What is the definition of Malignant Otitis Externa?
It is persistent severe ear infection that extends to involve the bone and soft tissue of the skull base.
It is also known as "necrotizing external otitis" as it is an aggressive infection rather than a malignancy.
Predisposing factors
- Diabetes: More than 90% of patients with malignant otitis externa have diabetes.
- Low immunity: as in AIDS and patients who take chemotherapy.
What are the causes of malignant otitis externa?
Organisms: Pseudomonas aeruginosa and Staphylococcus aureus are the most common causes, Proteus also exists in some cases.
Incidence: It occurs mostly in Old, diabetic patients.
Symptoms of malignant otitis externa
- Severe deep-seated pain, worse by night or by moving the head (Otalgia).
- Persistent foul-smelling yellow or green (purulent) discharge (Otorrhea).
- Persistent itching in the External auditory canal.
- Facial muscle weakness up to facial paralysis.
- Laryngitis may occur, leading to loss of voice.
Signs (examined by the doctor)
- Granulation in the floor of the external meatus producing scanty sanguineous discharge.
- Tenderness over the floor of external auditory canal, exacerbated by pulling on the pinna and putting pressure over the tragus.
- Conductive hearing decreased.
- Preauricular, Postauricular and and lateral cervical lymph nodes show the picture of Lymphadenopathy.
- If the infection extends to the temporomandibular joint and Parotid gland, Trismus may occur.
Investigations and laboratory studies
- Lab. tests: Blood glucose, ESR and Kidney function tests.
- Culture and Sensitivity.
- C.T temporal bone and skull base.
- Biopsy to exclude malignancy.
- Bone scan to assess severity and progress.
- PTA to assess the hearing.
How to diagnose malignant otitis externa?
Diagnosis of a case of malignant otitis externa depends on taking complete medical history to recognise predisposing factors as discussed above, and medical examination that should be confirmed by investigations.
A doctor should exclude other diagnoses that mimic Malignant Otitis Externa (Differential Diagnosis) which are:
- Squamous cell carcinoma of external audiory canal.
- Simple otitis externa (responds to topical antibiotics doesn't go beyond the soft tissue of EAC).
- Otitis media.
- Chronic suppurative otitis media.
- Cholesteatoma
- Mastoditis
What are the possible Complications of Malignant O.E?
Local spread to the base of the skull due to osteomyelitis producing paralysis of the facial, glossopharyngeal, vagus, accessory and hypoglossal nerves.
Treatment of Malignant Otitis Externa
1- Hospitalization.
2- Control of Diabetes Mellitus.
3- Antibiotics for at least 6 weaks:
A. Quinolones e.g Ciprofloxacin.
B. Aminoglycosides + carpenicillin.
C. Third or forth generation cephalosporins.
4. Local: Aural toilet and topical antibiotics.
5. Surgical debridement: only minor removal of dead bone.
Detailed management approach of malignant O.E with doses: Here
Detailed management approach of malignant O.E with doses: Here
References
Grandis, JR, Branstetter, BF, YuVL. "The changing face of malignant (necrotising) external otitis: clinical, radiological, and anatomic correlations". Lancet Infect Dis. vol. 4. 2004. pp. 34-39.Carfrae, M, Kesser, B. "Malignant Otitis externa". Otolaryngol Clin N Am. vol. 41. 2008. pp. 537-549.