adld leukodystrophyhypomyelinating leukodystrophymetachromatic leukodystrophy symptomsdemyelinating leukodystrophymitochondrial leukodystrophycongenital leukodystrophygloboid leukodystrophyleukodystrophy diagnosisleukodystrophy prognosisalexander leukodystrophymetabolic leukodystrophycerebral leukodystrophy