Incidence and distribution of neomembranes of dura mater.

Membranous or membranous-haemorrhagic lesions of the dura mater were found in 46 out of 1,044 consecutive necropsies after excluding those cases where their presence could be interpreted in terms of blood dyscrasia, local neoplastic processes, previous surgery, or marked craniocerebral trauma. The extent of old and recent manifestations of haemorrhage in the membranes increased in a statistically significant relation with their size and thickness. Lesions of different types, or degrees, respectively, were often combined in the same case; a remarkably high incidence of membranous lesions in the falx cerebri was noted. The observations indicate the presence of a progressive, repetitive process in neomembrane formation.