Accuracy of Ultrasound-Guided Superficial Trigeminal Nerve Blocks Using Methylene Blue in Cadavers

Objective. To describe a technique for and assess accuracy of ultrasound-guided supraorbital, infraorbital, and mental nerve injections in a cadaveric model. Prior studies have shown that peripheral trigeminal nerve injections can be beneficial for a subgroup of patients for whom surgical treatment is not appropriate. Accurate injection is necessary to limit side effects and improve its efficacy. Ultrasound guidance may improve the accuracy of an injection that is typically performed using a blind technique. Methods. A single operator completed 36 ultrasound-guided injections with methylene blue dye on six embalmed cadavers. Three cadavers were injected using an in-plane approach and three cadavers using an out-of-plane approach. Injections staining the target nerve were considered "accurate," whereas "inaccurate" injections resulted in no nerve staining. Results. The accuracy rate was 100% (18 of 18) for the in-plane approach and 94% (17 of 18) for the out-of-plane approach. Thirty-five injections were considered accurate (97%) with overflow, and one injection was inaccurate. Conclusion. This cadaveric investigation suggests that ultrasound guidance can be used to inject the peripheral trigeminal nerve with a high degree of accuracy. Clinicians should consider using ultrasound guidance to inject the trigeminal nerve for diagnostic or therapeutic purposes.