Trigeminal Neuropathic Pain With Complicated Pathophysiology Caused by a Low-Level Impacted Mandibular Third Molar: A Case Report

We report a case of neuropathic pain affecting the third branch of the trigeminal nerve caused by periodontitis associated with a low-level impacted mandibular third molar on the left side. The patient also experienced neuropathic pain in the second branch, which may have resulted from sensitization of the third branch. A 57-year-old woman presented with percussion and contact pain in the left maxillary second molar, along with burning pain extending from the left buccal region to the mandible. Pus discharge was noted from the periodontal pocket, and she was treated with anti-inflammatory medication and antibiotics. Although the pus discharge resolved, the pain persisted. The percussion and contact pain in the left maxillary second molar, as well as the burning pain from the left buccal area to the mandible, were diagnosed as neuropathic pain involving the left third branch of the trigeminal nerve, originating from inflammation of the left mandibular third molar. Persistent pain and allodynia in the second branch region were attributed to sensitization of the third branch. Pregabalin was added to her treatment, resulting in symptom relief. Imaging showed that the left mandibular third molar was low-level impacted and in close proximity to the inferior alveolar canal, which was identified as the source of the initial pain. The tooth was extracted under general anesthesia after pain symptoms improved. One month post-extraction, the patient experienced a flare-up of burning pain in the left maxillary second molar region and allodynia in the gingiva, as well as burning pain from the left buccal region to the mandible. Pregabalin was restarted but did not provide analgesic effects. Amitriptyline was then added, leading to pain relief. This case highlights the complex pathophysiology of neuropathic pain, which remains incompletely understood. Early intervention to relieve pain may be crucial to prevent chronic symptoms.