Review Question - QID 3712

The clinical presentation is consistent with a L4 radiculopathy. A L4/L5 far lateral (foraminal) disc herniation would compress the exiting root (L4) and cause these symptoms.

The location of a prolapsed lumbar disc determines its symptoms. Central disc herniations may give rise to back pain or cauda equina syndrome. Paracentral disc herniations (90-95% of cases) affect the traversing nerve root. Far lateral disc herniations (5-10%) affect the exiting nerve root.

Gregory et al. summarize physical signs in lumbar disc herniation. They state that the straight-leg-raise is the most sensitive (73-98% sensitive) test and the crossed straight-leg-raise is the most specific (88-98% specific) test for lumbar disc herniation. Other specific tests include weak ankle dorsiflexion (89% specific), absent ankle reflex (89% specific), and calf wasting (94% specific, but a late finding).

Illustration A shows how a paracentral L4/L5 disc herniation affects the traversing L5 root, but a far lateral L4/L5 disc herniation affects the L4 root. Illustration B shows the dermatomal distribution of pain with root involvement from L3 to S1.

Incorrect Answers:
Answer 1: Lumbar arachnoiditis will not give rise to radiculopathy. This patient did not have invasive spinal procedures that would put him at risk of this condition. Symptoms of arachnoiditis include chronic pain, numbness and tingling of the extremities, abnormal bowel, bladder and sexual function.
Answer 2: L4/L5 paracentral disc herniation would affect the traversing root (L5) and give rise to L5 radiculopathy.
Answer 3: L3/L4 far lateral (foraminal) disc herniation would affect the exiting root (L3) and give rise to L3 radiculopathy.
Answer 5: L5/S1 far lateral (foraminal) disc herniation would affect the exiting root (L5) and give rise to L5 radiculopathy.