title: Subtemporal transtentorial resection of cavernous malformations involving the pyramidal tract in the upper pons and mesencephalon.
abstract: BACKGROUND
  Lateral approaches to the brain stem for the resection of the cavernous malformations are preferred in order to avoid the structures within the floor of the fourth ventricle. The entry behind the pyramidal tract (PT) is usually carried out through the posterolateral surface of the brain stem. The more straightforward lateral approach below the temporal lobe is used rarely because of potential risks.
  
  
  METHODS
  The outcome after resection of the cavernomas involving the PT in the mesencephalon and the upper pons via the subtemporal transtentorial approach in nine patients was analysed. Mapping of the PT by direct electrical stimulation was used in the last four patients.
  
  
  RESULTS
  The subtemporal transtentorial approach enabled adequate exposure of the lateral and anterolateral surface of the midbrain and the upper pons. No adverse events from the elevation of the temporal lobe were encountered. Direct electrical stimulation using a bipolar electrode with the parameters of 100 Hz, 1 ms, and 3-9 mA evoked motor responses in three of four patients. It allowed placing the incision in the lateral surface of the midbrain behind the PT or between the fibres of the upper and the lower extremity. No worsening of the PT functions was observed in the series.
  
  
  CONCLUSIONS
  The subtemporal transtentorial approach enables adequate exposure of the lateral and the anterolateral surface of the mesencephalon and upper pons, allowing neurophysiological mapping of the PT and thus avoiding its damage during removal of the cavernoma.
authors.affiliation: Department of Neurosurgery, Comenius University, Derer's Faculty Hospital, Limbová 5, 811 04, Bratislava, Slovakia. juraj.steno@fmed.uniba.sk
authors.forename: Juraj
authors.initials: J
authors.lastname: Steňo
authors.forename: Ivan
authors.initials: I
authors.lastname: Bízik
authors.forename: Jana
authors.initials: J
authors.lastname: Steňová
authors.forename: Gabriela
authors.initials: G
authors.lastname: Timárová
mesh_terms: D000328:Adult; D001933:Brain Stem / Q000473:pathology / Q000601:surgery*; D020295:Brain Stem Neoplasms / Q000473:pathology / Q000601:surgery*; D002648:Child; D002675:Child, Preschool; D003388:Cranial Fossa, Posterior / Q000601:surgery; D005260:Female; D020786:Hemangioma, Cavernous, Central Nervous System / Q000473:pathology / Q000601:surgery*; D006801:Humans; D008297:Male; D008636:Mesencephalon / Q000473:pathology / Q000601:surgery*; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000379:methods*; D011149:Pons / Q000473:pathology / Q000601:surgery*; D011183:Postoperative Complications / Q000209:etiology / Q000517:prevention & control; D011712:Pyramidal Tracts / Q000473:pathology / Q000601:surgery*; D012189:Retrospective Studies; D013702:Temporal Lobe / Q000601:surgery; D055815:Young Adult