Lateral pterygoid muscle ultrasound-guided injection: A technical note.

[BACKGROUND] Temporomandibular disorders (TMDs) are a frequent cause of orofacial pain, causing functional disability and a negative impact on quality of life. Botulinum toxin (BTX-A) injection in lateral pterygoid muscle (LPM) is one of the treatment modalities proposed, but the blind puncture guided by EMG carries a risk of vascular puncture or diffusion of the toxin to nearby muscles. We describe an ultrasound-guided approach and evaluate the spread of the injection in a fresh human cadaver.

[METHODS] A fresh human cadaver was injected. An out-of-plane approach was performed using a convex probe, injecting 1.0 ml of 0.25% methylene blue dye into the LPM. After, a dissection was performed to isolate the lateral pterygoid muscle and assess the spread of the dye.

[RESULTS] Ultrasound-guided injection allowed to visualize in real-time the spread of the dye within the LPM. The deep and superficial muscles nearby to LPM were not stained by the dye, but upper and lower head of LPM was heavily stained.

[CONCLUSION] Ultrasound-guided approach for the injection of BTX-A into the LPM could be considered a successful and safe treatment for myofascial pain related to TMD. Therefore, further clinical studies are needed to study the reproducibility of ultrasound guided LPM injection and to evaluate the clinical results.