Imaging findings
These tumors are very difficult to identify in CT. If seen, they will appear as non-enhancing low attenuation lesions in the subcortical white matter.
Well circumscribed high T2 signal 'bubbles' located predominantly in the subcortical white matter.
T1: Hypointense.
T2/FLAIR: Hyperintense.
Contrast enhancement T1: No enhancement.
Diffusion: Absence of restricted diffusion.
Case Report
31-year-old men under study due to recent generalized tonic-clonic epileptic seizures.
Right temporoparietal corticosubcortical lesion, microcystic, hyperintense in T2 / FLAIR and with no contrast enhancement or alterations in perfusion maps (Fig 4, 5, 6, 7, 8, 9, 10, 11, 12).
68-year-old men with a left temporoparietal lesion suggestive of MVNT in follow-up for years.
Radiological follow-up shows that the left temporal lesion remains stable in terms of morphology, size and signal respect to previous MRI studies, finding indicative of the benignity of this type of lesions.
(Fig 13,14,15,16,17,18).
57-year-old woman in study due to recent headache.
Micronodular lesion in the right parietooccipital subcortical region, hypointense in T1 sequence, hyperintense in T2 / FLAIR sequences, with no enhancement after contrast administration and no perfusion map alterations.
(Fig. 19,20,21,22).
Differential diagnosis:
Dysembryoplastic-neuroepithelial-tumor - DNET
The are usually cortical, rather than subcortical lesions.
They often has hyperintense ring sign, which is described as a well defined rim of high signal, complete or incomplete, around the DNET on FLAIR sequences.
Focal cortical dysplasia (type II)
High T2 signal deep to the cortex usually associated with a radial glial band (transmantle sign) and with thickened abnormal overlying cortex.
Perivascular spaces
Usually more elongated along vessel long axis.
Hypointense on FLAIR.
Treatment and prognosis:
Because MVNT are benign tumors, they can, if asymptomatic, be followed by imaging alone. In symptomatic patients surgical resection is the treatment of choice.