Manual volumetric segmentation of brain hyperintensities on T2-weighted imaging (T2WI) and fluid-attenuated inversion recovery (FLAIR) sequences in children with neurofibromatosis type 1: inter-rater reliability and clinical correlates.

Background: Brain hyperintensities are frequently observed on T2-weighted imaging (T2WI) and fluid-attenuated inversion recovery (FLAIR) sequences of children with neurofibromatosis type 1 (NF1). This study aimed to quantitatively analyze the burden of brain hyperintensities in a large pediatric cohort of patients with NF1 using T2WI and FLAIR sequences, assess the inter-rater reliability of manual volumetric segmentation, and explore the relationship between hyperintensity volume and clinical correlates. Methods: A retrospective cross-sectional study was performed on the clinical and whole-body magnetic resonance imaging (WB-MRI) data of 108 children (aged <18 years) diagnosed with NF1 to analyze their clinical phenotypes and characteristics of brain hyperintensities. The volume of hyperintensities segmented manually was recorded on T2WI and FLAIR sequences, and the inter-reader reliability and consistency of segmentation were calculated. Multiple linear regression analysis was used to explore the relationship between cerebral hyperintensity volume and age, gender, and the presence of optic pathway gliomas (OPGs) or plexiform neurofibromas (PNFs). Results: Genetic testing identified 27.8% of 108 pediatric patients as familial cases. Clinical physical examination detected axillary/inguinal freckling (51.9%) and cutaneous neurofibromas (CNFs, 56.5%). WB-MRI revealed PNFs (74.1%)-distributed in the head and neck region, thoracoabdominal pelvis, and paravertebral plexus-as well as OPGs, characteristic bone lesions, and occasional moyamoya disease. Some 85 patients (78.7%) were found to have at least one hyperintensity, and the preferred locations were the cerebellar dentate nucleus (89.4%), brainstem (76.5%), and pallidum (72.9%). The mean age of children with hyperintensities in most brain regions ranged from 7.77 to 8.95 years, whereas the mean age in the deep white matter was relatively low (5.38 years). Intraclass correlation coefficient (ICC) and Bland-Altman plots showed good agreement between the two readers. Multiple linear regression analysis showed that the model was statistically significant (F=2.817, P=0.029). Hyperintensity volume was significantly negatively associated with age and OPGs, but not to gender or PNFs. Conclusions: WB-MRI enhances the detection rate of clinical phenotypes in NF1. On T2WI and FLAIR sequences, brain hyperintensities are relatively prevalent imaging findings in pediatric NF1 patients. Age and the presence of OPGs are independent predictors of hyperintensity volume.