Intradural extra-arachnoid lumbar disc herniation is a rare disease. Few MRI findings have been reported. We experienced an intradural extra-arachnoid lumbar disc herniation. We reviewed the preoperative MRI findings. Lumbar spine T2-weighted sagittal MRI showed that one line of the ventral dura was divided into two by a disc herniation. We speculated that the two lines comprised the dura and arachnoid and that a disc herniation existed between them. We believe that division of the ventral dural line on T2-weighted sagittal images is a characteristic finding of intradural extra-arachnoid lumbar disc herniation. The division of ventral dural line seemed to be a “Y,” and, thus, we called it the “Y sign.” The “Y sign” may be useful for diagnosing intradural extra-arachnoid lumbar disc herniation.

Introduction. Degenerative lumbar spinal disorder is common in Japan, and the L5 nerve root is commonly involved in this disorder. The symptoms of L5 radiculopathy are irradiating lateral leg pain, and numbness and weakness of tibialis anterior and the hip abductor muscle. There has been only one report on the results of surgery for hip abductor muscle weakness caused by degenerative lumbar spinal disorder.Patients and methods. In this study, we analyzed the strength of the hip abductor muscle before and after decompressive surgery in 26 cases and the relationship between the lumbar disc herniation (LDH) and lumbar spinal canal stenosis (LSCS) groups.Results. Of the total 26 cases, muscle strength improved in 23 cases (88%), with complete recovery in 17 cases (65%). In the LDH group, the improvement rate was 92%. In the LSCS group, the improvement rate was 68%. Although the improvement rate for the LDH group was higher than that for the LSCS group, the difference was not significant (P = 0.054).Discussion. Decompressive surgery may be an effective method to improve hip abductor muscle weakness in degenerative lumbar spinal disorder.

The incidence of lumbar spinal canal stenosis (LSCS) is increasing in Japan. Posterior lumbar decompression surgery, wide fenestration and laminectomy, for LSCS is a common treatment modality. Compared with posterior fusion surgery, posterior decompression surgery has been considered as less invasive. However, no reports regarding postoperative anemia following posterior decompression surgery have been published. In this retrospective study, we evaluated changes in hemoglobin values following wide fenestration in 80 patients with LSCS based on the number of operated levels, and also analyzed the differences between intraoperative and postoperative bleeding volume. Two patients required allogenic transfusion. The mean preoperative hemoglobin values were 13.6 g/dL and the mean postoperative minimum hemoglobin values were 11.2 g/dL. The mean hemoglobin values decreased by 1.8 g/dL in patients with one operated level (n = 15); 2.2 g/dL in those with two operated levels (n = 31); 2.6 g/dL in those with three operated levels (n = 23); and 3 g/dL in those with four operated levels (n = 11). The mean decrease in hemoglobin values was calculated as follows: 1.8 + 0.4 × (X − 1), where X was the number of operated levels. The mean intraoperative bleeding volume was 94 ml and the mean postoperative bleeding volume was 418 ml. Postoperative bleeding volume was significantly larger than intraoperative bleeding volume. Accordingly, postoperative hemoglobin values can be predicted in patients undergoing wide fenestration. Effective management of postoperative bleeding is necessary to prevent postoperative anemia.