Fourth ventricular schwannoma

Abstract

A schwannoma arising from the dorsum of the pontomedullary junction and presenting as an exophytic mass in the fourth ventricle is described. A ventricular schwannoma has not previously been reported in the literature. The presenting clinical and radiographic features and the pathology of this tumor are summarized, and an explanation is sought for its unusual location.

Tentorial Schwannoma Mimicking Meningioma -Case Report-

“…Several hypotheses have been suggested, such as origins in normal Schwann cells of the perivascular nerve plexus or meningeal branches of the trigeminal or anterior ethmoid nerves 5,8,14,15) ; ectodermal Schwann cells resulting from transformation of mesenchymal cells 4,7) ; seeded tumor cells 16) ; neural crest cells 7,12) ; sensory nerves supplying the tentorium 1) ; misplaced myelinated nerve fibers 11) ; and distorted embryogenesis. 13) The tumor in the present case showed no attachment to the surrounding cranial nerves, so may have originated from the tentorial branch of the trigeminal nerve. The tentorial branch of the trigeminal nerve branches from V1 and passes posteriorly, then distributes into the tentorium cerebelli.…”

Schwannoma of the Fourth Ventricle: The Eighth Case Report

“…Schwannomas correspond to 8% of brain tumors and 25% of spinal tumors (22). Most (95%) are extra-axial, but they can also be found within the brain and spinal cord parenchyma or ventricular system (4,16).…”

“…Although most commonly encountered in extra-axial locations, intra-axial schwannomas have been reported, including intraventricular lesions (4,5,7,8,13,20,25,27). Tumors arising specifically in the fourth ventricle are extremely rare and only 7 case reports have been described to date (14,16,18,22,29). Because Schwann cells do not cover the central nervous system, theories trying to explain the occurrence of intra-axial schwannomas are speculative (2, 4, 6-8, 12, 13, 16, 17, 19, 20, 22, 28, 29).…”

Intracerebral schwannomas: a rare disease with varying natural history

“…Schwann cells are not indigenous to the brain parenchyma. It has been proposed that the tumors arise from the differentiation of multipotent mesenchymal elements into Schwann cells, 20,21 conversion of the pial cells to Schwann cells, distorted embryogenesis, 40 displaced neural crest cells, 39 or misplaced myelinated nerve fibers. 13,36,38 Based on the frequent perivascular location of these tumors, an alternative pathogenic hypothesis includes these tumors arising from Schwann cells within the adrenergic nerve fibers of cerebral arterioles and the larger arteries within the subarachnoid space.…”

“…Schwann cell proliferation has been observed in patients following stroke or in individuals with diabetes mellitus. 8,34,40 On imaging, intracerebral schwannomas have been shown to display calcifications, cysts, and peritumoral edema. 19,30,31,50,57 Noncystic tumors have also been reported, most commonly in the frontal lobes.…”