UBOs are defined as areas of increased T2 signal intensity without mass effect or contrast enhancement most commonly found in the cerebellum, brainstem, and basal ganglia. UBOs are present in 43% to 93% of children with NF1.
The objective of a recent study was to investigate the possibility of including the presence of UBOs as a diagnostic criterion for NF1 in children.
The study has concluded that the sensitivity for the presence of unidentified bright objects (UBOs) for the diagnosis of neurofibromatosis type 1 (NF1) is 70%, with a specificity of 100%.
Children aged 2 to 18 years were divided into two groups. The case group consisted of 40 children with at least two diagnostic criteria for NF1 as established by the National Institutes of Health. The control group consisted of individuals referred for routine MRI for other complaints not related to NF1. Exclusion criteria included the presence of intracranial disease, infection, radiotherapy, chemotherapy, or tumoral infiltration.
MRIs were acquired independently and analyzed by two neuroradiologists according to a protocol, which was to identify UBOs, their location, and the presence of mass effect, contrast enhancement, or restrictive diffusion.
Results of the Study
Forty patients were included in the case group and 48 patients in the control group. The mean age at presentation was 11 years in the case group and 7 years in the control group. UBOs were seen in 70% of children with a diagnosis of NF1 and in none of the children in the control group. The sensitivity of the presence of UBOs in patients with NF1 was 70%. Accordingly, the specificity was 100%, and the positive predictive value was 100%.
The basal ganglia was the region most affected, followed by the thalamus. There was no restrictive diffusion abnormality, and no mass effect was associated with the UBOs.
The high frequency and specificity of the UBOs in children suspected of having NF1 on MRI are particularly useful when only specific regions such as the basal ganglia, cerebellum, and brainstem are considered. The authors subsequently recommend the inclusion of the presence of UBOs as a diagnostic criterion for NF1 in children.
A literature review discussed by the authors reports that these observations have also been published by others. However, this paper includes a larger study sample. Also, the known decreased frequency of UBOs in older NF1 patients may make this finding less reliable when dealing with older teens.
Nonetheless, the study is helpful in tying together much of the observational data gathered on a daily basis by neuroradiologists who interpret these studies and may help in aiding to make or exclude a diagnosis.
Author: Basil Hubbi, MD
Lopes Ferraz Filho JR, Munis MP, et al. Unidentified Bright Objects on Brain MRI in Children as a Diagnostic Criterion for Neurofibromatosis Type 1. Pediatr Radiol; 2008; 38 (March): 305-310:
Tags: contrast, CT, diagnostic, EFE, MR, mri, neuro, Neurofibroma, Neurofibromatosis, Neurofibromatosis Type 1, PE, Positive Predictive Value, rad, radiologist, radiotherapy, SPECT, TEE, ubo, Unidentified Bright Objects, UTI