MARKED TISSUE EOSINOPHILIA WITHIN ORGANIZING CHRONIC SUBDURAL-HEMATOMA MEMBRANES

Chronic subdural hematoma (CSDH) with membranes is a common problem in neurosurgery. Despite its frequency, the pathogenesis of this lesion is poorly understood. We conducted a systematic pathologic review, wit h clinical correlation, of all CSDH presenting to our institution over a two-year period which had undergone pathological examination. Surpr isingly, we found marked tissue eosinophilia in most CSDH membranes in the process of organization. Eosinophils were not evident in fresh he morrhage or in older membranes which were completely organized. These results demonstrated that eosinophils are frequently present in large numbers in the early phases of chronic subdural membrane (CSM) formati on but not associated with chronic, organized membranes. No specific c linical cause for tissue eosinophilia was identified in the cases revi ewed. Though the significance of these observations remains unclear, r ecognition of eosinophilia as a pathological feature of organizing CSM is important in order to avoid confusion with other diagnoses.