Specific Imaging Findings

The childhood form of X-linked adrenoleukodystrophy (X-ALD) shows the typical parieto-occipital pattern (up to 85% of patients) with symmetric involvement of the white matter, splenium and posterior body of corpus callosum. The progression pattern is centrifugal and postero-anterior starting from the splenium with sparing of subcortical U fibers. Contrast enhancement and reduced diffusion at the advancing lesion margins are characteristic, corresponding to active demyelination, axonal damage and inflammation. CT may show dystrophic calcifications within the affected areas. Brain stem lesions involving the corticospinal, corticobulbar, visual, and auditory tracts are frequently associated. The frontal variant (about 15% of cases) shows involvement of the frontal periventricular white matter, the genu and anterior body of the corpus callosum and the anterior limbs of internal capsules; the outer borders of the lesions may enhance with contrast. The atypical presentation of childhood cerebral X-ALD (2.5% of cases) is characterized by combined but separate involvement of the frontal and parieto-occipital white matter. Central portions of the X-ALD lesions show high ADC and low FA values, correlating with histologic findings. In addition to nonspecific decrease in NAA with increased lactate and choline, MRS shows elevated myo-inositol levels, which correlate with disease severity.

Adrenomyeloneuropathy (AMN) in adults is characterized by spinal cord atrophy often with signal changes in the posterior limbs of the internal capsules, brainstem (with relative sparing of tegmental structures), and cerebellar white matter.