Diffuse Leptomeningeal Glioneuronal Tumor of Childhood

Abstract

Diffuse leptomeningeal glioneuronal tumor is a newly defined entity under the neuronal and mixed neuronal-glial tumors category in the 2016 World Health Organization classification of brain tumors. In this series, we report clinical, radiologic, and histologic findings in 7 cases of diffuse leptomeningeal glioneuronal tumor. Our cases and literature review indicate that the most characteristic imaging finding is diffuse intracranial and intraspinal nodular leptomeningeal thickening and enhancement. This is often associated with small cyst-like, nonenhancing lesions. It should be noted that tumors sometimes bear nontypical features, for example, presenting as a solitary spinal cord mass without leptomeningeal involvement or with a dominant intracranial mass. In children with characteristic imaging findings and without clinical features of infection, the radiologist has an opportunity to promptly raise the possibility of diffuse leptomeningeal glioneuronal tumor, and thereby, affect streamlined diagnostic evaluation.

FIG 1.

DL-GNT with diffuse leptomeningeal disease. Axial and coronal postcontrast T1-weighted (A and B) MR images demonstrate diffuse intracranial nodular/mass-like leptomeningeal enhancement. This is most prominent within the basilar cisterns, with masslike enhancement at the level of the optic chiasm (arrow). Also seen is abnormal enhancement extending along both cranial nerve VII/VIII complexes (arrows). Abnormal enhancement extending along cranial nerves is not uncommon in this entity. Sagittal T1-weighted postcontrast fat-suppressed image of the thoracic spine (C) shows thick, nodular leptomeningeal enhancement predominantly along the dorsal thoracic cord. The constellation of imaging findings seen in this case is the most commonly described in DL-GNT.

FIG 2.

DL-GNT with diffuse “cyst-like” foci of T2 prolongation involving the brain and spine. Coronal T2-weighted image of the brain (A) demonstrates numerous foci of T2 prolongation located predominantly along the leptomeningeal surfaces of the cerebellum. These did not enhance after contrast administration or suppress on FLAIR (not shown). Also seen is hydrocephalus with transependymal edema as evidenced by abnormal periventricular T2 prolongation. Sagittal T2-weighted image of the cervicothoracic spine (B) in a different patient shows numerous small cervicothoracic intramedullary cyst-like lesions expanding the spinal cord. These cyst-like lesions are very suggestive of DL-GNT.

FIG 3.

DL-GNT with dominant intracranial parenchymal mass. Axial noncontrast head CT in a patient with findings of hydrocephalus (A) shows ill-defined calcification within the right basal ganglia (arrow). Basal ganglia germinoma was initially considered in the differential diagnosis. Axial T2-weighted MR imaging (B) shows an ill-defined, slightly expansile area of T2 prolongation within the right putamen, thalamus, and caudate head overlapping with the calcified region demonstrated on CT (arrows). Minimal enhancement was seen in the right anterior thalamus (not shown). Axial T1-weighted postcontrast image (C) shows numerous foci of nodular supratentorial leptomeningeal enhancement lining the basilar cisterns. Despite the atypical-appearing mass involving central gray matter, the presence of characteristic diffuse supra- and infratentorial nodular deposits led to prospective consideration of DL-GNT in the differential diagnosis.

FIG 4.

DL-GNT with isolated spinal cord mass. Sagittal T1-weighted postcontrast image of the cervical spine (A) demonstrates a small focal enhancing mass (long arrow) expanding the lower cervical spinal cord. Scattered areas of linear leptomeningeal enhancement are also seen along the dorsal (short arrows) and ventral aspects of the cord. Sagittal T2-weighted and T1-weighted postcontrast images of the spine (B and C) in another patient demonstrate a large hypointense, enhancing intramedullary mass extending from T2 to T5, with associated large, septated syrinx. These 2 examples highlight that intramedullary masses in DL-GNT can exhibit different appearances.