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Description
A man in his 20s presented with a 9 month history of anosmia, nasal obstruction and few episodes of confusion. He denied other symptoms such as seizures, epistaxis, headache or weight loss. Local ear, nose throat examination revealed a firm polypoidal mass in the posterior aspect of the right nasal cavity which was bleeding to touch.
MRI of the brain showed a large lobulated and dumbbell shaped heterogeneously enhancing mass expanding the right nasoethmoidal region with intracranial extension via the right cribriform plate. Foci of susceptibility dropout were seen, attributed to areas of calcifications or haemorrhagic changes. Some intracranial cystic alterations were also observed. The mass was not separable from the olfactory bulb. Overall, features were suggestive of an extra-axial tumour of the anterior cranial fossa with sinonasal extension (figure 1). Based on the clinical and imaging findings, our initial impression was esthesioneuroblastoma. The patient underwent endoscopic biopsy of right nasal mass. Histopathological sections examined revealed schwannoma with degenerative changes (figure 2).
(A,B) T2 axial and sagittal sequences showing a heterogeneously hyperintense T2 mass in the sinonasal region with extra-axial intracranial extension (arrows). Low-insensity foci were seen with which were attributable to calcifications or foci of haemorrhage. (C,D) The mass shows intense enhancement with areas of cystic change (arrowhead in C). Dumbbell shape of the mass was thought to be characteristic of esthesioneuroblastoma.
(A) Low power view showing hypo and hypocellular arrangement, (B) degenerative atypia, arrow pointing to nuclear atypia, (C) verocay body formation arrow pointing to nuclear palisade, (D) S-100 immunostaining. Features are consistent with schwannoma.
The patient was planned for neuronavigation guided bifrontal craniotomy for total resection of the tumour. Intraoperative findings were an off-white to yellowish moderately vascular extra-axial skull base lesion, eroding bone and extending into nasal cavity. Postoperative recovery was positive and on subsequent follow-up, nasal obstruction was relieved without evidence of relapse of the tumour.
Tumours of olfactory area are rare and include meningioma, adenoid cystic tumours, lymphoma, metastasis and esthesioneuroblastoma.1 2 Schwannomas are benign, slow-growing tumours originating from Schwann cells. Although they usually arise from vestibular division of eighth cranial nerve, rare cases are shown to arise from olfactory or optic nerve, even though they are devoid of Schwann calls.3 Radiological features of olfactory schwannomas include solid (57.5%) and cystic morphologies (30.3%), with varying contrast enhancement.2 3 Majority cases are midline with olfactory groove proximity.
According to our literature search, only few olfactory schwannomas have mimicked esthesioneuroblastoma with anterior cranial fossa involvement and paranasal sinus extension.4–7 However, none of these cases exhibited a characteristic dumbbell shaped configuration with involvement of the sinonasal cavity, as our case displayed. However, we propose that such lesions with haemorrhagic foci or cystic degeneration and well-circumscribed margins, without surrounding infiltration, should serve as a clue to radiologists, indicating a benign schwannoma. Due to its benign nature, total resection stands preferred treatment without adjunctive therapy. Relapses after total resection are therefore unlikely.8
Patient’s perspective
The diagnosis of a tumour initially filled me with apprehension, yet the revelation of its treatability was eye-opening for me. The day of the surgery arrived, and the hospital staff demonstrated utmost care and professionalism, putting me at ease before the procedure. Thankfully, the surgery went smoothly and as I woke up in recovery room, I felt a glimmer of hope for a healthier future. Now, I am grateful to say that I have fully recovered from the surgery. My sense of smell has returned. The medical team’s proficiency in both diagnosing and resecting was great, and my experience exemplifies how the symbiosis of medical prowess and genuine empathy can pave the way to successful recovery.
Learning points
Olfactory schwannoma is a rare tumour which is often underreported or misdiagnosed. Its origin in the anterior cranial fossa is still ambiguous.
Although a rarity, olfactory schwannoma should be kept in the differential diagnosis of extra-axial lesions of the anterior cranial fossa in young patients.
Olfactory schwannoma can present as dumbbell-shaped lesion with sinonasal extension via the cribriform plate and can mimic esthesioneuroblastoma.
Ethics statements
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Footnotes
Contributors The following authors were responsible for drafting of the text, sourcing and editing of clinical images, investigation results, drawing original diagrams and algorithms, and critical revision for important intellectual content: KK conceived the idea of the paper and wrote the initial draft with support from MMA. MMA performed data collection and analysis. ZA gave histopathological input as well as contributed to data interpretation. KH helped with design, supervision and overall planning. All authors contributed to critical review and approval of the final version of the manuscript. The following authors gave final approval of the manuscript: KK, MMA, ZA, KH.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.