Neuropathic pain in a patient with metastasis of a desmoplastic neurotropic melanoma to the trigeminal nerve: a case report

Abstract

A 39-year-old female presented to our clinic with nonradiating, sharp, burning pain localized to the left ear and left neck. The patient has a history of desmoplastic neurotropic melanoma (DNM) in her left chin area and had undergone previous resections and chemoradiation. She was initially diagnosed with DNM sixteen years prior. Shortly after, she underwent resection of the melanoma. One year after the resection, the patient had a recurrence of her cancer. She had a second surgery with subsequent interferon chemoradiation. The patient remained in remission until three years later, when she was found on MRI to have a metastasis to her left temporal lobe and left trigeminal nerve. Along with a complete resection of the tumor, she underwent a course of cisplatin and radiation. Subsequent to this treatment, she started experiencing worsening pain in her left ear and left neck. On examination, the patient had decreased sensation in her left face along the jawline towards the left lip. She was initiated on gabapentin and the dosage was slowly titrated to 800mg BID and 1200mg QHS. Unable to tolerate the high dosage of gabapentin, she was started on methadone 5mg BID and gabapentin was titrated to 800mg TID. On this regime, the patient achieved adequate control of her neuropathic pain. DNM is a rare type of spindle cell melanoma that is locally aggressive with a high risk of local recurrence. Metastasis to the trigeminal nerve from a DNM is a rare presentation and has been reported in four cases in the literature. Aggressive chemoradiation usually ensures diagnosis and resection. As a result, chemoradiation induced neuropathic pain can also be an expected complication in these patients. However, this is the first report of successful treatment of the neuropathic pain due to local tumor invasion or a side effect of chemotherapy treatment.