S010: ULTRASOUND ASSISTED MENTAL NERVE BLOCKS FOR LIP BRACHYTHERAPY: A CASE REPORT
Wendy W Yang1; Ryan Bridgeport1; Arianna Roman1; Leshawn Richards, MD2
1University of South Florida Morsani College of Medicine; 2H. Lee Moffitt Cancer Center & Research Institute
Introduction: Nerve blocks are commonly used for pain relief in instances where general anesthesia is not indicated. To achieve an adequate nerve block, one must inject anesthetic into the correct location. Proper placement of anesthetic for a mental nerve block, which provides local anesthesia for the lip and lower face, has been described previously, with many using the teeth as landmarks to locate the mental foramen. In edentulous patients, other techniques may be used to visualize the mental nerve. We describe the use of ultrasound in directing a bilateral mental nerve block in an edentulous patient undergoing brachytherapy needle placement for squamous cell carcinoma of the lower lip.
Case Description: An 85-year-old edentulous man with poorly-differentiated squamous cell carcinoma of the lower lip presented for temporary interstitial implant of the lower lip with brachytherapy needles for high dose rate brachytherapy treatment. This procedure facilitates the delivery of radiation therapy to the site of malignancy. Given an extensive cardiac history including atrial fibrillation and congestive heart failure, he was not a candidate for surgical excision, which would have additionally necessitated the removal of the entire bottom lip.
Figure 1. Patient's squamous cell carcinoma of the lower lip.
Preoperatively, a bilateral mental nerve block was achieved with 0.5% Bupivacaine administered under ultrasound guidance. The patient was then placed under Propofol monitored anesthesia care.
Figure 2. Ultrasound probe placement and corresponding image showing the left mental foramen (red arrow).
An ulcerated right lower lip lesion consistent with squamous cell carcinoma, 2.5 cm x 2 cm x 1.5 cm was noted. A bevel insertion needle was used to enter the skin inferior to the right commissure, lateral to the lesion. Next, a brachytherapy catheter was placed through the needle into the skin. The needle was removed, leaving the catheter in place. These steps were repeated at two other sites in the same area of the face. The patient tolerated catheter placement and his postoperative course was uneventful. On post-brachytherapy surveillance, a mass was found in the patient’s right neck, for which a neck dissection was performed.
Figure 3. Brachytherapy catheters in place on the patient's lower face, following a route parallel to the mouth.
Discussion/Conclusion: In edentulous patients such as the one described here, ultrasound guidance provides visualization of the mental foramen without the need to rely on dental landmarks. In literature, identification of the proper injection site for mental nerve blocks has been accomplished through visualizing dental landmarks, palpation, and ultrasound. Although dental landmarks are helpful for locating the mental foramen in many patients, locating the mental foramen in edentulous individuals can be challenging, and patients with teeth may vary in the anatomic location of their mental foramen. In addition to ensuring proper placement of local anesthetic, ultrasound guidance prevents unnecessary tissue trauma and resulting permanent nerve injury. We encourage the use of ultrasound-assisted bilateral mental nerve block as effective and safe pain management for patients who lack traditional anatomic landmarks of the mouth and cannot tolerate general anesthesia.