Lateral Intracanalicular growth of vestibular schwannomas and surgical planning

To assess the lateral growth pattern in adult patients with growing sporadic vestibular schwannomas (VSs) and to decide if repeat imaging is always necessary immediately preoperatively when determining the route of access for microsurgical excision.

Adults identified as having VS growth from serial scanning (3 scans per patient) between 1994 and 2007 in a single referral center. Neurofibromatosis Type 2 patients and those with tumor growth already to the fundus of the internal auditory canal were excluded.

Retrospective review of serial imaging.

Lateral growth (in millimeters) in the internal auditory canal.

Thirty subjects were identified who had continued serial imaging after documented growth, of whom 26 (87%)showed no lateral growth and 4 (13%) showed growth of 1 mm.This was determined over a median time period of 26 months(interquartile range, 20Y36.5 mo). The time frame between the second and third scans looked at the period of continued observation in this group of subjects in whom known previous tumor growth had occurred, which was 13 months (interquartile range, 9.25Y16.75 mo), and this is the most reliable time frame upon which a practice-changing decision regarding repeat scanning can be made from these data.

Sporadic VSs that are documented to be growing on serial imaging do not seem to grow to any significant degree in a lateral direction within the internal auditory canal.The results imply that scans performed within a year of any surgical intervention need not be repeated to assess concerns of any further lateral growth while accepting that repeat imaging may be required for other clinical reasons. Key Words:Internal auditory canal