Review Question - QID 595

Residual foraminal stenosis due to inadequate decompression is the most common explanation for persistent symptoms of leg pain following decompressive laminectomy for spinal stenosis.

The differential diagnosis for patients who have undergone previous spinal surgery but have persistent back and leg pain is large and includes (but is not limited to) recurrent neural compression, instability, recurrent herniation, infection, and cauda equina syndrome. These can be placed in two groups: 1) those in whom recurrent difficulties develop after initial symptom relief and 2) those have no interval improvement. Inadequate neural decompression results in no substantial improvement post-op as described in this question. Foraminal stenosis is technically challenging and is more likely to be the cause of residual compression.

Deen et al found the most common pattern in patients with early failure after laminectomy was the absence of neurogenic claudication and severe stenosis on preoperative imaging. They also found that the most common technical error was inadequate neural decompression.

Phillips et al emphasizes the need for a meticulous workup to identify the source of symptoms in this patient group. They argue in the absence of profound or progressive neurologic deficits, most patients with chronic back and leg pain who have undergone previous spinal surgery should be treated nonoperatively.

Figure A shows flexion-extension radiographs with no evidence of instability. Figure B is a T2-weighted sagittal MRI showing spinal stenosis at L4/5 due primarily to ligamentum hypertrophy. Illustration A shows the steps to a decompressive laminectomy. The foramen of both the exiting and descending nerve roots should be probed to ensure an adequate foraminal decompression.

Incorrect Answers:
Answer 1: Segmental instability is a common cause of persistent back and leg pain in patients who have degenerative spondylolisthesis treated with decompression alone. This patient has no evidence of listhesis on preoperative flexion-extension films.
Answer 2: Infection will likely develop slowly over time after a pain-free interval and likely involve axial pain rather than extremity pain.
Answer 3: Disk herniation and instability should be considered post-op if symptoms recur after a pain-free interval of months to years.
Answer 5: Cauda equina syndrome will present in the immediate postoperative period and is very rare and presents with saddle anesthesia and bowel and bladder symptoms.