Skull Base 2011; 21 - A068
DOI: 10.1055/s-2011-1274243

T3 and T4 Samii Classification of Acoustic Neurinomas: Detailed Operative Technique and Pitfalls to Preserve the Facial Nerve

Paulo H. Pires de Aguiar 1(presenter), Rogério Aires 1, Romulo Marques 1, Marcos V. Maldaun 1, Antonio M. Souza Filho 1, Carlos A. Zicarelli 1, Márcio F. Lehmann 1, Alexandros T. Panagopoulos 1, Renata F. Simm 1
  • 1São Paulo, Brazil

Objectives: The neurosurgeon should be experienced in the attempt to preserve hearing and facial function in acoustic neurinoma. The most difficult tumors to preserve the function are the T3 and T4 Samii classification neurinomas (T3S and T4S) due to volume, brainstem distortion, and neurovascular structures involved. The retrosigmoid approach is very important for the removal of acoustic neurinomas, especially when hearing preservation is attempted.

Methods: The authors presented their casuistic based on 15 T3S and 24 T4S neurinomas found in a review of 74 microsurgically treated acoustic neurinomas and 8 that were radiosurgically treated. Four patients with neurofibromatosis were excluded from the surgical casuistic, and only the sporadic neurinomas were included. The data from historical, clinical, radiological, and surgical records were reviewed, and the intraoperative details were analyzed.

Results: The rate of facial preservation was 100% in T1 schwannomas, 100% in T2 schwannomas, 86.67% in T3 schwannomas, and 86.67% in T4 schwannomas. The rate of preservation of hearing in this series was 92.85% in T1 schwannomas, 100% in T2 schwannomas, 46.67% in T3 schwannomas, and 16.67% in T4 vestibular schwannomas. Subtotal removal was accomplished in two patients with T3 schwannomas, and seven patients with T4 schwannomas, with small residual tumor in acoustic meatus. The overall rate of total removal was 90.55% in all groups.

The specific rate of resection was 100% of total removal in T1 schwannomas, 100% in T2 schwannomas, 86.67% (13/15) in T3 schwannomas and 75% (18/24) in T4 schwannomas. Six cases in 74 patients (8.1%) presented CSF postoperative leakage; in T3, we found 1 case in 15 (6.67%) and in T4 we found 5 cases in 24 (20.83%). Three cases had voluminous postoperative hydrocephalus.

Conclusion: The retrosigmoid access is a safe and effective approach for acoustic neurinomas, and T3S and T4S may be removed completely with good results for facial function; however, the results for functional hearing are still poor, even with the use of intraoperative-evoked potential.