Schwannomas of C1: A Novel Classification and Description of Growth Patterns Based on a Personal Series and Review of Literature.

Abstract

Background: Schwannomas of C1 are rare tumors. Because of the wide variation in their anatomy, and presentation and their rarity, there is no proper understanding of their pathological anatomy nor their optimal management.

Methods: A retrospective study of the C1 schwannomas operated by the author between 2000 and 2020 and a PubMed-based search of English literature were done to analyze data on the location and extent of the lesions, surgical approaches used, and operative outcomes. Using this data, a classification system was created indicating the location and extent of these lesions, depending on whether they were extradural (E) or intradural (I); with further subdivisions based on their relation to the vertebral artery, and cervicomedullary junction (CMJ).

Results: Six patients with C1 schwannoma were operated by the author in the said period. Literature search yielded 44 cases in 16 publications. The details of location and extent of tumor were available in 22 patients including six of this article. Most of the tumors were intradural (13/22), with six in intradural and extradural compartments. Specific growth patterns were identified and a theory for this is proposed. Different surgical approaches were used; the far lateral and the posterolateral in 9 patients each, and the posterior midline in 7 of 25 patients. Using the available data, preferred surgical approaches are also presented.

Conclusions: C1 schwannomas are a rare and complex group of tumors. The classification presented will help in understanding the growth pattern and pathological anatomy and choose the preferred surgical approach.