The nervous system of the human fetus undergoes rapid change, particularly in the very early part of development. The tissue that ultimately forms the spinal cord starts off as a sheet but by three to four weeks after conception, the edges of the sheet roll upward towards one another to form a tube. This tube then goes on to form the nervous system.
Abnormal Development Leading to Spinal Cord Malformations
At different points during this process, errors in formation can occur resulting in anomalies of the spinal cord. These are often called spina bifida, spinal dysraphism, tethered cord or birth defects of the spinal cord. The most accurate terms are spinal dysraphism or spina bifida.
A myelomeningocele (MMC) is the most severe form of spinal dysraphism. At birth, the spinal cord is covered only by a thin sheet of transparent tissue. This is considered to be an “open” lesion as there is no skin covering the nerve tissue. In addition, the spinal cord itself doesn’t form normally thus the function that would normally be controlled by that part of the spinal cord is lost. This usually includes some or all of leg movement and control of bowel and bladder function. As this is an open lesion, the threat of infection is a very real one. As such, it is typically recommended that babies with these lesions be operated upon to “close” the myelomeningocele by bringing soft tissue and skin to cover the lesion. This procedure is typically done in the first 48 to 72 hours of life. The goal of this surgery is to minimize the risk of infection. Unfortunately, nothing can be done to recover nerve function that is lost as a consequence of the myelomeningocele.
About 80 to 85% of patients with MMC have hydrocephalus (excess water in the brain cavities). This will require placement of a device called a ventricular shunt to drain the excess fluid. This procedure might be done at birth, if the condition is severe, but sometimes it is delayed until it becomes absolutely necessary (see information at this website on Hydrocephalus).
Nearly all patients with MMC also have a malformation of the back part of the brain, called a Chiari malformation (CM) type II. In this condition, the space for the brain stem and cerebellum is insufficient causing downward displacement of these tissues through the opening at the base of the skull called the foramen magnum. Treatment is reserved only for patients who develop problems directly related to the Chiari malformation. There are countless problems that can arise from a CM, but the most common are neck pain, visual disturbances, change in pitch/volume of the voice or cry, difficulty with swallowing (especially liquids), worsening of arm/leg strength, sleep apnea or syringomyelia (fluid build-up within the spinal cord).
Another problem that occurs in a delayed fashion is worsening of neurologic function related to a tethered cord. These patients develop back/leg pain, worsening of leg weakness, new numbness, new problems with gait, scoliosis (curvature of the spine), worsening of leg/foot bone abnormalities, or worsening of bowel/bladder control. Treatment is an operation to release the scar tissue and to allow the spinal cord to become free from its attachments to the spinal sac.
The best way to follow patients with MMC is in a comprehensive “Spina Bifida” clinic where all the specialists who care for their chronic needs can see them at one time. The clinic in Buffalo is called The Spina Bifida Clinic of Western New York. Specialists included in this program are pediatric physiatrists (rehabilitative medicine doctors), pediatric orthopaedic surgeons, pediatric urologists, physical therapists and pediatric neurosurgeons. In addition to routine examinations by each specialist, patients will be followed with urodynamics (bladder studies) and manual muscle tests (detailed strength assessments done by the physical therapist). This cooperative effort will allow for collaboration between specialists and has been proven in studies to be the best way to care for these patients. This will allow us to detect, as early as possible, problems that might arise from a CM or tethered cord.