Medicine
Cerebral Concussion
Quick fact
A concussion does not necessarily cause loss of consciousness; more than 90% of concussions occur without the person ever blacking out.
Why this is interesting
You’ve probably heard of concussions in sports, but what exactly happens inside your head when you get one? And why can a second blow be so dangerous?
Read the full explanation
Understanding Cerebral Concussion
Picture your brain as a soft, jelly-like organ floating inside a hard skull, cushioned by cerebrospinal fluid. When your head or body is struck suddenly, the brain sloshes against the inner walls of the skull. This impact can stretch and tear delicate nerve fibers (axons), altering the brain’s normal electrical and chemical activity. The result is a temporary disturbance in brain function—not structural damage visible on scans. Symptoms typically include headache, confusion, dizziness, nausea, sensitivity to light or noise, and memory or concentration problems. Most people recover fully within days to weeks with proper rest, but the brain is vulnerable during this window.
A deeper explanation
At the cellular level, concussion triggers a complex metabolic cascade. The mechanical force causes an uncontrolled release of neurotransmitters, especially glutamate, leading to an ion imbalance: potassium exits cells while calcium enters. To restore balance, the brain’s sodium‑potassium pumps work overtime, consuming large amounts of energy (ATP). This creates a period of reduced cerebral blood flow relative to demand, causing an energy crisis. Axonal stretching can also impair the transport of proteins and other molecules, potentially leading to long-term damage if repeated. The greatest immediate risk is second impact syndrome, where a second concussion before the first has healed can cause rapid brain swelling and death. This is why athletes must follow strict return-to-play protocols, which involve a gradual increase in cognitive and physical activity while monitoring symptoms. Understanding these mechanisms underscores why rest is not just ‘taking it easy’—it is a medical necessity for the brain’s recovery.