High-resolution diffusion MRI can help map the microstructure of the trigeminal nerve, improve treatment options for trigeminal neuralgia sufferers

The researchers noted that the pathophysiology of trigeminal neuralgia (TN) remains unknown and present treatments are conducted based on empirical evidence. Up to now, MRI has only been used to exclude other pathological conditions such as skull base tumors -- which can mimic TN -- but not to localize the affected area, improve treatment methods or evaluate the effects of such procedures.

For the study, researchers sought out to demonstrate the feasibility and advantages of ultra-high field diffusion MRI at the skull base, which could lead to improved TN characterization. Healthy volunteers were scanned on a 7T Siemens scanner with the following protocol: T1-, T2- and PD-weighted structural MRI with resolution 0.3x0.3x0.6mm3; diffusion MRI with 0.6x0.6mm2 in-plane resolution, 18 slices of 1.2mm, 100 gradient directions at b-value=1000s/mm2, 11 non-diffusion-weighted images, and TR/TE=5000/64ms. The results of this study, High-Resolution diffusion MRI of the Trigeminal Nerve using 7T MRI, will be presented by Andrew Grande, MD on May 1. Co-authors are Christophe Lenglet, PhD; Julien Sein, PhD; Julian Tokarev; Bharathi Jagadeesan, MD; and Pierre-François Van de Moortele, MD, PhD.

The researchers' imaging protocol generated high-resolution FA and ADC maps, as well as fiber orientation estimates successfully used to characterize the microstructure of the trigeminal nerve and its divisions at the skull base using deterministic and probabilistic tractography algorithms. The researchers concluded that their findings open up new possibilities for further understanding of the pathophysiology of TN, with the prospect of improving treatments based on this new knowledge.

"Trigeminal neuralgia is a rare disease with only 150,000 new cases per year, and has been described as perhaps the worse pain imaginable. Most patients experience shock or lightning-like shocks in their face triggered by various stimuli such as eating, wind, brushing teeth or just simply talking. Patients fear this stimuli and consequently avoid eating, or going outside or talking," said Andrew Grande, MD. "In this study, we have investigated the feasibility and advantages of ultra-high field magnetic resonance imaging (MRI), at 7 Tesla, of the skull base. 7T MRI, by comparison with clinical imaging typically performed at 1.5T or 3T, provides greater image resolution and contrast, thereby improving our ability to identify and assess the integrity of structures like the trigeminal nerve. More specifically, we have focused on high-resolution diffusion MRI, which characterizes the three-dimensional configuration and microstructural properties of axonal pathways. This work opens new and exciting possibilities to further our understanding of the pathophysiology of trigeminal neuralgia and, ultimately, improve available treatments. In the future, in addition to aiding our understanding of the pathophysiology of trigeminal neuralgia, such imaging may allow us to better diagnose and could potentially be used to guide some forms of treatment directly to the afflicted portion of the nerve."