DMSO Dual-Route Therapy for Refractory Tinnitus in Long-COVID and Post-COVID-19 Vaccine Injury

Inclusion Criteria: * Inclusion Criteria: Adults 18 to 70 years of age. Chronic subjective non-pulsatile tinnitus for at least 6 months. Bothersome tinnitus defined by a Tinnitus Handicap Inventory (THI) score ≥ 20 at screening. Documented history of post-acute sequelae of SARS-CoV-2 (PASC, long COVID) or post-COVID-19 vaccine injury, with tinnitus onset or clear worsening temporally associated with that event. Failure of at least two prior tinnitus therapies (for example, sound therapy, counseling or cognitive-behavioral approaches, pharmacologic treatments, or steroid therapy). Willing and able to provide informed consent. Able to complete telemedicine visits and electronic questionnaires in English and to attend a baseline in-person otolaryngology (ENT) evaluation. Exclusion Criteria: Objective or pulsatile tinnitus, or tinnitus primarily synchronous with the heartbeat. Active middle-ear infection, acute otitis media, tympanic membrane perforation, or current otorrhea. Recent exposure (within the past 3 months) to known ototoxic medications associated with new or rapidly worsening tinnitus. Known hypersensitivity or allergy to dimethyl sulfoxide (DMSO) or any component of the study formulations (betahistine, dexamethasone, lidocaine, levocarnitine, N-acetylcysteine, or excipients). Pregnancy or breastfeeding. Uncontrolled or severe psychiatric illness (for example, active psychosis, acute suicidality) that, in the opinion of the investigator, would interfere…