Spina Bifida Family Support
"Families Helping Families"
Myelomeningocele
Along with anencephaly, myelomeningocele is one of the most common forms of a neurulation
(neurula: an embryo in the stage from the development of neural tissue to the formation of the neural tube) defect; in this disorder, the primary problem appears to be failed closure of the caudal end of the neural tube. The etiology is probably multifactorial, with hereditary, nutritional, and possibly teratogenic (teratogenicity: the production or induction of malformations or monstrosities, esp. in an embryo or fetus.) factors playing a role. In this anomaly, the lower end of the spinal canal remains open, or is partially covered by skin and meninges (the three membranes covering the brain and spinal cord); the lumbosacral spinal cord and associated nerve roots are often malformed and dysfunctional. Affected babies are almost invariably born with additional defects, the most important of which is a type II Arnold-Chiari malformation of the posterior fossa, consisting of the downward displacement of the cerebellar vermis and medulla, distortion of the fourth ventricle, hydrocephalus, and sometimes any or all of the following abnormalities: syringomyelia (a disease of the spinal cord in which the nerve tissue is replaced by a fluid filled cavity), syringobulbia, aqudeuctal stenosis, and polymicrogyria.The degree of the clinical disability obviously depends on the rostral extent of the neurulation defect. Meningeal sacs that are confined to the L3-L5 level permit considerable retention of motor and sensory function in the legs. Such patients are therefore incontinent of urine and have significant proximal and distal muscle weakness but are nevertheless able to walk independently. Patients with defects extending into the lower thoracic spine are profoundly paraplegic and suffer significant flexion spinal deformities.
Although neurosurgical, orthopedic, and urological interventions can prolong survival and promote some degree of independent living, the most effective treatment for this disorder remains prevention. Because of the leakage of the fetal glycoprotein, alpha-fetoprotein, from blood vessels within the open defect into the amniotic sac, early amniocentesis can be used to diagnose neural tube defects. The location and extent of the defect may then be confirmed by ultrasound examination. The possibility that gestational folate deficiency may play a pathogenetic
(capable of producing disease) role has prompted the use of folate supplementation prior to conception in at-risk women, but the effectiveness of such treatment is still unclear.