Medical Fun Facts Episode 57: Ear Infections

It’s Easter Monday 17 April 2017.

Ear

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The human ear is a great spot for infections of all kinds. Before going straight to the bacteria and viruses, it’s important to understand a little simple anatomy.

The outer ear, is exposed to the environment and wherever you put your head. The middle ear is relatively protected but it has a direct connection with your oropharynx via the Eustachian tube. The inner ear though is the most protected area except that the nerve endings are bathed in the ultrafiltrate of serum. Whatever gets through the filtration system can get to the nerve endings.

Otitis externa or inflammation of the outer ear, is common in children, especially in the tropics. If you put your head underwater, your auditory canal gets damp and remains damp especially if the diameter of your auditory canal is small. In tropical conditions, not only can environmental bacteria cause infection but also fungi. Common, environmental, water-borne bacteria include Pseudomonas aeruginosa. It’s not just the water-borne bacteria, it’s the normal skin flora that can cause infections too. Commensal bacteria like the golden staph can cause furuncles and boils in the auditory canal. These can be exquisitely painful. Pseudomonal infections can also be painful, they often lead to a weeping thin discharge, and leave the skin swollen and boggy. If you ever look into someone’s ear and you see green or black fur, it’s probably fungus. Fungi in the genus Aspergillus are the most common to be found. You can sometimes determine the species based on the colour of the hyphæ, Aspergillus niger is black, Aspergillus flavus is yellow and Aspergillus fumigatus is green.

Diagnosing otitis external is usually simply made with an ear swab and setting it up for microscopy and culture. Quite often you can see fungal hyphæ in the Gram’s stain.

Treatment of otitis externa can be quite unpleasant and irritating. Sometimes ointments and drops including wicks are necessary to draw away the discharge and allow antibacterial and antifungal agents to work. Treatment can be painful and little kids hate having things stuck in their ears.

Prevention is often preferred but not always successful. In tropical areas where swimmer’s ear is common, it’s often recommended that a solution of vinegar and alcohol are used in the ear straight after showering and swimming. The aim is to dry out the auditory canal and inhibit growth of bacteria and fungi. It mostly works, but if there is a breech in the skin already, alcohol and vinegar solutions can sting quite a bit.

Middle ear infections are the bane of a small child’s existence. The problem is the Eustachian tube is a direct connection to the mouth and throat with all those lovely snot bacteria, viz., pneumococci, hæmophili and moraxellæ. These bacteria can cause lower respiratory infections in the right setting, and they’re commonly found in sinusitis. Because children have a narrow Eustachian tube, it cannot act as a drain as opposed to supplying bacteria to a normally clean area. When the middle ear is infected you can often see the fluid behind the ear drum or tympanic membrane. Because of the pressure build up in the middle ear, otitis media can also be very painful.

While most children with a middle ear infection will receive antimicrobials, the infection is usually self-limiting and antimicrobial therapy only helps a small proportion of patients. As children get older they have fewer infections because the Eustachian tube increases in diameter and can act as a drain. In children who have repeated middle ear infections, surgical intervention is often necessary. Persistent middle ear infection can lead to glue ear and deafness. This can lead to learning disability and poor performance in school despite normal intelligence. The usual surgical intervention is to insert a grommet in the ear drum to enable ventilation and reduce the infection risk.

Unfortunately, many doctors have a mistaken belief that an ear swab can be used to diagnose a middle ear infection. If the tympanic membrane is intact, it makes no sense. If the tympanic membrane has ruptured, pus discharging from the rent in the membrane will contain the infecting bacteria, but we already know the most likely culprits and there is no absolute way to collect a specimen without it being contaminated with skin commensals like golden staph and coagulase-negative staphylococci. The only accurate method is tympanocentesis. For this procedure, you need to insert a needle through the ear drum into the middle ear and aspirate the pus. As you can imagine, this can be really unpleasant and you don’t want to be doing it on most kids who are also quite irritable.

Bacterial infection of the inner ear is uncommon unlike viral vestibulitis which is infection of the vestibular apparatus. The inner ear is important for hearing and balance. It’s not uncommon for sudden onset of vertigo or dizziness to be caused by a viral infection. Often it is a Herpes simplex virus that causes the infection. This happened to me. I had sudden loss of balance, sudden deafness and severe tinnitus. While I can walk, it has taken years to be able to stand straight with my eyes closed. I remain deaf in one ear and I experience tinnitus all the time. This is one reason why I prefer not to socialise in places like pubs and clubs. I cannot hear what people are saying and the high background noise assures a sleepless night because of enhanced tinnitus.

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And so, ends another episode of Medical Fun Facts. You can find the show notes for every episode at my blog http://DrGaryLum.com/Blog

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