Embryology USMLE Step 1 Practice Question
A 2-day-old male presents with a prominent, fluid-filled sac at the lumbosacral spine noted at delivery. Vital signs show HR 145 bpm, RR 48, BP 65/42, and temperature 37.2°C. Physical examination reveals meninges and spinal cord tissue protruding through a midline vertebral defect. Neuroimaging confirms exposed neural elements without surrounding bone. The infant has intact lower extremity reflexes. Laboratory studies show normal cerebrospinal fluid parameters. A failure of which embryologic process most commonly causes this malformation?
Answer choices
- ADevelopment of primary vertebral ossification centers
- BDevelopment of the pedicle
- CFusion of the vertebral archesCorrect answer
- DDevelopment of the body
- EDevelopment of the superior articular process
- FClosure of the neural tube
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