Trigeminal Schwannoma - Case Report of a Rare Tumour

Abstract

Schwannomas are benign nerve tumours arising from the Schwann cells. Approximately 25-45% of schwannomas occurs in the head and neck region. Majority of schwannomas in the head and neck region arise from the vagus nerve. Trigeminal schwannomas account for about 0.2% of all intracranial tumours. Trigeminal schwannomas can originate from any section of the fifth cranial nerve, from the root to the distal extracranial branches, but majority develops from the Gasserian ganglion, usually growing in the middle cranium. Most common presenting symptom is facial pain. MRI is the imaging modality of choice and CT scan usually serves as a supplementary imaging especially for skull base tumours. 47 year old male patient presented to the outpatient department with complains of swelling over the left side of palate. Contrast enhanced CT scan demonstrated a large bilobed heterogeneously enhancing soft tissue lesion in the left infratemporal fossa with widened foramen ovale and extension of lesion into the Meckel's cave, larger contiguous component extending into ramus of mandible. MRI scan showed a large lobulated mass in the left masticator space with intracranial extension. Biopsy of the lesion was suggestive of schwannoma. The patient underwent left composite resection with dural repair and free flap reconstruction. Post operatively, on day 5 he developed features of meningitis for which he was treated conservatively and later discharged in stable condition. Trigeminal schwannomas are rare tumours with very low chance of malignant transformation which commonly presents with facial pain. MRI is the imaging modality of choice. Complete surgical excision is the treatment of choice.

Keywords: Infratemporal fossa; Schwannoma; Trigeminal nerve.

Fig. 1

MRI images – plain and contrast a,b – axial images ; c,d – coronal images ;e,f – sagittal images − 7.5 × 3.5 × 3.5 cm lobulated mass in the left masticator space with widening of foramen ovale and intracranial extension into meckels cave, inferiorly extending to molar region of mandible and marked widening of buccal and lingual cortex with multiple areas of cortical breach ,posteriorly extending into ramus of mandible, laterally displacing masseter, medially displacing pterygoid muscles

Fig. 2

Specimen showing bilobed trigeminal schwannoma

Fig. 3

a. Section show spindle cells with mild nuclear pleomorphism arranged in interlacing bundles b. Thick walled vessel c. Numerous hemosiderin laden macrophages d. Necrosis e. Verocay bodies f. IHC - S100 positive g. IHC - Ki67 less than 1%

Fig. 4

Classification of trigeminal schwannomas – Ramina et al.