To investigate the significance of atrophy of the trigeminal nerve (cistern portion) in the diagnosis of primary trigeminal neuralgia.

We retrospectively analyzed 59 PTN (primary trigeminal neuralgia) patients (experimental group) and 25 patients with hemifacial spasms (control group) admitted to Department of Neurosurgery, the Affiliated Hospital of Qingdao University from February 2014 to January 2016. The MRI data were used to measure and compare the volumes and CSAs of bilateral trigeminal nerves (cistern portions) in coronal plane. We investigated the relationship of trigeminal nerve atrophy to the type of offending vessels, neurovascular compression regions and extent.

The mean volume of the trigeminal nerve on the affected side (63.3±14.5 mm³) was significantly less than that on the contralateral side (74.4±16.5 mm³) or in the control group (73.2±13.8 mm³) (all P<0.05). Similarly, the mean CSA of the trigeminal nerve on the affected side (3.8±1.1 mm²) was significantly smaller than that on the contralateral side(4.6±1.3 mm²) or in the control group(4.9±1.1 mm²)(all P<0.05). The differences of trigeminal nerves in their volumes (14.5%±3.8 %) and CSAs (11.0%±2.8 %) between the two sides in the PTN group were greater than those in the control group (volume: 3.7%±1.2%, CSA: 2.9%±0.7%) (P<0.001). The CSA difference between the two sides was significantly greater in the arterial compression group (11.9%±4.3%) than venous compression group (4.8%±1.9%) (P=0.016), and greater in the degree III and II compression groups than degree I compression group (P=0.022).

Trigeminal nerve (cistern portion) atrophy might be associated with PTN and have certain value for the diagnosis of PTN.

Trigeminal neuralgia; Diagnosis; Atrophy; Microvascular decompression; Volume; Cross-sectional area