Neural Tube Defects- Spina Bifida:

 Spina Bifida is a Spinal Neural Tube Defect caused by the vertebral arch of the spinal column (from the base of the skull to the sacrum) being unformed or incompletely formed, but is most commonly found in the lumber region (where the vertebrae at the base of the neural tube haven’t closed). This could result in the exposure of the spinal cord or meninges (three layers of protective tissue called the dura mater, arachnoid mater, and pia mater that covers the brain and spinal cord). You can surgically close this exposure.

Spina Bifida can be classified as Spina Bifida Occulta or Spina Bifida Cystica.

Spina Bifida Occulta is the most common form of Spina Bifida and is the “closed” form of Spina Bifida, where the skin is intact and there is no exposure of the meninges or spinal cord. However at least one of the vertebrae is malformed/ not fully developed. Sometimes, this is also called Occult Spinal Dysaphism which is when the spinal nerves or meninges are mixed up with their surrounding structures, causing complications.  There are usually no neurological sequelae or long-term consequence with Spina Bifida Occulta but scoliosis/ other spinal deformities could develop along with lower back pain. Also, other problems such as bladder infections and incontinence, constipation or reduced feeling/numbness in the legs or feet could develop.

Spina Bifida Cystica is the “open” form, where there are visible signs of Spina Bifida (a cyst/sac on the back). There are 3 types of Spina Bifida Cystica:

  • Meningocele: This is the least common form of Spina Bifida and is when the cyst contains cerebrospinal fluid or meninges. There’s no spinal neural fluid in the sac. Development of the Spinal Cord may be affected. Meningocele does not necessarily cause neurological symptoms.

  • Myelomenigocele: This is the most common form of Spina Bifida Cystica and is where the cyst contains tissue and cerebrospinal fluid, nerves and part of the spinal cord. This means that the spinal cord will not develop properly or will be damaged, leading to some paralysis and the loss of feeling below the damage part of the cord.

  • Rachischisis: This is the most severe form of Spina Bifida Cystica and is often associate with anencephaly. It is where the spine lies widely open and the neural plate has spread out on to the surface.

AFP screening and Ultrasound are used to diagnose Spina Bifida. It is thought that AFP screening is 80% sensitive for Spina Bifida Cystica. The foetal head is examined in the Ultrasound scan, especially the shape of the skull/ appearance of the cerebellum.  Signs usually include the skull being lemon shaped and the flattening/loss of the median sulcus (banana shaped).

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