title: [Chronic subdural hematoma associated with arachnoid cyst--study of the mechanism of its development].
abstract: A significant number of cases of chronic subdural hematoma associated with middle fossa arachnoid cyst has been reported in literature, but sufficiently tenable explanation for co-occurrence of both lesions has not yet proposed. In this study, authors try to elucidate mechanisms involved in development of chronic subdural hematoma and arachnoid cyst in the same patient. Eighteen cases with arachnoid cyst in the middle fossa were diagnosed by CT scan during last 5 years in our institute. Among these, five patients had chronic subdural hematoma additionally to their middle fossa arachnoid cyst. Analysis of clinical, roentgenological data and operative findings in our five cases and reviewing of cases reported so far in the literature makes clear the following characteristics in this pathological condition. 1) Patients of chronic subdural hematoma associated with arachnoid cyst were obviously younger than patients with usual chronic subdural hematoma. 2) Chronic subdural hematoma developed in the same side to the associated arachnoid cyst. 3) Characteristic changes in the skull on x-ray films indicated the long lasting existence of middle fossa arachnoid cyst. On the other hand, history of cases suggested that chronic subdural hematomas had developed within recent 1-3 months. 4) Intracranial pressure tended to remain normal or slightly elevate. 5) Abnormal, small veins which run on the surface of the membranous capsule of arachnoid cyst and bridge the Sylvian fissure were not infrequently found at operation. These veins were not able to visualized on routine angiography. On the basis of these clinical and pathological characteristics, authors infer a mechanism for development of subdural hematoma associated with arachnoid cyst. The presence of middle fossa arachnoid cyst must increase a compressibility of the intracranial content, especially of the ipsilateral cerebral hemisphere and it predisposes for development of chronic subdural hematoma.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000293:Adolescent; D000328:Adult; D001099:Arachnoid; D001927:Brain Diseases / Q000150:complications* / Q000601:surgery; D002908:Chronic Disease; D003560:Cysts / Q000150:complications* / Q000601:surgery; D006408:Hematoma, Subdural / Q000209:etiology* / Q000601:surgery; D006801:Humans; D008297:Male