Modified translabyrinthine approach and hearing preservation: imaging evaluation

Abstract

To establish if the computed tomography (CT) and magnetic resonance imaging (MRI) appearances of the vestibule, after the removal of vestibular schwannoma by a modified translabyrinthine approach, correlate with a successful outcome, defined as hearing preservation. Our study group consisted of 16 patients with vestibular schwannoma. All patients' pre-operative hearing was graded as class one or two according to the Gardner-Robertson scale. On MRI scans, the schwannoma, including the intracanalicular segment, were less than 2 cm in size in all the patients. The intracanalicular portion involved the fundus of the internal auditory canal in seven patients. In the remaining nine patients, the schwannoma had spread to involve two-thirds of the meatus, sparing its lateral third. The state of the labyrinth, in particular the integrity of the vestibule, was evaluated by CT scans and MRI prior to and following surgery. The schwannoma was completely removed in all patients. None showed any signs of persistence or tumoral relapse on the post-operative MRI. The final follow up showed that seven patients had maintained their hearing function (i.e. four patients with class one hearing and three with class two). The MRI vestibular signal on the T2-weighted images was well depicted only in patients with hearing preservation. Bony vestibular integrity was observed in the CT scans of all cases with hearing preservation, and also in three cases with failure of hearing preservation. Our results confirm that total isolation and maintenance of an anatomically intact vestibule, as depicted by MRI examination, is one of the fundamental factors for successful preservation of hearing function following modified translabyrinthine approach schwannoma removal.