Some people are born with hearing loss. Others acquire it later in life. Bacterial meningitis (infection of the protective covering of the brain and spinal cord) is the most common cause of acquired hearing loss worldwide; and permanent hearing loss is the most common serious complication of bacterial meningitis. Nearly 10 percent of survivors of bacterial meningitis will have permanent hearing loss. Today, some of the most common causes of meningitis leading to permanent hearing are cytomegalovirus, group B streptococcal and Streptococcus pneumoniae or pneumococcus. Pneumococcus is particularly dangerous to hearing as it can release a toxin that causes direct damage to the cells of the inner ear. Meningococcal meningitis, another common bacterial cause of meningitis, can also result in hearing loss.
Hearing loss may occur as early as six hours after the onset of meningitis. A number of factors may result in loss of hearing, including:
• increased pressure resulting from brain swelling
• release of inflammatory chemicals into the fluid that bathes the brain
• direct spread of infection along the auditory canal
• inflammation of the inner ear
• direct injury to inner ear cells.
Some research suggests that permanent hearing loss may be reduced in patients with bacterial meningitis who are treated with corticosteroids as well as antibiotics. Further studies may better define the use of corticosteroids to improve outcomes in survivors of bacterial meningitis, especially in children. Other studies are looking at the ability of newer therapies to reduce the serious effects that result from bacterial meningitis, including hearing loss.
Vaccines for two common childhood infections – Haemophilus influenzae type b (also called Hib) and Streptococcus pneumoniae – have dramatically decreased the number of cases of meningitis caused by these bacteria. Over the next decade, new vaccines against meningococcal meningitis may similarly reduce the occurrence of this disease and its complications.
Eric J. Stern, M.D., is an epidemic intelligence service officer with the Centers for Disease Control and Prevention’s Meningitis and Special Pathogens Branch in Atlanta, Ga. Dr. Stern attended medical school at Boston University and completed his pediatrics residency at the University of California, San Diego.
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