Frontal Lobe Intraparenchymal Schwannoma
- Background:
- Nerve sheath tumors, most common of which are schwannomas, account for 8% of primary brain tumors. They are benign in nature and mainly relate to cranial nerves; 90% involve the vestibular nerve.
- Intraparenchymal schwannomas are very rare and though their origin remains uncertain, possible explanations include:
- conversion of pial to Schwann cells
- periarterial and perivascular nerve plexus Schwann cell existence
- presence of similar myelinated cells in the tela choroidea
- Clinical Presentation:
- Is that of any other patient with a central nervous system mass: raised intracranial pressure, focal neurologic symptoms, and seizures
- Unlike vestibular schwannomas, they are most prevalent in children and young adults.
- Key Diagnostic Features:
- Superficial or periventricular in location; well-demarcated and rounded or oval in shape
- Hypo- or isointense on T1WI, heterogeneous on T2WI (likely owing to calcification), and demonstrates homogenous contrast enhancement
- Central necrotic or peripheral cystic areas are frequently seen, sometimes secondary to hemorrhage.
- Calcification is more commonly seen compared with vestibular schwannoma, as is perilesional edema and gliosis.
- Diffusion restriction is not present as in vestibular schwannoma.
- Differential Diagnoses:
- Lymphoma: often shows homogenous enhancement; however, would tend to restrict on DWI
- Infiltrative astrocytoma: lesion tends to be more heterogeneous with variable enhancement depending on the tumor grade
- Meningioangiomatosis: lesions often show minimal or no contrast enhancement and variable degree of calcification
- Histology:
- The morphology was typical of schwannoma, with mostly Antoni A pattern, formation of Verocay bodies, and S100-positivity.
- The pattern was not that of meningioangiomatosis, in which there is perivascular proliferation of spindle cells, which are S100-negative.
- The lack of GFAP and CD34 expression excludes a glioma and a solitary fibrous tumor, respectively.
- Treatment:
- Surgical resection: the prognosis is very good following resection, with recurrence being rare.
- Schwannomas are slow-growing tumors that involve the nerve sheath rather than the nerve itself, so they can often be resected separately.
