Characterisation of a Novel Radiological Entity in Neurofibromatosis Type 1 - Diffuse Neurofibromatous Tissue

Objectives: To describe the prevalence, demographics and characteristics of a novel radiological entity in neurofibromatosis type 1: diffuse neurofibromatous tissue (DNFT) Design: Aretrospective, descriptive review of MDT and radiology notes. Methods: Of the 1049 patients from the NF1 adult radiology MDT minutes (2009–2021), 77 patients with DNFT were identified and clinical data were collected. MRI scans from 20 DNFT cases were interpreted. Results: Although overall gender distribution of DNFT was roughly even, it was more prevalent in females (73.9%) at the sacroiliac joint—where this entity was most common (29.9%). DNFT often involves the fibrous part of the sacroiliac joint and is seen as diffuse, streaky infiltrating tissues that cause bone erosion without mass effect. The period prevalence of scoliosis and dural ectasia on corresponding spinal levels with spinal DNFT was 62.8 and 51.2%, respectively (n=43). Conclusions: This is the first reported descriptive study of DNFT in NF1 and the first to describe its MRI features in detail. The predilection for the sacroiliac joint and the possible associations with scoliosis and dural ectasia provide important insights that can form the basis for future studies whilst also suggesting the need for active surveillance of this tissue in NF1 patients.