Master the board step 3

Master the Boards: USMLE Step 3
Back Pain
Disc Herniation
A 45-year-old man with a history of back pain for several months presents with
sudden-onset severe back pain that came on when he was moving a television.
He describes an “electrical shock” that shoots down his leg, which is worse when
he coughs or strains and is partially relieved by flexing his legs. The pain has prevented
him from ambulating. Straight leg raising gives excruciating pain. What is
the next step in management?
a. CT of the spine
b. Dexamethasone
c. Immediate surgery
d. Ibuprofen and brief bed rest
e. MRI of the spine
Answer: D. This is the classic presentation of lumbar disc herniation. It occurs almost
exclusively at L4–L5 or L5–S1. Peak age is 43–46. Anti-inflammatories and a brief period
of bed rest is all that is needed at this stage. Immediate surgical compression is needed
if the history suggests cauda equina syndrome (look for bowel/bladder incontinence,
flaccid anal sphincter, and saddle anesthesia). MRI can confirm both disc herniation and
cauda equina, but do not answer MRI in classic cases of disc herniation. Trial of antiinflammatories
is also the first step in management.
Basic Science Correlate
A sluggish ankle jerk reflex is suggestive of pathology at S1/S2. A sluggish
patellar reflex is suggestive of pathology at L4/L5.
Lumbar Disc Herniation
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