from Medical topics
Published online by Cambridge University Press: 18 December 2014
Spina bifida is a congenital neural tube defect, characterized by a fault in the spinal column in which one or more vertebrae fail to form properly leaving a gap or split. Spina bifida occulta is a common condition in which the bones may be incomplete but the defect is covered by skin and the spinal cord usually is unaffected, hence most people do not have any symptoms or clinical problems. Spina bifida aperta refers to an open defect of the spine in which the spinal cord does not form properly and is exposed. There are two forms; meningocele and myelomeningocele. In meningocele, the visible cyst on the back contains cerebrospinal fluid (CSF) and the meninges but no nerve tissue. In the more common and serious myelomeningocele, the cyst contains both the nerve tissue and its coverings, hence there is always some degree of paralyses and loss of sensation below the affected vertebrae. Spina bifida is often associated with malformations of the brain stem and cerebellum (Arnold Chiari malformations) and hydrocephalus (Shonkoff & Marshall, 1990). Hydrocephalus occurs when there is an abnormal accumulation of CSF within the ventricles and or subarachnoid space of the brain.
The incidence of spina bifida varies from country to country, for example, the incidence in Ireland is 8 per 1000 live births whilst in South East Asia the condition is rare (Chauvel, 1991).
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