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T2-weighted scans demonstrate extensive abnormal signal continuously from medulla through pons and midbrain into the thalami and basal ganglia bilaterally. Patchy further areas of isolated abnormal signal extend to the subcortical region of both cerebral hemispheres. There is no positive mass effect associated with these changes. The underlying ventricles and cortical sulci are normal in size for a patient of this age. T1-weighted scans show small areas of minimally elevated signal corresponding with T2 abnormal signal is in the deep white matter of the left frontal lobe.
Both diffusion restriction and amorphous contrast enhancement involves the inferior aspect of the right frontal lobe, extending as far inferiorly as gyrus rectus.
The predominant abnormality on both single voxel and chemical shift spectroscopy is slightly elevated choline to creatine ratio and reduced NAA. No significant lipid and lactate signal seen. No definite perfusion abnormality detected.
Extensive, predominantly white matter abnormality in the absence of mass effect makes demyelination the most likely cause. Contrast enhancement has been described in progressive multifocal leucoencephalopathy (PML) induced by some immunosuppressants. Gray matter involvement has also been described in single episode acute disseminated encephalomyelitis.
The apparently complete lack of mass effect, limited contrast enhancement and only slight choline elevation on MRS makes lymphoma less likely.