Headless foetus-anencephaly

Anencephaly : Imaging of the cranial vault is reliable at 11 weeks making the diagnosis of anencephaly possible at this early gestational age. In the first trimester the cerebral hemispheres have not yet eroded away but with absence of the cranium  in the Sagittal view the “ Mickey Mouse sign” has been shown to be 100 % sensitive and specific for lethal anomalies associated with a missing cranium including anencephaly and acrania.

Neural Tube Defects

The incidence cause and recurrence risk of neural tube defects are reported in Tables 9-1 through 9-3 . There are several different forms of neural tube defects .

Anencephaly is characterized by the absence of the cranial vault and telencephalon. The diagnosis is made by ultrasound in the second and third trimesters and relies upon demonstration of the absence of the cranial vault . In addition most cases can be confidently identified by 11 to 13 weeks gestation . At this time the fetal head can be recognized as overtly abnormal owing to lack of an ossified calvarium .

TABLE 9-1  Incidence of Neural  Tube Defects
Geographic  Area	Spina Bifida incidence per 1000 Births	Anencephaly Incidence per 1000 Births
South Wales	4.1	3.5
Southampton	3.2	1.9
Birmingham ,UK	2.8	2.0
Charleston
White	1.5	1.2
Black	0.6	0.2
Alexandria	0	3.6
Japan	0.3	0.6

Modified from Brocklehurst G: Spina bifida . In vinken PJ. Bruyn GW : Handbook of clinical Neurology . Amsterdam , Elsevier/ North Holland Biomedical Press 1978 ,vol 32 pp 519-578.

The terms acrania and exencehaly have also been used to describe this appearance these represent early stages in the development of anencephaly. The outcome of anencephaly is uniformly fatal.

What ate the  Recognized Causes of Neural Tube Defects

Multifactorial Inheritance Anencephaly myelomeningocele meningocele and encephalocele Mendelian Syndromes Pallister Hall syndrome Meckel gruber syndrome ,autosomal recessive (phenotype includes occipital encephalocele and rarely anencephaly ) Median cleft face syndrome possibly autosomal dominant (phenotype includes anterior encephalocele) Robert syndrome autosomal recessive (phenotype includes anerior encephalocele) Syndrome of anterior sacral meningomyelocele and stenosis ( dominant either autosomal or X- linked ) Jarcho-Levin syndrome autosomal recessive (phenotype includes meningomyelocele ) HARD (E) syndrome (hydrocephalus agyria retinal dysplasia +  encephalocele ) autosomal recessive (phenotype includes encephalocele ) Chromosome Abnormalities Trisomy 13 Trisomy 18 Triploidy Other abnormalities such as unbalanced translocations and ring chromosome Probably Hereditary but Mode of Transmission Not Established Syndrome of occipital encephalocele myopia and retinal dysplasia Anterior encephalocele among Bantus and Thais Teratogens Valproic acid (spina bifida) Phenytoin Carbamazepine Aminopterin/ amethopterin (anecephaly and encephalocele ) Exposure to high heat caused by fever Monozygotic twinning Maternal Predisposing Factors Diabetes mellitus (anencephaly more frequently than spina bifida ) obesity Methyltetrahydrofolate reductase (MTHER) gene carrier Specific Phentoype without Known Cause Syndrome of craniofacial and limb defects secondary to amniotic bands (phenotype includes multiple encephaloceles) Cloacal exstrophy (phenotype include myelocystocele) Sacrococcygeal teratome (phenotype includes myelomeningocele)

The 11 auditable conditions and detection rates (reproduced with permission from NHS FASP)
Condition	Detection rate (%)
Anencephaly	98
Open spina bifida	90
Cleft lip	75
Diaphragmatic hernia	60
Gastroschisis	98
Exomphalos	80
Serious cardiac abnormalities	50
Bilateral renal agenesis	84
Skeletal dysplasias	60
Trisomy 18 (Edwards syndrome )	96
Trisomy 13 (Patau syndrome )	95

ABC  of soft markers : Revision class

Second trimester soft markers were all initially described and used to refine the risk of trisomy in women in high risk groups. With the introduction of routine second trimester anomaly scanning the low risk population was subjected to the same level of ultrasound assessment. This coupled with apprehension of the threat of litigation encouraged widespread disclosure of all scan findings in many units however minor they appeared or however low the association with fetal trisomy.

The majority of women who attend for second trimester anomaly scans have had some form of screening either first trimester nuchal screening or second trimester biochemical screening . These women are not screened positive until they reach a threshold usually a risk greater than one in 250. For the vast majority of women with a low risk screening result the presence of a single soft marker will not adjust this result into the screen positive group. Some units have therefore opted either to ignore soft markers completely or to only advise mothers of the increased risk of trisomy if two or more soft markers were identified during the anomaly scan.

How best to standardize the tests? To standardize  the use of soft markers identified during an anomaly scan the NHS FASP has included guidance on this issue. It is recommended that the term ‘Down soft marker ‘ should no longer be used . The ultrasound findings of choroid plexus cysts dilated cistern magna echogenic foci in the heart and a two vessel cord should no longer initiate a referral for aneuploidy counseling. However increased nuchal  translucency greater than 6 mm dilated renal pelvis (greater than 7 mm ventriculomegaly (greater than 10 mm) and echogenic bowel ( with the same density as bone) all associated with multiple pathologies in addition to aneuploidy should be referred for further assessment and if indicated additional testing.

Don’t believe Prof S K Pal: He is a great liar!!! Please do remember: Be very cautious when U speak or pass some adverse comments about abnormal foetus in womb:-Remember that , like Dr Pal’s who often posts  falsely , similarly soft markers reports MoM  / San reports  can yield “”FALSE POSITIVE SCAN FINDINGS “”

 Vagaries of san report! Why scan  reports even with best machine  go wrong and as a result after 6 months of your declaration when the baby is delivered by some other doctor:-your private chamber  is ransacked as U communicated  at  19-21 weeks that “ that your foetus is is having such & such abnormality.””. Pl be doubly cautions. .  Irregularities seen during the anomaly ultrasound examination may be real and even persistent over several scans but following delivery no abnormality can be found in the neonate and repeated investigations proves normal . Common examples of these irregularities are cystic areas within the fetal abdomen chest and pelvis dilated loops of bowel abnormalities in the brain tissue and echogenic areas within the chest or abdomen . Clearly at the time of fetal ultrasound parents need to be informed of the findings and of the possible diagnosis that they represent. For many parents there ensures a period of anxious waiting until delivery when ore formal investigations can establish the veracity of the antenatal findings.

Why reports go wrong? During a routine anomaly scan the sonographer may be unable for a variety of reasons to confirm that an organ is normal .Once more a period of anxiety ensues for parents while a second opinion is organised and the findings are either confirmed or refuted. There are no good national studies looking at the number of scans requiring neither a second opinion nor the mean time that parents have to wait for clarity.

The psychological impact of these events on parents is often poorly appreciated. It is important that adequate support systems exist within each department to help  parents cope with the weeks of uncertainty until such time as a clear diagnosis is reached.

FALSE NEGATIVE SCAN FINDINGS: causes & explanations; We must know the limitations of all tets including Hb /PPBS LH, FSH.

While some parents face weeks of uncertainty others may have been reassured by an apparently normal scan only to be shocked by the diagnosis of a fetal abnormality either at a later stage in the pregnancy or following delivery. There are several reasons why this may occur. The mandatory views for a routine 20 week anomaly scan are determined by individual departments. Abnormalities may therefore be missed because they do not fall into the list of structures to be evaluated. Even with the most stringent protocols  in place some abnormalities cannot be detected as they are very difficult to detect at 20 weeks or they may not present until a late stage in pregnancy. For example the diagnostic features of critical aortic stenosis ans duodenal atresia may not be evident in the second trimester fetus. Likewise the stomach may appear in an appropriate position at 18 weeks of gestation but may be clearly seen within the chest cavity at 26 weeks owing to a diaphragmatic hernia. The  other abnormalities commonly missed for this reason are hydrocephalus microcephaly renal abnormalities cleft palate ovarian cysts  and other types of CHD. In addition despite repeated ultrasound scans limitations in imaging particularly in women who are obese may never the overcome and abnormalities may be missed. Finally as the RADIUS study demonstrated abnormalities may not be recognised because of inadequately trained personnel or inappropriate machinery being used for the examination . For this reason the Royal College of Obstetricians and Gynaecologists and the NHS FASP have detailed the competency that is expected of personnel undertaking routine anomaly scans.

Association with other abnormalities:-Anencephaly demonstrated in 18 weeks anomaly scan:- , Very sad, But as U are taking remuneration for scan and report is for Prof S K Pal’s patient  case U must search other associated anomalies which may accompany Anencephaly. ;; Do not hand over incomplete report pl. For instance , if a woman comes to us for whites -   As because Pt has come to us for this solo complaint  it is untrue / unlawful that we  should not measure her BP, weight her ,listen to her  chest  or  palpate for hepatosplenomeagly .  That what is medical wisdom or say  Dictum:-We know that in ANENCEPHALY  there is absence of the cerebral hemispheres and most of the cranial vault . This results in prominent orbits and the typical frog like appearance on transabdominal ultrasound. It is lethal condition occurring more commonly in female fetuses.

ADDITIONAL ANOMALIES

Detection of a structural abnormality on ultrasound should always lead to a thorough search for additional anomalies since their presence can alter the diagnosis management  and implications for a future pregnancy . For example a fetus with an isolated neural tube defect and in exomphalos which could indicate trisomy 18 a generally lethal condition. Alternatively a neural tube defect and polycystic kidneys suggest a diagnosis of Meckel –Gruber syndrome which has a recurrence risk of one in four in contrast to a recurrence risk of 1/25 for an isolated lesion. In the presence of multiple defects karyotyping should be offered . Preconceptional folic acid supplementation 0.4 mg daily reduces the incidence of neural tube defects . Women who have had a previously affected pregnancy or who are taking anticonvulsants should take a higher daily dose (4mg.)