Severity analysis of neurovascular contact in patients with trigeminal neuralgia: assessment with the inner view of the 3D MR cisternogram and angiogram fusion imaging

Abstract

Background and purpose: Neurovascular contact (NVC) of the trigeminal nerve is not only detected at the affected trigeminal nerve in patients with trigeminal neuralgia (TN) but is also observed at the asymptomatic nerves on the side contralateral to the TN as well as in normal nerves in control subjects. The frequency and severity of the NVC among the affected, contralateral, and normal trigeminal nerves were analyzed by 3D MR cisternogram and angiogram fusion imaging in relation to the cause of TN.

Materials and methods: The inner view of the fusion MR imaging projected from inside the trigeminal nerve was used. The severity of the NVC was classified as none, simple, moderate, or severe, according to the nerve circumference in contact with the vessel. The NVC was analyzed in the affected nerves (n = 66) and the contralateral nerves (n = 66). Forty patients underwent microvascular decompression surgery, and 26 were treated medically. The NVC at the normal trigeminal nerves (n = 78) was studied in 39 control subjects without symptoms of TN.

Results: The NVC in the affected trigeminal nerve was observed more frequently and much more severely than that at the contralateral and normal trigeminal nerves in controls (P < .01). Additionally, the NVC in the surgical patients was more severe than that in the medically treated patients (P < .01).

Conclusions: Severity analysis of the NVC with the inner view of the fusion MR imaging may provide useful information in the diagnosis of TN and can be a helpful adjunct in treatment planning for patients with TN.

Figures

Fig 1.

Schematic illustration of the severity analysis of the NVC. Severity of the NVC was determined by the extent of the nerve circumference in contact with the vessel and classified into 4 groups: severe, NVC with the vessel contacting the trigeminal nerve covering >20% of the nerve circumference; moderate, with

Fig 2.

Severe NVC at the affected trigeminal nerve. A, MinIP image of the source MR cisternogram (MRC). B, Operative photograph (OP-1) before decompression of the NVC at MVD surgery. C, Operative photograph (OP-2) after surgical decompression. D and E, Preoperative simulation images of the 3D MR cisternogram and angiogram fusion imaging, projected left posterolaterally (the view-position box at the right corner and indicated by a red curved arrow in A). The offending transverse pontine vein compresses the trigeminal nerve directly and the trunk of the SCA indirectly. F, Illustrative sketch of the simulation images. G and H, Inner views of the fusion MR imaging, projected posteroanteriorally along the nerve axis, viewed from inside the rootlet of the nerve at the brain stem (the view-position box at the right corner and indicated by a yellow arrowhead in A), showing the 3D anatomic relationship of the NVC. The contour of the trigeminal nerve is severely compressed by the complex of the transverse pontine vein and the trunk of the SCA. I, Illustrative sketch of the inner view. CN-V indicates the trigeminal nerve; SCA-r, rostral branch of the superior cerebellar artery; SCA-c, caudal branch of the superior cerebellar artery; SCA-t, trunk of the superior cerebellar artery; PCA, posterior cerebral artery; BA, basilar artery.