Brain MRI
Axial T1- and T2-weighted and FLAIR images show signal abnormalities with the appearance of cysts in the white matter predominantly in the posterior part of the brain.
Biochemical abnormalities
Cytochrome c oxidase activity is between 3 and 36% of the mean control values in skeletal muscle biopsies and between 25-60% of the mean control values in cultured skin fibroblasts. Activities of mitochondrial complexes I, II and III are within the normal range.
Neurological regression after the acute episode
Except for one of the subjects described by Melchionda et al. (2014), who never developed overt neurological symptoms, with the exception of variable tremor, the patients present dysarthria and gait difficulties at onset, which occurs in childhood between 2 and 5 years of age. The signs of regression include spastic tetraparesis, ataxia and sensorimotor polyneuropathy.
Outcome at recovery
The clinical phenotype either stabilizes or ameliorates after the acute episode. In some cases the neurological abnormalities are observed after an acute febrile illness possibly due to intercurrent infection. The motor function is frequently affected, leading to mild spastic tetraparesis and ataxia. The cognitive function is decreased in some cases and normal in others. The dysarthria can either resolve or remain.