Article
Geometric changes in the internal acoustic canal in vestibular schwannoma – prognostic significance for postoperative hearing preservation
Formveränderung des inneren Gehörgangs infolge eines vestibulären Schwannoms – Prognostische Bedeutung für den postoperativen Erhalt des Hörvermögens
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Published: | May 8, 2019 |
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Objective: We focused on the changes in the internal acoustic canal (IAC) caused by the tumor and their prognostic significance for patient’s postoperative outcome.
Methods: One hundred twenty-five consecutive patients surgically treated in our Institute for vestibular schwannoma were included in this study. The Hannover classification was used to assess the extension of the tumor. After automatic fusion of the CT and MRI sequences and its verification, the following measurements were performed on both tumor and healthy side: Volume (VIAC); maximal diameter of the IAC (DIAC) and length of the IAC (LIAC). A statistical analysis was performed.
Results: The mean VIAC on tumor and on healthy side were respectively 0.271 and 0.169 cm3. The mean DIAC was 9.438 on tumor side and 7.034 contralateral. The mean length of the canal was 10.192 on tumor and 9.810 on the healthy side. The correlations tests showed significant correlations of both postoperative hearing deficit and degree of hearing loss with:
- 1.
- VIAC on the tumor side;
- 2.
- the difference between the VIAC on the tumor and healthy side;
- 3.
- the DIAC on the tumor side;
- 4.
- the difference between the DIAC on the tumor and healthy side.
Conclusion: We observed that increased IAC volume and diameter are negative prognostic factors for hearing preservation. Hypnothetical mechanisms could be a long-standing compression of the auditory nerve and an increased vulnerability of the inner ear structures during the drilling of IAC.