Early microsurgery on thoracolumbar spinal extradural arachnoid cysts: Analysis of a series of 41 patients

Spinal extradural arachnoid cysts: A novel formation mechanism and dural defect location technology

Purpose

The formation mechanism of spinal extradural arachnoid cysts (SEACs) remains unclear. There are several hypotheses for the formation of SEACs, but none of them can fully explain its pathological findings and surgical procedures. In this study, we retrospectively analyzed the cases of SEACs, aiming to clarify the formation mechanism of SEACs. In addition, we summarize a concise method for locating dural defects preoperatively and formulate a putative explanation of this method.

Methods

The clinical data of 14 patients with SEACs underwent surgery in our hospital from January 2017 to December 2021 were retrospectively analyzed.

Results

Fourteen patients were identified during the study period. The cysts all spanned the T12/L1 segment, and dural defects were also located at the T12/L1 level (2 cases not recorded) as well as the middle or the upper-middle level of the cysts. Nine cases were treated with total cyst excision, 2 cases were treated with dural defect closure only, and 3 cases were treated with total cyst excision and dural defect closure. Histopathological examination demonstrated that the cyst wall contained both the arachnoid epithelial and compact fibrous connective tissue. The symptoms were relieved in all patients, and no recurrence was observed.

Conclusions

According to intraoperative and pathological findings, the dural outer layer cyst (DOLC) is a more reasonable hypothesis about SEACs formation. When CT myelography or cinematic MRI cannot determine the location of the dural defect preoperatively, it can be located according to the middle level of the SEACs with high accuracy.

Impact of Surgical Timing on Neurological Outcomes for Spinal Arachnoid Cyst: A Single Institution Series

Objective

Spinal arachnoid cysts (SACs) are rare lesions that often present with back pain and myelopathy. There is a paucity of literature evaluating the impact of surgical timing on neurological outcomes for primary SAC management. To compare long-term neurological outcomes in patients who were managed differently and to understand natural progression of SAC.

Methods

We conducted a retrospective analysis of adult patients treated for SAC at our institution from 2010 to 2021, stratified into 3 groups (conservative management only, surgical management, or conservative followed by surgical management). Study outcome measures were neurological outcomes as measured by modified McCormick Neurologic Scale (MNS), postoperative complications, and cyst recurrence. Nonparametric analysis was performed to evaluate differences between groups for selected endpoints.

Results

Thirty-six patients with SAC were identified. Eighteen patients were managed surgically. The remaining 18 patients were managed conservatively with outpatient serial imaging, 7 of whom (38.9%) ultimately underwent surgical treatment due to neurological decline. Most common presenting symptoms included back pain (50.0%), extremity weakness (36.1%), and numbness/paresthesia (36.1%). Initial/preoperative (p = 0.017) and 1-year postoperative (p = 0.006) MNS were significantly different between the 3 groups, but not at 6 weeks or 6 months postoperatively (p > 0.05). Additionally, at 1 year, there was no difference in MNS between patients managed surgically and those managed conservatively but ultimately underwent surgery (p > 0.99).

Conclusion

Delayed surgical intervention in minimally symptomatic patients does not seem to result in worse long-term neurofunctional outcomes. At 1 year, postoperative MNS were significantly higher in both surgical groups, when compared to the conservative group highlighting worsening clinical picture regardless of preoperative observational status.