Olfactory schwannoma-case report-

Abstract

Intracranial schwannomas preferentially arise from the vestibular branch of the eighth nerve, and rarely from the trigeminal nerve, facial nerve, and lower cranial nerves. Anterior cranial fossa schwannomas are extremely uncommon and few details about them have been reported. The patient was a 39-year-old woman whose chief complaints were anosmia and frontal headache for 2 years. The gadolinium (Gd)-enhanced magnetic resonance imaging (MRI) showed an extra-axial mass from ethmoid sinus to right frontal base region near the midline, with solid enhancement in lower portion and multicystic formation in upper portion. The tumor was totally resected via basal subfrontal approach. At operation, the tumor had cystic portion with marginal calcification and the anterior skull base was destructed by the tumor. The olfactory bulb was involved, and the tumor capsule did not contain neoplastic cells. The histopathological diagnosis was schwannoma. We report a rare case of anterior cranial fossa schwannoma with literature review.

Keywords: Olfactory nerve; Schwannoma.

Fig. 1

Contrast axial computerized tomography (CT) scan demonstrating large lobulated inhomogenous density tumor in right anterior cranial fossa area (A). Coronal CT scan showing erosion of the superomedial portion of right orbital wall and tumor localized in the cribriform plate (B). Three dimensional CT scan of the skull base demonstrating erosion of the cribriform plate (C).

Fig. 2

An axial magnetic resonance imaging (MRI) with gadolinium showing an extra-axial mass in the right frontal region near midline and elevating the right frontal lobe (A). On the coronal and sagittal MRI with gadolinium showing a solid enhancement in the inferior portion of tumor and multi-septated rim enhancement in the superior portion of tumor with extension to ethmoid sinus and periorbital area (B and C).

Fig. 3

Postoperative gadolinium enhanced axial (A) and coronal (B) magnetic resonance imaging scan demonstrating total tumor resection with mild hemorrhagic scar in previously tumor site.

Fig. 4

Histopathological examination of the surgical specimen showing the tumor consisted of alternating areas of compact, elongated cells (Antoni type A) and less cellularized tumor areas (Antoni type B) (H & E, ×200) (A and B). Photomicrographys of immunohistochemical examination showing the tumor cells were positive for S-100 protein (C) and negative for epithelial membrane antigen (IHC×400) (D).