Electrode-array insertion trauma

Threading a stiff electrode array through the scala tympani's tightening spiral can rupture the basilar membrane, tear the spiral ligament, fracture the osseous spiral lamina, or translocate the array into scala vestibuli — mechanical insults that destroy residual hair cells, provoke inflammation and intracochlear fibrosis/ossification, and can accelerate spiral ganglion loss. Insertion trauma is the main enemy of hearing preservation and a determinant of long-term electrode-neuron distance and impedance.

Mitigation is a design-and-surgery problem: lateral-wall (versus perimodiolar) or thin/flexible arrays, slow insertion (tens of seconds to minutes), round-window rather than cochleostomy approaches, real-time feedback (electrocochleography monitoring, or emerging force-sensing/robotic insertion tools), and anti-inflammatory drug elution. Atraumatic is relative — even textbook insertions cause some intracochlear reaction — which is why drug-eluting and softer arrays, and eventually regenerative interfaces, are active frontiers.