Olfactory Schwannomas – A Case Series with Long-TermOutcomes

Abstract

Background: Olfactory schwannomas are rare tumors arising from olfactory groove whose pathogenesis is still not understood. Only a few case-reports are available and their long-term outcome remains vague. We report the surgical outcome of five patients of olfactory schwannomas with one having over twenty years of follow up.

Methods: A retrospective review all intracranial schwannomas operated at our centre over last 20 years was done from which five primary cases of tumor located in the subfrontal/anterior cranial fossa floor were analysed. Also, a systematic review of pertinent previous English language literature was conducted using PubMed.

Results: Four of five olfactory schwannoma cases were seen in young females. Anosmia/hyposmia and symtopms of raised intracranial pressure were the most common presentations. Radiologically, these tumors were solid cystic arising from olfactory groove having areas of haemorrhage and necrosis. Most of the lesions (5 out of 6 surgeries: one recurrent) were operated via the sub-frontal approaches, either lateral or anterior. We noted that the presence of bony erosion warrants a robust anterior cranial fossa floor repair, as postoperative cerebrospinal fluid rhinorrhoea was present in two out of three patients. These tumors had good planes of cleavage with the surrounding brain parenchyma but have the surgical challenge of identification and prevention of injury to anterior cerebral arteries. Aggressive resection could be achieved in all patients and long-term follow-up was favourable. Also, when resected completely, they do not require adjuvant therapy.

Conclusion: Though other anterior cranial fossa tumors are close differentials, olfactory schwannomas are unique in terms of clinical behaviour, histopathological profile and surgical excision philosophy, the latter being warranted by more frequent repair of the skull base. More evidences are required to support appropriate theories of origin of these tumors.