Diffusion Tensor Magnetic Resonance Imaging of Trigeminal Nerves in Relapsing Herpetic Keratouveitis

Abstract

BackgroundCorneal hypoesthesia is the landmark of HSV and VZV keratitis and can lead to neurotrophic keratitis. Diffusion tensor imaging (DTI) is a new magnetic resonance imaging (MRI) derived technique, which offers possibilities to study axonal architecture. We aimed at assessing the potential impact of recurrent HSV or VZV-related keratitis on the axonal architecture of trigeminal nerves using DTI.DesignProspective non-interventional study.ParticipantsTwelve patients and 24 controls.MethodsDTI using MRI of the trigeminal fibers and corneal esthesiometry using the Cochet-Bonnet esthesiometer were acquired for patients affected by unilateral and recurrent HSV or VZV-related keratitis (3 months after the last corneal inflammatory event), and control subjects with no history of ocular or neuronal disease affecting the trigeminal pathways.Main Outcome MeasuresFractional anisotropy (FA) and apparent diffusion coefficient (ADC) were compared between the 2 eyes of both patients and controls, and correlated with corneal esthesiometry.ResultsFA was lower in the trigeminal fibers ipsilateral to the affected eye compared to the non-affected side (0.39±0.02 versus 0.46±0.04, P=0.03). This difference was more important than the intra-individual variability observed in controls. Concomitantly, the asymmetry in ADC results was significantly correlated with the loss of corneal sensitivity in the affected eye.ConclusionsCorneal hypoesthesia related to HSV and VZV keratitis is associated with persistent modifications in the architecture and functionality of the trigeminal fibers. These results add further explanation to the pathogenesis of HSV and VZV-induced neurotrophic keratitis, which may occur despite an apparent quiescence of the disease.

Neurotrophic keratopathy

“…reduced sensations not only in the affected eye but also in the unaffected eye (Rousseau et al, 2015;M'Garrech et al, 2013;Jabbarvand et al, 2015). Unilateral herpes simplex and herpes zoster keratitis is associated with bilateral loss of corneal nerve receptors and dendritic cell infiltration (Hamrah et al, 2010;Cavalcanti et al, 2018) .The findings are mirrored in studies on rabbits with unilateral trigeminal axotomy, wherein bilateral loss of corneal nerves and immune cell infiltration was demonstrated (Yamaguchi et al, 2016;Yamaguchi et al, 2013).…”

Is There a Magnetic Resonance Imaging-Discernible Cause for Trigeminal Neuralgia? A Structured Review

“…Of the 25 included studies, there were seven anatomical-only studies, nine DWI-only studies, and nine studies that fell into both categories (see Figure 1). Four of the DWI-only studies performed trigeminal nerve visualization only [45–47, 49] while the remaining twenty-one studies in the review inspected the neural alterations associated with TN. Anatomical imaging and DWI results are discussed separately in the upcoming sections, with further distinction made between studies that compare TN patients to healthy controls and studies that compare the affected and unaffected sides of the trigeminal nerve.…”

“…Four of the DWI studies [45–47, 49] tracked the trigeminal nerve for visualization purposes. Visualizing the trigeminal nerve is important for understanding the nerve’s microanatomy and understanding where abnormalities and damage in the nerve can occur when looking at the nerve in TN patients.…”

Mapping fine-scale anatomy of gray matter, white matter, and trigeminal-root region applying spherical deconvolution to high-resolution 7-T diffusion MRI

“…We took advantage of the increased SNR of dMRI at 7-T compared with 3-T MRI and of the potential of fODFs to resolve fine-scale structures in the brain, such as in the cerebellopontine angle. Pathological changes to the extrapontine parts of the trigeminal nerve were reported [38,39,41], and the necessity of fiber-tracking its intra-and extrapontine parts was recently reported while comparing different algorithms, including CSD [42].…”

“…Recently, radiation-induced damage to the trigeminal nerve (nerve V) were found using dMRI [35]. High-resolution dMRI is required for characterization of diffusion properties of CNs, especially of the thinner CNs (such as nerves IV, IX, XI, XII), which typically exhibit an extension of only a few millimetres, and of CNs, which have a complex composition of several radixes or subnerves (such as nerves V, VII, VIII, X-XII) or of the intrapontine parts of CNs, which often cross with local brainstem fibers [35][36][37][38][39][40][41]. For instance, because intrapontine fibers of the trigeminal nerve exhibit similar relaxation behavior to that of the surrounding pontine fiber tracts, only direction-dependent information as provided by high-resolution dMRI can depict these different fiber distributions and their courses.…”