Rare Lumbar Epidural Lesions: Differentiating Chronic Spontaneous Lumbar Epidural Hematoma from Lumbar Synovial Cyst-A Single-Center Comparative Study.

Background and Objectives: Chronic spontaneous lumbar epidural hematoma (CSLEH) is a rare condition that may mimic a lumbar synovial cyst clinically and radiologically, making accurate preoperative diagnosis challenging. This study aimed to compare the clinical and magnetic resonance imaging (MRI) characteristics of CSLEHs and lumbar synovial cysts and to identify features that may facilitate their preoperative differentiation. Materials and Methods: This retrospective single-center study included 16 adult patients who underwent surgical decompression for symptomatic extradural lesions located between T12 and S1 and were ultimately diagnosed with either CSLEH or lumbar synovial cyst. Based on definitive intraoperative findings with histopathological confirmation when applicable, patients were classified into a CSLEH group (n = 6) or a lumbar synovial cyst group (n = 10). Demographic characteristics, clinical presentation, MRI findings, lesion localization, neurological deficits, pain severity assessed using the Visual Analog Scale (VAS), and postoperative outcomes were compared between the groups. Results: Patients with CSLEHs had a significantly shorter symptom duration (p = 0.001), more frequent anticoagulant use (p = 0.008), and a higher prevalence of motor weakness (p < 0.001) and sensory deficits (p = 0.001) than those with lumbar synovial cysts. Preoperative pain severity was significantly greater in the CSLEH group (p < 0.001). No significant differences were observed in MRI signal characteristics or lesion distribution between the groups. Surgical decompression was associated with marked postoperative pain improvement in both groups, with a greater reduction in VAS scores (ΔVAS) in the CSLEH group (p = 0.007). No postoperative complications were observed. Conclusions: CSLEH should be considered in the differential diagnosis of lumbar synovial cyst, particularly in patients with a relatively short symptom duration, anticoagulant use, and progressive neurological deficits. Although conventional MRI remains essential for preoperative evaluation, substantial overlap in MRI characteristics may limit reliable differentiation between these entities. Integration of clinical and radiological findings may improve preoperative diagnostic suspicion, while surgical exploration can provide both definitive diagnosis and effective neural decompression.