Long-Term Effects of Concussions From Car Accidents

Concussion as a Mild Traumatic Brain Injury

A concussion is a mild traumatic brain injury, or mild TBI. MedlinePlus lists vehicular accidents among the causes and explains that a sudden jarring movement can make the brain bounce or twist inside the skull.

The word “mild” describes how a patient looks when first examined. Researchers in the TRACK-TBI recovery study classified an injury as mild based on an admission Glasgow Coma Scale score of 13 to 15.

The National Institute of Neurological Disorders and Stroke ranks accidents involving motor vehicles, bicycles, and pedestrians as the third most common cause of traumatic brain injury.

Early Signs After a Car Accident

Headache, confusion, and trouble concentrating are among the first signs of a concussion. MedlinePlus lists these symptoms of a milder brain injury:

• Confusion, trouble concentrating, or not thinking clearly
• Drowsiness or being hard to wake
• Headache
• Memory loss for events just before or after the injury
• Nausea and vomiting
• Flashing lights or light sensitivity
• Sleep changes

MedlinePlus says most people with a mild TBI never pass out, and a person can have a mild TBI and not realize it. The CDC notes that some symptoms appear right away while others may not appear for hours or days after the injury.

The CDC lists danger signs in adults that need emergency care. They include a headache that gets worse and does not go away, repeated vomiting, slurred speech, one pupil larger than the other, seizures, and drowsiness that makes waking difficult.

TRACK-TBI Recovery Findings

The TRACK-TBI study published in JAMA Neurology enrolled 1,154 people with mild TBI at 11 US level I trauma centers and compared them with 299 people who had orthopedic injuries that did not involve the head.

At 2 weeks, 87% of the mild TBI group reported some functional limitation. At 12 months, 53% did, compared with 38% of the orthopedic group. The researchers measured these limits with the Glasgow Outcome Scale Extended, which rates injury-related limits across broad areas of life. A score below the top mark means some part of normal life has not returned.

A systematic review of 101 prognosis studies by the International Collaboration on Mild Traumatic Brain Injury Prognosis states that most adults “recover over 1 year” and that persistent symptoms were more likely in people with more symptoms early on and more emotional stress.

Normal CT Scan Results

A normal head CT scan does not mean a concussion has healed or never happened. The NINDS states that clinically validated imaging and blood tests “can’t always detect damage from mild, concussive injuries.”

A TRACK-TBI analysis in JAMA Network Open looked only at patients with the highest Glasgow Coma Scale score of 15 and a head CT showing no acute injury. Of the 659 patients followed at 6 months, 56% had not fully recovered. Among participants with incomplete recovery, 88% (479 of 546) said they had not returned to their pre-injury life.

MRI can find injuries CT misses. In an earlier TRACK-TBI imaging study, 27% of patients with a normal admission CT had an abnormal brain MRI about 12 days later. Brain contusions and small areas of bleeding along nerve fibers on MRI were each tied to poorer outcomes at 3 months.

These findings make the treating doctors’ notes the main record of a concussion when scans look normal. More severe injuries that do show on imaging are described in car accident brain injuries.

Predictors of Persistent Symptoms

Years of education, mental health conditions before the injury, and a prior brain injury were the strongest predictors of symptoms 6 months later in a TRACK-TBI pilot study of 277 patients. After the researchers validated their model, all of its predictors together explained 14% of the variation in symptoms, so they cannot tell any one person how recovery will go.

The same systematic review from the International Collaboration on Mild Traumatic Brain Injury Prognosis found that common post-concussion symptoms are not unique to brain injury and also occur after other injuries. Poorer recovery was tied to poorer mental and physical health before the injury and to more stress related to the injury.

The NINDS reports that most people recover fully from a first concussion within a few weeks and that recovery from a second or third concussion is “generally slower.” MedlinePlus adds that the risk of long-term brain changes is higher after more than one traumatic brain injury.

Mood and Stress Disorders

In the TRACK-TBI mental health study in JAMA Psychiatry, 20.0% of people with mild TBI showed signs of post-traumatic stress disorder, major depression, or both at 3 months and 21.2% at 6 months, compared with 8.7% and 12.1% among people with orthopedic injuries.

The study found higher risk in people with less education and a history of mental health problems. Mood changes, being easily upset, and trouble with memory can also appear during ordinary concussion recovery, according to MedlinePlus.

Dementia Risk Studies

A study of 357,558 veterans in JAMA Neurology found that mild TBI without loss of consciousness carried a hazard ratio of 2.36 for a dementia diagnosis compared with a matched group without TBI. Across all TBI severities, 6.1% of veterans with a TBI developed dementia during follow-up, compared with 2.6% of those without one.

A Danish national registry study of 2,794,852 people found a hazard ratio of 1.24 for all-cause dementia after traumatic brain injury of any severity compared with people without one. The risk rose with the number of injuries, from a hazard ratio of 1.22 after one injury to 2.83 after five or more.

Both studies measured associations in large groups, so neither predicts dementia for a particular person after a single concussion.

Chronic Traumatic Encephalopathy Research Gaps

Chronic traumatic encephalopathy, or CTE, can only be diagnosed for certain after death. The StatPearls review of CTE on the National Library of Medicine describes it as a progressive neurodegenerative condition “commonly observed in individuals involved in contact sports or military service” with a higher risk of repeated head injuries.

Clinical criteria now describe a living syndrome that includes cognitive, behavioral, and mood symptoms, but a definite diagnosis still requires examining brain tissue after death. The CTE research base centers on repeated impacts, which is different from a single concussion in a car accident. The condition itself is explained further under CTE after car accidents.

Symptom Records Over Time

The TRACK-TBI researchers recommended follow-up visits about 2 weeks after injury for patients with a normal CT, so clinicians can spot incomplete recovery early. The 12-month TRACK-TBI study also called for more systematic follow-up of mild TBI patients to reduce the risk of chronic problems.

The record of a concussion is built from repeat visits: symptom checklists, cognitive testing, and notes on work, sleep, and mood. MedlinePlus advises contacting a provider when symptoms are not improving after 2 or 3 weeks. The car accident injuries hub lists related conditions.