This randomized controlled trial integrates baseline observational ultrasound analysis to assess the clinical efficacy of trigger point bloodletting therapy for primary trigeminal neuralgia and explore peripheral ultrasound mechanisms of trigger point lesions and treatment response. Eligible subjects are adults aged 18-75 with unilateral classic primary trigeminal neuralgia and confirmed trigger points in the orbicularis oris muscle.

The primary research question is whether 8-week trigger point bloodletting achieves a greater reduction in Brief Pain Inventory-Facial total score (primary endpoint) than oral carbamazepine. Secondary questions explore inter-side differences in orbicularis oris thickness, elasticity and microvascular perfusion, correlations between ultrasound biomarkers, pain severity and disease duration, as well as differential dynamic ultrasound changes under the two treatments and their links to pain relief.

Participants complete baseline assessments: demographic data, medical history, pain, anxiety, depression and quality-of-life scales, trigger point mapping, and bilateral orbicularis oris ultrasound (grayscale imaging, shear wave elastography, superb microvascular imaging). Subjects are randomly assigned 1:1 to bloodletting intervention or carbamazepine control for 8 weeks. The bloodletting group receives twice-weekly sterile trigger point pricking with cupping bleeding at suitable sites. The control group takes guideline-based individualized carbamazepine, with all subjects maintaining daily pain and medication diaries.

Follow-up evaluations occur at Weeks 2, 4, 6 and 8, covering pain scoring, trigger point re-evaluation and adverse event monitoring. Post-treatment bilateral orbicularis oris ultrasound is performed at Week 8 to quantify changes in soft tissue structure and microcirculation. All adverse reactions and concurrent medications are documented throughout the trial. Baseline observational analysis compares pretreatment bilateral facial muscle ultrasound features and correlates imaging indicators with clinical pain, to provide objective imaging evidence for peripheral sensitization pathology of trigger points in trigeminal neuralgia patients.