title: Factors in the natural history of chronic subdural hematomas that influence their postoperative recurrence.
abstract: OBJECTIVE
  Factors affecting the postoperative recurrence of chronic subdural hematomas (CSDHs) have not been sufficiently investigated. The authors have attempted to determine features of CSDHs that are associated with a high or low recurrence rate on the basis of the natural history of these lesions and their intracranial extension.
  
  
  METHODS
  One hundred six patients (82 men and 24 women) harboring 126 CSDHs who were treated at Tokyo Kosei Nenkin Hospital between January 1989 and April 1998 were studied. Types of CSDHs were classified according to hematoma density and internal architecture, and the intracranial extension of the hematomas were investigated. The postoperative recurrence rate was calculated for each factor. Based on the internal architecture and density of each hematoma, the CSDHs were classified into four types, including homogeneous, laminar, separated, and trabecular types. The recurrence rate associated with the separated type was high, whereas that associated with the trabecular type was low. Chronic subdural hematomas are believed to develop initially as the homogeneous type, after which they sometimes progress to the laminar type. A mature CSDH is represented by the separated stage and the hematoma eventually passes through the trabecular stage during absorption. Based on the intracranial extension of each hematoma, CSDHs were classified into three types, including convexity, cranial base, and interhemispheric types. The recurrence rate of cranial base CSDHs was high and that of convexity CSDHs was low.
  
  
  CONCLUSIONS
  Classification of CSDHs according to the internal architecture and intracranial extension may be useful for predicting the risk of postoperative recurrence.
authors.affiliation: Department of Neurosurgery, Teraoka Memorial Hospital, Ashina gun, Hiroshima, Japan. hnakaguchi@hi-ho.ne.jp
authors.forename: H
authors.initials: H
authors.lastname: Nakaguchi
authors.forename: T
authors.initials: T
authors.lastname: Tanishima
authors.forename: N
authors.initials: N
authors.lastname: Yoshimasu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004322:Drainage; D005260:Female; D020200:Hematoma, Subdural, Chronic / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D015985:Precipitating Factors; D012008:Recurrence; D012720:Severity of Illness Index; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D017211:Treatment Failure