Cognitive fatigue after a brain injury is not the same as being physically tired or needing more sleep. It is a distinct neurological phenomenon, and patients often describe it as a kind of mental wall — a sudden, dramatic drop in the ability to think, focus, or communicate, often after relatively modest mental effort.

Here is what makes it different from typical tiredness:

• It can hit quickly and without obvious warning
• Rest may not resolve it the way a nap resolves physical fatigue
• Concentration-heavy tasks — reading, driving, following a conversation — can trigger it faster
• It often co-occurs with increased headaches, irritability, and word-finding difficulties

From a neurological standpoint, a brain recovering from injury has to work significantly harder to perform the same tasks it handled automatically before. That extra metabolic demand depletes neural resources faster, and the brain signals its limits in ways that feel nothing like ordinary exhaustion.

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