Revision 64 for 'Dysembryoplastic neuroepithelial tumor'All Revisions
Dysembryoplastic neuroepithelial tumor
Dysembryoplastic neuroepithelial tumors (DNET) are benign (WHO Grade I) slow growing tumors arising from either cortical or deep grey matter. The vast majority are centered in cortical grey matter, arise from secondary germinal layers and are frequently associated with cortical dysplasia (up to 80% of cases). They characteristically cause intractable partial seizures (see temporal lobe epilepsy).
It is a mixed glial-neural neoplasm a multi-nodular architecture and a heterogenous cellular composition.
The temporal lobe is the most common location, but all parts of the CNS containing grey matter are potential locations.
- temporal lobe: over 60% of cases
- frontal lobe: 30% of cases
- caudate nucleus
- cerebellum: presentation is then more commonly with ataxia rather than seizures
- if cortical may scallop the inner table of of the skull vault (44-60%) but no erosion.
- the cranial fossa can be minimally enlarged at times
- calcification in 20-40% (more common histologically)
- low density
- no enhancement
Typically seen as a cortical lesion with hardly any surrounding vasogenic edema
- T1: generally low signal
- T2: generally high signal with high signal 'bubbly appearance'
- FLAIR: mixed signal intensity with bright rim sign (see case 2). This sequence is helpful in identifying the small peripheral lesions with similar intensity to CSF.
- DWI: no restricted diffusion
- GE (gradient echo): hemosiderin staining uncommon as bleeding into DNETs is only occasional; calcification is not infrequent
- SWI: areas of signal drop out may be seen.
T1 C+ (Gd):
- may show enhancement in ~20-30% of cases 5
- enhancement may be heterogeneous or a mural nodule
- MR spectroscopy: non-specific although lactate may be present
Treatment and prognosis
They demonstrate essentially no growth over time, although very gradual increase in size has been described. As expected prognosis is excellent and even though these lesions are often incompletely resected, tumor progression is uncommon. Additionally even in cases of incomplete resection, seizures frequently cease.
The differential diagnosis will depend on the location of the tumor.
If in the mesial temporal lobe consider
- tumors (in order of decreasing frequency)
See also: temporal lobe tumors