2026 Proffered Presentations
S233: PROTON DENSITY MAGNETIC RESONANCE IMAGING FOR EVALUATION OF NEUROVASCULAR COMPRESSION IN TRIGEMINAL NEURALGIA
Alicia Chen; Nicholas Koontz; Ichiro Ikuta; Yuxiang Zhou; Justin Cramer; Mayo Clinic Arizona
Background and purpose: Trigeminal neuralgia is a debilitating neuropathic disorder characterized by unilateral stabbing pain within the distribution of one or more divisions of the trigeminal nerve and is classically attributed to vascular compression of the trigeminal nerve root. More advanced neurovascular compression is predictive of post-surgical symptomatic relief following microvascular decompression. Improving pre-operative imaging characterization of trigeminal neurovascular compression should aid in surgical patient selection and surgical planning.
Thin section MRI is essential for identifying vascular compression. High resolution heavily T2 weighted imaging (generally a CISS or SPACE seqeunce) is generally performed for this indication and provides excellent contrast between CSF and neurovascular structures but poor contrast between the trigeminal nerve and adjacent vessels, limiting assessment of mass effect of vessel on the nerve. We hypothesized that a proton density sequence would provide superior discrimination between the trigeminal nerve and vascular structures and improve the characterization of trigeminal vascular compression.
Materials and methods: Retrospective review was performed of high-resolution trigeminal protocol MRIs performed at our institution at 7 Tesla and 3 Tesla by 4 and 3 board-certified neuroradiologists respectively. At 7T, small field of view PD and SPACE imaging sequences and at 3T, small FOV PD, SPACE, CISS imaging sequences without contrast, and CISS with contrast were assessed. We placed regions of interest (ROIs) on the trigeminal nerve root entry zone (REZ), the closest artery and vein to the trigeminal REZ, the middle cerebellar peduncle, and cerebellopontine CSF. Contrast between vessels and nerves, noise, and CSF signal homogeneity were calculated for each sequence at each magnet strength, and the results were compared among sequences using ANOVA, paired-t tests, and Wilcoxon signed-rank tests.
Results: At 7T, PD demonstrated superior contrast between nerve and artery signal with less noise compared to the heavily T2 weighted appearing SPACE imaging sequence. At 3T, PD demonstrated superior contrast between nerve and artery signal followed by the post-contrast CISS. Post-contrast CISS demonstrated superior contrast between nerve and vein signal. These findings were significant at p<0.001.
Conclusions: The trigeminal PD sequence demonstrated superior contrast between the trigeminal nerve and artery signal compared to heavily T2 weighted appearing SPACE and CISS sequences. This is valuable in assessing trigeminal vascular compression and should be helpful in surgical evaluation and planning.
Figure 1: ROI Placement. (A) 7T PD image showing a 5 mm ROI was placed over CSF in the prepontine cistern as near to the trigeminal nerve as possible. (B) 7T PD image showing a 5 mm ROI was placed over the middle cerebellar peduncle. (C) 7T PD showing additional ROIs placed over a trigeminal nerve (yellow), adjacent artery (red), and adjacent vein (blue) on one slice. (D) 7T SPACE image also showing nerve (yellow), artery (red), and vein (blue) ROIs.