Blood-brain barrier disruption

Blood-brain barrier disruption is the mechanical breach of the neurovascular unit during and after electrode insertion. Severing microvasculature admits blood-borne proteins (albumin, fibrinogen, immunoglobulin G) and peripheral macrophages into the neuropil, and the accompanying microhemorrhage deposits iron and activates the clotting and complement cascades — all potent inflammatory triggers in tissue that is normally immune-privileged.

Whereas a single insertion injury might resolve, persistent or repeated leakage is the more damaging pattern: a stiff device tethered to the skull grinds against pulsating tissue with every heartbeat, chronically re-opening the barrier. Sustained BBB compromise is now viewed as a key reason inflammation around implants stays chronic rather than resolving, linking mechanical design directly to the biological response.