Interdural Spinal Arachnoid Cyst Case Study and Review of Literature with Operative Technical Considerations

Introduction Spinal arachnoid cysts are commonly encountered throughout all age groups and are often managed observantly, but a minority cause symptoms requiring intervention. These cysts can be caused by congenital malformations, trauma, inflammation, or even occur spontaneously. A vast majority of arachnoid cysts in the spine are extradural, and about 10% are intradural. One type of intradural cyst occurs between two leaflets of the dura, described as an interdural cyst. Case Report This case report describes a 47-year-old female with an interdural arachnoid cyst spanning the thoracolumbar region (T11-L3). Initially, the patient was asymptomatic but later presented with progressive neurologic symptoms, including intermittent back pressure, heaviness in her legs, paresthesia, urinary hesitancy, and decreased sensation in the perineal area. Surgical intervention via direct lumbar laminectomy was performed from the bottom of T11 to the top of L3, revealing an interdural cyst without communication to the subarachnoid space. Thus, surgical fenestration was performed to establish a pathway between the cyst and the subarachnoid space to alleviate symptoms and prevent recurrence. Discussion The absence of communication between the cyst and the subarachnoid space suggests alternative mechanisms, such as a ball valve mechanism, contributing to cyst expansion. A comprehensive review of existing literature on interdural cysts underscores the necessity for revised classification systems, considering both their fluid content and communication with the subarachnoid space. Conclusions The proposed classification of interdural cysts based on CSF analysis and connection to the subarachnoid space may guide operative management and provide more information on the etiology. This classification system could refine outcome data in the operative management of interdural spinal cysts.