IMAGING OF DYSEMBRYOPLASTIC NEUROEPITHELIAL TUMORS. A STUDY OF 6 CASES Amina EL KHAMLICHI*, Meriem FIKRI*, Yasser ARKHA**, Najoua ECH- CHERIF EL KETTANI*, My Rachid EL HASSANI*, Abdeslam EL KHAMLICHI**, Mohamed JIDDANE* PANARAB’12 * Department of Neuroradiology * Department of Neuroradiology ** Department of Neurosurgery Hôpital des Spécialités, CHU Ibn Sina, Rabat, Morocco NR28

Introduction Dysembryoplastic Neuroepithelial Tumors (DNTs) include a large morphological spectrum of tumors which carcinologically These tumors are seen in young patients with intractable partial epilepsy. Dysembryoplastic Neuroepithelial Tumors (DNTs) include a large morphological spectrum of tumors which histologically resemble gliomas but are carcinologically perfectly stable lesions. These tumors are seen in young patients with intractable partial epilepsy. The purpose of this study is to The purpose of this study is to evaluate CT and MRI features of dysembryoplastic neuroepithelial tumors.

Materials and methods Our study concerns 6 cases of between 1998 and Our study concerns 6 cases of dysembryoplastic neuroepithelial tumors histopathologically confirmed and diagnosed in patients who underwent corticectomies between 1998 and Table. Patient’s characteristics Characteristics No. of patients (n = 6) (%)  Sex: Male Male Female Female  Age: Mean (yr) Mean (yr) Range (yr) Range (yr) Adults (> 16 yr) Adults (> 16 yr) Children (< 16 yr) Children (< 16 yr)  Histological forms : Complex form Simple form No specific form ± 15 6 – % 33 % 67 % 83 % 0 % 17 %

Materials and methods Clinical symptoms : o Grand mal epilepsy (n = 2) o Pharmacoresistant partial seizures (n = 3) o Absence seizure (n = 1) o Symptoms beginning : * before age of 20 years : n = 4 * after age of 20 years : n = 2 o Symptoms of raised intracranial pressure (n = 1) o Neurological deficit (n = 0)

Materials and methods All patients underwent brain MRI and CT. All patients underwent brain MRI and CT. CT examination included axial and coronal sections before and after contrast administration. MRI examination included T1 and T2 axial, sagittal and coronal sections both pre- and postcontrast. FLAIR were also utilised.

Materials and methods Studied parameters : Studied parameters : Location and topography Location and topography Signal on T1, T2 Signal on T1, T2 Contrast enhancement Contrast enhancement Calcifications and cystic component Calcifications and cystic component Size Size Limits Limits Mass effect Mass effect Peritumoral edema Peritumoral edema

Results In all cases  a single focal supratentorial lesion on CT and MRI examinations Location :* Location : * Temporal lobes (67%) : right (n = 3) and left (n = 1) * * Right posterior parietal lobe (n = 1) * * Left frontotemporal lobe (n = 1) Case 3 Case 6 Case 4 Case 5

Results CT scan :* CT scan : * Hypodense lesion (n = 6) * * ± Calcifications (n = 3) * * Non-enhancing tumor or faint enhancement of solid portion. Case 2 Case 4 Case 1

Results MRI :* MRI : * Hypointense on T1-WI (n=6) * * Hyperintense on T2-WI and Flair images (n=6) Case 2 Case 6

Results Contrast enhancement :* Contrast enhancement : * Ring shaped (n = 3) * * Nodular pattern (n = 2) * * No enhancement (n = 1) Case 4 Case 5 Case 6

Results Lesion pattern :* Lesion pattern : * Pseudocystic, multilobulated (n=5) Case 6 Case 3 Case 5 Case 4

Results Mass effect : Mass effect : Minimal (n = 2), absent (n = 4) Peritumoral edema: Peritumoral edema: Minimal (n = 1), absent (n = 5) Case 2 Case 3 Case 4

Discussion 0.4 – 1.3 % of all brain tumors 0.4 – 1.3 % of all brain tumors Histopathology :  Specific glioneuronal element : columnar structure made up of bundles of axons lined by small tumoral oligodendrocytes.  3 histological forms : * simple : a unique specific glioneuronal element * complexe : - a specific glioneuronal element - a multinodular architecture - foci of cortical dysplasia * non specific : no specific glioneuronal element or multinodular architecture

Discussion Imaging Three : Three radiological features of DNT, not sensitive and not specific, are helpful for the diagnosis : cortical topography cortical topography no « digit like » peritumoral edema no « digit like » peritumoral edema no mass effect no mass effect CT scan : o Well-circumscribed hypodense lesion, which usually appears as non enhancing mass ± Focal enhancement in 21 % of cases ± Focal enhancement in 21 % of cases ± Calcifications in 36 % of cases ± Pseudocystic aspect in 50 % of cases ± « Scalloping » o Brain CT was reported as normal in 10 % of cases (isodense small lesion)

Discussion MRI +++: o T2 Weighted Images +++ o Tumor topography : cortex and/or subcortical white matter involvement o Hypersignal on T2 WI: 100 % o Polymorphic aspect : « nodular » (77%) or « megagyri » configuration (23%) o Tumor size : 8 – 60 mm o Microcystic pattern is common : « soap bubbles » appearance o True cyst is rare (7%) [size less to 1 cm]

Discussion Imaging features according to the histologically forms :  Simple form  pseudo-cystic, well delineated, homogenous appearance with no calcifications or any appearance with no calcifications or any enhancement after contrast examination enhancement after contrast examination  Complexe form  ring-like contrast enhancement, calcifications calcifications  Non specific form  nodular enhancement, « megagyri » pattern, calcifications pattern, calcifications

Discussion Positive diagnosis : The diagnosis of DNT must be considered when the following criteria are associated : o MRI : intracortical lesion with no mass effect and no peritumoral edema o Histological feature resemble gliomas but without lymphocytic infiltrates o Partial seizures o Partial seizures with or without secondary generalization o Symptoms beginning before 20 years of age o No neurological deficit or stable congenital deficit Differential diagnosis : * Ganglioglioma * Low grade oligodendroglioma * Low grade oligodendroglioma

Discussion Follow-up : * DNTs are carcinologically stable lesions * Absence of recurrences after total resection In our study, the mean follow-up was 21 months. One patient develop In our study, the mean follow-up was 21 months. One patient developed tumor recurrence appeared 2 years after incomplete primary resection

Conclusion DNTs is a recently defined category of tumors in young patients. These tumors histologically resemble gliomas but behave as stable lesions. MR imaging allows a better knowledge of their characteristic imaging features. Three radiological features of DNT are helpful for the diagnosis: cortical location, absence of mass effect and no peritumoral edema.

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