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Endoscope-Assisted Retrosigmoid Intradural Suprameatal Approach for Surgical Treatment of Trigeminal Schwannomas

Samii, Madjid MD, PhD*; Alimohamadi, Maysam MD*,‡; Gerganov, Venelin MD, PhD*

doi: 10.1227/NEU.0000000000000478
Technique Assessment

BACKGROUND: Trigeminal schwannomas are the most common intracranial nonvestibular schwannomas, and the dumbbell-shaped subtype is the most challenging.

OBJECTIVE: To evaluate the efficiency and safety of the endoscope-assisted retrosigmoid intradural suprameatal approach (EA-RISA) for dumbbell trigeminal schwannomas and to compare EA-RISA with classic RISA.

METHODS: A retrospective study of all patients with trigeminal schwannomas was performed with a focus on dumbbell tumors. Tumors were classified according to a modified Samii classification. Extent of tumor removal, outcome, and morbidity rates in the 2 subgroups were compared.

RESULTS: Twenty patients were enrolled: 8 had dumbbell-shaped tumors (type C1), 8 had middle fossa tumors (A1-3), 3 had extracranial extension (D2), and 1 had posterior fossa tumor. Gross total resection was achieved in 15 and near-total resection in 5 patients. In 4 patients with dumbbell tumors, the classic RISA (Samii approach) was used; EA-RISA was used in the other 4 patients. The extent of petrous apex drilling was determined individually on the basis of the anatomic variability of suprameatal tubercle and degree of tumor-induced petrous apex erosion; in 2 patients, only minimal drilling was needed. The endoscope was applied after microsurgical tumor removal and in 3 of 4 patients revealed a significant unrecognized tumor remnant in the anterolateral and superolateral aspects of the Meckel cave. Thus, the EA-RISA technique allowed gross total resection of the tumor.

CONCLUSION: The EA-RISA enlarges the exposure obtained with the classic RISA. Its judicious use can help achieve safe and radical removal of dumbbell-shaped trigeminal schwannomas (C1 type).

ABBREVIATIONS: EA-RISA, endoscope-assisted retrosigmoid intradural suprameatal approach

GTR, gross total resection

NTR, near-total resection

RISA, retrosigmoid intradural suprameatal approach

STR, subtotal resection

*International Neuroscience Institute, Hannover, Germany;

Iranian International Neuroscience Institute, Brain and Spinal Injury Research Center, Tehran University of Medical Sciences, Tehran, Iran

Correspondence: Maysam Alimohamadi, MD, International Neuroscience Institute Rudolf-Pichlmayr-Straße 4D, 30625 Hanover, Germany. E-mail:

Received April 14, 2014

Accepted June 11, 2014

© 2014 by Lippincott Williams & Wilkins, Inc.
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