Magnetic resonance imaging evaluation of masticatory muscle changes in patients with primary trigeminal neuralgia before microvascular decompression.

Primary trigeminal neuralgia (PTN) is characterized by chronic neuropathic pain. There are few studies exploring masticatory muscle changes in patients with PTN. This study evaluated the changes in the masticatory muscles using magnetic resonance imaging (MRI) and the predictive factors of masticatory muscle changes in patients with PTN. The radiologic outcomes of 52 patients with PTN and 58 healthy adults were evaluated. The temporalis, lateral pterygoid, medial pterygoid, and masseter muscles were assessed using MRI. Atrophy and edema of the masticatory muscles were noted. Multivariate analyses were conducted to identify factors associated with masticatory muscle atrophy. Among the PTN group, the right side (61.5%) and mandibular branch (53.9%) were the most affected. Muscle atrophy of the temporalis (P < .001), medial pterygoid (P = .016), lateral pterygoid (P = .031), and masseter (P = .001) were significantly higher in the PTN group than in the control group. Lateral pterygoid edema was significantly higher in the PTN group (P < .001). However, no significant difference was found in the temporalis and masseter edema between the two groups. Logistic regression analysis demonstrated that neurovascular conflict (NVC) significantly predicted mastication muscle atrophy (P = .037). Patients with PTN had higher rates of masticatory muscle atrophy and edema. The assessment of NVC may be a preoperative imaging biomarker to predict atrophy in PTN.