Trigeminal neuralgia diffusivities using Gaussian process classification and merged group tractography

Abstract

Imaging of trigeminal neuralgia (TN) has demonstrated key diffusion tensor imaging-based diffusivity alterations in the trigeminal nerve; however, imaging has primarily focused on the peripheral nerve segment because of previous limitations in reliably segmenting small fiber bundles across multiple subjects. We used Selective Automated Group Integrated Tractography to study 36 subjects with TN (right-sided pain) and 36 sex-matched controls to examine the trigeminal nerve (fifth cranial nerve [CN V]), pontine decussation (TPT), and thalamocortical fibers (S1). Gaussian process classifiers were trained by scrolling a moving window over CN V, TPT, and S1 tractography centroids. Fractional anisotropy (FA), generalized FA, radial diffusivity, axial diffusivity, and mean diffusivity metrics were evaluated for both groups, analyzing TN vs control groups and affected vs unaffected sides. Classifiers that performed at greater-than-or-equal-to 70% accuracy were included. Gaussian process classifier consistently demonstrated bilateral trigeminal changes, differentiating them from controls with an accuracy of 80%. Affected and unaffected sides could be differentiated from each other with 75% accuracy. Bilateral TPT could be distinguished from controls with at least 85% accuracy. TPT left–right classification achieved 98% accuracy. Bilateral S1 could be differentiated from controls, where the affected S1 radial diffusivity classifier achieved 87% accuracy. This is the first TN study that combines group-wise merged tractography, machine learning classification, and analysis of the complete trigeminal pathways from the peripheral fibers to S1 cortex. This analysis demonstrates that TN is characterized by bilateral abnormalities throughout the trigeminal pathway compared with controls and abnormalities between affected and unaffected sides. This full pathway tractography study of TN demonstrates bilateral changes throughout the trigeminal pathway and changes between affected and unaffected sides.

A novel indicator to predict the outcome of percutaneous stereotactic radiofrequency rhizotomy for trigeminal neuralgia patients: diffusivity metrics of MR-DTI

“…It was important to try and analyze whether FA values on every segment of the CNV could portend recurrence shortly after radiofrequency treatment. TN is characterized not only by diffusion abnormalities on the CNV when compared to controls, but also by abnormalities between the affected and unaffected sides of the TG 18 , 31 , 39 . By combining diffusivity metrics of the bilateral CNVs, the current study results suggest the following findings may herald effective PSR treatment: normal FA value of the unaffected side of the CNV (4/4, 100%); an FA value < 0.30 in the affected side of the TG (9/10, 90%); and a normal FA value of the affected side REZ (6/7, 86%).…”

“…Magnetic resonance-DTI images, including high-resolution T1-weighted 3D-sagittal anatomical images and DTI images, were acquired from a 3.0 Tesla Siemens MR scanner 18 , 22 . Anatomical images: in-plane voxel size = 0.9 × 0.9 mm 2 , slice thickness = 0.9 mm, 192 slices, matrix = 256 × 256, field of view = 24 × 24 cm 2 , echo time (TE) = 2.3 ms, repetition time (TR) = 2300 ms, and inversion time = 900 ms. DTI protocol: spin-echo EPI sequence, b value = 0 and 1000 s/mm 2 , 12 b0 Averages, 3 b1000 Averages, 72-direction, in-plane voxel size = 2 × 2 mm 2 , slice thickness of 2 mm with no gap, 30 continuous slices, matrix size = 256 × 256, field of view = 25 × 25 cm 2 , flip angle = 90°, TE = 95 ms, TR = 4100 ms.…”

“…To obtain diffusivity metrics (FA, MD, AD, and RD) of the CNV (Fig. 2 ), the centroid was placed in each tract segment on the successive coronal slices of scalar maps, then the position of the centroid was validated on the 3D planes and the CNV tracts 15 , 18 . In total, 1 to 3 DTI scans (preoperative, postoperative, and follow-up) were performed on patients in the TN group and one scan performed on participants in the control group.…”

“…Recently, the DTI studies 9 , 18 – 20 in patients with TN has focused on the root entry zone (REZ) of the CNV; however, no studies on abnormal trigeminal ganglion (ab-TG) have been reported. The aim of this was to investigate whether changes in diffusivity metrics during radiofrequency treatment in TN patients with ab-TG of TN could be correlated with outcomes.…”

Functional MRI–Guided Motor Cortex and Deep Brain Stimulation for Intractable Facial Pain: A Novel, Personalized Approach in 1 Patient

“…The surgical targets were chosen using evidence from previous studies and were individualized to this patient based on fMRI results. Although fMRI has been used to characterize factors that play a role in the mechanism of TN, 10,11,[35][36][37][38][39] fMRI has not been used to plan targets for central neuromodulation in the manner reported here. Because cold and light touch stimuli were known triggers for this patient's acute pain episodes, both stimuli were separately applied to the face during fMRI, which demonstrated increased BOLD signal and activation of both the thalamus and precentral regions.…”