Anterior skull base olfactory tumours, which is what? A case report and review.

Intracranial schwannomas not originating from cranial nerves are rare. In this paper, we report a case of a 50-year-old male who presented with worsening headaches, diplopia and nausea over two years. Radiological imaging revealed a large tumour arising from the olfactory groove region with a preoperative diagnosis of olfactory groove meningioma (OGM). Intraoperatively, the tumour originated from the region of the attachment of the falx to the crista galli. The patient recovered without complication and histopathology reported an unexpected diagnosis of WHO Grade 1 schwannoma. However, as olfactory groove schwannomas (OGSs) cannot be distinguished from olfactory ensheathing cell tumours (OECTs), it is possible that the tumour could have been either an OGS or an OECT. Distinguishing between OGSs, OECTs and OGMs preoperatively is difficult. OGMs exhibit distinct histopathological features from OGSs/OECTs, however, OGSs and OECTs currently cannot be distinguished from each other. Here, we review the literature to discuss the differentiating features and cellular origins of these three tumours.