title: Third nerve palsy caused by compression of the posterior communicating artery aneurysm does not depend on the size of the aneurysm, but on the distance between the ICA and the anterior-posterior clinoid process.
abstract: OBJECTIVE
  Third nerve palsy (TNP) caused by a posterior communicating artery (PCoA) aneurysm is a well-known symptom of the condition, but the characteristics of unruptured PCoA aneurysm-associated third nerve palsy have not been fully evaluated. The aim of this study was to analyze the anatomical features of PCoA aneurysms that caused TNP from the viewpoint of the relationship between the ICA and the skull base.
  
  
  METHODS
  Forty-eight unruptured PCoA aneurysms were treated surgically between January 2008 and September 2013. The characteristics of the aneurysms were evaluated.
  
  
  RESULTS
  Thirteen of the 48 patients (27%) had a history of TNP. The distance between the ICA and the anterior-posterior clinoid process (ICA-APC distance) was significantly shorter in the TNP group (p<0.01), but the maximum size of the aneurysms was not (p=0.534).
  
  
  CONCLUSIONS
  Relatively small unruptured PCoA aneurysms can cause third nerve palsy if the ICA runs close to the skull base.
authors: Department of Neurosurgery, National Hospital Organization Beppu Medical Center, Japan. Electronic address: ananm@hosp.go.jp.
authors: Mitsuhiro
authors: M
authors: Anan
authors: Department of Neurosurgery, National Hospital Organization Beppu Medical Center, Japan.
authors: Yasuyuki
authors: Y
authors: Nagai
authors: Department of Neurosurgery, Oita University Faculty of Medicine, Japan.
authors: Hirotaka
authors: H
authors: Fudaba
authors: Department of Neurosurgery, Oita University Faculty of Medicine, Japan.
authors: Takeshi
authors: T
authors: Kubo
authors: Department of Neurosurgery, Oita University Faculty of Medicine, Japan.
authors: Keisuke
authors: K
authors: Ishii
authors: Department of Neurosurgery, Kawano Neurosurgical Hospital, Japan.
authors: Kumi
authors: K
authors: Murata
authors: Department of Neurosurgery, Kawano Neurosurgical Hospital, Japan.
authors: Yoshinori
authors: Y
authors: Hisamitsu
authors: Department of Neurosurgery, Kawano Neurosurgical Hospital, Japan.
authors: Yoshihisa
authors: Y
authors: Kawano
authors: Department of Radiology and Neurosurgery, Nagatomi Neurosurgical Hospital, Japan.
authors: Yuzo
authors: Y
authors: Hori
authors: Department of Radiology and Neurosurgery, Nagatomi Neurosurgical Hospital, Japan.
authors: Hirofumi
authors: H
authors: Nagatomi
authors: Department of Neurosurgery, Oita University Faculty of Medicine, Japan.
authors: Tatsuya
authors: T
authors: Abe
authors: Department of Neurosurgery, Oita University Faculty of Medicine, Japan.
authors: Minoru
authors: M
authors: Fujiki
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017542:Aneurysm, Ruptured / Q000150:complications / Q000473:pathology*; D001921:Brain / Q000473:pathology*; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000150:complications / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015840:Oculomotor Nerve Diseases / Q000209:etiology* / Q000473:pathology*; D019291:Skull Base / Q000473:pathology*
keywords: ICA-APC distance; PCoA aneurysm; Third nerve palsy