A 48-year-old labourer has left-sided back and groin pain radiating down the anteromedial thigh and shin, with weakness of knee extension and a depressed left knee jerk. MRI shows a far lateral (foraminal) disc prolapse at L4-L5. Which nerve root is compressed?

• A Exiting L3 root
• B Traversing L5 root
• C Exiting L4 root ✓
• D Traversing S1 root

Explanation

In a far lateral or foraminal L4-L5 herniation the fragment lies lateral to the pedicle where the exiting L4 root leaves the canal, so it compresses L4 rather than the traversing L5 root compressed by a common paracentral L4-L5 disc. Quadriceps weakness and an absent knee jerk reflect the L4 myotome and reflex. This exiting root pattern is the classic discriminator of extraforaminal discs.

Reference: Bailey and Love's Short Practice of Surgery, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.