Department of Neurosurgery, Madurai Medical College, Madurai, India.
Spine (Phila Pa 1976). 2009 Nov 15;34(24):2654-61. doi: 10.1097/BRS.0b013e3181b541c9.
A retrospective review.
The aim of this study is to highlight one of the under recognized and under reported aspects of ossification of the ligamentum flavum (OLF), namely, dural ossification in OLF and to discuss the incidence, radiologic signs, causes as well as the surgical and prognostic implications of dural ossification in OLF.
OLF is being increasingly recognized as a cause of myelopathy. One of the surgical pitfalls in the management of this condition is ossification of the dura mater in OLF. Preoperative identification of ossified dura mater will be helpful to the surgeon to modify the surgical technique and to counsel patients regarding the risks of surgery.
A retrospective analysis of a database of OLF maintained by this author was done to identify cases of OLF where there was intraoperative evidence of dural ossification and dural laceration. Only those patients who had both computed tomography (CT) and magnetic resonance imaging (MRI) were included in the analysis. Patients with MR imaging alone were excluded from the analysis as CT evaluation was not done routinely in the earlier part of the study. Nurick's grading was used to assess the neurologic status before and after surgery. The CT and MR images of these patients were analyzed to identify radiologic signs of dural ossification. The pattern of dural ossification, if present, was noted. The intraoperative and postoperative complications were recorded.
During the study period from 1997 to 2006, there were 20 patients with OLF who had both CT and MR imaging evaluation. Of these 20 patients, 8 had intraoperative evidence of dural ossification and these patients also sustained dural laceration during surgery. Of these 8 patients, CT evidence of dural ossification was found in 7. In the remaining one patient, there was no radiologic evidence of dural ossification. The radiologic signs of dural ossification as depicted in the bone windows of CT were of 2 types: (1) the "tram track sign," where there was a hyperdense bony excrescence with a hypodense center and (2) the "comma sign," where there was evidence of ossification of one-half of the circumference of the duramater. Of these 7 patients, 4 developed cerebrospinal fluid (CSF) leak following surgery and 1 of these 4 patients developed meningitis. Neurologic function improved by one Nurick's grade in 5 of the 7 patients. In the remaining 2 patients, there was no change in the neurologic status.
Dural ossification is a common finding in OLF. There are 2 radiologic signs of dural ossification, namely, the "tram track sign" and the "comma sign." Preoperative identification of dural ossification might help the surgeon to anticipate and appropriately deal with dural laceration during surgery. This will also help to counsel patients regarding the risks of surgery for OLF. The surgical and prognostic implications of dural ossification are being discussed.
回顾性研究。
本研究旨在强调黄韧带骨化（OLF）中一个未被充分认识和报道的方面，即黄韧带骨化中的硬脑膜骨化，并讨论硬脑膜骨化在 OLF 中的发生率、影像学特征、原因以及手术和预后的影响。
OLF 正日益被认为是一种导致脊髓病的原因。在这种情况下进行手术管理的一个手术陷阱是 OLF 中的硬脑膜骨化。术前识别骨化硬脑膜将有助于外科医生修改手术技术，并就手术风险向患者提供咨询。
对作者维护的 OLF 数据库进行回顾性分析，以确定术中存在硬脑膜骨化和硬脑膜撕裂的 OLF 病例。仅纳入同时接受计算机断层扫描（CT）和磁共振成像（MRI）检查的患者进行分析。仅接受 MRI 检查的患者被排除在分析之外，因为在研究的早期阶段未常规进行 CT 评估。术前和术后使用 Nurick 分级评估神经功能状态。分析这些患者的 CT 和 MRI 图像以识别硬脑膜骨化的影像学特征。如果存在，记录硬脑膜骨化的模式。记录术中及术后并发症。
在 1997 年至 2006 年期间，有 20 例 OLF 患者同时接受 CT 和 MRI 检查。在这 20 例患者中，8 例术中发现硬脑膜骨化，这些患者在手术中也发生硬脑膜撕裂。在这 8 例患者中，7 例 CT 发现硬脑膜骨化证据。在另一位患者中，没有影像学证据表明硬脑膜骨化。CT 骨窗显示硬脑膜骨化的影像学特征有 2 种类型：（1）“火车轨道征”，表现为高密度骨赘伴低密度中心；（2）“逗号征”，表现为硬脑膜半周的骨化。在这 7 例患者中，4 例术后发生脑脊液漏，其中 1 例并发脑膜炎。7 例患者中有 5 例神经功能改善 1 个 Nurick 分级。在其余 2 例患者中，神经功能状态没有变化。
硬脑膜骨化在 OLF 中较为常见。硬脑膜骨化有 2 种影像学特征，即“火车轨道征”和“逗号征”。术前识别硬脑膜骨化可能有助于外科医生预测并适当处理手术中硬脑膜撕裂，这也有助于向患者提供有关 OLF 手术风险的咨询。本文还讨论了硬脑膜骨化的手术和预后影响。
