Case Report: Ramsay Hunt syndrome with simultaneous bilateral vestibular dysfunction as the initial manifestation in a patient with a history of breast cancer.

Background: Ramsay Hunt syndrome (RHS) typically presents with unilateral otalgia, herpes zoster oticus, ipsilateral peripheral facial palsy, and often ipsilateral vestibulocochlear involvement. Bilateral/contralateral vestibular dysfunction is extremely rare. Case presentation: A 60-year-old female with a history of right breast cancer presented to our clinic with 1 week of vertigo, followed by 2 days of right-sided facial deviation and otalgia. Physical examination revealed vesicular eruptions around the right ear and external auditory canal, right-sided peripheral facial palsy, spontaneous horizontal-rotatory nystagmus (with a fast phase to the left), and postural instability. Further evaluation confirmed bilateral vestibular hypofunction: the video head impulse test showed reduced gains and/or saccades in all canals; bithermal caloric testing demonstrated bilateral vestibular weakness (sum of slow-phase velocity: 10.1°/s); and symptom assessments yielded a visual analog scale (VAS) score of 7/10 and a dizziness handicap inventory (DHI) total score of 52. Facial nerve electrophysiological testing indicated significant impairment of the right facial nerve, with an amplitude reduction exceeding 50%. The stapedial reflex, Hallpike-Dix test, Roll test, pure-tone audiometry, brain and cranial nerve MRI, and routine laboratory tests showed no significant abnormalities. A diagnosis of RHS with bilateral vestibular dysfunction was established, and treatment was administered per current guidelines, including antiviral therapy, oral corticosteroids, analgesics, anti-vertigo medications, acupuncture, and vestibular rehabilitation. After 2 weeks, symptoms (facial palsy, otalgia, herpes zoster, and dizziness) improved slightly, with crusting of the herpes lesions. At the 3-month follow-up, the herpes zoster had resolved without residual pain, though mild residual dizziness (VAS 2, DHI 20) and facial weakness persisted. Conclusions: This case shows rare bilateral vestibular involvement and initial vestibular impairment preceding RHS (distinct from classical ipsilateral or rare post-RHS contralateral patterns). Elucidating the specific pathogenic mechanisms underlying this presentation holds significant clinical importance for understanding bilateral vestibular involvement.