Remote leptomeningeal dissemination in olfactory neuroblastoma mimicking multiple parasagittal meningiomas: a diagnostic and therapeutic challenge

Background Olfactory neuroblastoma (ON) is a highly aggressive and locally recurrent neoplasm. Distant systemic metastases are not uncommon, but remote leptomeningeal dissemination is extremely rare. Case Description We report 2 cases of ON previously treated with endoscopic endonasal radical surgical resection and radiotherapy. After a relatively long period of disease-free survival, multiple leptomeningeal lesions were seen around the sagittal sinus giving a radiologic appearance of parasagittal meningiomas. Both patients underwent surgery and multimodal treatment with radiotherapy and chemotherapy for the disseminated disease. Pathologic examination confirmed the parasagittal lesions as metastatic ON. Conclusions A high suspicion of secondary disease should be maintained in patients with previous history of ON and parasagittal leptomeningeal enhancing lesion, particularly when multiple lesions are detected around the sagittal sinus. Radical resection and multimodal treatment are warranted to improve long-term outcome. Understanding the venous drainage route as a potential pathway for remote seeding from the primary site of disease has therapeutic implications. We postulate that en-bloc tumor resection and proximal sagittal sinus ligation might reduce potential for leptomeningeal metastasis.