title: Cognard type V intracranial dural arteriovenous shunt: case reports and literature review with special consideration of the pattern of spinal venous drainage.
abstract: BACKGROUND
  Prompt diagnosis of intracranial dural arteriovenous shunt (DAVS) with spinal venous drainage, classified as Cognard type V, is difficult. We investigated the angiographic and magnetic resonance imaging (MRI) characteristics of Cognard type V DAVS to determine the reason for the difficulty in early diagnosis.
  
  
  METHODS
  We systematically reviewed 54 published and 3 new cases of Cognard type V DAVS. The pattern of venous drainage was classified on the basis of relative dominance of the anterior and posterior spinal veins with the use of angiograms. T2-weighted sagittal MRIs were used to detect signal flow voids of enlarged spinal veins. Types of venous drainage were determined in 49 of the 57 cases. Twenty-eight and 8 cases showed a dominance of anterior and posterior spinal venous drainage, respectively. In 13 cases, venous drainage was equally distributed through the anterior and posterior spinal veins. Of 41 cases with an abnormally dilated anterior spinal vein, MRIs were available for 25 cases. Signal flow voids of enlarged anterior spinal veins were detected in 9 cases (36.0%), whereas dilatation of the posterior spinal veins was apparent in 9 of 16 cases (56.3%). Overall, MRI detected enlargement of either anterior or posterior spinal veins in 15 of 41 cases (36.6%).
  
  
  CONCLUSIONS
  In Cognard type V DAVS, anterior venous drainage is dominant. Because the anterior spinal veins are located subpially, flow voids are less prominent on sagittal T2-weighted MRI. This may lead to difficulties in diagnosing. Evaluation with MR angiography may compensate for these limitations.
authors.affiliation: *Department of Neurosurgery and ‡Department of Neuroendovascular Therapy, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan §Department of Neurosurgery, Kohnan Hospital, Sendai, Miyagi, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Haryu
authors.forename: Toshiki
authors.initials: T
authors.lastname: Endo
authors.forename: Kenichi
authors.initials: K
authors.lastname: Sato
authors.forename: Takashi
authors.initials: T
authors.lastname: Inoue
authors.forename: Akira
authors.initials: A
authors.lastname: Takahashi
authors.forename: Teiji
authors.initials: T
authors.lastname: Tominaga
mesh_terms: D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000175:diagnosis*; D018810:Magnetic Resonance Angiography; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D013116:Spinal Cord / Q000098:blood supply* / Q000473:pathology; D014680:Veins