Diffusion tensor imaging in trigeminal neuralgia: beyond the normal morphology

Abstract

BackgroundTrigeminal neuralgia (TN) is an electric-like recurrent pain of a sudden onset and is localized to the area supplied by the trigeminal nerve, and the patients are usually free in between the attacks. It’s one of the most common causes of facial pain and is commonly induced by mechanical irritation, and there’s strong evidence suggesting an insult at the trigeminal nerve root which is usually caused by a neurovascular compression. The aim of the study was to evaluate the role of diffusion tensor imaging (DTI) in the detection of microstructural changes of normal appearing trigeminal nerve in patients with trigeminal neuralgia and the correlation between DTI parameters and pain severity.ResultsThirty one cases were included in the study (16 patients with TN and 15 healthy controls) underwent MRI with diffusion tensor imaging. The fractional anisotropy (FA) values of the trigeminal nerves were recorded and then comparison between the affected and unaffected sides in TN patients and healthy controls was done, also the degree of FA reduction was correlated with the pain severity in TN groups. The mean FA value of the affected trigeminal nerves was 0.43 ± 0.083, while that of the unaffected sides was 0.56 ± 0.058. The mean FA value of the trigeminal nerves in the healthy controls was 0.54 ± 0.057. A significant statistical differences was found between affected and unaffected sides (P < 0.00001) and between the affected sides and healthy controls (P < 0.0003), while no statistically significant difference was detected between the unaffected side and the healthy controls. A strong negative correlation was found between the pain score and the degree of FA reduction (P < 0.001).ConclusionsDiffusion tensor imaging is a functional MRI technique which can detect the microstructural changes in the normal appearing trigeminal nerves in patients with trigeminal neuralgia with a strong negative correlation between the severity of pain and the degree of FA reduction of the affected trigeminal nerve.