Epilepsy associated tumors: Review article

Abstract

Long-term epilepsy associated tumors (LEAT) represent a well known cause of focal epilepsies. Glioneuronal tumors are the most frequent histological type consisting of a mixture of glial and neuronal elements and most commonly arising in the temporal lobe. Cortical dysplasia or other neuronal migration abnormalities often coexist. Epilepsy associated with LEAT is generally poorly controlled by antiepileptic drugs while, on the other hand, it is high responsive to surgical treatment. However the best management strategy of tumor-related focal epilepsies remains controversial representing a contemporary issues in epilepsy surgery. Temporo-mesial LEAT have a widespread epileptic network with complex epileptogenic mechanisms. By using an epilepsy surgery oriented strategy LEAT may have an excellent seizure outcome therefore surgical treatment should be offered early, irrespective of pharmacoresistance, avoiding both the consequences of uncontrolled seizures as well as the side effects of prolonged pharmacological therapy and the rare risk of malignant transformation.

Keywords: Dysembryoplastic neuroepithelial tumor; Epilepsy; Epilepsy surgery; Ganglioglioma; Glioneuronal tumors; Lesionectomy; Long-term epilepsy associated tumors; Low grade tumors.

Figure 1

Ganglioglioma World Health Organization grade I of the right posterior middle temporal gyrus. Axial FLAIR T2-w (A) and coronal IR T1-w (B) images show inhomogeneous cortical-subcortical mass extending within the deep white matter and reaching the ependymal layer. The tumor presents a combination of solid, cystic and calcified components. The latter is better identified on coronal T2*-w sequence (C). Post-contrast axial T1-w image (D) shows no pathological enhancement and axial CT scan (E) confirms the calcified component. Coronal IR T1-w image (F) demonstrates lesion resec-tion; G: Histological examination evidences a biphasic neoplastic population, with neu-ronal and glial elements.

Figure 2

Gangliocytoma and Mesial Temporal Sclerosis MTS (dual pathology). Coronal Flair T2 (A) and T1-w images (B) demonstrate a right hippocampal atrophy with signal hyperintensity on FLAIR. The ipsilateral temporal horn is dilated. Axial T1-w pre- (C) and post-contrast injection (D) show a non-enhancing multicystic lesion with calcification near the optic tract. The right mammillary body is atrophic (arrowhead); E: Neoplastic ganglion cells exhibit disorganized clusters and show abnormal cytologic features; F: Hippocampal specimen displays ILAE hippocampal sclerosis type 1, with severe pyramidal cell loss in both CA1, CA3 and CA4 sectors.

Figure 3

Ganglioglioma World Health Organization grade I of the left temporo-mesial cortex. The tumor shows heterogeneous cortical-subcortical high signal on axial proton density weighted image (A). It appears partially cystic on coronal IR T1 (B) FLAIR T2 (C), T1 (D) weighted sequences. Post-contast T1-w image displays nodular, intense and homogenous enhancement (E). Low-magnification view shows a vaguely lobulated, hypocellular vascularized neoplasia, with scattered lymphocytic infiltrates (F).

Figure 4

Ganglioglioma and associated focal cortical dysplasia IIa. Coronal FSE T2-w (A, B) demonstrate a temporo-mesial heterogeneously hyperintense lesion. Post-contrast coronal T1-w (C) shows enhancement of the tumor and adjacent leptomeninges. A signal abnormality extending from the surface of the ventricle to the pole (arrowheads in D) and adjacent anomalous sulci (arrow in A) were suspicious for FCD, subsequently histologically confirmed. Microscopy evidenced a tumor composed of ganglion cells intimately intermixed with astrocytic elements (E) and focal cortical dysplasia with dysmorphic neurons (FCD Type IIa) (F).

Figure 5

DNET of the right uncus. Axial T2-w (A) and sagittal 3D T1-w (B) reveal a cystic cortical mass well-demarcated, without perilesional oedema or mass effect. On coronal FLAIR T2-w image (C) the tumor is variably hypo- and isointense. Post-contrast axial T1-w sequence (D) shows no enhancement. Histological examination shows a tu-mor characterized by the “specific glioneuronal element”, typical of DNET, (E), while the cortex adjacent to the tumor displays cortical lamination abnormalities compatible with FCD type IIIb (F); the latter was not depicted at MR study.

Figure 6

Extra temporal DNET. Sagittal 3D T1 (A) coronal IR T1 (B) and FLAIR T2-w (C) demonstrate a cystic wedge-shaped lesion in the right fronto-orbital gyrus. On FLAIR T2-w the tumor is slightly hypointense with a faint hyperintense rim. On post contrast coronal T1-w images there is no enhancement uptake (D); E: Post-surgical scan on cor-onal IR T1-w; F: Microscopic study evidences the presence of floating neurons, a feature of DNET, in microcystic areas lined with oligo-like cells.

Figure 7

Pleomorphic xanthoastrocytoma World Health Organization grade II. Axial T2 w (A) and coronal IR T1-w (B) images show temporo-polar mixed signal intensity cortical mass with a small cystic component anteriorly (arrow in A). Post-contrast coronal SE T1w (C) shows a well-delineated, peripherally located enhancing nodule. (D) Microscopically the tumor is characterized by huge cytologic atypia, a vaguely fascicular arrangement and scattered eosinophilic granular bodies.

Figure 8

Pilocytic astrocytoma World Health Organization grade I of the right frontal lobe. Axial FLAIR T2-w (A) and coronal lR T1-w (B) images show a cortical-subcortical lesion, with cystic component, with minimal mass effect. The tumor appears well de-marcated (C) on 3D sagittal sequence and displays nodular and homogeneous en-hancement on post-contrast axial T1-w images (D). Perfusion study doesn’t show any rCBV increase within the lesion (E). MR Spectroscopy (MRS) study (F) reveals elevation in choline and reduction in NAA. (G) Histological examination shows a tumor com-posed of areas rich in myxoid material, elongated glial elements with uniform nuclei and numerous eosinophilic granular bodies.

Figure 9

Temporo-mesial astrocytoma World Health Organization grade II. Axial FLAIR T2-w (A) shows a left temporal hyperintense mass, involving mainly the hippocampus. The lesion is slightly hypointense on T1-w image (B) and does not demonstrate enhancement after gadolinium injection (C). Perfusion study reveals no significant rCBV increase (D). MRS study shows a faint NAA reduction, a slight Cho elevation and high mI, expression of low grade glioma (E). Postsurgical axial FLAIR T2-w (F). (G) This histological picture exhibits in the left side a portion of hippocampus and in the right side an infiltrating astrocytoma, composed of fibrillary elements with varying degree of hypercellularity.

Figure 10

Focal cortical dysplasia with balloon cells (Taylor). Axial (A) and sagittal (B) reformatted fat-saturated 3D FLAIR images show a left temporo-mesial cortical thicken-ing (arrow) and white matter tapering to the temporal horn of the lateral ventricle (arrowheads). MR spectroscopy shows normal metabolite concentrations (C). (D) Histol-ogy demonstrates the presence of typical balloon cells, showing large and opalescent glassy eosinophilic cytoplasm.

Figure 11

Gangliogliomas World Health Organization grade I of the left temporo-mesial region and focal cortical dysplasia IIa subtype associated. Axial and coronal T1-w images (A-B) show thickening of amygdala and uncus (arrow in B). Axial and coronal FLAIR T2-w images (C-D) present blurring and adjacent subcortical high signal abnormality compatible with a focal cortical dysplasia (FCD). Microscopy evidenced a glioneuronal tumor, with scattered binucleated ganglion cells, compatible with a gan-glioglioma (E) and dysmorphic neurons in the adjacent cortex (FCD Type IIa) (F).

Figure 12

Gangliogliomas and focal cortical dysplasia IIa. Sagittal 3D T1-w (A), coronal FLAIR T2-w (B) and axial T2-w (C) reveal an inhomogeneous mass, involving the right hippocampus and the temporal pole. Due to the size of the tumor, the associated dysplasia is not clearly visible. Histological examination demonstrates the presence of a glioneuronal tumor with small ganglion cells in a desmoplastic stroma (D) and of dysmorphic neurons in the adjacent cortex (focal cortical dysplasia Type IIa) (E).