title: Idiopathic fourth ventricle outlet obstruction successfully treated by endoscopic third ventriculostomy: a case report.
abstract: BACKGROUND
  Fourth ventricle outlet obstruction (FVOO) is a rare cause of obstructive hydrocephalus. We describe a case of idiopathic FVOO that was successfully treated with endoscopic third ventriculostomy (ETV).
  
  
  METHODS
  A 3-year old boy without any remarkable medical history presented with a headache and vomiting. Computed tomography (CT) images, which had incidentally been taken 2 years previously due to a minor head injury, showed no abnormality. Magnetic resonance imaging on admission showed tetra-ventricular hydrocephalus associated with the dilatation of the fourth ventricle outlets, without any obstructive lesions. However, CT ventriculography, involving contrast medium injection through a ventricular catheter, suggested mechanical obstruction of the cerebrospinal fluid (CSF) at the fourth ventricle outlets. Thus, the patient was diagnosed with FVOO and ETV was performed; the hydrocephalus was subsequently resolved. Although hydrocephalus recurred 1 year postoperatively, re-ETV for the highly stenosed fenestration successfully resolved this condition.
  
  
  CONCLUSIONS
  ETV should be considered for FVOO treatment, particularly in idiopathic cases without CSF malabsorption.
authors.affiliation: Department of Neurosurgery, Teine Keijinkai Hospital, 1-40, Maeda 1-12, Teine-ku, Sapporo, 006-8555 Japan ; Department of Neurosurgery, Hokkaido University Graduate School of Medicine, North 15 West 7, Kita-ku, Sapporo, 060-8638 Japan.
authors.forename: Yukitomo
authors.initials: Y
authors.lastname: Ishi
authors.affiliation: Department of Neurosurgery, Teine Keijinkai Hospital, 1-40, Maeda 1-12, Teine-ku, Sapporo, 006-8555 Japan.
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Asaoka
authors.affiliation: Department of Neurosurgery, Hokkaido University Graduate School of Medicine, North 15 West 7, Kita-ku, Sapporo, 060-8638 Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kobayashi
authors.affiliation: Department of Neurosurgery, Hokkaido University Graduate School of Medicine, North 15 West 7, Kita-ku, Sapporo, 060-8638 Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Motegi
authors.affiliation: Department of Neurosurgery, Teine Keijinkai Hospital, 1-40, Maeda 1-12, Teine-ku, Sapporo, 006-8555 Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Sugiyama
authors.affiliation: Department of Neurosurgery, Teine Keijinkai Hospital, 1-40, Maeda 1-12, Teine-ku, Sapporo, 006-8555 Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Yokoyama
authors.affiliation: Department of Neurosurgery, Teine Keijinkai Hospital, 1-40, Maeda 1-12, Teine-ku, Sapporo, 006-8555 Japan.
authors.forename: Sumire
authors.initials: S
authors.lastname: Echizenya
authors.affiliation: Department of Neurosurgery, Teine Keijinkai Hospital, 1-40, Maeda 1-12, Teine-ku, Sapporo, 006-8555 Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Itamoto
keywords: ETV; Endoscopic third ventriculostomy; FVOO; Fourth ventricle outlet obstruction; Hydrocephalus