Spina Bifida is a neural tube defect and is a developmental anomoly which occurs very early in pregnancy. The neural tube develops to form the spinal cord, brain and spine. When Spina Bifida occurs, the tube is split and one or more vertebrae (small bones of the back) fail to form properly, thus leaving a gap. There are three main types of Spina Bifida:

Spina Bifida occulta where the only sign of the malformation is a dimple or hair at the site of the defect on the skin of the back. This condition is very mild and is usually symptomless although occasionally there may be continence problems and difficulties with mobility.

In Spina Bifida cystica a sac or cyst is visible on the back covered by a thin layer of skin. There are two forms: a meningocele and a myelomeningocele. In a meningocele the sac contains tissues which cover the spinal cord and cerebro-spinal fluid. The nerves are not normally badly damaged and there is little or no malfuction. This is the least common form of Spina Bifida. Myelomeningocele is the most common and severest form and is characterised by the inclusion in the sac of nerves and part of the spinal cord as well as tissue and cerebral-spinal fluid. Some degree of paralysis and loss of sensation occur below the site of the defect. The extent of the diability is dependent on the extent of nerve damage.

Cranium Bifida is a failure of the development of the bones in the Skull. In this form the sac is called an encephalocele. In some cases part of the brain is also enclosed in the sac while in others it contains only tissue and cerebro-spinal fluid. Anencephaly (absent brain) and iniencephaly (badly malformed brain) may also occur and in such cases the child will not survive.

Hydrocephalus is caused by an imbalance between the production and absorption of cerebro-spinal fluid in the brain. About 80% of people with Spina Bifida will have Hydrocephalus.

Inheritance Patterns:   Spina Bifida has some genetic predisposition. Where a couple have an affected child there is a 1 in 25 chance of an affected pregnancy. For an affected person, the risk of an affected child is 1 in 25.

Pre-Natal Diagnosis: A raised alpha-feto protein blood test at 16 weeks can indicate the presence of a neural tube defect. Amniocentesis at 16-18 weeks and detailed ultrasound scanning (at over 16 weeks) can also identify neural tube defects. Unfortunately diagnostic screening for Spina Bifida is not 100% accurate. It is now known that taking Folic acid supplement of 0.4mg daily prior to conception and for the first 3 months of pregnancy reduces the risk of all women of having a baby with Spina Bifida. Women considered at risk should take a higher dose (4mg) as prescribed by their doctor.

Further information available from:

Association of Spina Bifida and Hydrocephalus (ASBAH),
42 Park road
Peterborough
Cambridgeshire
PE1 2UQ
(Tel: 01733 555988   Fax: 01733 555985)

e-mail: postmaster@asbah.demon.co.uk

Return to the Medical Index

ASBAH http://www.asbah.demon.co.uk is a Registered charity No.249388 and was formed after groups of parents got together in the 1960's for mutual support. It offers:

• Practical help and information to individuals with Spina Bifida and/or Hydrocephalus and their families.
• Trained ASBAH advisors to visit families
• Specialist advisors in mobility, continence, education etc.

Activities:

• Study days
• Residential courses for families of affected children