4.3 External auditory canal mycosis
In addition, we also observed some patients may develop external auditory meatus mycosis in our study. In fact, we didn‘t find any reports about the mycosis of the external auditory canal after IT. The possible reason is that our vertigo center admits a large number of patients in southern China, including more than 250 meniere’s disease patients every year. Due to the large number of patients, some rare complications may be observed in our center.
In our study, the incidence of mycosis of the external auditory canal after dexamethasone injection in the tympanum is higher than that of lidocaine alone, and the most likely risk factor is dexamethasone due to patients who were injected dexamethasone in the tympanic cavity may be at risk for immunosuppression and opportunistic infection. Leav et al.[13]reported a case of invasive pulmonary aspergillosis in a patient with asthma who was treated with high-dose inhaled fluticasone(1760mgdaily) which was significantly higher than the standard dosage in clinical practice (440mg twice daily).This suggests that steroid can lead to immunesuppression, and the higher the concentration, the greater the chance of an opportunistic infection. This is consistent with what we observed in our study, all the patients who were infected by the fungal were treated with 5mg/ml of dexamethasone, while patients treated with 2mg/ml showed no signs of fungal infection. It may suggest that we should reduce the concentration of dexamethasone as much as possible on the premise of ensuring the therapeutic effect.
In addition, the warm and humid environment in southern China is one of the special factor of fungal external auditory meatus. First of all, fungi can easily reproduce in a warm environment. Our hospital is located in the south of China where belongs to a subtropical region, with an average temperature of over 22.5℃, while the appropriate growth temperature of fungi is between 20-35℃.Secondly, Guangzhou is close to the ocean and there are no big mountains to prevent the warm and humid air flow coming from the ocean reaching Guangzhou. And this warm and humid environment is very favorable for the growth of fungi[14].
The third factor may be the one that clinicians need to be urgently concerned about is iatrogenic infections, which include the whole treatment process is not standardized or the use of fungus-infected drugs. If the syringe is not properly sterilized during drug extraction, a small amount of fungal spores may be iatrogenic into the eardrum or external auditory canal, which may cause local propagation and spread of the fungus. Treatment with fungus-contaminated steroids is one of the most direct causes of fungal infection. Kauffman CA[15]found that 751 patients were reported with fungal infection and 64died in 2012. In the end, they found that most patients had undergone epidural injection and a few osteoarticular injection with fungus-contaminated methylprednisolone acetate, resulting in a significant number of intracranial and intra-articular infections. Therefore, the government must carry out the most stringent quality control requirements for the production of drugs.