To present a patient with adolescent idiopathic scoliosis who developed a significant neurological deficit after posterior spinal fusion, in association with anemia on postoperative day two. A 14-year-old otherwise healthy female underwent a T3-L3 instrumented posterior spinal fusion for idiopathic scoliosis which was uneventful. Immediate post-operative clinical examination was unremarkable but at postoperative day three the patient developed generalized lower extremity weakness with inability to stand and an urinary retention needing continuous intermittent catheterization program. Her hemoglobin (Hg) dropped from 10 g/dL on postoperative day one to 6.2 g/dL at day two, despite no significant bleeding was noticed. Compressive etiology was ruled out by postoperative myelogram-CT. The patient started to improve significantly after transfusion support. At three months follow-up the patient was neurologically normal. Close clinical neurological evaluation over 48 to 72 hours is needed in order to detect unexpected delayed paralysis following scoliosis surgery. .