At least once a month, I encounter a patient who has suffered a sudden onset significant hearing loss in one ear. One moment, hearing was fine... and the next moment, hearing had significantly degraded without any apparent triggering event (ie, shooting gun, loud fireworks, loud concert, etc). No other symptoms are present. Just the hearing loss. Ear examination is normal without any earwax or ear fluid presence. Hearing test shows nerve hearing loss present in the affected ear.
There are several hypothesis as to why this may occur including vascular (ie, ear mini-stroke), auto-immune, neurological (ie, multiple sclerosis), tumor (ie, acoustic neuroma), and infectious. The prevailing opinion is that such sudden sensorineural hearing loss is due to a viral infection that only affected the hearing nerve or cochlea, and nothing else. Every so often, a MRI scan obtained will demonstrate inflammation of the hearing nerve or cochlea, but most of the time, the MRI scan does come back normal. Bloodwork (if obtained), does come back normal as well.
So, what's the proof that a viral infection causes sudden sensorineural hearing loss if all studies (except for the hearing test) comes back normal?
The evidence mainly comes from autopsies. Starting in the 1950s, any patients who suffered from sudden sensorineural hearing loss who then unexpectedly died, underwent an autopsy whereby the inner ear and surrounding structures were removed and carefully examined for possible causes (not of death, but the sudden hearing loss). Dr. Schuknecht reported 8 such cases in 1962 and 1973. The temporal bones (which contain the inner ear and hearing nerve) showed atrophy of the organs of Corti, tectorial membranes, and striae vasculares in varying combinations and severity. These pathological changes were judged to be more like those occurring in labyrinthitis of known viral etiology than those following experimentally in- duced vascular lesions in animals.
Over the ensuing decades, an additional 9 cases were reported supporting a viral etiology. The most recent studies on this topic occurred in 1986 and 2000, when Harvard and House Ear researchers reported an additional 16 cases that showed similar lesions consistent with known cases of viral cochleitis.
The 1986 Harvard results are summarized in the table below followed by the 2000 House Ear results:
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| Source: The pathology of idiopathic sudden sensorineural hearing loss. Arch Otorhinolaryngol. 1986;243(1):1-15. doi: 10.1007/BF00457899 |
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| Source: Idiopathic sudden sensorineural hearing loss: temporal bone histopathologic study. Ann Otol Rhinol Laryngol. 2000 Jun;109(6):527-32. doi: 10.1177/000348940010900601. |
The first thing to note is that historically speaking, the viral culprit responsible for the majority of sudden hearing losses were due to measles and rubella. Of course, keep in mind that many of the studies were performed on patients who died prior to 1971 when the MMR vaccine (measles, measles, and rubella) was introduced.
After the introduction of the MMR vaccine, herpes zoster (which causes shingles and chicken pox due to the varicella-zoster virus) became the dominant viral culprit and is now currently thought to be the main cause of sudden sensorineural hearing loss in patients.
Fortunately, starting in 2005, the varicella vaccine was added to the MMR vaccine, to make the combined MMRV vaccine. So it is entirely possible that kids born after 2005 who received the MMRV vaccine (given around age 1 and 5 years old) will not be at risk for sudden sensorineural hearing loss in their lifetime. That said, those of us who only obtained the MMR vaccine would still be at risk. Of course, this is ignoring the fact that more and more kids are not getting this vaccine at all due to the anti-vaccine movement, so sudden hearing loss may still be a "thing" that ENTs will continue to see and treat for the foreseeable future.
Treatment for sudden sensorineural hearing loss is controversial. Antivirals have been found to be ineffective. Most ENTs will treat with oral steroids, steroid injections into the middle ear, and/or hyperbaric oxygen.
References:
The pathology of idiopathic sudden sensorineural hearing loss. Arch Otorhinolaryngol. 1986;243(1):1-15. doi: 10.1007/BF00457899. [link to full article]The pathology of sudden deafness. Laryngoscope 72:1142-1157. 1962
The pathology of sudden deafness. Acta Otolaryngol (Stockh) 76:75-97. 1973.
Herpes zoster auris associated with facial nerve palsy and auditory nerve symptoms. Acta Otolaryngol (Stockh) 63:533-550. 1967.
Pathological findings and surgical implications in herpes zoster oticus. Adv Otorhinolaryngol 31 : 184190. 1983
Inner ear pathology due to measles. Ann Otol Rhinol Laryngol 63 :754-771. 1983.
Inner ear pathology following maternal rubella. Ann Otol Rhinol Laryngol 62 : 1201-1218. 1953.
Inner ear pathology in deafness due to mumps. Ann Otol Rhinol Laryngol 69:918-935. 1960
Histopathological findings in the inner ear caused by measles. J Laryngol Otol 90:173-181. 1976.
Temporal bone pathology in herpes oticus. Ann Otol Rhinol Laryngol 81:331-338. 1972
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