There are many reasons why left-sided tinnitus develops into bilateral tinnitus, which may be caused by inflammation of the middle ear or neurogenic tinnitus, and you should go to the hospital to get a clear explanation of the cause and targeted treatment. 1. Otitis media: Inflammation of the middle ear cavity, tympanic membrane perforation and other factors can stimulate the inner ear organs, such as affecting the cochlea and the auditory nerve to induce tinnitus. If otitis media develops bilaterally from the left side, tinnitus may also develop bilaterally. However, it is difficult to guarantee that the treatment of otitis media can cure tinnitus symptoms, and even surgical intervention may not be able to relieve tinnitus. 2. Neurogenic tinnitus: Unilateral or bilateral tinnitus should also be considered as a possible cause of neurogenic tinnitus. It may be related to a variety of factors such as inner ear blood circulation disorders, viral infections, and acoustic neuroma. You can use methylcobalamin tablets, vitamin B and other symptomatic treatment, but also need to do a good job of ear protection, to avoid direct contact with the noise, while doing a good job of body regulation. After the symptoms of tinnitus, should consult a doctor in time, and clarify the specific causes of the disease, under the guidance of the doctor to choose the appropriate drugs and treatment programs.