Cause of idiopathic sudden sensorineural hearing loss: The stress response theory

Figure 1 Characteristics of the lateral wall stress response. A-D: The lateral wall is composed of the stria vascularis (SV) and the spiral ligament, in which there are four types of fibrocytes (I-IV). Intraperitoneal lipopolysaccharide (LPS) injection mainly activates nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) (red dots) in the type II fibrocytes asymmetrically between the two ears. However, local LPS injection (i.e., intratympanic injection) does not induce the activation. Noise exposure activates NF-κB in type I fibrocytes symmetrically at first. Systemic cisplatin injection activates NF-κB in the whole lateral wall, outer hair cells (HCs), and the spiral limbus, and causes HC loss; E: Mild energy failure of the lateral wall causes transient threshold shift (TTS); F: However, severe energy failure causes permanent threshold shift (PTS) with degeneration of cochlear lateral wall, and mild degeneration of the organ of Corti. HL: Hearing loss.