Review Question - QID 3797

The patient is presenting with a left-sided paracentral disc herniation at the L3-L4 level. The disc would impinge on the traversing L4 nerve root, leading to weakness in the tibialis anterior muscle and/or quadriceps muscle.

While most lumbar disc herniations present with pain radiating down the leg, some patients may have an accompanying motor weakness. A combination of the clinical examination and imaging findings can typically help determine the level of pathology. Paracentral herniations will affect the traversing nerve root, while foraminal and far lateral herniations will affect the exiting nerve root. The innervation of the tibialis anterior is either L4 or L5 dominant, split about evenly in the general population. If L4 is involved, quadriceps weakness may also be present. If L5 is involved, extensor hallucis longus weakness may also be present.

Weinstein et al. examined four-year outcomes in patients undergoing surgery versus conservative management of lumbar disc herniations the Spine Patient Outcomes Research Trial (SPORT). In the as-treated analysis, patients undergoing surgery greater improvement in all primary outcomes except work status.

Radcliff et al. looked at the outcomes of lumbar microdiscectomy in patients who were given epidural steroid injections (ESI). They found no difference in short-term or long-term outcomes in patients who had ESIs versus those who did not prior to surgery.

Overdevest et al. investigated 150 patients with lumbar disc herniations who presented with either a moderate or severe motor deficit, and looked at outcomes depending on whether patients were treated with early surgery or prolonged conservative treatment. They found at 1-year follow-up complete recovery of motor deficit in 81% of patients allocated to early surgery and in 80% of patients allocated to prolonged conservative treatment. They conclude that while patients treated with early surgery had faster recovery of the motor deficit compared with prolonged conservative treatment, the difference was no longer significant at 1 year.

Figure A is T2 axial MRI showing a large left-sided paracentral disc herniation at the L3-L4 level impinging the traversing nerve root. Illustration A labels the exiting L3 nerve root and transversing L4 nerve root seen in Figure A.

Incorrect Answers:
Answer 1: Extensor hallucis longus is innervated by L5.
Answer 3: Gastrocnemius is innervated by S1.
Answer 4: Psoas major is innervated by lumbar plexus branches from L1-L3.
Answer 5: Flexor hallucis longus is innervated mostly by S1 and some S2.