title: A suggestion of modified classification of trigeminal schwannomas according to location, shape, and extension.
abstract: BACKGROUND
  Comprehensive knowledge of the anatomical features of trigeminal schwannomas (TSs) is essential in planning surgery to achieve complete tumor resection. In the current report, we propose a modified classification of TSs according to their location of origin, shape, and extension into the adjacent compartment, and discuss appropriate surgical strategies with this classification.
  
  
  METHODS
  We retrospectively analyzed 49 patients with TS who were treated surgically by a single neurosurgeon at the Asan Medical Center between 1993 and 2013.
  
  
  RESULTS
  There were 22 males and 27 females, with the median age of 40 years (range, 21-75 years). Median tumor size was 4.0 cm in diameter (2.0-7.0 cm). Tumors were classified as follows: Type M (confined to the middle fossa; 8 cases, 19.0%), P (confined to the posterior fossa; 2 cases, 4.8%), MP (involving equally both middle and posterior fossae; 5 cases, 11.9%), Mp (predominantly middle fossa with posterior fossa extension; 6 cases, 14.3%), Pm (predominantly posterior fossa with middle fossa extension; 16 cases, 38.1%), Me (predominantly middle fossa with extracranial extension; 4 cases, 9.5%). Surgical approach was chosen depending on the tumor classification. More specifically, a frontotemporal craniotomy and extradural approach with or without zygomatic or orbitozygomatic osteotomy was applied to M- or Mp-type tumors; a lateral suboccipital craniotomy with or without suprameatal approach was applied to the majority of P- or Pm-type tumors; and a posterior transpetrosal approach was used in four tumors (three Pm and one MP). Gross total resection was achieved in 95.9% of patients, and the overall recurrence rate was 4.1% (2 patients). Postoperatively, trigeminal symptoms were improved or unchanged in 51.0% of cases (25 patients). Surgical complications included meningitis (5 patients) and cerebrospinal fluid leakage (3 patients). There was no mortality.
  
  
  CONCLUSIONS
  TSs are well to be classified with our modified classification and able to be removed effectively and safely by selecting appropriate surgical approaches.
authors.affiliation: Department of Neurosurgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Seong Kyun
authors.initials: SK
authors.lastname: Jeong
authors.affiliation: Department of Neurosurgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Eun Jung
authors.initials: EJ
authors.lastname: Lee
authors.affiliation: Department of Neurosurgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Yun Hee
authors.initials: YH
authors.lastname: Hue
authors.affiliation: Department of Neurosurgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Young Hyun
authors.initials: YH
authors.lastname: Cho
authors.affiliation: Department of Neurosurgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jeong Hoon
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Chang Jin
authors.initials: CJ
authors.lastname: Kim
keywords: Classification; Neurilemmoma; Surgical procedure; Trigeminal nerve