A 56-year-old woman experienced persistent excruciating pain with peroneal nerve injury in the anterior aspect of the lower leg after knee surgery. In our pain clinic, we diagnosed the patient with complex regional pain syndrome and performed lumbar sympathetic neurolysis (LSN) with absolute alcohol at the 3rd lumbar vertebra (L3). After the next follow-up, she complained of continuous dull low back pain, anal dysregulation, and fecal incontinence. We performed magnetic resonance imaging (MRI) to rule out other existing pathologies of back pain. On MRI, the nucleus pulposus was moderately extruded to the central zone with inferior sequestration at L2/3, and moderate central canal stenosis was observed at L2/3. She underwent partial laminectomy with discectomy at L2 level. We were not sure of the cause of disc herniation, but we strongly suspected that LSN at the L3 vertebral level was related to the pathology. Therefore, we discuss this unusual case.