Brain MRI and proton MRS findings in infants and children with respiratory chain defects

The aim of this study is to describe neuroimaging patterns in children with respiratory chain (RC) defects using magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy (MRS) and to assess their role in the diagnostic evaluation.

Neuroimaging studies of 49 children (newborn to 15 years old) with biochemical evidence of RC defect were reviewed. Patients were divided in 3 groups ("definite" = 24, "probable" = 14, "possible" = 11) according to Modified Adult Criteria for the diagnosis of RC defect. Eighty-one MRI studies were reviewed for deep gray and white matter changes, degree of myelination, cerebral and cerebellar atrophy, and 67 proton MRS studies were assessed for the presence or absence of lactate elevation, as well as NAA/Cr ratio. The findings were compared among the 3 groups with chi-square test.

All patients with "pure" myopathy had normal imaging studies. In patients with CNS involvement, significant differences in the frequency of imaging abnormalities among groups were found for deep gray matter (43 %/8 %/0 %; p = 0.01) and for the presence of lactate elevation on proton MRS (81 %/31 %/0 %; p = 0.001).

Brain MRI and proton MRS abnormalities were observed only in association with clinical CNS involvement. Deep gray matter signal abnormalities on structural imaging and lactate elevation on proton MRS were more frequently observed in the "definite" group and represent neuroimaging markers for RC mitochondriopathy.