Checking for brain damage involves a combination of watching for specific warning signs, undergoing a physical neurological exam, and in many cases getting brain imaging. The approach depends on whether you’re dealing with a fresh injury, where speed matters most, or lingering symptoms that developed over days or weeks. Here’s what each stage of evaluation actually looks like.
Warning Signs That Need Immediate Attention
After any blow to the head, certain symptoms signal that the brain is in danger right now. Seizures, one pupil noticeably larger than the other, and repeated vomiting are among the clearest red flags, especially within the first 24 hours. Loss of consciousness, confusion that worsens over time, clear fluid draining from the nose or ears, and weakness on one side of the body all point toward serious injury that requires emergency care.
In children under two, the signs look different. Because young children can’t describe their symptoms, caregivers need to watch for changes in normal behavior, unusual irritability, refusal to eat, and swelling on the scalp (particularly if it’s not on the forehead, since non-frontal swelling raises more concern). Children aged two and older share more overlap with adult symptoms: vomiting, severe headache, and any loss of consciousness are the key indicators that something may be wrong inside the skull.
What Happens During a Neurological Exam
A neurological exam is the foundation of any brain damage evaluation. It’s a series of physical tests a doctor performs in the room with you, no machines required. The goal is to check whether the brain’s major pathways are working correctly by testing the twelve cranial nerves, each of which controls a specific function.
Your doctor will ask you to follow a finger with your eyes in an H-shaped pattern to check the nerves that control eye movement. They’ll shine a light in your eyes to see if your pupils constrict equally. You’ll be asked to smile, puff out your cheeks, and raise your eyebrows so the doctor can spot any facial asymmetry. They may test your hearing by whispering near one ear while covering the other, or touch your face with a cotton swab and a pin tip to check whether sensation is intact on both sides. You’ll likely be asked to shrug your shoulders against resistance and turn your head against the doctor’s hand to test the nerves controlling neck and shoulder muscles.
If the injury is acute, the Glasgow Coma Scale is one of the first tools used. It scores three things: whether your eyes open on their own, in response to sound, or only to pain; whether your verbal responses are oriented, confused, or absent; and whether your body obeys commands, withdraws from pain, or doesn’t move at all. The combined score ranges from 3 to 15, with lower numbers indicating more severe impairment.
Concussion-Specific Testing
For suspected concussions, particularly in sports, clinicians use a structured protocol called the SCAT6 (Sport Concussion Assessment Tool, version 6). It goes well beyond asking “how do you feel?” and includes several layers of evaluation that you can partly understand even if you’re checking yourself or a family member.
The cognitive portion tests orientation by asking what month, day, and year it is, and what time it is within an hour. It includes immediate memory tasks like recalling a list of words over three trials, and concentration tasks like reciting digits backward or saying the months of the year in reverse order as quickly as possible. There’s also a delayed recall test later to see if those words stuck.
Balance testing is equally important. The modified Balance Error Scoring System has you stand on both legs, in a heel-to-toe tandem stance, and on one leg, counting any wobbles or corrections. A timed tandem gait test asks you to walk heel-to-toe along a line as quickly as possible without stepping off. An optional version adds counting backward by sevens while walking, which challenges the brain to handle two tasks at once.
The symptom checklist is one of the most revealing parts. You rate 22 symptoms on a scale from 0 to 6, covering headaches, pressure in the head, nausea, dizziness, blurred vision, sensitivity to light and noise, feeling “in a fog,” difficulty concentrating, fatigue, trouble sleeping, and emotional changes like irritability or sadness. This self-report helps track whether symptoms are improving or worsening over time.
Brain Imaging: CT Scans and MRI
CT scans are the first-line imaging tool in emergencies. They’re fast, widely available, and excellent at detecting the things that can kill you quickly: bleeding inside the skull, skull fractures, and large areas of swelling. If you arrive at an emergency room after a head injury, a CT scan is typically what you’ll get first.
MRI is better at finding subtler damage. It picks up small bleeds, areas of bruising in the brain tissue, and diffuse axonal injury, which is damage to the long nerve fibers that connect different brain regions. These injuries are often invisible on CT scans. For anyone whose symptoms don’t match a “normal” CT result, MRI is the logical next step.
That said, even standard MRI has real limitations. Conventional MRI detects damage to these nerve fibers in only about half of cases. The reason comes down to resolution: a typical brain MRI divides the brain into roughly 300,000 tiny cubes called voxels, but the brain contains around 10 billion cells, meaning each cube represents roughly 30,000 neurons. Damage spread thinly across those cells can be invisible at that scale. A specialized technique called diffusion tensor imaging (DTI) is significantly more sensitive because it tracks the movement of water molecules along nerve fibers, revealing disruptions in pathways that look normal on standard scans. DTI isn’t available everywhere and is still used more in research settings, but it’s becoming more common in clinical practice for patients with unexplained symptoms after head injury.
Blood Tests for Brain Injury
An FDA-cleared blood test can now help determine whether someone needs a CT scan after a head injury. The test measures two proteins that leak from damaged brain cells into the bloodstream. One comes from the supportive cells surrounding neurons, and the other from the neurons themselves. When levels of these proteins are elevated, it suggests the brain has been physically injured.
The whole-blood version of this test can be used within 24 hours of injury, while an earlier plasma-based version has a 12-hour window. The test doesn’t diagnose brain damage on its own. Instead, it helps doctors decide whether imaging is necessary, potentially sparing patients from unnecessary CT scans and their associated radiation exposure. This is especially valuable for children, where minimizing radiation matters most.
Deciding if a Child Needs a CT Scan
Doctors use a validated set of criteria called the PECARN algorithm to determine which children are at very low risk after a head injury and can safely skip a CT scan. The criteria differ by age.
- Children under 2: Considered low risk if they have a normal mental status, are behaving normally according to their caregiver, had no loss of consciousness, had no serious injury mechanism (like a fall from significant height or a car crash), have no scalp swelling outside the forehead, and show no signs of a skull fracture.
- Children 2 to 15: Considered low risk if they have a normal mental status, no loss of consciousness, no serious injury mechanism, no vomiting, no severe headache, and no signs of a fracture at the base of the skull.
If all the criteria in the relevant age group are met, the child has a very low chance of a significant brain injury. If any single criterion is not met, the doctor will weigh the specific findings to decide whether a CT scan or a period of observation is the better path.
Cognitive Screening for Longer-Term Damage
When the concern isn’t an acute injury but rather ongoing cognitive problems, doctors use standardized screening tools. The two most common are the Mini-Mental State Exam (MMSE) and the Montreal Cognitive Assessment (MoCA). Both are scored from 0 to 30, with higher scores reflecting better function.
The MMSE focuses mainly on memory and language. The MoCA casts a wider net, testing executive function (planning, problem-solving, mental flexibility) and visuospatial skills (understanding where things are in space, copying drawings) in addition to memory. The MoCA is generally considered more challenging and better at catching milder deficits, which makes it more useful for people who seem mostly fine in conversation but are struggling with daily tasks that require complex thinking.
Full neuropsychological testing goes deeper still, sometimes lasting several hours. It evaluates processing speed, attention, verbal fluency, problem-solving, and emotional regulation through a battery of tasks. This level of testing is most useful for people dealing with persistent problems after a brain injury, helping to pinpoint exactly which cognitive functions are affected so that rehabilitation can be targeted.
When Symptoms Persist for Weeks or Months
Post-concussion syndrome is diagnosed when symptoms from a brain injury last well beyond the expected recovery window. The ICD-10 defines it as symptoms persisting longer than three weeks. The DSM-IV requires cognitive deficits in attention or memory plus at least three of the following lasting three months or more: fatigue, sleep disturbance, headache, dizziness, irritability, mood changes, or apathy and personality changes.
The challenge with post-concussion syndrome is that imaging often looks normal. Standard CT and MRI may show no abnormalities even when the person is clearly impaired. This doesn’t mean the damage isn’t real. It means the injury is at a microscopic level that current routine imaging can’t always capture. In these cases, the diagnosis rests on clinical symptoms, cognitive testing results, and the timeline linking those problems to the original injury. If you’re weeks or months out from a head injury and still experiencing headaches, brain fog, difficulty concentrating, or emotional changes that weren’t there before, those symptoms themselves are the evidence that something in the brain hasn’t fully recovered.