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

Characteristics No. 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 topography Signal on T1, T2 Contrast enhancement Calcifications and cystic component Size Limits Mass effect Peritumoral 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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