Hearing conservation surgery for acoustic tumors--a clinical-pathologic correlative study

Area of Science:

• Neurosurgery
• Otolaryngology
• Neuropathology

Background:

• Hearing preservation surgery for eighth nerve schwannomas aims to remove tumors while maintaining auditory function.
• Preoperative criteria, including tumor size (≤1.5 cm medial to porus acusticus), speech discrimination (≥80%), and hearing level (≤30 dB pure-tone average), are used to select surgical candidates.

Purpose of the Study:

• To histologically analyze eighth nerve schwannoma tissue from patients meeting established preoperative criteria for hearing preservation surgery.
• To evaluate the adequacy of current preoperative criteria in predicting successful hearing preservation.

Main Methods:

• Review of 22 cases of solitary eighth nerve schwannoma with available tissue for histologic fiber analysis.
• Assessment of tumor size, speech discrimination scores, and pure-tone averages against established preoperative criteria.
• Histologic examination of tumor-nerve interfaces to assess fiber integrity and infiltration.

Main Results:

• Only one of 22 cases met all three preoperative criteria; only three met any two criteria.
• Histologic analysis revealed significant cochlear nerve and eighth nerve trunk fiber destruction and tumor infiltration in all cases.
• Even the single case meeting all criteria showed severe infiltration, with no identifiable nerve fibers crossing the tumor in some sections.

Conclusions:

• Current preoperative criteria for selecting patients for hearing preservation surgery in eighth nerve schwannoma cases are inadequate.
• Significant histologic evidence of nerve damage suggests that complete tumor removal while preserving hearing may exceed current surgical capabilities.
• Further refinement of selection criteria and surgical techniques is necessary to improve hearing preservation outcomes.