Predicting pain relief: Use of pre-surgical trigeminal nerve diffusion metrics in trigeminal neuralgia

• Published in: NeuroImage clinical Vol. 15; pp. 710 - 718
• Main Authors: Hung, Peter S-P, Chen, David Q, Davis, Karen D, Zhong, Jidan, Hodaie, Mojgan
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier 01.01.2017
• Subjects: Adult; Aged; Diffusion Tensor Imaging; Female; Humans; Image Interpretation, Computer-Assisted; Male; Middle Aged; Neurosurgical Procedures; Pons - diagnostic imaging; Regular; Treatment Outcome; Trigeminal Nerve - diagnostic imaging; Trigeminal Neuralgia - diagnostic imaging; Trigeminal Neuralgia - surgery; (AD), axial diffusivity; (ROI), region of interest; (MVD), microvascular decompression; Multi-tensor tractography; (MR), magnetic resonance; Surgical outcome; Chronic facial pain; Trigeminal neuralgia; (FSPGR), fast spoiled gradient-echo; (TN), trigeminal neuralgia; (MD), mean diffusivity; (RD), radial diffusivity; (DTI), diffusion tensor imaging; (GKRS), Gamma Knife radiosurgery; (XST), eXtended Streamline Tractography; Treatment response prediction; (FA), fractional anisotropy
• ISSN: 2213-1582; 2213-1582
• DOI: 10.1016/j.nicl.2017.06.017

Trigeminal neuralgia (TN) is a chronic neuropathic facial pain disorder that commonly responds to surgery. A proportion of patients, however, do not benefit and suffer ongoing pain. There are currently no imaging tools that permit the prediction of treatment response. To address this paucity, we used diffusion tensor imaging (DTI) to determine whether pre-surgical trigeminal nerve microstructural diffusivities can prognosticate response to TN treatment. In 31 TN patients and 16 healthy controls, multi-tensor tractography was used to extract DTI-derived metrics-axial (AD), radial (RD), mean diffusivity (MD), and fractional anisotropy (FA)-from the cisternal segment, root entry zone and pontine segment of trigeminal nerves for false discovery rate-corrected Student's -tests. Ipsilateral diffusivities were bootstrap resampled to visualize group-level diffusivity thresholds of long-term response. To obtain an individual-level statistical classifier of surgical response, we conducted discriminant function analysis (DFA) with the type of surgery chosen alongside ipsilateral measurements and ipsilateral/contralateral ratios of AD and RD from all regions of interest as prediction variables. Abnormal diffusivity in the trigeminal pontine fibers, demonstrated by increased AD, highlighted non-responders (n = 14) compared to controls. Bootstrap resampling revealed three ipsilateral diffusivity thresholds of response-pontine AD, MD, cisternal FA-separating 85% of non-responders from responders. DFA produced an 83.9% (71.0% using leave-one-out-cross-validation) accurate prognosticator of response that successfully identified 12/14 non-responders. Our study demonstrates that pre-surgical DTI metrics can serve as a highly predictive, individualized tool to prognosticate surgical response. We further highlight abnormal pontine segment diffusivities as key features of treatment non-response and confirm the axiom that central pain does not commonly benefit from peripheral treatments.