the vital supportive column.  However, the joints of the spine act collectively, with the sume of movements in all the joints allowing movements such as bending forward, back, and to the side.

The normal spine begins its primary period of development in the third and fourth weeks of fetal growth, before any other adult structures have even begun to take shape.   A primitive structure known as the neural plate folds over on itself and its edges fuse to create the neural tube , which later becomes the central nervous system, including the brain and spinal cord.   Running alongside the neural tube are a series of somites , segments of specialized tissue that eventually differentiates into bone, muscle, and skin.   The derivatives of bone tissue are called sclerotomes , and they are programmed to migrate and surround the neural tube (i.e. the future spinal cord).   In front of the neural tube, sclerotomes grow to become the vertebral bodies , the main supportive constituents of the vertebral column, which are separated by intervertebral disks .   In back of the neural tube, the sclerotomes form structures called vertebral arches, which eventually wrap around the spinal cord and fuse together, creating a bony encasement for the delicate nervous tissues.   The movement and activity of all of these primitive tissues during fetal development is controlled by a process called induction, in which the tissues send precisely-tuned biochemical signals to one another.   Remarkably, each of the primitive cells becomes programmed to carry out a specific function, but one that is constantly changing according to the inductive signals it gets from its neighbors.

What causes spina bifida?

Spina bifida occurs when there is some type of disruption to the process of induction in the tissues that form the vertebral arches, described above.   For reasons that are unknown, the tissues of one or more sclerotomes receive faulty biochemical signals, or do not receive a signal at all.   As a result, the cells on either side do not migrate all the way around the neural tube and fuse, as normally programmed.   The future spinal column therefore has a gap in its bony surface, which exposes the future spinal cord underneath to potential injury.   For spina bifida patients, this injury often results in destruction of some of the cells at the level of the spinal defect.   Because the normal signals sent from the brain down to the extremities and from the extremities up to the brain must pass through this injured area, the signals get disrupted or interrupted, causing spasticity and/or paralysis.

While the embryological mechanism of spina bifida is relatively well understood, the causes that trigger the mechanism remain largely idiopathic , or unknown. There is some evidence to suggest a genetic contribution to the development of spina bifida, given that siblings of children born with spina bifida have a 3-4% chance of being born with the condition themselves.   This risk climbs to 10% if two previous siblings were born with the defect.   The association of the ingestion of folate to the process of induction and the prevention of spina bifida is not completely understood either, although folate is known to play a role in the normal division process of cells, which occurs rapidly in the growing fetus. While much about the origins of this relatively common disorder remains unclear, there is ongoing research at a number of academic medical centers throughout the U.S. to improve the prevention and treatment of spina bifida.

How is it diagnosed?

Diagnosis of spina bifida today is often made during the antenatal period, with the use of ultrasound or other sophisticated imaging technologies.   When the condition is less severe and is not evident on ultrasound, it can usually be made at or around the time of birth, if not from visual inspection of the spinal region, then from neonatal physical exams that may reveal paralyis, spasticity, or a palpable defect in the vertebral column.

How is it treated?

As previously mentioned, orthopaedic surgeons are playing a larger role in the management of spina bifida than in the past because of the greater number of children that survive as newborns and live longer with the condition and its musculoskeletal effects.   Despite this development and the advent of newer, more effective operations for treating different clinical features of the condition, orthopaedic surgeons have actually decreased the number surgeries performed for spina bifida in recent years.   This has been due to mounting evidence that children may lead easier and happier lives with fewer surgeries, despite the biomechanical and physiological corrections in the musculoskeletal system that result from surgery.   Therefore, an emphasis has been placed on the non-operative orthopaedic principles of spina bifida treatment, along with the most critical and effective operations, which can radically improve children's lives.   Several important, non-orthopaedic principles of spina bifida treatment are discussed above in the ?Some basic facts about spina bifida' section and should also be read and considered.

Treatment of spina bifida depends on the level of the spinal column that is affected by the condition and the resulting deficits and level of functionality that exist.   One important concept in the treatment of the young child is that of ambulation (i.e. walking).   Infants and young children should be encouraged and assisted in meeting the same developmental milestones as that of non-affected children, such as sitting at around 6 months, standing at around 10 months, and walking by 12 to 15 months.   Despite the fact that in adolescence or adulthood, a patient's condition will likely worsen and require bracing, crutches, or a wheelchair, early ambulation is critical in preventing other orthopaedic conditions, such as clubfoot or contractures in the leg muscles, and maximizing cognitive development and basic motor skills.   Depending on the child's general neurologic status ? the presence of any major brain conditions, their sensory awareness and balance, and the presence of spasticity in the extremities ? different patients will have varying degrees of success with the challenge of ambulation and general mobility.   As a child grows and gains weight (often times too much weight in spina bifida patients, for whom obesity is a known problem), walking can become increasingly difficult and more fatiguing, as more energy is expended to carry the weight.   However, research suggests that virtually all children benefit from trying their best to achieve normal physical activity at a young age.   Orthopaedic treatment designed to assist ambulation may consist of bracing, as well as stretching or surgical correction of contractures, which may be necessary to initiate bracing.

Orthotics, or braces, for spina bifida patients are designed to help stabilize unstable or weak joints, to decrease the chance of formation of contractures, and to assist in a child's posture and general stability of the lower extremities. Traditionally, metal-based braces have been used for maximum stability and remain necessary for some children.   However, others may prefer the newer, lighter plastic braces that have been developed, which can be shaped to an individual's limbs and are generally more aesthetically pleasing to patients, but may be more uncomfortable in hot weather.   The standing frame, or parapodium, is frequently an appropriate measure of bracing in a child between 10-18 months of age, when independent standing is important to balance, head control, and upper extremity motor development. Orthopaedic surgeons will choose the appropriate types of bracing and bracing regimen over time, based on the level of the injury.

A variety of surgical operations are also employed by orthopaedic surgeons for corrections of bony deformities or muscle imbalances as a result of spina bifida.   Among the most common are spinal surgeries, such as operations for scoliosis or kyphosis, which are common in children with thoracic or high spinal paralysis.   When surgery is recommended or pursued, it is done so because it has the best chance of drastically improving a child's mobility and improving a patient's quality of life.

Coping with spina bifida

Spina bifida is a serious disorder with a significant impact on the lifestyle of affected children and their families. The condition also carries a high mortality rate, with around 10-15% of affected children dying before the age of four.   However, most patients today live for many years, and with early, appropriate management, children with the condition can have a bright future and a high quality of life.   Many patients go on to engage in wheelchair sports and a wide range of other activities.   When orthopaedic surgery is indicated, outcomes are generally excellent and the physical status, comfort, and mobility of patients improve considerably as a result. Among the most important goals for parents should be to become educated about the specifics of their child's condition and to remain optimistic and positive about their opportunities to live a happy and rewarding life, despite the challenges that spina bifida can present.

Other questions

Naturally, you may have other questions about spina bifida that are not answered in the above summary. As your orthopaedic surgeons, we welcome any and all questions you may have, which we urge you to pose during your next office visit. We have also listed several additional websites below that further explain spina bifida and some of the services and support groups available to children with the disease and their parents:

Spina Bifida Association of America: http://www.sbaa.org
Association for Spina Bifida and Hydrocephalus: http://www.asbah.org
Children with Spina Bifida: A Resource Page for Parents:
http://www.waisman.wisc.edu/~rowley/sb-kids/index.htmlx
International Federation for Hydrocephalus & Spina Bifida: http://www.ifglobal.org/



 
 

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