Anencephaly Health Dictionary

This is one of the most common of the congenital (present at birth) malformations. It is one of the three types of neural-tube anomaly, the other two being ANENCEPHALY and cranium bi?dum. It takes two main forms – spina bi?da occulta being much the commoner. There is a de?cit in the posterior part of the SPINAL COLUMN, usually in the LUMBAR region, and it is generally asymptomatic unless the underlying spinal cord is affected. Occasionally it is associated with a hairy patch or birthmark on the back, and a few children develop a mild spastic gait or bladder problems.

Much more serious is spina bi?da cystica, in which the spinal-wall defect is accompanied by a protrusion of the spinal cord. This may take two forms: a meningocele, in which the MENINGES, containing CEREBROSPINAL FLUID, protrude through the defect; and a meningomyelocele, in which the protrusion contains spinal cord and nerves.

Meningocele is less common and has a good prognosis. HYDROCEPHALUS and neurological problems affecting the legs are rare, although the bladder may be affected. Treatment consists of surgery which may be in the ?rst few days of life or much later depending upon the precise situation; long-term follow-up is necessary to pick up any neurological problems that may develop during subsequent growth of the spine.

Meningomyelocele is much more serious and more common, accounting for 90 per cent of all cases. Usually affecting the lumbo-sacral region, the range of severity may vary considerably and, while early surgery with careful attention in a minor case may achieve good mobility, normal bladder function and intellect, a more extensive protrusion may cause complete ANAESTHESIA of the skin, with increased risk of trauma; extensive paralysis of the trunk and limbs, with severe deformities; and paralysis and insensitivity of the bladder and bowel. Involuntary movements may be present, and hydrocephalus occurs in 80 per cent of cases. The decision to operate can only be made after a full examination of the infant to determine the extent of the defect and any co-existent congenital abnormalities. The child’s potential can then be estimated, and appropriate treatment discussed with the parents. Carefully selected patients should receive long-term treatment in a special centre, where full attention can be paid to all their various problems.

There is growing evidence of the value of vitamin supplements before and during pregnancy in reducing the incidence of spina bi?da. Parents of affected infants may obtain help, advice, and encouragement from the Association for Spina Bi?da and Hydrocephalus which has branches throughout the country, or the Scottish Spina Bi?da Association.... spina bifida

A protein that is produced in the liver and gastrointestinal tract of the fetus and by some abnormal tissues in adults.

Alpha-fetoprotein (AFP) can be measured in the maternal blood from the latter part of the 1st trimester of pregnancy, and its concentration rises between the 15th and 20th weeks.

Raised levels of are associated with fetal neural tube defects, such as spina bifida or anencephaly, and certain kidney abnormalities. High levels of also occur in multiple pregnancies (see pregnancy, multiple) and threatened or actual miscarriage. levels may be unusually low if the fetus has Down’s syndrome. For this reason, measurement of blood is included in blood tests, which are used to screen pregnant women for an increased risk of Down’s syndrome.

levels are commonly raised in adults with hepatoma (see liver cancer), cancerous teratoma of the testes or ovaries, or cancer of the pancreas, stomach, or lung.

For this reason, is known as a tumour marker.

(AFP) levels can be used to monitor the results of treatment of certain cancers; increasing levels after surgery or chemotherapy may indicate tumour recurrence.

However, levels are also raised in some noncancerous conditions, including viral and alcoholic hepatitis and cirrhosis.... alpha-fetoprotein

Defects and disorders of the brain, which may have one of numerous causes including infection, injury, brain tumour, or a lack of blood or oxygen (hypoxia). Because the brain is encased in the skull, any space-occupying tumour, brain abscess, or haematoma creates raised pressure, which impairs the function of the whole brain. Brain disorders that are localized in a small region may affect a specific function such as speech (see aphasia). More often, damage is more diffuse and the symptoms can be varied and numerous. Some brain disorders are congenital due to genetic or chromosomal disorders, as in Down’s syndrome. Structural defects that arise during the development of the fetus in the womb include hydrocephalus and anencephaly.

Reduced oxygen supply may occur at birth, causing cerebral palsy. Later in life, cerebral hypoxia can result from choking or from arrest of breathing and heartbeat. From middle age onwards, cerebrovascular disease is the most important cause of brain disorder. If an artery within the brain becomes blocked or ruptures, leading to haemorrhage, the result is a stroke. The brain may also be damaged by a blow to the head see head injury).

Infection within the brain (encephalitis) may be due to viral infection. Infection of the membranes surrounding the brain (meningitis) is generally due to bacterial infection. Creutzfeldt–Jakob disease is a rare, fatal brain disease associated with an infective agent called a prion which, in some cases, has been linked with (bovine spongiform encephalopathy), a disease in cattle.

Multiple sclerosis is a progressive disease of the brain and spinal cord. Degenerative brain diseases include Alzheimer’s disease and Parkinson’s disease. Emotional or behavioural disorders are generally described as psychiatric illnesses; but the distinction between neurological and psychiatric disorders is now much less clear.... brain, disorders of

Delivery of a dead fetus after the 24th week of pregnancy. The cause is unknown in many cases. Some stillborn babies have severe malformations, such as anencephaly, spina bifida, or hydrocephalus. Other possible causes include a maternal disorder, such as antepartum haemorrhage or hypertension, or severe Rhesus incompatibility. The risk of stillbirth is increased if the mother has a severe infection during pregnancy.... stillbirth

adj. describing a condition that is believed to have resulted from the interaction of genetic factors, usually polygenes, with an environmental factor or factors. Many disorders, e.g. spina bifida and anencephaly, are thought to be multifactorial.... multifactorial

adj. describing a baby born after 42 weeks of gestation (calculated from the first day of the last menstrual period). Such a birth can be associated with maternal diabetes or with *anencephaly in the fetus. —postmaturity n.... postmature

Ultrasound, or ultrasonic, waves comprise very-high-frequency sound waves above 20,000 Hz that the human ear cannot hear. Ultrasound is widely used for diagnosis and also for some treatments. In OBSTETRICS, ultrasound can assess the stage of pregnancy and detect abnormalities in the FETUS (see below). It is a valuable adjunct in the investigation of diseases in the bladder, kidneys, liver, ovaries, pancreas and brain (for more information on these organs and their diseases, see under separate entries); it also detects thromboses (clots) in blood vessels and enables their extent to be assessed. A non-invasive technique that does not need ionising radiation, ultrasound is quick, versatile and relatively inexpensive, with scans being done in any plane of the body. There is little danger to the patient or operator: unlike, for example, XRAYS, ultrasound investigations can be repeated as needed. A contrast medium is not required. Its reliability is dependent upon the skill of the operator.

Ultrasound is replacing ISOTOPE scanning in many situations, and also RADIOGRAPHY. Ultrasound of the liver can separate medical from surgical JAUNDICE in approximately 97 per cent of patients; it is very accurate in detecting and de?ning cystic lesions of the liver, but is less accurate with solid lesions – and yet will detect 85 per cent of secondary deposits (this is less than COMPUTED TOMOGRAPHY [CT] scanning). It is very accurate in detecting gall-stones (see GALL-BLADDER, DISEASES OF) and more accurate than the oral cholecystogram. It is useful as a screening test for pancreatic disease and can di?erentiate carcinoma of the pancreas from chronic pancreatitis with 85 per cent accuracy.

Ultrasound is the ?rst investigation indicated in patients presenting with renal failure, as it can quickly determine the size and shape of the kidney and whether there is any obstruction to the URETER. It is very sensitive to the presence of dilatation of the renal tract and will detect space-occupying lesions, di?erentiating cysts and tumours. It can detect also obstruction of the ureter due to renal stones by showing dilatations of the collecting system and the presence of the calculus. Adrenal (see ADRENAL GLANDS) tumours can be demonstrated by ultrasound, although it is less accurate than CT scanning.

The procedure is now the ?rst test for suspected aortic ANEURYSM and it can also show the presence of clot and delineate the true and false lumen. It is good at demonstrating subphrenic and subhepatic abscesses (see ABSCESS) and will show most intra-abdominal abscesses; CT scanning is however better for the retroperitoneal region. It has a major application in thyroid nodules as it can di?erentiate cystic from solid lesions and show the multiple lesions characteristic of the nodular GOITRE (see also THYROID GLAND, DISEASES OF). It cannot differentiate between a follicular adenoma and a carcinoma, as both these tumours are solid; nor can it demonstrate normal parathyroid glands. However, it can identify adenomas provided that they are more than 6 mm in diameter. Finally, ultrasound can di?erentiate masses in the SCROTUM into testicular and appendicular, and it can demonstrate impalpable testicular tumours. This is important as 15 per cent of testicular tumours metastasise whilst they are still impalpable.

Ultrasonic waves are one of the constituents in the shock treatment of certain types of gallstones and CALCULI in the urinary tract (see LITHOTRIPSY). They are also being used in the treatment of MENIÈRE’S DISEASE and of bruises and strains. In this ?eld of physiotherapy, ultrasonic therapy is proving of particular value in the treatment of acute injuries of soft tissue. If in such cases it is used immediately after the injury, or as soon as possible thereafter, prompt recovery is facilitated. For this reason it is being widely used in the treatment of sports injuries (see also SPORTS MEDICINE). The sound waves stimulate the healing process in damaged tissue.

Doppler ultrasound is a technique which shows the presence of vascular disease in the carotid and peripheral vessels, as it can detect the reduced blood ?ow through narrowed vessels.

Ultrasound in obstetrics Ultrasound has particular applications in obstetrics. A fetus can be seen with ultrasound from the seventh week of pregnancy, and the fetal heart can be demonstrated at this stage. Multiple pregnancy can also be diagnosed at this time by the demonstration of more than one gestation sac containing a viable fetus. A routine obstetric scan is usually performed between the 16th and 18th week of pregnancy when the fetus is easily demonstrated and most photogenic. The fetus can be measured to assess the gestational age, and the anatomy can also be checked. Intra-uterine growth retardation is much more reliably diagnosed by ultrasound than by clinical assessment. The site of the placenta can also be recorded and multiple pregnancies will be diagnosed at this stage. Fetal movements and even the heartbeat can be seen. A second scan is often done between the 32nd and 34th weeks to assess the position, size and growth rate of the baby. The resolution of equipment now available enables pre-natal diagnosis of a wide range of structural abnormalities to be diagnosed. SPINA BIFIDA, HYDROCEPHALUS and ANENCEPHALY are probably the most important, but other anomalies such as multicystic kidney, achondroplasia and certain congenital cardiac anomalies can also be identi?ed. Fetal gender can be determined from 20 weeks of gestation. Ultrasound is also useful as guidance for AMNIOCENTESIS.

In gynaecology, POLYCYSTIC OVARY SYNDROME can readily be detected as well as FIBROID and ovarian cysts. Ultrasound can monitor follicular growth when patients are being treated with infertility drugs. It is also useful in detecting ECTOPIC PREGNANCY. (See also PREGNANCY AND LABOUR.)... ultrasound

A developmental failure affecting the spinal cord or brain of the embryo. The most serious defect is anencephaly (total lack of a brain), which is fatal. More common is spina bifida, in which the vertebrae do not form a complete ring around the spinal cord. Spina bifida can occur anywhere on the spine, but it is most common in the lower back.

There are different forms of spina bifida. In spina bifida occulta, the only defect is a failure of the fusion of the bony arches behind the spinal cord, which may not cause any problems. When the bone defect is more extensive, there may be a meningocele, a protrusion of the meninges, or a myelomeningocele, a malformation of the spinal cord. Myelomeningocele is likely to cause severe handicap, with paralysis of the legs, loss of sensation in the lower body, hydrocephalus, and paralysis of the anus and bladder, causing incontinence. Associated problems include cerebral palsy, epilepsy, and mental handicap.

Surgery is usually performed a few days after birth. In mild cases, the defect can usually be corrected, but in myelomeningocele, some handicap will remain.

Genetic factors play a part in neural tube defects, which show multifactorial inheritance. Couples who have had an affected child or who have a family history of neural tube defects should seek genetic counselling. The risk of a neural tube defect occurring can be substantially reduced if the mother takes folic acid supplements for a month before conception and during the early part of the pregnancy.

Ultrasound scanning and amniocentesis allow accurate antenatal testing for neural tube defects.... neural tube defect