Trigeminal Pontine Sign: From Imaging to Diseases Beyond Trigeminal Neuralgia

Abstract

The so-called trigeminal pontine sign has been described as a marker of different diseases, from multiple sclerosis to herpetic infections. First, it has been proposed as linear hyperintensity in the pons on the Magnetic Resonance Imaging (MRI) of patients with multiple sclerosis and trigeminal neuralgia. After these descriptions, it has been reported as incidental findings in the same patients and in patients with HSV or VZV infections. In addition, patients with neuromyelitis optica spectrum disorders (NMOSD) have been more rarely described with this neuroradiological sign. In this review, the main anatomical and neuroradiological issues underlying the trigeminal pontine sign are described, together with the limitations of the published studies from the clinical and neuroimaging point of view. Finally, the association with different diseases is detailed.

Keywords: MRI; NMOSD; VZV; multiple sclerosis; trigeminal nerve; trigeminal pontine sign.

Figure 1

Axial FLAIR MRI in a patient with multiple sclerosis and trigeminal symptoms on the right side, showing, in ascending slices, panel (a1–a4), hyperintense signal in both trigeminal tract and a bilateral trigeminal pontine sign (red arrows). In panel (b), the coronal FLAIR is proposed, showing the longitudinal extension of pontine hyperintensities. In the panel (c), the axial oblique FLAIR slice, focused on the plane of cisternal TN, is reconstructed, showing a bilateral hyperintensity of both TN and intrapontine segment (red arrows).

Figure 2

In the same patient shown in Figure 1, a post-contrast T1W MRI is proposed, focused on the plane of the cisternal TN (same plane as in Figure 1c), without contrast enhancement.

Figure 3

Three-month follow-up MRI of the same patients as in Figure 1 and Figure 2, after steroid treatment, showing a strong reduction in pontine hyperintensities with persisting hyperintense trigeminal tract in ascending axial FLAIR slices from (a–c).

Figure 4

Six-month follow-up MRI of the same patients as in Figure 1, Figure 2 and Figure 3, showing further improvement of the findings with persisting linear hyperintensity along the TN course (red arrows) in ascending axial FLAIR slices from (a–c).

Figure 5

Patient with VZV recurrent infections: Axial panel (a1,a2) and coronal panel (a3) FLAIR MRI showing a bilateral trigeminal pontine sign. In panel (b), DWI and ADC slices at the same level. In panel (c), a supratentorial small vessel disease pattern is detailed with white-matter hyperintensities in the supratentorial location. In panels (d,e), the axial and coronal post-contrast T1W-MRI shows the lack of contrast enhancement of the pontine lesion.