Spina bifida

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Spina bifida

Nervous system

Autonomic nervous system disorders

Horner syndrome

Orthostatic hypotension


Spina bifida


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USMLE® Step 1 questions

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High Yield Notes

13 pages


Spina bifida

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USMLE® Step 1 style questions USMLE

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A 1-hour-old boy is being evaluated in the nursery due to a hairy patch on the lower back. He was born to a 24-year-old primigravida who did not receive prenatal care. The patient’s mother took prenatal vitamins throughout the pregnancy and did not use tobacco, alcohol, or illicit drugs. The patient’s vitals are within normal limits. Physical examination shows a comfortable infant moving all 4 limbs spontaneously. Rectal examination reveals normal anal sphincter tone. Examination of the lower back shows a small, flat, hairy patch. Palpation of the area reveals a gap. Which of the following is the most likely diagnosis?  

External References

First Aid









spina bifida p. 718

Meningocele p. 505

Meningomyelocele p. 505

Spina bifida

Dandy-Walker syndrome p. 506

labs/findings p. 718

neural tube defect p. 505

Spina bifida cystica p. 505


Content Reviewers

The term “spina bifida” comes from the latin “split spine,” which is actually a pretty good description, because spina bifida is a birth defect where the tissue on the left and right side of the back that normally come over the spinal cord to protect it, don’t completely meet up to form a nice seal, leaving behind various degrees of an opening right down the middle of the lower back.

Very early on in fetal development, the ectoderm, which is the outer layer of the fertilized egg, starts to develop a bit of a ridge that eventually becomes the neural tube.

This neural tube goes on to become the spinal cord, the brain, as well as tissues that enclose and protect them, called the meninges, and spina bifida occurs when a portion of this neural tube fails to close properly, typically in the lower back.

This constitutes a defect or absence of the vertebral arches due to failure of mesoderm to organize over the region of the defect, and it may or may not involve the underlying meninges and neural tissue

Alright so there are three main types of spina bifida, the first is myelomeningocele, also called meningomyelocele, and this is the most severe of the three and occurs when the spinal cord and the surrounding meninges protrude out of an opening in the bony vertebrae and are held together by a sack of skin that pouches out from the back.

In really severe cases, there is no skin at all, and the nerves of the spinal cord are therefore exposed, a condition called ‘open spina bifida, and this can cause serious damage to the exposed nerves as well as risk an infection, resulting in symptoms like loss of sensation or paralysis in the areas of the body below the damaged site, bladder or bowel movement problems, seizures, as well as leg and foot deformities.


Spina bifida is a congenital birth defect of embryonic development where there is incomplete closing of the vertebral column and membranes around the spinal cord. There are three main types: spina bifida occulta, meningocele, and myelomeningocele. In Spina bifida occulta there is only a small gap in the bones of the spine, and the spinal cord and surrounding tissue don't protrude. In meningocele, the meninges protrude through the opening in the spinal column, but the spinal cord itself is not affected. In myelomeningocele, there is a protrusion of the spinal cord and nerves through the opening of the spinal cord. For treatment, prenatal surgery is done to close myelomeningocele, but this surgery can be dangerous to the developing fetus as well as the mother. In cases where postnatal surgery is chosen, it is often done within the first few days of an infant's life to minimize the risk of infection like meningitis.


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