A preliminary study of diffusion tensor imaging in root entry zone of primary trigeminal neuralgia.

Objective: Primary Trigeminal Neuralgia (PTN) is a common and refractory neurological disease. Conventional vascular compression theory could not completely explain the etiology and pathogenesis of PTN. This study used diffusion tensor imaging (DTI) to demonstrate the microstructural changes of root entry zone (REZ) region in PTN patients. Materials and methods: DTI sequences was performed on PTN patients and healthy controls (HCs). Clinical data included affected side, disease course and visual analogue scale (VAS) were collected. Quantitative DTI variables such as FA, MD, AD and RD of the root entry/Exit zone (REZ) were measured and compared in PTN/HCs, affected/unaffected side, and pre/post operation groups. The PCoA was established to conduct overall differences between PTN group and the HCs. Results: A total of 17 patients with PTN (mean age 59.29 ± 8.53; 5 men) and 34 HCs (mean age 57.70 ± 6.37; 10 men) were included. Lower FA value of the affected side of PTN group was observed compared to the unaffected side and the HCs (p = 0.001), whereas the values of MD, AD and RD were significantly increased (p < 0.001). Moreover, the decrease of FA value was recovered post operation. PCoA results of the comprehensive indexes can significantly distinguish PTN group from HCs (r = 0.500, p < 0.001). Conclusion: Quantitative variables derived from DTI in REZ had significantly different profiles between PTN patients and HCs, which were associated with VAS situation and the disease course of PTN. The comprehensive index established on DTI variables were of great potential to reveal the microstructure changes in PTN patients and predict the therapeutic effect.

Utility of DTI (Diffusion Tensor Imaging) Metrics to Study Microstructural Changes of Trigeminal Nerve in Patients with Trigeminal Neuralgia (TN).

Aims: To study the trigeminal nerve tractography and assessment of diffusion tensor imaging (DTI) parameters by comparing the values of fractional anisotropy (FA) of trigeminal (V) nerve on the affected side with that of the unaffected opposite side. Materials and Methods: Prospective comparative study done for one year included 30 patients who presented with trigeminal neuralgia and 30 controls who did not have any present or past history of neurological or neurosurgical symptoms were enrolled in the study. Results: Most common age of presentation of TN is >50 years, and the commonly involved branch is V2 (maxillary branch of the trigeminal nerve). Most of the patients were having symptoms for more than 1 year. The superior cerebellar artery was the most common vessel compressing the V nerve at the root entry zone (REZ), followed in the order by anterior inferior cerebellar artery and petrosal vein. Neurovascular compression (NVC) was more commonly seen in the study group when compared with the control group. In all the patients in the study group, fractional anisotropy (FA) was decreased on the affected side as compared to the unaffected side. In the study group, 10 patients were having NVC on both sides, but FA was significantly decreased only on the affected side. No significant difference in FA values at the REZ of bilateral V nerves in the control group. Conclusion: DTI metrics of the trigeminal nerve is a very helpful imaging technique in patients with trigeminal neuralgia. It not only helps in anatomical imaging but also reinforces the association between NVC and TN.

Differences in the Clinical Characteristics of Persistent Idiopathic Facial Pain (Atypical Odontalgia) Patients with or Without Neurovascular Compression of the Trigeminal Nerve.

BACKGROUND: Persistent idiopathic facial pain (PIFP) is the unexplained pain along the territory of the trigeminal nerve, including nonorganic tooth pain called atypical odontalgia (AO). Though PIFP is debilitating to patients' livelihood and well-being, its pathophysiology remains poorly understood. Although neurovascular compression (NVC) of the trigeminal nerve is known to be associated with trigeminal neuralgia (TN), the relationship between NVC and other orofacial pains has not been fully elucidated. METHODS: In this study, we investigated the differences in the characteristics of PIFP (primarily AO) patients in the presence or absence of NVC. A retrospective analysis was performed on data from 121 consecutive patients who had been diagnosed with unilateral PIFP according to the criteria of the International Classification of Headache Disorders (ICHD)-3 and underwent magnetic resonance imaging scans of the head. RESULTS: In the group without NVC, characteristic findings were significant for psychiatric morbidity, somatization, and pain disability, when compared with the group with NVC. Furthermore, the group without NVC exhibited significant headache, noncardiac chest pain, shortness of breath, and pain catastrophizing. CONCLUSIONS: These results suggest that PIFP patients can be divided into two groups: one consistent with a neuropathic pain phenotype when NVC is present and a functional somatic symptom phenotype when presenting without NVC. Our findings may enable a more precise understanding of pathophysiology of PIFP and lead to better treatment strategies.