الفهرس 
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Abstract
Myelomeningocele is open form of neural tube defect (NTD). Neural tube defect is a general term for a congenital malformation of the central nervous system (CNS). One of the most frequent congenital malformations occurring secondary to failure of closure of the neural tube. The NTD cases are categorized as either anencephaly (lack of closure in the region of the head) or spina bifida (lack of closure below the head; SB) that occur in approximately equal frequencies at birth. Spina bifida encompasses several subgroups of defects including myelomeningocele (MM), meningocele, and lipomeningocele. Among these, MM (protrusion of the nervous tissue and its covering through a defect in the vertebrae) is by far the most common, accounting for greater than 90% of SB cases.
Myelomeningocele have complex and multifactorial etiologies in which both genetic, life style and environmental factors appear to be involved. chromosomal anomalies can be associated with NTDs, but represent only 2% to 16% of isolated NTDs. Several observations support the view that genetic factors are involved in NTDs formation: first, an increased risk in some ethnic groups (e.g., Irish and Mexican) and second, the high recurrence risk for siblings of affected individuals.
Unambiguous evidence of the effectiveness of periconceptional folic acid in preventing the majority of NTD, reported by MRC of the United Kingdom, has been available since 1991 Periconceptional consumption of folic acid supplements is strongly recommended for women who have had affected pregnancy or have a family history of NTD. We completely agree that in the management of neural tube defects ‘prevention is better than cure.
The incidence of NTDs (of which myelomeningocele is the most common) is highly variable and depends upon ethnic, geographic, and nutritional factors. A worldwide incidence ranging from 1.0 to 10.0 per 1,000 births.
Myelomeningocele can be diagnosed prenatally in over 80% of all cases by maternal serum alpha-fetoprotein (MSAFP) and high-resolution obstetrical ultrasound. Pathologic MSAFP levels (2–2.5 times the normal MSAFP level) and positive ultrasound findings can be followed by amniocenteses for acetylcholinesterase, alpha-fetoprotein and chromosomal analysis.
Neurologic complications in patients with myelomeningocele are related to a variety of CNS and spinal cord pathologies. Hydrocephalus is one of the most common complications of myelomeningocele. Seizures occur in 10-30% of affected children and adolescents. These can be related to brain malformation, or they may be a sign of shunt malfunction or infection. The Chiari type II malformation is present anatomically in almost all patients with myelomeningocele and can result in hindbrain hernia and/or upper cervical spinal cord dysfunction.
Myelomeningocele is the most common cause of neurogenic bladder dysfunction in children. The nature of the urinary tract dysfunction in myelomeningocele depends on the level and extent of the spinal cord lesion. Bowel dysfunction occurs in children with MMC because in them the recto-anal inhibitory reflex is maintained but the defecation urge is not present.
Skin breakdown occurs in 85-95% of children with myelomeningocele before young adulthood, and recurrent decubitus ulcers can lead to prolonged morbidity and functional disability. Both congenital and acquired orthopedic deformities are seen in patients with myelomeningocele. Examples of congenital deformities, which are present at birth, are kyphosis, hemivertebrae, teratologic hip dislocation, clubfoot, and vertical talus. Acquired developmental deformities are related to the level of involvement and are caused by muscle imbalance, paralysis, and decreased sensation in the lower extremities.
Until the end of the last century, MMC typically occurring at the end of the first gestational month in the lumbosacral area of the spinal cord. Also, the most serious neurological and developmental problems including the rather complex Chiari II malformation, hydrocephalus, paraparesis or paraplegia, neuropathic voiding problems of bladder and rectum.
The first histological descriptions of postnatal MMC lesions showing signs of mechanical trauma, neural tissue degeneration, and massive inflammation. Doctors suggested that this marked spinal cord damage was most likely caused by labor and a harmful passage through the narrow birth canal that crushed and abraded the openly exposed and thus extremely vulnerable neural tissue.
This quite pathophysiological understanding instantly fuelled the intriguing idea that timely in utero protective coverage of a MMC lesion could stop the otherwise progressing spinal cord destruction and thus salvage neurologic function at birth.
Fetal endoscopic interventions have already conquered a certain position in the field of prenatal medicine. Of note, this procedure do not involve formal surgical steps like cutting, preparing, resecting, and suturing of tissues, or meticulous hemostasis, all of which are indispensable for a neurosurgically correct MMC repair. In theory, a minimally invasive repair variant looks attractive, in particular if the well-documented benefits associated with postnatal endoscopic operations would also be present in the prenatal setting.
Open fetal surgery like endoscopic repair of MMC, patients referred to a fetal surgery center first undergo an initial screening to determine if an in-person evaluation is appropriate. The overall steps used during fetal repair are similar to those of the postnatal procedure. These include identification of the neural placode, separation of the placode from the surrounding epithelium, identification and closure of the dura, and elevation of the surrounding soft tissues and closure of the skin. The major difference between the pre- and postnatal procedures is the tenuous nature of the fetal tissues. The neural placode is extremely fragile, and even limited manipulation leads to loss of tissue integrity.
Successful fetal surgery requires the active participation and interaction of several clinical teams. Each group has a specific role with overlap often required at different points of the evaluation and treatment plan. Similar to other multidisciplinary groups, a weekly case discussion allows for a review of prospective patients and their preoperative considerations, as well as ongoing follow-up of postoperative patients. Extensive counseling with the patient and family is critical before the patient can be expected to reach a carefully considered decision and before informed consent can be obtained.
During late childhood, individuals with spina bifida tend to have higher levels of depressive symptoms and lower levels of self-esteem than unaffected individu¬als. They also have social difficulties, including social immaturity and passivity, having fewer friends and social contacts outside school, and having fewer romantic relationships during adolescence. Most of these difficulties seem to be maintained into young adulthood. Children and adolescents with spina bifida also depend more on adults for guidance, show less intrinsic motivation at school and exhibit less behavioural autonomy at home. They express their own viewpoints less frequently than typically developing individuals during family interactions.
The mortality rate among young people with spina bifida is ~1% per year between 5 and 30 years of age, with the rate being highest among those with the highest-level lesions. Among survivors, the quality of the individ¬ual’s health tends to decline from adolescence to young adulthood, presumably owing to difficulties in navigat¬ing the transition to adult health care.