4.1 Complications
A lot of studies [7-10]had found that nearly one fifth of the overall study population suffered complications, the majority of these side effects were technique-related, very transient and self-resolving. They included transient dizziness/vertigo postinjection, ear fullness and slight otalgia during injection which can be all caused by the immediate injection technique. But in our study we have found some steroid-related side effects, including tympanic membrane atrophy thinning and external auditory canal mycosis.
4.2 Tympanic membrane atrophy thinning
In our study, tympanic membrane atrophy thinning were observed in 5 ears. The tympanic membrane is composed of three layers: the upper cortex, the fibrous layer and the mucosal layer. Keratinocytes, fibroblasts and the extracellular matrix (ECM) are the main components of the tympanic membrane. The damage of keratinocytes, fibroblasts and ECM will affect the morphology and function of the tympanic membrane. In 1978, Wilson et al.[11]reported that steroid can modify fibroblasts in vitro and inhibit the activity of these cells to varying degrees. Schoepe et al.[12]found that the proliferation and ECM protein synthesis of keratinocytes and fibroblasts were suppressed by steroid. Thereby, the stratum corneum got thinner, followed by an increased transepidermal water loss. Then, the epithelial layer lost its tensile strength and elasticity caused by the water loss and the degraded ECM. So the steroid can make the epithelial layer atrophy and steroid-induced tympanic membrane atrophy is characterized by a profound increase in transparency of skin, a cigarettepaper-like consistency accompanied by an increased fragility, tearing, bruising, thin, shiny, and telangiectatic which is consistent with what we had found in the 5 cases of tympanic membrane atrophy thinning in this study. The membrane presented increased transparency, more shiny, and visually felt thin. It was worth noting that the five patients in our study had no tympanic membrane perforation during the entire observation period, so tympanic membrane atrophy near the injection port was not the result of healing after tympanic membrane perforation.