Purpose or Case Report: Isolated developmental delay (IDD) is commonly encountered in daily practice and the cause is frequently unknown. Conventional MR Imaging usually fails to reveal an abnormality.MR Spectroscopy (MRS) can assess variations in metabolite ratios and correlate this with abnormalities in brain structure such as disorders of myelination. However, the normal ranges of these metabolites is not well established in children and vary by age. We sought to use the data from multivoxel 3T MRS to characterize the metabolite ratios in different parts of the brain as a function of age in children with IDD vs age-matched controls.
Methods & Materials: All MRI with MRS done on 3T for children with IDD between Jan to Oct 2018 at a tertiary pediatric hospital were reviewed after excluding patients with prematurity, metabolic disorders, trauma, syndromes or genetic abnormalities. (n=103, mean age 79m, range 7 to 214m)
MRI of age-matched controls with no delay who had MRI performed for other reasons and reported as normal were reviewed (n=52, mean age 83m, range 12 to 180m). There were a total of 39 pts <3 yr vs 116 >3 yr (98 M, 57 F).
NAA/Cho, NAA/Cr, Cho/Cr ratios from basal ganglia and thalami for right and left sides were recorded. ANOVA was performed to test for statistically significant (p<0.05) differences in metabolite ratios between children with IDD and controls and between children younger and older than 3 years.
Results: There was no statistically significant difference in metabolite ratios between the two groups. The NAA/ Cr and NAA/ Cho ratios showed a significant increase with age. There was significant regional variation, with higher metabolite ratios containing NAA in the thalami than basal ganglia. Cho/Cr ratios across all ages and locations had average values 1.08-1.23, and 95% CI upper bound 1.30-1.52. This did not vary significantly by age or between normal/dev delay. During this period MRS identified three patients with creatine deficiency.
Conclusions: Metabolite ratios at 3T multivoxel brain MR spectroscopy of children show typical changes, primarily an increase in NAA, with increasing age, in keeping with progressive brain maturation.Cho/Cr ratios up to 1.5 were normal, unaffected by age or presence of developmental delay. The developmental delay cohort had MRS profiles nearly indistinguishable from normal subjects of the same age. Overall, brain MR spectroscopy findings in young children should be interpreted cautiously, with an awareness of age-related normal variation.