title: Petrous and sphenoid arachnoid cysts: diagnosis and management.
abstract: BACKGROUND
  Intraosseous arachnoid cysts are rare and difficult to diagnose. The purpose of this study was to describe the clinical and radiological semiology of petrous and sphenoid arachnoid cysts and to propose a specific management strategy.
  
  
  METHODS
  This was a retrospective, descriptive study of patients with arachnoid cysts, which utilized CT, MRI, and the patients' medical histories.
  
  
  RESULTS
  Ten patients were included in this study. On CT, the lesions were lytic with bony delineation. On MRI, the lesions exhibited the same signals as cerebrospinal fluid and were not enhanced after contrast. On fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted sequences, the arachnoid cysts' signal disappeared, which is a key feature for eliminating the diagnosis of cholesteatoma. Two patients underwent surgery because of misdiagnosis, either with a meningocele or a cholesteatoma.
  
  
  CONCLUSIONS
  MRI FLAIR and diffusion-weighted sequences, together with osseous CT scans, help to distinguish arachnoid cysts from meningoceles and avoid unnecessary surgeries with potential complications.
authors.affiliation: Department of Head and Neck Surgery, Lariboisière Hospital, AP-HP, Université Paris-Diderot, Sorbonne Paris-Cité, Paris, France.
authors.forename: Judith
authors.initials: J
authors.lastname: Adrien
authors.affiliation: Department of Head and Neck Surgery, Lariboisière Hospital, AP-HP, Université Paris-Diderot, Sorbonne Paris-Cité, Paris, France.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Verillaud
authors.affiliation: Department of Neurosurgery, Lariboisière Hospital, AP-HP, Université Paris-Diderot, Sorbonne Paris-Cité, Paris, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Bresson
authors.affiliation: Department of Head and Neck Surgery, Lariboisière Hospital, AP-HP, Université Paris-Diderot, Sorbonne Paris-Cité, Paris, France.
authors.forename: Hugo
authors.initials: H
authors.lastname: Tran
authors.affiliation: Department of Head and Neck Surgery, Lariboisière Hospital, AP-HP, Université Paris-Diderot, Sorbonne Paris-Cité, Paris, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Kania
authors.affiliation: Department of Head and Neck Surgery, Lariboisière Hospital, AP-HP, Université Paris-Diderot, Sorbonne Paris-Cité, Paris, France.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Sauvaget
authors.affiliation: Department of Neuroradiology, Lariboisière Hospital, AP-HP, Université Paris-Diderot, Sorbonne Paris-Cité, Paris, France.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Guichard
authors.affiliation: Department of Head and Neck Surgery, Lariboisière Hospital, AP-HP, Université Paris-Diderot, Sorbonne Paris-Cité, Paris, France.|EA REMES, Université Paris Diderot, Sorbonne Paris-Cité, Paris, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Herman
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016080:Arachnoid Cysts / Q000175:diagnosis* / Q000628:therapy*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D010579:Petrous Bone / Q000000981:diagnostic imaging / Q000473:pathology*; D011379:Prognosis; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013100:Sphenoid Bone / Q000000981:diagnostic imaging / Q000473:pathology*; D014057:Tomography, X-Ray Computed / Q000379:methods; D057832:Watchful Waiting; D055815:Young Adult
keywords: CT scan; fluid-attenuated inversion recovery (FLAIR) and diffusion weighted MRI; imaging assessment; intraosseous arachnoid cyst; meningocele