Abstract
Patients: A 63-year-old woman presented with right facial pain and numbness. Two years ago, she had a fall, which resulted in right facial fracture. Gradually, she experienced a throbbing pain triggered by touch. The patient then consulted the Orofacial Pain Clinic of Tokyo Medical and Dental University Hospital due to continuous pain. Allodinia and hyposentibility of the right face, innervated by the second branch of trigeminal nerve were observed on physical examination. Additionally, based on the semmes-Weinstein monofilament test, we diagnosed her condition as trigeminal neuropathy/post-traumatic trigeminal neuropathic pain （ICOP-1 4. 1. 2. 3）. After treatment with 7.5g/day of Keishikajutubuto, a type of Kampo medicine, near-infrared light therapy, iontophoresis, and needle energization, the duration of pain reduced and the intensity of pain attenuated. Long-term vitamin B12 supplementation and a total of 24 near-infrared light therapy sessions were performed. Two years after the start of the treatment, her pain intensity had reduced and the range of abnormal sensations had reduced compared to that at the first hospital presentation; however, the abnormal sensations still persisted．
Discussion: Post-traumatic trigeminal neuropathic pain was in defined in ICOP-1 in 2020, as “pain, in a neuroanatomically plausible area within the distribution（s） of one or both trigeminal nerve（s）,” and “Onset within 6 months after the injury．” Somatosensory symptoms are characterized by the presence of negative signs such as hypoesthesia or hyperalgesia, or positive signs such as hyperalgesia or allodynia, or both, as noted in the footnote. In this case of trigeminal neuropathy of the infraorbital nerve, long-term use of vitamin B12 supplements and near-infrared therapy reduced the pain and abnormal sensations such as allodynia and hypoesthesia in a case of trigeminal neuropathy of the infraorbital nerve after a long period of onset．
Conclusions: Our case suggests that even late onset of treatment of post-traumatic trigeminal neuropathic pain in the infraorbital nerve region with continuous pharmacotherapy and physical therapy can successfully alleviate the symptoms．
