Case Report: Local Anesthetic-induced Hypoglossal Nerve Injury

Petree, Garren

Introduction: Nerve injuries have long been reported as a potential complication of local anesthetic injections. The exact mechanism of injury is unclear but theories considered include needle trauma, hemorrhage, edema and toxicity from the local anesthetic solution. Most commonly the inferior alveolar and lingual nerves are affected. A literature search found published reports of traumatic injury to the hypoglossal nerve due to procedures including oral intubation, bronchoscopy, branchial cyst surgery, and carotid endartectomy. Pathological causes are noted to include odontogenic infection, tumors, central nervous system infections and radiation exposure. A search of current published literature found no previously reported injuries to the hypoglossal nerve related to local anesthetic injections.

Materials and Methods: This case report describes a 64-year-old female patient who presented to the University of Tennessee in Knoxville with findings of isolated right hypoglossal and lingual nerve injuries after receiving 4% prilocaine and 4% articaine local anesthetic injections in the floor of the mouth in preparation for a restorative dental procedure. Due to difficulty obtaining adequate anesthesia, injections were placed in the floor of the mouth adjacent to tooth #31 in an attempt to obtain anesthesia. After consent for release, medical records were obtained and reviewed from the referring general dentist and medical providers. Complete evaluation with brain imaging was performed to rule out other causes such as cerebrovascular accident, tumor or other underlying neurological processes. The patient was evaluated and followed with serial evaluations at the University of Tennessee, Knoxville by Dr. Jack E. Gotcher. Initial evaluation demonstrated significant speech dysarthria, tongue atrophy, and rightward deviation. Sensory changes included hypoesthesia to pinprick, light touch and pressure of the right dorsal tongue. The patient was followed every 3 months for serial sensory testing consisting of 2-point discrimination, pinprick, light touch, pressure and directional brush sensitivity.

Results: The patient was diagnosed with right lingual and hypoglossal nerve injuries related to local anesthetic injections of 4% articaine and 4% prilocaine. Treatment consisted of speech therapy with exercises, speech strategies and vitalstim therapy. Improvement was noted in, tongue weakness, range of motion and sensory changes after several months of treatment. Speech dysarthria and intelligibility improved to 85% of the patient’s baseline.

Conclusions: In the absence of a surgical procedure in the area, it is probable that the patient had an injection injury or an injury from the local anesthetic agents to both the hypoglossal nerve and the lingual nerve on the right side. The hypoglossal nerve injury would be possible with an injection in the right floor of the mouth. This area is anatomically contiguous with the right submandibular triangle and to Lesser’s triangle which contains the more proximal pathway of the hypoglossal nerve. If local anesthetic rested in this area with close approximation to the hypoglossal nerve, it might result in a chemical alteration of nerve function. The same pathways would also apply to a lingual nerve hyposthesia or parasthesia. It remains unclear if the 4% concentration of articaine and prilocaine contributed to the pathology. Treatment is conservative with speech therapy and sensory mapping.

References:

1.Malamed SF. Local anesthetics: dentistry’s most important drugs—clinical update 2006. J Calif Dent Assoc 2006;34(12):971-976.

2.Pogrel, M. A., & Thamby, S. R. I. (2000). Permanent nerve involvement resulting from inferior alveolar nerve blocks. The Journal of the American Dental Association, 131(7), 901-907.