title: Rapid resolution of symptomatic acute subdural hematoma: case report.
abstract: BACKGROUND
  Only a few cases showing spontaneous resolution of acute subdural hematoma (ASDH) have been reported. Several possible mechanisms of spontaneous resolution of ASDH have been reported. Two possible hypotheses have been suggested: (1) the hematoma is diluted by cerebrospinal fluid (CSF) due to tearing of the arachnoid membrane and is washed out, (2) the hematoma is compressed by the pressure produced by acute brain swelling and redistributed. In this article, we report a patient with a rapid spontaneous resolution of an ASDH and discuss the mechanisms.
  
  
  METHODS
  We experienced a case of a spontaneous resolution of symptomatic ASDH within only 3 hours. Characteristic serial changes on computed tomography (CT) corresponding to neurologic changes were obtained.
  
  
  RESULTS
  Serial CT findings showing changes corresponding to neurologic fluctuation were obtained. The characteristic features of the CT findings are as follows: (1) participation of CSF at the lateral portion of the hematoma was recognized during the early period after injury, (2) no cerebral contusion was identified, (3) acute cerebral swelling was not identified, (4) when the neurologic state deteriorated, the hematoma had not enlarged, but there was an increase in the low-density area corresponding to participation of the CSF and midline shift was recognized.
  
  
  CONCLUSIONS
  Spontaneous resolution of ASDH depends on both dilution due to CSF participation and redistribution of the blood; but acute cerebral swelling is not a necessary condition. Elasticity of the brain and absence of cerebral contusion obstructing the outflow of the cerebrospinal fluid is optimal.
authors.affiliation: Department of Neurosurgery, Seikeikai Hospital, Osaka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Matsuyama
authors.forename: T
authors.initials: T
authors.lastname: Shimomura
authors.forename: Y
authors.initials: Y
authors.lastname: Okumura
authors.forename: T
authors.initials: T
authors.lastname: Sakaki
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D006408:Hematoma, Subdural / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology; D006801:Humans; D008297:Male; D012075:Remission, Spontaneous; D014057:Tomography, X-Ray Computed