To describe a case of bilateral trigeminal neuropathy as the primary manifestation of renal cell carcinoma (RCC), that improved clinically and radiographically with tumor resection.

Facial pain can be an atypical symptom of malignancies, often attributed to direct brainstem/nerve compression, referred pain from the vagus nerve, or meningeal carcinomatosis. Additionally, facial pain has been proposed as a paraneoplastic syndrome involving cranial nerves. RCC is a common urological malignancy and can involve paraneoplastic syndromes in 20%. However, there are no prior reports of facial pain as a primary manifestation of RCC.

A 52-year-old male with factor VIII deficiency experienced new-onset, constant, dull facial pain in the right V2 distribution. Despite treatment with carbamazepine, the pain worsened and became bilateral prompting an ED visit. Phenotypically, the pain was consistent with burning mouth syndrome and trigeminal neuropathy. Examination revealed bilateral facial (V2) tenderness without focal deficits. Subsequent MRI brain detected bilateral trigeminal nerve enhancement but no structural lesions or compression.  Further work-up revealed a 2.2 cm right renal mass on abdominal CT. He received multiple outpatient infusions and oral medications with minimal facial pain improvement. Following a right partial nephrectomy performed 3.5 months after symptom onset, biopsy confirmed RCC confined to the kidney. He followed up 1.5 months post-tumor resection and reported significant improvement in facial pain. A repeat brain MRI displayed near-complete resolution of prior bilateral trigeminal nerve enhancement, and neuropathic pain medications were successfully discontinued. The symptomatology implies paraneoplastic in nature, secondary to RCC.

To our knowledge, this represents the first reported case of trigeminal neuropathy associated with RCC, featuring pain phenotypically consistent with burning mouth syndrome and bilateral trigeminal nerve enhancement on imaging. The patient's clinical and radiographic improvement post-tumor resection emphasizes the significance of considering paraneoplastic neuropathy in cases of trigeminal neuropathic pain and conducting thorough secondary work-up.