Review Question - QID 108832

The most likely diagnosis in this newborn infant is spina bifida occulta, a type of neural tube defect. Spina bifida is a well known complication of valproic acid, which is often used as an antiepileptic agent.

A tuft of hair overlying a newborn’s lumbosacral region is characteristic of spina bifida occulta. Spina bifida occulta is a form of neural tube defect, a group of conditions in which the neurpores fail to fuse, resulting in a connection between the amniotic cavity and the spinal canal. The occult form is the most common and least severe form of neural tube defects. More severe forms of neural tube defects include meningocele and myelomeningocele, which involve herniation of the meninges (meningocele) or meninges and spinal cord (meningomyelocele). Risk factors for neural tube defects include low folate intake, altered folate metabolism due to valproic acid, and low serum folate levels due to folate antagonists such as methotrexate, and sulfasalazine.

Incorrect Answers:
Answer 1: Lithium is a mood stabilizer used in the treatment of bipolar disorder. Taking lithium during pregnancy is associated with the development of Ebstein’s anomaly – an abnormality of the tricuspid valve – in the fetus. It is not associated with neural tube defects.

Answer 2: Ethosuximide is an anti-epileptic medication that is primarily used to treat absence seizures in children. It is rarely taken in adults and is not associated with the development of neural tube defects.

Answer 3: Warfarin is an anticoagulant that is used to treat deep venous thrombosis and pulmonary embolism. Taking warfarin during pregnancy is associated with the development of fetal warfarin syndrome, which is characterized by skeletal abnormalities such as nasal hypoplasia, scoliosis, and limb abnormalities. However, it is not associated with neural tube defects.

Answer 4: Gentamicin is an aminoglycoside antibiotic. Taking gentamicin during pregnancy is contraindicated because it is ototoxic to the fetus. However, it is not associated with the development of neural tube defects.

Bullet Summary:
Low maternal folate due to inadequate dietary intake or medication-mediated folate antagonism (i.e., valproic acid) is associated with an increased risk of neural tube defects.