Combination of Fluid-Attenuated Inversion Recovery (FLAIR) and Diffusion Tensor Imaging (DTI) for Visualization and Microstructural Assessment of the Trigeminal Nerve
Background: Trigeminal Neuralgia (TN) is a chronic facial pain condition commonly associated with neurovascular compression of the trigeminal nerve (cranial nerve V—CNV). Visualizing CNV and objectively assessing its microstructural integrity in vivo are important in better understanding TN. Previous attempts to do so using MRI diffusion tensor imaging (DTI) have been hindered by magnetic inhomogeneities caused by fluid, bone, and air interactions in the skull base near CNV. We hypothesised that combining fluid-attenuated inversion recovery (FLAIR) with standard DTI MRI would result in superior delineation of CNV
Objectives: To generate a rapidly-acquired CNV-specific FLAIR-DTI MRI sequence, and to compare it with conventional DTI sequences.
Methods: Three DTI sequences were developed at the Peter S. Allen MR Research Centre on a 3-Tesla Siemens Magnetom Prisma MRI scanner: i) whole-brain DTI multiband sequence; ii) whole-brain DTI sequence using typical literature-reported acquisition parameters; and iii) axial-slab FLAIR-DTI combination sequence. Eight healthy controls underwent a single scanning session during which all sequences were obtained. Explore DTI toolbox was used to extract CNV tract characteristics (e.g., length, diameter, fractional anisotropy). CNV visualization and tract characteristics were compared across sequences.
Results and Conclusions: CNV tract characteristics vary significantly across DTI sequences, but FLAIR-DTI results in superior signal-to-noise for all positions along CNV. Selection of DTI sequence can impact visualization and assessment of integrity of CNV, which may be of importance in interpreting imaging studies in TN (or of other cranial nerves).
Conclusion: There was no statistical difference between trough levels except at infusion 5. However, most patients were dose optimized and went into clinical remission by infusion 5. ATI levels were negative and all patients had detectable IFX levels, which suggests that early dose adjustment may reduce the risk of ATI formation.