Uncommon cause of trigeminal neuritis and central nervous system involvement by herpes labialis: a case report

BACKGROUND: Trigeminal neuropathy is characterized by numbness in the region innervated by the trigeminal nerves, with or without neuropathic weakness in the muscles of mastication. Trigeminal neuritis is a form of trigeminal neuropathy in which the lesion is caused by an inflammation. Herein, we report a patient with trigeminal neuritis due to central nervous system (CNS) involvement of herpes labialis (HL) infection, which was successfully treated with anti-viral and anti-inflammatory agents. CASE PRESENTATION: A young healthy female presented with numbness in the left hemiface for two weeks. She had a preceding typical HL infection on left facial lip one week before the sensory symptom onset. Brain magnetic resonance imaging revealed high signal intensities and asymmetrical thickening with enhancement along the cisternal segment of the left trigeminal nerve. Additionally, brain MR angiography showed multifocal stenoses in the M1 segment of the middle cerebral artery and the cavernous portion of the internal carotid artery. Cerebrospinal fluid (CSF) examination showed mild pleocytosis with normal protein level, glucose ratio, but CSF polymerase chain reaction assay for specific anti-viral antibodies including herpes simplex virus was negative, and CSF culture also did not identify a specific pathogen. The results of serologic testing including tumor markers and autoimmune markers were all unremarkable. A tentative diagnosis of trigeminal neuritis as a complication of HL involving the CNS was made considering the clinical, neuroradiological, and laboratory findings of the patient. Therefore, the patient was treated with intravenous methylprednisolone and acyclovir for 10 days. After the treatments, her sensory disturbance was markedly improved. Brain MRI at the 3-month follow-up also demonstrated improvement of previously identified high signal intensity lesions and multifocal intracerebral artery stenoses. CONCLUSION: HL is usually a self-limiting, benign disease without complications, but rarely presents as trigeminal neuritis due to CNS involvement. Therefore, meticulous evaluation may be necessary if trigeminal neuritis or CNS involving symptoms occur after HL.