gms | German Medical Science

Objective: In this prospective study diffusion tensor imaging (DTI) was used to evaluate the influence of clinical and anatomical parameters on structural alterations within the 5^th cranial nerve in patients with trigeminal neuralgia (TN) due to neurovascular compression.

Method: Overall 81 patients (40 men, 41 women; mean age 60 ± 5 years) with typical TN were included, who underwent microsurgical decompression (MVD). A single shot DTI-EPI-sequence with 15 different diffusion directions (3.0 T MR scanner (Signa HDx, GE, USA)) was acquired along with a 0.6mm isotropic three-dimensional fast imaging employing steady state acquisition sequence (3D-FIESTA) for anatomic correlation. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were correlated with intra-operative and clinical findings.

Results: DTI analyses revealed significantly lower fractional anisotropy (FA) values within the root entry zone of the affected trigeminal nerve compared to the contralateral side (p=0.05). This also included 3 patients without MRI-finding of a neurovascular conflict and 14 patients that showed an asymptomatic contralateral contact. Intra-operatively, a nerve compression was always confirmed and concerned an arterial conflict in 73 and a venous conflict in 8 patients. No differences were seen between an arterial of venous type of compression. Lower FA values were found already 5 months after symptom onset; no correlation, however, was found with duration of symptoms or severity of compression.

Conclusions: DTI analysis allows quantification of structural alterations even in those patients without any discernible neurovascular contact on MRI. Moreover, our findings support the hypothesis that both arteries and veins can cause structural alterations that lead to TN. These aspects might be useful for treatment decision.