Adjacent Double–Nerve Root Contributions in Unilateral Lumbar Radiculopathy

A 46-year-old woman with prior left L4–5 diskectomy 9 months prior, who presented with recurrent left-sided gluteal, posterior thigh, knee, and shin pain and was referred for left-sided nerve root block and steroid administration. Preprocedural MR imaging demonstrated postoperative changes on the left at L4–5, with a scar and root distortion involving the left L4 and L5. Injection of the L4 root reproduced the patient's gluteal and thigh pain, like sciatica, consistent with prominent furcal nerve contribution from L4 to L5. Injection of the L5 root reproduced the patient's shin pain only. She was completely pain-free after the procedure. A, Axial T2-weighted MR image demonstrates postoperative changes on the left, with distortion of the corner of the canal (arrow) affecting the L5 root, and the foraminal region (arrowhead) affecting the left L4. B, Axial T1-weighted image after contrast administration demonstrates a postoperative scar in the canal (arrow) and neural foramen (arrowhead) on the left, involving the L5 and L4 roots.

A 58-year-old man with left-sided leg pain that projected to the thigh, knee, calf, ankle, and foot, referred for nerve root block and steroid administration. Preprocedural MR imaging demonstrated a prominent disk bulge/protrusion at L3–4 and L4–5, suggesting a possible L4 and L5 root involvement. Injection at L4 reproduced the patient's calf and ankle pain, consistent with a significant furcal nerve contribution to L4 from L5, with injection at L5 reproducing a component of the patient's foot and toe pain. A, Axial T2-weighted image at L3–4 demonstrates a prominent asymmetric diffuse disk bulge, with distortion of the left lateral recess (arrow), likely affecting the L4 root. B, Axial T2-weighted image at L4–5 demonstrates a prominent diffuse disk bulge and asymmetric central disk protrusion, with distortion of the left lateral recess (arrow), very likely affecting the left L5 root.