Clinical and radiological features of spinal extradural arachnoid cysts: Valve-like mechanism involving the nerve root fiber as a possible cause of cyst expansion.

BACKGROUND: Although a valve-like mechanism has been proposed for expansion of spinal extradural arachnoid cysts (SEACs), the detailed mechanism remains unclear. Moreover, closure of the communication site is essential during surgery, but the method to identify the communication site remains unclear. The aim of this study was to determine the detailed mechanism of expanding SEACs through retrospective analysis of SEAC cases undergoing surgery and to elucidate the characteristics of the communication sites. METHODS: The authors retrospectively evaluated 12 patients with SEACs who underwent surgery between 2000 and 2014 and analyzed their perioperative findings. RESULTS: Dural defects were detected in 11 out of 12 patients, and a valve-like mechanism was observed in 7 patients, wherein a nerve root fiber moved back and forth through the dural defect along with the flow of cerebrospinal fluid (CSF) between the intradural space and the extradural arachnoid cysts. The dural defect was located at the thoracolumbar junction in 7 patients, below the distal end of the bridging ossification in 2, at the level of vertebral wedge deformity in 2, and at the level of disc herniation in 1. CONCLUSIONS: A valve-like mechanism was observed in 7 of the 12 patients, which suggests that it could serve as a mechanism of SEAC formation. The communication sites were variously located at the end of ossification in patients with diffuse idiopathic skeletal hyperostosis (DISH), wedge deformity of the vertebral body, or disc herniation, indicating the contribution of mechanical stress to SEAC formation.

A multi-center study of reoperations within 30 days of spine surgery.

PURPOSE: To investigate the incidence and causes of reoperations within 30 days of spine surgery. METHODS: Patients who underwent spine surgery between 2002 and 2012, at one of 9 institutions, were enrolled. The causes of all reoperations, within 30 days of the index surgery, were reviewed. The incidence of reoperations within 30 days were calculated and compared according to the preoperative diagnosis, use of instrumentation, surgical level, and approach. Moreover, the distribution of the causes for reoperations within the 30-day period was also assessed. RESULTS: The overall incidence of reoperations, within 30 days of spine surgery, was 1.6% (175/10,680). Patients who underwent instrumentation procedures demonstrated a higher incidence of reoperations than patients who underwent procedures without instrumentation (P < 0.001). Moreover, patients diagnosed with preoperative trauma had a higher incidence of reoperation than those with other diagnoses (P < 0.001). Surgical site infection (SSI), postoperative epidural hematoma, pedicle screw malposition, and inadequate decompression were the four main causes of reoperation. Motor paralysis, due to epidural hematoma, was the predominant cause of reoperations during the hyper-acute phase (0-1 days, postoperatively), whereas SSI was the dominant cause during the sub-acute phase (11-30 days, postoperatively). CONCLUSIONS: This large, multi-center study indicated the causes and incidence of reoperations, within 30 days of the initial spinal surgery. Based on these data, spinal surgeons can provide patients with information that allows them to better understand the surgical risk and expected post-surgical management.

Lumbar Spinal Surgery in Patients With Parkinson Disease: A Multicenter Retrospective Study.

STUDY DESIGN: A multicenter, retrospective study. OBJECTIVE: To identify the factors that affect surgery-related complications and to clarify the surgical strategy for treating lumbar disorders in Parkinson disease (PD). SUMMARY OF BACKGROUND DATA: Previous studies have reported a high complication rate for spinal surgery in patients with PD. Because of the limited number of studies, there are no guidelines for spinal surgery for PD patients. METHODS: We retrospectively reviewed the records for 67 PD patients who underwent lumbar spinal surgery. The patients were divided into 3 groups: 12 patients underwent laminectomy (Laminectomy), 24 underwent fusion surgery (Fusion) for lumbar canal stenosis, and 31 underwent corrective surgery for spinal deformity (Deformity). We assessed surgery-related complications in each group. The Cox proportional hazards model was used to identify the factors that predicted surgical failure. RESULTS: The percentages of patients who experienced failure of the initial surgery were 33.3% in the Laminectomy group, 45.8% in the Fusion group, and 67.7% in the Deformity group. The rates of implant failure were high in the Fusion and Deformity groups (33.3% and 38.7%, respectively). The Deformity group had a high rate of postoperative fracture (41.9%). These complications occurred at the most caudal site within a year after surgery and resulted in progression of kyphotic deformity. Multivariate analysis revealed that preoperative lumbar lordosis angle (LL) (per -1 degree) was associated with a failure of the initial surgery (hazard ratio, 1.024; 95% confidence interval, 1.008-1.04; P=0.003). CONCLUSIONS: We have demonstrated that a small preoperative LL increases the risk for failure of the initial surgery. Attaining and maintaining the proper lumbar lordosis with rigid fixation may be necessary in PD patients with a small preoperative LL.