title: Endoscope-assisted retrosigmoid intradural suprameatal approach for surgical treatment of trigeminal schwannomas.
abstract: BACKGROUND
  Trigeminal schwannomas are the most common intracranial nonvestibular schwannomas, and the dumbbell-shaped subtype is the most challenging.
  
  
  OBJECTIVE
  To evaluate the efficiency and safety of the endoscope-assisted retrosigmoid intradural suprameatal approach (EA-RISA) for dumbbell trigeminal schwannomas and to compare EA-RISA with classic RISA.
  
  
  METHODS
  A retrospective study of all patients with trigeminal schwannomas was performed with a focus on dumbbell tumors. Tumors were classified according to a modified Samii classification. Extent of tumor removal, outcome, and morbidity rates in the 2 subgroups were compared.
  
  
  RESULTS
  Twenty patients were enrolled: 8 had dumbbell-shaped tumors (type C1), 8 had middle fossa tumors (A1-3), 3 had extracranial extension (D2), and 1 had posterior fossa tumor. Gross total resection was achieved in 15 and near-total resection in 5 patients. In 4 patients with dumbbell tumors, the classic RISA (Samii approach) was used; EA-RISA was used in the other 4 patients. The extent of petrous apex drilling was determined individually on the basis of the anatomic variability of suprameatal tubercle and degree of tumor-induced petrous apex erosion; in 2 patients, only minimal drilling was needed. The endoscope was applied after microsurgical tumor removal and in 3 of 4 patients revealed a significant unrecognized tumor remnant in the anterolateral and superolateral aspects of the Meckel cave. Thus, the EA-RISA technique allowed gross total resection of the tumor.
  
  
  CONCLUSIONS
  The EA-RISA enlarges the exposure obtained with the classic RISA. Its judicious use can help achieve safe and radical removal of dumbbell-shaped trigeminal schwannomas (C1 type).
authors.affiliation: *International Neuroscience Institute, Hannover, Germany; ‡Iranian International Neuroscience Institute, Brain and Spinal Injury Research Center, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Madjid
authors.initials: M
authors.lastname: Samii
authors.forename: Maysam
authors.initials: M
authors.lastname: Alimohamadi
authors.forename: Venelin
authors.initials: V
authors.lastname: Gerganov
mesh_terms: D000328:Adult; D000368:Aged; D035301:Cranial Fossa, Middle; D003388:Cranial Fossa, Posterior; D003390:Cranial Nerve Neoplasms / Q000473:pathology / Q000601:surgery*; D019723:Endoscopes; D005260:Female; D006801:Humans; D008297:Male; D008866:Microsurgery / Q000295:instrumentation*; D008875:Middle Aged; D009442:Neurilemmoma / Q000473:pathology / Q000601:surgery*; D012189:Retrospective Studies; D016896:Treatment Outcome; D020433:Trigeminal Nerve Diseases / Q000473:pathology / Q000601:surgery*; D055815:Young Adult