A rare case of cellular schwannoma involving the trigeminal ganglion

Cystic trigeminal schwannomas

Trigeminal Schwannomas are less than 1% of intracranial tumors, of which only 7% have a cystic component. We documented 2 cases of males with cystic trigeminal Schwannomas, their symptoms, the diagnosis process and the imaging characteristics. In addition, a review of the literature is performed, with emphasis on the radiological classification of this rare entity, that constitutes a diagnostic challenge for the radiologist, who has an essential role in the approach to the disease and therefore in its management.

Intracranial cellular schwannomas: a clinicopathological study of 20 cases

AIMS

Cellular schwannoma is a specific subtype of schwannoma, prone to misinterpretation as a malignant neoplasm. Involvement of the intracranial compartment by these tumours is extremely rare. We aim to characterise this clinicopathological subgroup.

METHODS AND RESULTS

We identified a total of 20 cellular schwannomas with predominant intracranial involvement. The mean age of the patients at the time of surgery was 37 years (range = 16-81), with a slight female predominance (1.5:1 ratio). The most common sites were the eighth (n = 8) and fifth (n = 6) cranial nerves. Three tumours involved the anterior cranial fossa/olfactory groove, and a single case involved the glossopharyngeal nerve. All tumours met established criteria for cellular schwannoma, and were composed of interlacing fascicles of spindle cells lacking Verocay bodies with minimal Antoni B pattern and variable chronic inflammation and foamy histiocytes. Rare findings included haemosiderin deposition (n = 6), necrosis (n = 4), brisk mitotic activity (>10 mitoses per 10 high-power fields) (n = 2), focal epithelioid morphology (n = 2), myxoid areas (n = 2), neuroblastoma-like pattern (n = 1) and granular cells (n = 1). Immunohistochemical stains demonstrated expression of Schwann cell markers (S100 protein, SOX10, collagen IV) and preserved H3 K27 trimethylation in all cases tested. Fourteen patients had postoperative follow-up, ranging from 2 months to 21 years (mean = 66 months). In patients with follow-up, local recurrence/persistence developed in six cases; five tumours were initially incompletely resected. No metastatic disease or deaths were reported.

CONCLUSIONS

Intracranial cellular schwannomas share morphological and immunophenotypical features with cellular schwannomas at others sites may demonstrate locally aggressive growth but appear to lack metastatic potential.

CELLULAR SCHWANNOMA OF THE GREATER SUPERFICIAL PETROSAL NERVE PRESENTING WITH ABDUCENS NERVE PALSY AND XEROPHTHALMIA

OBJECTIVE

Cellular schwannomas (CS) are rare in the cranial space. This report is the first of a patient with a greater superficial petrosal nerve CS presenting with abducens nerve palsy and xerophthalmia.

CLINICAL PRESENTATION

A 16-year-old female patient presented with a 1-month history of diplopia. Neurological examination was normal except for the presence of right abducens nerve palsy. Schirmer's test revealed decreased tear secretion in the right eye. Computed tomography and magnetic resonance imaging showed a mass in the right petrous apex. It was thought that the schwannoma in our patient originated from the greater superficial petrosal nerve, based on the location of the tumor in addition to the absence of partial Horner's syndrome and a persistent decrease in tear secretion. INTERVENTION: The tumor was exposed with the use of a right subtemporal extradural approach and removed entirely. Pathological evaluation of the tumor revealed a CS.

CONCLUSION

The abducens nerve palsy improved completely in the follow-up period, but the decreased tear secretion did not resolve. CS is one of the subtypes of ordinary schwannomas and exhibits malignant features on microscopic examination, although it has a good clinical prognosis. No adjuvant treatment was applied because of the tumor's benign character. The greater superficial petrosal nerve schwannoma should be considered in the differential diagnosis of the abducens nerve palsy and petrous apex mass.