title: Advances in open microsurgery for cerebral aneurysms.
abstract: BACKGROUND
  Endovascular techniques introduced strong extrinsic forces that provoked reactive changes in aneurysm surgery. Microsurgery has become less invasive, more appealing to patients, lower risk, and efficacious for complex aneurysms, particularly those unfavorable for or failing endovascular therapy.
  
  
  OBJECTIVE
  To review specific advances in open microsurgery for aneurysms.
  
  
  METHODS
  A university-based, single-surgeon practice was examined for the use of minimally invasive craniotomies, surgical management of recurrence after coiling, the use of intracranial-intracranial bypass techniques, and cerebrovascular volume-outcome relationships.
  
  
  RESULTS
  The mini-pterional, lateral supraorbital, and orbital-pterional craniotomies are minimally invasive alternatives to standard craniotomies. Mini-pterional and lateral supraorbital craniotomies were used in one-fourth of unruptured patients, increasing from 22% to 28%, whereas 15% of patients underwent orbital-pterional craniotomies and trended upward from 11% to 20%. Seventy-four patients were treated for coil recurrences (2.3% of all aneurysms) with direct clip occlusion (77%), clip occlusion after coil extraction (7%), or parent artery occlusion with bypass (16%). Intracranial-intracranial bypass (in situ bypass, reimplantation, reanastomosis, and intracranial grafts) transformed the management of giant aneurysms and made the surgical treatment of posterior inferior cerebellar artery aneurysms competitive with endovascular therapy. Centralization maximized the volume-outcome relationships observed with clipping.
  
  
  CONCLUSIONS
  Aneurysm microsurgery has embraced minimalism, tailoring the exposure to the patient's anatomy with the smallest possible craniotomy that provides adequate exposure. The development of intracranial-intracranial bypasses is an important advancement that makes microsurgery a competitive option for complex and recurrent aneurysms. Trends toward centralizing aneurysm surgery in tertiary centers optimize results achievable with open microsurgery.
authors.affiliation: Department of Neurological Surgery, University of California, San Francisco, San Francisco, California.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Davies
authors.forename: Michael T
authors.initials: MT
authors.lastname: Lawton
mesh_terms: D017542:Aneurysm, Ruptured / Q000601:surgery; D003399:Craniotomy / Q000379:methods; D006801:Humans; D002532:Intracranial Aneurysm / Q000209:etiology / Q000601:surgery*; D008866:Microsurgery / Q000379:methods; D009364:Neoplasm Recurrence, Local / Q000601:surgery*