Diffuse high-grade glioma with gliomatosis cerebri pattern mimicking symmetric white matter disease.

Diffuse gliomas with gliomatosis cerebri (GC) growth pattern are rare infiltrative tumors whose radiological presentation frequently mimics non-neoplastic white matter diseases. Strictly bilateral and symmetric involvement represents an exceptionally rare presentation, powerfully evoking leukodystrophy or metabolic leukoencephalopathy and constituting a major diagnostic pitfall. We report a 46-year-old woman with a 7-month history of progressive cognitive decline, dysarthria, and spastic paraparesis. CT demonstrated a hypodense corpus callosum lesion without enhancement. MRI revealed diffuse bilateral and remarkably symmetric T2/FLAIR white matter hyperintensities extending through the corpus callosum without gadolinium enhancement. Diffusion-weighted imaging showed focal restricted diffusion at lesion margins and within the splenium. MR spectroscopy demonstrated elevated choline (Cho/Cr ≈2), decreased N-acetylaspartate, prominent myo-inositol elevation, and a subtle creatine increase. Stereotactic biopsy confirmed high-grade diffuse glial proliferation with 5 mitoses per 10 high-power fields and IDH wild-type status. Unlike previously reported GC cases mimicking demyelinating disease with asymmetric multifocal involvement and low-grade histology, this case is distinguished by its strict bilateral symmetry and high-grade IDH wild-type biology. Symmetry does not exclude malignancy, and multimodal advanced MRI is essential to avoid diagnostic delay.