From The MS Information Sourcebook, produced by the National MS Society.
Hearing loss is an uncommon symptom of MS. About 6% of people who have MS complain of impaired hearing. In very rare cases, hearing loss has been reported as the first symptom of the disease. Deafness due to MS is exceedingly rare, and most acute episodes of hearing deficit caused by MS tend to improve.
Hearing loss may take place during an acute exacerbation. An exacerbation is a sudden worsening of an MS symptom or symptoms, or the appearance of new symptoms, which lasts at least 24 hours and is separated from a previous exacerbation by at least one month. An exacerbation is also known as an attack, a relapse, or a flare.
Linked to Other Symptoms That Suggest Brainstem Damage
Hearing loss is usually associated with other symptoms that suggest damage to the brainstem—the part of the nervous system that contains the nerves that help to control vision, hearing, balance, and equilibrium. Hearing deficits caused by MS are thought to be due to inflammation and/or scarring around the eighth cranial nerve (the auditory nerve) as it enters the brainstem, although plaques at other sites along the auditory pathways could also contribute to hearing problems. Plaques are abnormal areas that develop on nerves whose myelin—the fatty sheath that surrounds and protects nerve fibers—has been destroyed. Plaques cause the nerve impulses to be slowed or halted, producing the symptoms of MS.
Because hearing deficits are so uncommon in MS, people with MS who do develop hearing loss should have their hearing thoroughly evaluated to rule out other causes.