ADRENOLEUKODYSTROPHY-MRI

X-linked recessive disorder which occurs due to deficiency of peroxisomal enzyme Acyl Coa Synthetase. It is a white matter demyelination involving occipital lobes and splenium in bilateral and symmetric pattern (demyelination moves from centre to periphery). Males between 3-10 yrs of age are affected. Auditory pathways are involved commonly with sparing of subcortical white matter. On NECT, large symmetric low density lesion are seen in peritrigonal parieti-occipital white matter. Enhancement is noted in advancing rim surrounded with peripheral nonenhancing edematous zone. Calcifications may be seen. On MRI, central necrotic zone appears low on T1, high on T2. Intermediate zone enhances following contrast administration. Peripheral zone appears hypointense on T1 and high on T2. In one study, published in AJNR Vol 18, Issue 1, medullary and pontine corticospinal tract involvement was present in eight out of ten patients with ALD. So, pontomedullary corticospinal tract involvement is a common finding in ALD and is unusual in other leukodystrophy. On diffusion weighted images, advancing rim of demyelination shows restricted diffusion and appears as bright signal which is very well documented in our case.