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Malignant Otitis Externa
ALTERNATIVE NAMES: Temporal bone osteomyelitis; skull base osteomyelitis.
DEFINITION: Aggressive bacterial infection affecting the temporal bone and skull base.
WHAT IS GOING ON IN MY BODY? Malignant otitis externs is actually a poor definition for this disease process. This is not a malignant entity, although it is an aggressive infectious process that affects the temporal bone and skull base. The temporal bone is the part of the skull that houses the inner ear and through which pass the facial nerve, carotid artery, jugular vein (lateral sinus), and the mastoid. Malignant otitis externs develops in individuals with compromised immune systems, most notably diabetics. Diabetics with poorly controlled blood sugars have dysfunction of a white blood cell type that is involved in attacking acute infections. The infection initially begins in the external canal as an acute otitis externs (see acute otitis externs, swimmer's ear). The bacteria causing the acute otitis externs is often Pseudomonas aeruginosa or Staphylococcus aureus which invades through the skin lining the bony ear canal and then into the bony ear canal itself. Left unchecked, it spreads rapidly into the rest of the temporal bone with damage to structures within the temporal bone itself. One possible reason that diabetics may be more susceptible is that their ear wax has less acidity. A less acid environment favors growth of pseudomonas.
WHAT ARE THE SIGNS AND SYMPTOMS? The initial signs and symptoms are those of acute otitis externs with pain in the opening to the ear canal and auricle, purulent drainage from the ear canal, and low-grade fever. As the infection spreads into the bone, severe pain occurs with thickening and inflammation in the skin overlying the temporal bone, particularly around the outer ear. Fevers often occur. Upon examination, there is significant swelling and infected material in the external canal, and there may be swelling of the skin around the ear. If the infection begins to compromise structures within the temporal bone, such as the facial nerve, then facial paralysis or weakness may be present. If it affects the lateral sinus portion of the jugular vein, then an infected clot can form within it causing lateral sinus thrombosis characterized by high, spiking fevers and eventual sepsis. Should the infection progress to affect the inner ear, then nerve-related hearing loss and vertigo may ensue. Since the temporal bone is adjacent to the brain, brain abscess, meningitis, or subdural abscess formation can occur. The most notable finding on physical examination is a polyp (a fleshy swelling), or granulation tissue (a very red, irregular growth) overlying the bony floor of the ear canal.
WHAT ARE THE CAUSES AND RISKS? As previously mentioned, this entity develops in individuals with some defect in their immune system who develop an acute otitis externs that then begins to invade into the bone of the external canal and temporal bone.
HOW TO PREVENT THE DISEASE: Early identification and aggressive treatment of external canal infection in susceptible individuals is the best way to keep the process from spreading. Since most cases begin as outer ear canal infections and most of those are from water contamination of the ear canal, then the best means of preventing malignant otitis externs is keeping water out of the ears. If water contamination occurs, then instituting drying measures, such as blow dryers or several drops of rubbing alcohol mixed with hydrogen peroxide or antibiotic ear drops, can help prevent the disease.
HOW IS IT DIAGNOSED? It is diagnosed based upon clinical examination and history. Blood testing can reveal if the erythrocyte sedimentation rate is elevated, which is often an indication of long-term inflammation and is usually elevated in cases of osteomyelitis. CT scanning or MRIs may delineate the areas of infected bone. Bone scans, which are nuclear medicine studies looking for bone destruction and regrowth, will often indicate the presence of osteomyelitis. Radioactively labeled white blood cells can also be helpful in delineating the degree of osteomyelitis. Cultures of the ear canal can indicate the offending organism, which helps in guiding appropriate antibiotic therapy.
WHAT ARE THE LONG-TERM EFFECTS? For successfully treated malignant otitis externa, usually no long-term effects result. However, for those individuals who have disease that is not treated or is not responding to therapy, spread of the infection intracranially or damage of other temporal bone structures is possible.
AM I PUTTING OTHERS AT RISK? No.
WHAT ARE THE TREATMENTS? For those individuals whose disease is identified early, intravenous antibiotics with topical antibiotic therapy may arrest the disease process. It is vital that any underlying immune deficiency be corrected or stabilized if possible. Hyperbaric oxygen therapy has shown itself to be a very useful adjunctive treatment in this disease process. Lastly, if the intravenous antibiotics, hyperbaric oxygen therapy, and topical antibiotic therapy are ineffective, then surgical resection of the diseased bone is the last line of defense.
WHAT ARE THE SIDE EFFECTS TO THE TREATMENTS? The side effects would be specific to those antibiotics employed. Hyperbaric oxygen therapy is tolerated well in most individuals. The main problem is equalizing middle ear pressure while in the pressure chamber. This can be alleviated by placing pressure equalization tubes in the tympanic membrane. Side effects to surgery would include those complications common to any operation on the temporal bone, such as facial nerve paralysis, vertigo, hearing loss, and taste disturbance.
WHAT HAPPENS AFTER TREATMENT? If treatment is successful, the osteomyelitis is arrested, and the symptoms resolve. The granulation tissue or polyp sitting in the ear canal resolves.
HOW DO I MONITOR THE DISEASE? A high index of suspicion needs to be held on both the part of the patient and the physician. Progressive worsening and unrelenting symptoms of acute otitis externa in a susceptible individual must trigger immediate investigation and initiation of medical management.
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