A 15-YEAR-OLD BOY was referred with progressive left lower extremity weakness, severe lower back pain, and an abnormal gait for 2 months. He underwent a double herniorrhaphy at age 6 months and was diagnosed with kyphoscoliosis at age 13 years. On physical examination, he weighed 53 kg and was 180 cm tall. There was circumduction of the left lower extremity. The left thigh circumference was 2 cm smaller than the right, and the left gluteal muscles were atrophic. There was decreased pain sensation, and muscle tone was increased; however, motor strength was decreased, particularly in the hip flexors. Babinski signs were present bilaterally.