Specific Imaging Findings. MRI shows diffuse cerebral white matter swelling and T2 hyperintensity with involvement of U-fibers and early appearance of typical subcortical cysts, particularly in the frontotemporal regions, best shown by FLAIR and T1WI. Over time these cysts may increase in size and number. The corpus callosum and internal capsules are relatively preserved. Subtle signal changes may be present within the brainstem, especially along the pyramidal tracts. Cerebellar white matter is usually of a mildly abnormal signal and not swollen. The deep gray matter structures are intact and there is no abnormal contrast enhancement. Brain atrophy develops on follow-up studies. A more benign variant is characterized by milder initial findings with subcortical cysts limited to the temporal region. In this form, the white matter abnormalities and cysts decrease over time. In adults with the disease, atrophy is present instead of brain swelling, with enlargement of the ventricles and other CSF spaces. On ADC maps there is increased diffusivity of the affected white matter. MRS shows decreased levels of all metabolites in cystic areas and decreased NAA within white matter lesions. Pertinent Clinical Information Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is characterized by early macrocephaly (developing during the first year of life) and delayedmotor and cognitive deterioration. Mild delay in gross motormilestones is followed by slowly progressive ataxia and spastic paraparesis. Mental deterioration and seizures develop in later stages of the disease. Minor head trauma may induce temporary deterioration. Extrapyramidal disorders (dystonia and athetosis), dysphagia and speech problems can appear in the second and third decades.
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