Systematic review of WHO grade 4 astrocytoma in the cerebellopontine angle: the impact of anatomic corridor on treatment options and outcomes

Background: Despite advances in multimodal oncologic therapies and molecular genetics, overall survival (OS) for high-grade astrocytomas remains poor. We present an illustrative case and systematic review of rare, predominantly extra-axial WHO grade 4 astrocytomas located within the cerebellopontine angle (CPA) and explore the impact of anatomic location on diagnosis, management, and outcomes. Methods: A systematic review of adult patients with predominantly extra-axial WHO grade 4 CPA astrocytomas was conducted following the PRISMA guidelines through December 2022. Results: 18 articles were included comprising 21 astrocytomas: 13 exophytic tumors arising from cerebellopontine parenchyma, and 8 tumors originating from a cranial nerve root entry zone. Median OS was 15 months with one-third of cases demonstrating delayed diagnosis. Gross total resection, molecular genetic profiling, and use of ancillary treatment were low. We report the only patient with an integrated IDH-1 mutant diagnosis, who, after subtotal resection and chemoradiation, remains alive at 40 months without progression. Conclusion: The deep conical-shaped corridor and abundance of eloquent tissue of the CPA significantly limits both surgical resection and utility of device-based therapies in this region. Prompt diagnosis, molecular characterization, and systemic therapeutic advances serve as the predominant means to optimize survival for patients with rare skull base astrocytomas.