An 82-year-old woman with Alzheimer dementia is brought to the office for evaluation of new-onset drooling. The patient lives in a nursing home, and the staff noticed that she has been having liquid drip out of the right side of her mouth when they feed her. She has also been very tearful over the past 2 weeks, particularly at night when she wakes up crying and clutching her ear. The patient has type 2 diabetes mellitus that requires insulin and multiple medications. Her last hemoglobin A1c was 8.5%. Temperature is 38 C (100.4 F), blood pressure is 140/90 mm Hg, pulse is 96/min, and respirations are 18/min. Physical examination of the right ear canal shows granulation tissue with a surrounding white drainage in the floor of the canal. The tympanic membrane is clear and mobile to pneumatic otoscopy. There is facial asymmetry with some downward deviation of the right corner of the mouth. Which of the following is the most likely causative organism for this patient's condition?
Necrotizing (malignant) otitis externa | |
Risk factors |
|
Microbiology |
|
Clinical |
|
Treatment |
|
This patient with apparent ear pain (eg, clutching her ear while crying), facial nerve weakness, and granulation tissue in the external auditory canal (EAC) likely has necrotizing (malignant) otitis externa (NOE), an osteomyelitis of the skull base. Patients, who are generally elderly with diabetes mellitus, typically have severe, deep-seated ear pain and otorrhea that is unresponsive to topical medications. Granulation tissue on the floor of the EAC at the border between the bony-cartilaginous junction is characteristic.
Spread of the infection from the EAC can affect surrounding structures, including cranial nerves. This patient's facial drooping and resultant drooling reflects damage to cranial nerve VII (CN VII). Progression can also lead to temporomandibular joint involvement, meningitis, brain abscess, and death. NOE is most often caused by Pseudomonas aeruginosa, which has pro-inflammatory adhesins (leading to granulation tissue formation) and secretes tissue-degrading proteases (leading to infection spread). Mortality rate was >50% prior to the introduction of antipseudomonal antibiotics (eg, ciprofloxacin). As with other cases of osteomyelitis, a prolonged antibiotic course (eg, 6-8 weeks) is required.
(Choice A) Aspergillus species are a very rare cause of NOE. They can cause fungal otitis externa, which presents with an insidious onset of ear itchiness (with mild-to-moderate pain) and small black spores on white debris seen in the EAC.
(Choice B) Ramsay Hunt syndrome (ie, herpes zoster infection in the ear) presents with ear pain, facial nerve palsy, hearing loss, vertigo, and typically a vesicular rash in the EAC, auricle, or face. Pain may precede the appearance of the rash by 1-5 days; however, in this patient with 2 weeks of symptoms, the absence of the rash and the presence of granulation tissue makes NOE much more likely.
(Choice D) Patients with poorly controlled diabetes mellitus are susceptible to invasive fungal sinusitis from Rhizopus species, which cause a black eschar on the nasal turbinates (due to tissue necrosis from vascular invasion) and lead to life-threatening, rapidly progressive infections.
(Choice E) Streptococcus pneumoniae is a common cause of otitis media but does not typically cause NOE. This patient has a clear tympanic membrane with no middle ear fluid, making otitis media unlikely.
Educational objective:
Necrotizing (malignant) otitis externa represents osteomyelitis of the skull base and is most commonly caused by Pseudomonas aeruginosa. The characteristic presentation consists of severe ear pain and ear drainage; granulation tissue may be seen in the ear canal. Progression of the infection may lead to cranial neuropathies.