title: Supratentorial subdural hematoma following microvascular decompression: a report of four cases.
abstract: BACKGROUND
  Microvascular decompression has become an accepted surgical technique for the treatment of trigeminal neuralgia, hemifacial spasm, and other cranial nerve rhizopathies. However, critical complications still exist, and postoperative hemorrhage is one of the most life threatening complications following microvascular decompression. Most of the hemorrhages occur in the infratentorial region, and we found only four reports of supratentorial acute hemorrhages following microvascular decompression. Here, we report four cases of such hematomas and discuss the potential underlying mechanisms. Moreover, we discuss methods for handling such complications.
  
  
  METHODS
  Between 2004 and 2015, four patients developed postoperative hemorrhages, all of which were supratentorial subdural hematomas. The hematomas occurred ipsilaterally in two cases and contralaterally in two cases. All of the patients were treated conservatively and discharged without clinical symptoms.
  
  
  RESULTS
  Although several intracranial hematomas have been reported distant from the craniotomy site, few reports of remote subdural hematomas after microvascular decompression exist. Draining large amounts of intraoperative cerebrospinal fluid may induce brain shifts and tearing of the small bridging veins. Of our four cases, two were ipsilateral and two were contralateral, and the side of the hemorrhage may suggest possible mechanisms of remote subdural hematomas in microvascular decompression. Although a lateral position for microvascular decompression mainly extends ipsilateral bridging veins, a postoperative supine position can extend bilateral veins equally. Therefore, we assumed that, supratentorial subdural hematomas occurred when the patients were returned to the supine position at the end of the microvascular decompression surgery. We may be able to prevent supratentorial subdural hematomas with the application of sufficient amounts of artificial cerebrospinal fluid immediately after a microvascular decompression.
  
  
  CONCLUSIONS
  We suggest that it is important to avoid excessive CSF aspiration and to compensate for the cerebrospinal fluid loss with artificial cerebrospinal fluid adequately in order to avoid subdural hematomas after microvascular decompression. In addition, immediate postoperative CT scan is recommended even if the MVD has performed uneventfully.
authors.affiliation: Department of Neurosurgery, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192 Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Nozaki
authors.affiliation: Department of Neurosurgery, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192 Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Sugiyama
authors.affiliation: Department of Neurosurgery, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192 Japan.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Sameshima
authors.affiliation: Department of Neurosurgery, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192 Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kawaji
authors.affiliation: Department of Neurosurgery, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192 Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Namba
keywords: Acute subdural hematoma; Microvascular decompression; Remote hemorrhage; Supratentorial hemorrhage