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Nonvestibular Schwannoma
KEY FACTS
Terminology
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Benign encapsulated nerve sheath tumor composed of differentiated neoplastic Schwann cells
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99% of all schwannomas associated with cranial nerves
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95% involve CN8
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< 1% of all intracranial schwannomas are intraparenchymal
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Imaging
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CT
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Iso- to slightly hyperdense compared with brain
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Adjacent bone, foramina may show smooth, scalloped enlargement
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Avid, sometimes heterogeneous enhancement
-
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MR
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Heterogeneously hyperintense on T2WI, FLAIR
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100% enhance (avid, heterogeneously)
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Peritumoral arachnoid cyst common
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Top Differential Diagnoses
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Cranial nerve schwannoma [enlarged, enhancing cranial nerve(s)]
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Metastases
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Lymphoma
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Multiple sclerosis
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Neurofibromatosis type 2
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Schwannomatosis
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Parenchymal schwannoma (rare)
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Ganglioglioma
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Pleomorphic xanthoastrocytoma
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Pilocytic astrocytoma
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Pathology
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Spindle-shaped neoplastic Schwann cells
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Single cell type with 2 basic histologic patterns
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High cellularity (Antoni A pattern)
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Low cellularity ± lipidization ± cystic degeneration (Antoni B pattern)
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Axial graphic depicts classic “dumbbell” trigeminal schwannoma. The dural ring of Meckel cave
constricts the expansile lesion, with the cerebellopontine angle (CPA) segment
and the Meckel cave segment
forming the dumbbell.
constricts the expansile lesion, with the cerebellopontine angle (CPA) segment and the Meckel cave segment forming the dumbbell.
Axial T1WI shows a typical “dumbbell” trigeminal schwannoma with the Meckel cave segment
and the large cerebellopontine angle segment
constricted in the middle by the ring of dura
at the entrance to Meckel cave.
and the large cerebellopontine angle segment constricted in the middle by the ring of dura at the entrance to Meckel cave.
Axial FLAIR in the same case shows that the lesion
is heterogeneously hyperintense relative to the cerebrospinal fluid in the 4th ventricle
and adjacent CPA cistern
.
is heterogeneously hyperintense relative to the cerebrospinal fluid in the 4th ventricle and adjacent CPA cistern .
T1 C+ FS in the same case shows that the trigeminal schwannoma enhances intensely but somewhat heterogeneously
. There is a small arachnoid cyst
adjacent to the tumor, a relatively common finding with cranial nerve schwannomas.
. There is a small arachnoid cyst adjacent to the tumor, a relatively common finding with cranial nerve schwannomas.
TERMINOLOGY
Abbreviations
-
Nonvestibular schwannoma (nVS)
Synonyms
-
Neurilemmoma, neurinoma
Definitions
-
Benign encapsulated nerve sheath tumor composed of differentiated neoplastic Schwann cells
IMAGING
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