Imaging findings and MRI patterns in a cohort of 18q chromosomal abnormalities

BACKGROUND AND PURPOSE: The abnormalities of long arm of chromosome 18 (18q) constitute a complex spectrum. We aimed to systematically analyze their MRI features. We hypothesized that there would be variable but recognizable white matter and structural patterns in this cohort.

MATERIALS AND METHODS: In this retrospective cohort study, we included pediatric patients with a proven abnormality of 18q between 2000-2022. An age and sex matched control cohort was also constructed.

RESULTS: Thirty-six cases, median MRI age 19.6 months (4.3 – 59.3), satisfied our inclusion criteria. Majority were females (25, 69%, F:M ratio 2.2:1). Fifty MR imaging studies were analyzed and 35 (70%) had delayed myelination. Two independent readers scored brain myelination with excellent interrater reliability. Three recognizable evolving MRI patterns with distinct age distributions and improving myelination scores were identified – PMD-like (9.9 months, 37), intermediate (22 months, 48) and washed-out pattern (113.6 months, 53). Etiologically, MRIs were analyzed across three subgroups - 18q- (34, 69%), trisomy 18 (10, 21%) and ring chromosome 18 (5, 10%). Ring chromosome 18 had the highest myelination lag (27, P value = 0.005) and multifocal white matter changes (P value = 0.001). Trisomy 18 had smaller pons and cerebellar dimensions (APD pons P value = 0.002, CC vermis P value <0.001 and TCD P value = 0.04).

CONCLUSIONS: In this cohort of 18q chromosomal abnormalities, MRI revealed recognizable patterns correlating with improving brain myelination. Imaging findings appear to be on a continuum with more severe white matter abnormalities in ring chromosome 18 and greater prevalence of structural abnormalities of pons and cerebellum in trisomy 18.

ABBREVIATIONS: 18q-: 18q deletion; CC: corpus callosum; CC-APD: CC anteroposterior diameter; FOD: fronto-occipital diameter; TCD: transverse cerebellar diameter; APD: anteroposterior diameter; CCD: craniocaudal diameter; MBP: myelin basic protein; PMD: Pelizaeus-Merzbacher Disease; GWMD: gray-white matter differentiation