adld leukodystrophymetachromatic leukodystrophy symptomsdemyelinating leukodystrophymitochondrial leukodystrophycongenital leukodystrophygloboid leukodystrophyleukodystrophy diagnosisinfantile leukodystrophyleukodystrophy prognosisalexander leukodystrophymetabolic leukodystrophycerebral leukodystrophy