Magnetic resonance imaging-based classification of trigeminal nerve-superior cerebellar artery relationships

The trigeminal nerve (TN) is frequently implicated in neurovascular conflicts, most commonly with the superior cerebellar artery (SCA), its predominant arterial counterpart in the cerebellopontine angle.

To examine the relationship between the SCA and TN utilizing high-resolution magnetic resonance imaging and evaluated whether particular anatomical configurations predispose to clinically significant contact.

Magnetic resonance imaging scans from 80 patients (160 sides) were retrospectively analyzed, excluding cases with pathological processes affecting the TN. Using multiplanar reconstruction, the TN root was identified and its spatial relationship with the SCA was evaluated.

Eight distinct topographic patterns were identified. The SCA most commonly coursed superior (30.6%), lateral (18.8%), or superolateral (17.5%) to the TN. Medial configurations, although less frequent, were associated with the shortest artery-nerve distance (mean 1.85 ± 1.28 mm) and significantly higher contact rates (P < 0.001). Overall, SCA-TN contact was observed in 14.4% of sides, but only 20% of these patients reported ipsilateral facial numbness. Variations in SCA origin (basilar artery, posterior cerebral artery, or common origin) and duplication did not significantly influence the artery-nerve distance.

Although SCA-TN contact is relatively frequent, only particular medial and superior configurations seem to predispose individuals to symptomatic compression. These observations are consistent with cadaveric and surgical evidence highlighting the significance of root entry zone contact in trigeminal neuralgia. Vascular contact alone should not serve as a diagnostic criterion; instead, geometric configuration and related nerve alterations must also be incorporated into preoperative assessment.