Review Question - QID 101900

A tuft of hair in the lumbosacral region is consistent with spina bifida occulta, a neural tube defect (NTD). NTDs are commonly associated with folate deficiencies. Valproate is a folate antagonist, thus contributing towards the development of spina bifida occulta.

NTDs result when the neuropores fail to fuse during week 4 of embryogenesis. The abnormality is associated with low folic acid intake during pregnancy, reduced folic acid absorption, or impaired enzymatic pathways involving folate, sometimes caused by drugs including methotrexate and the antibiotics trimethoprim/sulfamethoxazole (or Bactrim).

The 3 important types of NTDs for the USMLE Step 1 are:
1. spina bifida occulta (least severe, dura intact, no herniation)
2. spina bifida with meningocele (meninges herniate through defect and form CSF-filled sac, but spinal cord remains in spinal canal)
3. spina bifida with meningomyelocele (meninges and spinal cord herniate through defect)

Incorrect Answers:
Answer 1: Chloramphenicol is a bacteriostatic antibiotic that targets the 50S ribosomal subunit used infrequently to treat H. influenza and bacterial meningitis. It is contraindicated in pregant women because it may cause "gray baby syndrome."
Answer 2: Gentamicin is an aminoglycoside antibiotic contraindicated in pregant women because it is ototoxic to the fetus.
Answer 3: Lithium is used in the treatment of bipolar disorder. It is contraindicated in pregnant women because it may cause Ebstein's anomaly (tricuspid valve abnormality) in the fetus.
Answer 5: Folic acid is recommended for pregnant women and women who expect to become pregnant to prevent NTDs in the neonate.