title: Histological analysis of clipped human intracranial aneurysms and parent arteries with short-term follow-up.
abstract: BACKGROUND
  Surgical clipping of intracranial aneurysms is the gold standard for the prevention of rupture. However, the biological processes that occur following clipping are poorly understood. To better understand these effects, retrieved and clipped human intracranial aneurysms were examined histologically.
  
  
  METHODS
  At autopsy, 17 aneurysms from 10 patients were retrieved 3-21 days after clipping. The tissues were embedded in paraffin, and microtome sections were stained using hematoxylin-eosin and Movat pentachrome. Using light microscopy, clip placement relative to the internal elastic lamina of the parent artery, endothelialization of the aneurysm neck, thrombus organization inside the aneurysm sac, inflammation in the sac, wall, and parent artery, and atherosclerotic changes were determined.
  
  
  RESULTS
  Despite complete reconstruction of the artery with the clip, diseased vessel wall was frequently observed outside the clip. By 10 days postsurgery, the beginnings of endothelialization and neointima formation were observed at the neck. However, the neck coverage was variable and incomplete at these early time points. Thrombus organization inside the aneurysm sac was rarely observed, and inflammatory cells were not present inside the aneurysm sac. Inflammatory cells were commonly observed in the aneurysm wall, and atherosclerotic change was present in each sample.
  
  
  CONCLUSIONS
  Complete aneurysm exclusion and apposition of healthy arterial wall occurred infrequently in our series. Endothelialization and neointima formation at the aneurysm neck take some time to complete and are often incomplete. The effectiveness of aneurysm clipping is related to the mechanics of aneurysm exclusion rather than the processes of endothelialization and neointima formation.
  
  
  CONCLUSIONS
  Complete aneurysm exclusion and apposition of healthy arterial wall occurred infrequently in our series. Endothelialization and neointima formation at the aneurysm neck take some time to complete and are often incomplete. The effectiveness of aneurysm clipping is related to the mechanics of aneurysm exclusion rather than the processes of endothelialization and neointima formation.
authors.affiliation: Research Institute of Neurointervention/Department of Neurology, Paracelsus Medical University, Christian Doppler Clinic, Ignaz Harrer Strasse 79, 5020 Salzburg, Austria. m.killer@salk.at
authors.forename: Monika
authors.initials: M
authors.lastname: Killer-Oberpfalzer
authors.forename: Martin
authors.initials: M
authors.lastname: Aichholzer
authors.forename: Serge
authors.initials: S
authors.lastname: Weis
authors.forename: Bernd
authors.initials: B
authors.lastname: Richling
authors.forename: Russ
authors.initials: R
authors.lastname: Jones
authors.forename: Renu
authors.initials: R
authors.lastname: Virmani
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Cruise
mesh_terms: D000328:Adult; D000368:Aged; D001158:Arteries / Q000473:pathology* / Q000601:surgery; D001167:Arteritis / Q000473:pathology; D050197:Atherosclerosis / Q000473:pathology; D001344:Autopsy; D004730:Endothelium, Vascular / Q000473:pathology / Q000503:physiopathology; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D058426:Neointima / Q000473:pathology / Q000503:physiopathology; D011183:Postoperative Complications; D013927:Thrombosis / Q000473:pathology