malignant otitis externa diseases of external ear

Otitis externa diseases of external ear

1. Malignant Otitis Externa

2. It is vicious and potentially life threatening infection of the soft tissues of external ear and surrounding structures, quickly spreading to involve the periosteum and temporal bone of the skull base. This may be associated with involvement of the cranial nerves, carotid artery and jugular vein.

3. Nomenclature Condition was first described in 1959 as ‘ Pyocutaneous Osteomyelitis of the temporal bone’. In 1968, it was termed as ‘Malignant Otitis Externa’ Necrotizing Otitis Externa Skull Base Osteomyelitis

4. Predisposing Factors Diabetes in elderly Defect in immunity Microangiopathy and endarteritis Change in cerumen pH HIV/AIDS Bacterial Fungal Pharmacological immunosuppression Chemotherapy Steroid use States like Leukemia and lymphoma

5. Microbiology Bacterial Organisms Pseudomonas aeruginosa  90% of cases Staphylococcus aureus , Staphylococcus epidermidis , Proteus mirabilis , Klebsiella oxytoca , Klebsiella pneumonia,

6. Fungal Organisms Aspergillus fumigatus (Most common fungal organism) Others include Aspergillus niger , Aspergillus flavus , Candida sp. And Malassezia sp.

7. Clinical Manifestations Exquisite Otalgia (75-100% cases)  Severe throbbing and non-remitting pain extending to TMJ, more at night. Purulent fetid otorrhea (45-100% cases) Hearing loss Fever: rare

8. As bony destruction and inflammation progresses medially through the skull base to the foramina, cranial neuropathies ensue Facial Nerve Paralysis (in up to 25% of patients). Children with skull base osteomyelitis usually develop facial nerve palsies earlier.

9. The disease can spread medially and subsequently affects nerves around the jugular foramen. Glossopharyngeal Nerve Vagus Nerve Accessory Nerve Hypoglossal Nerve Further spread of disease can affect abducens and trigeminal nerves around the petrous apex, and also the optic nerve.

10. Meningitis, cerebral abscess and sigmoid sinus thrombosis are late signs. Parotitis and trismus due to masseter myositis and temporomandibular joint involvement is a rare clinical feature.

11. Examination shows: Purulent otorrhoea in tender and edematous EAC. Floor of the ear canal may reveal granulation tissue or exposed bone. Patients with HIV infection often lack granulation tissue.

12. Diagnosis The diagnosis is based on the constellation of clinical, laboratory and radiographic findings. Clinical Findings Laboratory Findings ESR Bacterial and Fungal Culture Biopsy

13. Imaging Studies High-resolution Computed Tomography (CT) Scan is valuable in diagnosing Bone erosion Reduced bone density Soft tissue abnormalities inferior to the temporal bone

14. Magnetic resonance imaging (MRI) is generally good at Soft tissue differentiation Bone marrow edema.

15. Technetium-99m-methylene-diphosphonate (99mTc-MDP) scintigraphy Almost 100% sensitivity. Radiotracer accumulates in areas of high osteoblastic activity Has low specificity as it is also positive in malignancy Single Photon Emission Computed Tomography (SPECT) provides Good anatomic localization May highlight areas of bony involvement before the CT scan.

16. Gallium-67-citrate scanning Utilized to monitor treatment response Specific and Sensitive Accumulates in Granulocytes and Bacteria Active Osteomyelitis  Tc-99m (+), Ga-67 (+) Non-active Osteomyelitis  Tc-99m (+), Ga-67 (-)

17. Treatment Aural Toilet of the EAC. It enables control of granulations and pain. Aggressive Glycemic Control in diabetic patients can be as crucial a management strategy as systemic antimicrobial therapy. Use of Topical Anti-microbial Therapy in these cases is controversial as it may make culture of the pathological organism difficult.

18. Systemic Anti-microbial Therapy: Long term systemic culture-directed antimicrobial therapy is the mainstay of treatment. Duration of therapy Depends upon the resolution of symptoms (6-8 weeks) Depends upon Gallium-67 Scan Fluoroquinolone (Ciprofloxacin) is the initial treatment of choice due to its antipseudomonal activity and good bone penetration in osteomyelitis.

19. Pseudomonas resistant to fluoroquinolones Cephalosporin active for pyocyanin (i.e. ceftazidime, cefepime) Penicillin (i.e. ticarcillin) Aminoglycosides Amphotericin B is the most common treatment for fungal MOE. Voriconazole and Itraconazole have also been used on a more limited basis.

20. Hyperbaric Oxygen as an adjunct to systemic antimicrobial therapy increases the partial pressure of oxygen Relieving hypoxia Enhancing the oxidative killing of microbes.

21. Surgery has a limited role in the management of MOE. To obtain specimens for culture To locally debride dead necrotic tissue (circumferential Petrosectomy) To exclude malignancy To decompress Facial nerve for complete facial palsies