Quantitative MRI of dorsal root ganglion alterations in neurofibromatosis type 1 patients with or without pain.

Neurofibromatosis type 1 (NF1) is a genetic disorder characterised by skin and nervous system anomalies, primarily involving glial cells and nerve tumours. Pain, particularly chronic pain, is a significant but often overlooked symptom in NF1 patients, affecting their health-related quality of life. The dorsal root ganglion (DRG) is essential for pain signal transmission, yet in vivo studies of DRG in NF1 patients are lacking. This prospective study included 20 NF1 patients (8 with neuropathic pain) and 28 healthy controls. Magnetic resonance imaging (MRI) scans of lumbosacral DRG (L5 + S1) were performed using a 3-T scanner. Quantitative MRI techniques were applied to assess DRG volume, T2 relaxation time, and proton density (PD). Statistical analyses compared NF1 patients and controls, and NF1 patients with and without pain. NF1 patients had a significantly larger DRG volume and higher quantitative T2 and PD values compared to controls. Furthermore, DRG PD was significantly higher in NF1 patients with neuropathic pain than in those without pain. Receiver operator characteristic curve analysis identified DRG PD as the best discriminator of pain in NF1 patients, with an area under the curve of 0.84, indicating relevant and useful discriminatory power. NF1 patients showed objective macrostructural and microstructural DRG injury changes using dedicated DRG MRI, discriminating neuropathic pain status from non-pain status at the disease-symptom group level. These findings highlight the potential of DRG MRI to quantify DRG pathology in vivo and to determine the risk of functional pain status by imaging. The identification of structural and microstructural changes of the DRG by quantitative MRI provides a novel in vivo biomarker for understanding neuropathic pain mechanisms, pain risk assessment and treatment monitoring in NF1. Dorsal root ganglia (DRG) in NF1 are enlarged by 176.3% in MRI. In quantitative MRI of DRG NF1, T2 relaxation time is increased by 22.9% and PD by 8.4%. DRG PD can distinguish a painful from a non-painful NF1 phenotype.