Specific Imaging Findings

Desmoplastic infantile ganglioglioma (DIG) is an extra-axial mass consisting of a large cyst with a solid superficial component. The cystic portion is hypodense on CT, T1 hypointense and T2 hyperintense, with variable signal intensity on FLAIR images (isointense or slightly hyperintense to CSF). The cystic component is invariably associated with a mural, meningeal-based mass or plaque, which is iso- to slightly hyperdense on CT, isointense to gray matter on T1, with a typical very low signal intensity on T2-weighted images (due to its fiber-rich content). Post-contrast images show marked enhancement of the solid portion along with enhancement extending to the adjacent leptomeninges and dura. Typically it shows non-enhancing walls and may appear multilobulated due to the presence of septations; areas of enhancement may at times be present within the cystic septa. Calcification and hemorrhagic foci are usually absent whereas perifocal edema is variable and often very prominent. Diffusion imaging can demonstrate reduced diffusivity in the solid portion whereas MR spectroscopy shows elevated choline and reduced NAA peaks with near-normal myo-inositol levels. In rare cases, diffuse dissemination may be present at the time of diagnosis.

Pertinent Clinical Information

Affected infants present with asymmetric macrocrania, bulging of the fontanels and other nonspecific symptoms such as seizures and vomiting. DIG typically has a favorable prognosis, confirmed by absence of recurrence following surgical removal. However, incomplete excision occurs in about 30% of cases due to the lack of a definite cleavage between the tumor and the surrounding brain and sometimes due to infiltration of eloquent CNS structures.