The Relationship Between Hematoma and Pachymeninges in an Interdural Hematoma: Diagnosis and Surgical Strategy

Background: The exact location of a hematoma in relation to the pachymeninges contributes to typical radiographic presentations. However, because of the complexity of hematoma evolution and neomembrane formation, an unexpected intraoperative finding can lead to a change of surgical strategy. In addition, the concentration of hemoglobin and its degradation products, the integrity of red blood cells, and the infiltration of fibroblasts, polymorphonuclear neutrophils, and macrophages are factors that affect the imaging characteristics on computed tomography and magnetic resonance imaging as the hematoma ages. Case Description: An interdural hematoma (IDH)—a hemorrhage that splits the periosteal dura mater from the meningeal dura mater—is an extremely rare occurrence, and the diagnosis requires confirmation by surgical or pathologic findings. By presenting a case of an IDH that was misdiagnosed as a chronic subdural hematoma before surgery, and reviewing the literature, we propose the radiologic characteristics of presenting both dural border sign and dural beak sign on magnetic resonance imaging as a specific indicator for IDH preoperatively. Conclusions: A careful evaluation of cerebral expansion before membranectomy was mandatory intraoperatively. For IDH, wide inner membranectomy (i.e., excision of meningeal dura mater) should not be necessary. An IDH should be considered as a distinct disease category when evaluating an extra-axial hematoma despite its rarity, because the characters of radiologic, histopathologic findings are different. In addition, surgical strategy varies for epidural or subdural hematoma in different hematoma stages.