Review Question - QID 5890

The patient presents with MRI suggestive of far lateral disc herniation at the L3-L4 disc space. He would be expected to have symptoms in L3 nerve distribution, near the medial epicondyle of the femur. Associated motor manifestations may include quadriceps weakness and/or diminished patellar reflex.

Far lateral disc herniations constitute approximately 5-10 percent of disc hernations in the lumbar spine. Given the more vertical anatomy of lumbar nerve roots, at a given disc level, a central or paracentral herniation will affect the traversing nerve root (e.g. nerve root of level below) and a far lateral herniation will affect the exiting nerve root (e.g. nerve root of the level above). Similar to the more common central and paracentral herniations, approximately 90% of patients will improve without surgical intervention. When surgical intervention is needed, the paraspinal approach of Wiltse is utilized.

Marquadt et al. reported long term outcomes of surgical management of far lateral disc herniations. At an average of 146 months follow up, 56.3% of patients had complete relief of symptoms and 27.6% had permanent residual symptoms. Over 75% of patients subjectively rated their outcomes as excellent.

Figure A and B are T2 and T1 axial MRI images, respectively, showing the L3-L4 disc space with a left far lateral disc herniation. Figure C is a left parasagittal T2 MRI image showing impingement on the L3 nerve root. Structures are labeled in illustration A. Illustration B shows the dermatomes of the lower extremity.

Incorrect Answers:
Answers 1 and 3: A far lateral disc herniation will affect the exiting L3 nerve root.
Answer 2: Impingement on the L3 nerve root will lead to symptoms near the medial epicondyle of the femur. The skin over the medial malleolus is innervated by the L4 nerve root
Answer 5: A far lateral disc herniation would not impinge on the segmental vessels. Further, given the abundant collateral flow, there would be no symptoms with vessel compression.