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 Neurosurgery

Hôpital des Spécialités, CHU Ibn Sina, Rabat, Morocco

NR28

Introduction

• 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 evaluate CT and MRI features of dysembryoplastic neuroepithelial tumors .

Materials and methods• Our study concerns 6 cases of dysembryoplastic neuroepithelial

tumors histopathologically confirmed and diagnosed in patients who underwent corticectomies between 1998 and 2011.

Table. Patient’s characteristics

CharacteristicsNo. of patients

(n = 6) (%)

Sex: Male Female Age: Mean (yr) Range (yr) Adults (> 16 yr) Children (< 16 yr) Histological forms :

Complex formSimple formNo specific form

42

16 ± 156 – 26

24

501

67 %33 %

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 = 2o Symptoms of raised intracranial pressure (n = 1)o Neurological deficit (n = 0)

Materials and methods

• 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 :Location and topographySignal on T1, T2Contrast enhancementCalcifications and cystic componentSizeLimitsMass effectPeritumoral edema

Results• In all cases a single focal supratentorial lesion on CT and MRI

examinations• Location : * Temporal lobes (67%) : right (n = 3) and left (n = 1)

* Right posterior parietal lobe (n = 1)* Left frontotemporal lobe (n = 1)

Case 3Case 6 Case 4Case 5

Results• CT scan : * Hypodense lesion (n = 6)

* ± Calcifications (n = 3)* Non-enhancing tumor or faint enhancement of solid

portion.

Case 2 Case 4Case 1

Results• MRI : * Hypointense on T1-WI (n=6)

* Hyperintense on T2-WI and Flair images (n=6)

Case 2 Case 6

Results• Contrast enhancement : * Ring shaped (n = 3)

* Nodular pattern (n = 2)* No enhancement (n = 1)

Case 4 Case 5 Case 6

Results• Lesion pattern : * Pseudocystic, multilobulated (n=5)

Case 6

Case 3

Case 5

Case 4

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

Case 2 Case 3 Case 4

Discussion• 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

DiscussionImaging

Three radiological features of DNT, not sensitive and not specific, are helpful for the diagnosis :

• cortical topography• no « digit like » peritumoral edema• no mass effect

CT scan:oWell-circumscribed hypodense lesion, which usually appears as non

enhancing mass ± 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

involvemento Hypersignal on T2 WI: 100 %o Polymorphic aspect : « nodular » (77%) or « megagyri »

configuration (23%)o Tumor size : 8 – 60 mmo Microcystic pattern is common : « soap bubbles »

appearanceo 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 enhancement after contrast examination Complexe form ring-like contrast enhancement, calcifications Non specific form nodular enhancement, « megagyri » pattern, calcifications

DiscussionPositive 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

edemao Histological feature resemble gliomas but without lymphocytic

infiltrates o Partial seizures with or without secondary generalizationo Symptoms beginning before 20 years of ageo No neurological deficit or stable congenital deficit

Differential diagnosis : * Ganglioglioma * 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 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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