After a Brain Injury, the Damage Keeps Spreading. A New…

After a Brain Injury, the Damage Keeps Spreading. A New Study Found How. Every intensivist and trauma surgeon knows this pattern. A patient comes in with traumatic brain injury. You manage the primary injury. And then, sometimes hours later, the lungs start failing. Vascular permeability increases. Secondary oedema develops in organs that were never touched. The mechanism driving that systemic cascade has never been fully explained. A study published in Arteriosclerosis, Thrombosis, and Vascular Biology this month identifies a specific molecular pathway responsible and it involves something nobody expected to find circulating in peripheral blood. When a brain is injured, it releases mitochondria directly into the bloodstream. Not mitochondrial fragments. Not mitochondrial DNA alone. Structurally intact, metabolically active mitochondria: circulating as free particles in peripheral blood. The researchers detected these extracellular mitochondria, which they call exMt, in blood samples from 28 patients with isolated TBI. Levels correlated directly with injury severity as measured by Glasgow Coma Scale score. The more severe the injury, the higher the circulating exMt. In mouse models, plasma exMt peaked at three hours post-injury — the same window in which TBI-induced endotheliopathy is known to peak clinically. This is where the mechanism becomes clinically important. The circulating exMt bind to endothelial c