| Mastoiditis | |
|---|---|
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| Side view of head, showing surface relations of bones. (Mastoid process labeled near center.) | |
| Specialty | Otorhinolaryngology |
Mastoiditis is the result of an infection that extends to theair cells of theskull behind the ear. Specifically, it is an inflammation of themucosal lining of themastoid antrum andmastoid air cell system inside[1] themastoid process. The mastoid process is the portion of thetemporal bone of the skull that is behind the ear. The mastoid process contains open,air-containing spaces.[2][3] Mastoiditis is usually caused by untreated acuteotitis media (middle ear infection) and used to be a leading cause of child mortality. With the development ofantibiotics, however, mastoiditis has become quite rare in developed countries where surgical treatment is now much less frequent and more conservative, unlike former times.[2]
There is no evidence that the drop in antibiotic prescribing for otitis media has increased the incidence of mastoiditis, raising the possibility that the drop in reported cases is due to a confounding factor such as childhood immunizations againstHaemophilus andStreptococcus. Untreated, the infection can spread to surrounding structures, including the brain, causing serious complications.[4] While the use of antibiotics has reduced the incidence of mastoiditis, the risk of masked mastoiditis, a subclinical infection without the typical findings of mastoiditis has increased with the inappropriate use of antibiotics and the emergence ofmultidrug-resistant bacteria.[5]
Some commonsymptoms andsigns of mastoiditis includepain, tenderness, and swelling in the mastoid region. There may be ear pain (otalgia), and the ear or mastoid region may be red (erythematous). Fever or headaches may also be present. Infants usually shownonspecific symptoms, includinganorexia,diarrhea, orirritability. Drainage from the ear occurs in more serious cases, often manifesting as brown discharge on the pillowcase upon waking.[4][6]
The pathophysiology of mastoiditis is straightforward: bacteria spread from the middle ear to themastoid air cells, where the inflammation causes damage to the bony structures.Streptococcus pneumoniae,Streptococcus pyogenes,Staphylococcus aureus,Haemophilus influenzae, andMoraxella catarrhalis are the most common organisms recovered in acute mastoiditis. Organisms that are rarely found arePseudomonas aeruginosa and other Gram-negative aerobic bacilli, and anaerobic bacteria.[7]P. aeruginosa, Enterobacteriaceae, S. aureus andanaerobic bacteria (Prevotella,Bacteroides,Fusobacterium, andPeptostreptococcus spp.) are the most common isolates in chronic mastoiditis.[8] Rarely,Mycobacterium species can also cause the infection. Some mastoiditis is caused bycholesteatoma, which is a sac of keratinizing squamous epithelium in the middle ear that usually results from repeated middle-ear infections. If left untreated, the cholesteatoma can erode into the mastoid process, producing mastoiditis, as well as other complications.[4]
The diagnosis of mastoiditis is clinical—based on themedical history andphysical examination. Imaging studies provide additional information; The standard method of diagnosis is viaMRI scan although aCT scan is a common alternative as it gives a clearer and more useful image to see how close the damage may have gotten to the brain and facial nerves. Planar (2-D)X-rays are not as useful. If there is drainage, it is often sent forculture, although this will often be negative if the patient has begun taking antibiotics.Exploratory surgery is often used as a last resort method of diagnosis to see the mastoid and surrounding areas.[2][9]
If ear infections are treated in a reasonable amount of time, the antibiotics will usually cure the infection and prevent its spread. For this reason, mastoiditis is rare in developed countries. Most ear infections occur in infants as the eustachian tubes are not fully developed and don't drain readily.[citation needed]
In all developed countries with up-to-date modern healthcare the primary treatment for mastoiditis is administration ofintravenous antibiotics. Initially, broad-spectrum antibiotics are given, such asceftriaxone. As culture results become available, treatment can be switched to more specific antibiotics directed at the eradication of the recovered aerobic andanaerobic bacteria.[8] Long-term antibiotics may be necessary to completely eradicate the infection.[4] If the condition does not quickly improve with antibiotics, surgical procedures may be performed (while continuing the medication). The most common procedure is amyringotomy, a small incision in thetympanic membrane (eardrum), or the insertion of atympanostomy tube into the eardrum.[9] These serve to drain the pus from the middle ear, helping to treat the infection. The tube is extruded spontaneously after a few weeks to months, and the incision heals naturally. If there are complications, or the mastoiditis does not respond to the above treatments, it may be necessary to perform amastoidectomy: a procedure in which a portion of the bone is removed and the infection drained.[4]
With prompt treatment, it is possible to cure mastoiditis. Seeking medical care early is important. However, it is difficult for antibiotics to penetrate to the interior of the mastoid process and so it may not be easy to cure the infection; it also may recur. Mastoiditis has many possible complications, all connected to the infection spreading to surrounding structures.Hearing loss is likely, or inflammation of thelabyrinth of theinner ear (labyrinthitis) may occur, producingvertigo, and an ear ringing may develop along with the hearing loss, making it more difficult to communicate. The infection may also spread to thefacial nerve (cranial nerve VII), causingfacial-nerve palsy, producing weakness or paralysis of some muscles of facial expression, on the same side of the face. Other complications includeBezold's abscess, an abscess (a collection of pus surrounded by inflamed tissue) behind thesternocleidomastoid muscle in the neck, or asubperiosteal abscess, between the periosteum and mastoid bone (resulting in the typical appearance of a protruding ear). Serious complications result if the infection spreads to the brain. These includemeningitis (inflammation of the protective membranes surrounding the brain),epidural abscess (abscess between the skull and outer membrane of the brain), dural venousthrombophlebitis (inflammation of thevenous structures of the brain), orbrain abscess.[2][4]
In the United States and other developed countries, theincidence of mastoiditis is quite low, around 0.004%, although it is higher in developing countries. The condition most commonly affects children aged from two to thirteen months, when ear infections most commonly occur. Males and females are equally affected.[3]
