A traumatic brain injury (TBI) is a change in how the brain works caused by an external force (like a fall, collision, or impact). It can affect thinking, mood, sleep, balance, and daily function—even when scans look normal.
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Why it matters: TBI is often “invisible,” and symptoms can appear right away or develop over time. Clear documentation and follow-up help people get the right plan instead of being told to “just wait.”

What it can look like: Headache/head pressure; brain fog; memory or attention issues; dizziness/balance problems; light/noise sensitivity; sleep disruption/fatigue; irritability/anxiety/mood changes; reduced performance at work/school.Severity range

• Mild (mTBI/concussion)
• Moderate
• Severe

How clinicians check it: History + symptom timeline; neurologic exam (balance/coordination/eye movements); objective testing as needed (cognitive and/or vestibular/ocular testing).

Common misunderstandings: A normal CT/MRI does not automatically rule out concussion/mild TBI; “mild” describes early presentation, not how hard recovery feels; symptoms can be real without a visible lesion on imaging. TBI is defined by mechanism and impact on function, not just imaging results.

Key takeaway: TBI is a brain-function change after external force—and it often benefits from tracking symptoms and function over time.‍

Wellness disclaimer: This glossary entry is for education and does not replace medical care.