Delayed Symptomatic Entrapment and Herniation of Lumbar Nerve Root Due to a Prior Durotomy Defect Initially Misdiagnosed As Arachnoiditis: A Case Report

Incidental durotomies are well-known complications of spine surgery. They are often identified and repaired intraoperatively, with a preference for primary rather than secondary repair. We present the case of a middle-aged male with worsening radicular pain six months after spinal surgery complicated by a durotomy defect. His pain was worse with coughing or standing. Magnetic resonance imaging identified an L3-L5 extradural fluid collection in the lumbar spinal canal and an empty sac sign. Computed tomography lumbar myelogram identified clumping of the cauda equina nerve roots at L2-L3 and an empty sac sign at L4-L5 and L5-S1, concerning adhesions and arachnoiditis. The patient's unusual worsening of symptoms and a history of a durotomy defect with secondary repair led to suspicion of an alternative cause. Surgical exploration identified the left L5 nerve root herniated through the durotomy defect. Reduction of the nerve root herniation with primary repair of the durotomy was performed, and the patient experienced immediate relief that was stable at his one-month follow-up. This case features an unusual presentation of a delayed herniated nerve root through a prior durotomy defect with entrapment. We highlight the importance of a high degree of caution in cases of increased radicular pain following spinal surgery with a known durotomy, particularly when symptoms do not support the clinical presentation of arachnoiditis. Additionally, primary repair of durotomies should be undertaken whenever possible to avoid this potential complication.