title: Development of a pontine cyst after endovascular coil occlusion of a basilar artery trunk aneurysm: case report.
abstract: OBJECTIVE
  Cyst formation within the brain parenchyma after endovascular coil occlusion of an intracranial aneurysm is a previously undescribed occurrence. We describe a 70-year-old woman who presented with a symptomatic pontine cyst 1 year after uncomplicated stenting and Guglielmi detachable coil occlusion of an unruptured basilar artery trunk aneurysm.
  
  
  METHODS
  A 70-year-old woman presented with an episode of transient dysequilibrium and gait difficulty. Magnetic resonance imaging and cerebral angiography demonstrated a 15-mm distal basilar artery trunk aneurysm. Endovascular stenting and coil occlusion of the aneurysm were performed without technical complications. One year after the initial treatment, the patient developed progressive dysarthria, dysphagia, diplopia, and left hemiparesis. A large pontomesencephalic cyst adjacent to the coiled basilar aneurysm was identified on magnetic resonance imaging scans.
  
  
  METHODS
  A subtemporal craniotomy and decompression of the pontomesencephalic cyst were performed. The patient's symptoms of brainstem dysfunction improved temporarily but recurred within 2 months, necessitating reoperation for cyst drainage and placement of a cyst-peritoneal shunt.
  
  
  CONCLUSIONS
  Intra-axial cyst formation after stenting and endovascular occlusion of an intracranial aneurysm is an unusual occurrence and should be considered in the differential diagnosis of new neurological deficits after endovascular treatment. The pathophysiological mechanism of cyst formation in this case is not known.
authors.affiliation: Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota 55905, USA. friedman.jonathan@mayo.edu
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Friedman
authors.forename: Jon I
authors.initials: JI
authors.lastname: McIver
authors.forename: Frederic P
authors.initials: FP
authors.lastname: Collignon
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Nichols
authors.forename: David G
authors.initials: DG
authors.lastname: Piepgras
mesh_terms: D000368:Aged; D021721:Balloon Occlusion / Q000009:adverse effects*; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects*; D001927:Brain Diseases / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000473:pathology; D001933:Brain Stem / Q000000981:diagnostic imaging* / Q000473:pathology*; D002533:Cerebral Angiography; D003560:Cysts / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000473:pathology; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging* / Q000473:pathology / Q000628:therapy*; D008279:Magnetic Resonance Imaging