677C>T and 1298A>C polymorphisms of methylenetetrahydropholate reductase gene and biochemical parameters in Turkish population with spina bifida occulta.

AIM: This study aimed to investigate the 677C > T and 1298A > C MTHFR gene polymorphisms and their metabolic effects on the levels of folate, vitamin B12 and homocysteine in the serum of Turkish spina bifida occulta (SBO) patients and healthy individuals in disease. MATERIAL AND METHODS: A case-control study was performed to detect 677C > T and 1298A > C MTHFR gene polymorphisms in 39 SBO patients and 34 healthy individuals. The folate, vitamin B12 and homocysteine concentrations in the serum of SBO and healthy individuals were evaluated and compared with MTHFR gene polymorphisms. RESULTS: 677 CC/CT/TT MTHFR genotype frequency differences between the SBO patients and controls were not significant (x(2)=3.325, P=0.068; x(2)=1.479, P=0.224; x(2)=0.275, P=0.600; respectively). 1298A > C MTHFR genotype frequency differences between the SBO patients and controls were significant (x(2)=8.477, P=0.004). The frequencies of the Aand C alleles of the 1298A > C polymorphism did not differ in a statistically significant manner between the groups (x(2)=0.576, P=0.448). The biochemical parameters were not significantly different between SBO patients and healthy individuals (P > 0.05). CONCLUSION: The 677C > T and 1298A > C polymorphisms of the MTHFR gene cannot be regarded as major risk factors for SBO in the Turkish patients 677TT homozygosity may affect the metabolism of homocysteine.

GDNF plasma levels in spina bifida: correlation with severity of spinal damage and motor function.

Glial-derived neurotrophic factor (GDNF) is one of several powerful survival factors for spinal motoneurons that play a key role in sprouting, synaptic plasticity, and reorganization after spinal cord damage. The aim of this study was to investigate the expression of GDNF in plasma of children with spina bifida (SB) and to determine its correlation with both the severity of spinal cord damage and the motor function of these patients. To measure the GDNF expression, we collected plasma samples from 152 children with SB and in 149 matched controls. Endogenous GDNF levels were quantified using a two-site immuno-enzymatic assay. The statistical analysis was performed using the Mann-Whitney two-tailed two-sample test. In children with SB the mean levels of GDNF (131.2 +/- 69.6 pg/mL) were significantly higher (p < 0.001) with respect to the mean levels of the control group (102.7 +/- 6.8 pg/mL). Moreover, in open SB, the GDNF levels (139.2 +/- 81.1 pg/mL) were significantly higher (p < 0.05) with respect to closed SB (117.2 +/- 41.3 pg/mL). In terms of the motor function of patients, we found that in children with poorer motor function, the GDNF levels (134.5 +/- 67.4 pg/mL) were higher, but not statistically significant (p < 0.1), than in patients with better motor outcome (122.3 +/- 72.2 pg/mL). Our study demonstrates GDNF over-expression in children with SB. This upregulation is significantly associated with the severity of spinal cord damage in SB patients and appears to correlate with poor motor function of children, representing an important biochemical marker of the severity of spine injury.

Trisomy 9 mosaicism in a child with a tethered cord.

A two and a half-year-old girl was diagnosed with trisomy 9 mosaicism that was detected in 22% of skin fibroblasts but was not evident in blood. This child manifests some clinical features not previously reported in trisomy 9 mosaicism including a thoracic syringomyelia and a tethered cord due to an extradural lipoma with intradural involvement. DNA analysis showed that she did not have uniparental disomy in her dominant disomic cell line.

Insulin-like growth factors (IGF) 1 and 2 in human foetal plasma and relationship to gestational age and foetal size during midpregnancy.

IGF-1 and IGF-2 were measured by specific radioimmunoassay after acid-ethanol extraction of plasma obtained by foetoscopy from 20 normal foetuses aged 15-23 weeks. IGF-1 and IGF-2 levels were 36 +/- 11 and 162 +/- 55 ng/ml, respectively. In comparison, levels in cord blood were 84 +/- 58 and 264 +/- 176 ng/ml, respectively, and in adult plasma were 410 +/- 106 and 818 +/- 272 ng/ml. Both IGF-1 and IGF-2 were in the normal foetal range in a further three foetuses with anencephaly and two foetuses with spina bifida. No sex difference was observed. IGF-1 was positively correlated with foetal body weight (P less than 0.001), placenta weight (P less than 0.02) and with body length measured crown-rump (P less than 0.01) or crown-heel (P less than 0.02). No correlation between IGF-2 and body weight, length, placenta weight or gestational age was found. Both IGF-1 and IGF-2 are present in the human foetal circulation earlier in gestation than has previously been demonstrated, the levels being low throughout this period of gestation in comparison with adult plasma.

Hyperzincemia in anencephaly and spina bifida: a clue to the pathogenesis of neural tube defects?

Zinc is essential for normal embryogenesis and may have particular importance for closure of the human neural tube. Compared to 258 controls, we found increased zinc content in umbilical cord serum in eight of nine newborn anencephalics (p less than 0.02) and three infants with spina bifida (p less than 0.001). Increased zinc levels were bound to serum albumin or alpha-2-macroglobulin (alpha 2M) in infants with neural tube defects (NTD). In NTD-mothers, total serum zinc was similar to controls, but there was a shift in the distribution of zinc from alpha 2M to albumin. Fetal hyperzincemia and elevated maternal albumin-bound zinc suggest that the NTD-fetus receives but does not use zinc normally.

[Unusual course of alpha-fetoprotein levels in a case of spina bifida detected by prenatal diagnosis]. / Evolution particulière des taux d'alpha foeto-protéine dans un cas de spina bifida détecté par dépistage prénatal.

The authors report the observation of a case of spina bifida detected at the 18th week from a systematic prenatal screening at the C.H.R. in Toulouse, from the assay of alpha foeto-protein on filter paper. The course of total alpha foeto-protein was particularly unique: high levels found at the 18th week with a progressive decrease in concentration until totally normal level was reached during the 28th week. Ecography confirmed the diagnosis of spina bifida. Total alpha foeto-protein concentration was also found at normal level during the 28th week in serum and in amniotic fluid. Therapeutic abortion confirmed the diagnosis of spina bifida. The authors discuss this unique course of alpha foeto-protein levels from the 18th week of development to the 28th week, made possible by this rather valuable observation.

The efficacy of a serum screening service for neural-tube defects: the South Wales experience.

Serum-alpha-fetoprotein (AFP) levels were measured in more than 15 000 pregnant women in an investigation designed to examine the operational issues entailed in a large-scale population screening programme for antenatal detection of neural-tube defects. The proportion of open neural-tube defects (ONTD) terminated as a result of serum screening was 56.1% (66.6% for anencephaly and 40.7% for open spina bifida). The principle causes of poor efficacy were: failure of pregnant women to undergo screening (18.2% of ONTD were not screened); failure of the screening test to detect ONTD (20.4% of those screened were below the 90th centile); decisions against termination of detected ONTD (14% of ONTD detected by serum AFP were not terminated). Given present practices and knowledge it is doubtful whether overall efficacy levels above 65% for open spina bifida can be achieved under normal service conditions. The establishment of a regional or national screening programme on grounds of clinical efficacy alone may be premature. The decision would seem to hinge principally around a careful consideration of the economic issues.

KIE: In 1976, the Department of Health and Social Security provided funding to the South Wales Anencephaly and Spina Bifida Screening Group to examine the operational issues entailed in a large-scale screening program for prenatal detection of neural tube defects. The results of the study of serum alpha-fetoprotein levels in 15,000 pregnant women are reported. It is concluded that the establishment of a regional or national screening program on grounds of clinical efficacy alone is probably premature.

Amniotic-fluid alpha-fetoprotein measurement in antenatal diagnosis of anencephaly and open spina bifida in early pregnancy. Second report of the U.K. Collaborative Study on Alpha-fetoprotein in Relation to Neural-tube Defects.

PIP: Results of a collaborative study performed in the United Kingdom of the correlation between amniotic fluid alpha fetoprotein (AFP) levels and occurrence of open neural tube defects (NTDs) are presented. AFP measurement between 13 and 24 weeks of pregnancy was investigated as a tool for diagnosing NTDs early in pregnancy. Data on 13,105 singleton pregnancies without fetal NTDs and on 385 with fetal NTDs (222 with anencephaly and 152 with spina bifida) were collected. The percentage of unaffected pregnancies with amniotic fluid AFP values equal to or greater than a given cut-off level (expressed as a multiple of the normal median) increased with gestational age, but similar percentages could be obtained by using different cut-off levels at different gestational ages such as 2.5 times median at 13-15 weeks, 3 times at 16-18, 3.5 at 19-21, and 4 at 22-24 weeks. Using these cut-off levels, 98% (120/123) of spnia bifida cases and 98% (218/222) of anencephalics gave positive results; .48% (61/12,804) of unaffected singleton pregnancies not associated with miscarriage also gave positive results (excluding 7 positive results relating to cases of serious fetal malformations). Where amniotic fluid samples were blood-free, detection rates were the same (98% and 98%), but the false positive rate was much lower (.27%, i.e., 31/11,625). In the study area as a whole, the estimated approximate odds of having a fetus with open spina bifida, given 1 amniocentesis sample for AFP measurement, are 18:1 among women with AFP equal to or greater than 2.5 times the median at 16-18 weeks, 5:1 among women who have previously had an infant with an NTD, and 1:2 among other women. The corresponding odds for all open NTDs are approximately 35:1, 9:1, and 1:1, respectively. Raising the cut-off levels by .5 times the median at every gestational period reduced the detection en spina bifida to 93% and reduced the false positive rate to .24%.^ieng

[Prenatal diagnosis of congenital defects through the determination of alpha fetoprotein]. / Pränatale Diagnostik angeborener Fehlbildungen durch Alpha-Fetoprotein-Bestimmung.

The prenatal diagnosis of neural tube defects is based on elevated alpha-fetoprotein (AFP) concentrations in the amniotic fluid as well as in the maternal serum. Amniocentesis has to be performed in those women who already gave birth to an affected child and have the high risk to bear another. On the other hand more than 90% of the newborns with anencephaly and spina bifida are born by mothers without any increased risk in anamnesis. Therefore maternal serum screening is indicated in all pregnant women to rule out a neutral tube defect. The pittfalls of a general serum screening are discussed an a survey of the datas from different international centers is presented.

Some problems of alpha-fetoprotein screening.

In two years of a routine screening programme for the detection of neural-tube defects over 6000 women had serum-alpha-fetoprotein (A.F.P.) measured. As a result, 80 women carrying live singleton fetuses were offered amniocentesis under ultrasound control. All neural-tube defects detected at birth were recorded and necropsies were done routinely on abortuses, thus permitting evaluation of the screening programme in terms of false negatives and false positives. 16 amniotic-fluid A.F.P.s were abnormal, 1 for an unaffected fetus; and 2 others were normal for fetuses which had closed lesions. At the serum-A.F.P. stage, 3 lesions were missed. The detection-rate compares favourably with those of other series. However, in a pilot study, routine ultrasonic assessment of gestation yielded a substantial proportion of cases where a serum-A.F.P. deemed normal or abnormal when gestation was assessed clinically would have been misleading. Loss of normal fetuses subsequent to amniocentesis (5 in this series) also has to be taken into account.

Avoidance of anencephalic and spina bifida births by maternal serum-alphafetoprotein screening.

Screening of 11 585 pregnant women between 16 and 20 completed weeks' gestation for raised serum-alphafetoprotein (A.F.P.) levels showed that the birth of 81.4% of babies with open neural-tube defects could be avoided. The screening test was sensitive enough to detect 93% of those affected and serum-A.F.P. levels above the point at which intervention shouldbe considered were found in 1.7% of pregnancies. After 75.2% of false-positives had been excluded by ultrasonography or by a repeat of the serum test, only 0.63% of pregnancies proceeded to amniocentesis, 46.6% of amniocenteses showed raised amniotic A.F.P. levels due to fetal abnormality. Fetal loss by abortion or perinatal death after amniocentesis occurred in 0.034% of pregnancies screeded, 75% being associated with threatened abortion before amniocentesis. There were no terminations of normal pregnancies due to false-positive amniotic A.F.P. results. It is concluded that voluntary maternal serum-A.F.P. screening has a valuable role in antenatal care.