Pet Scans Reveal Abnormal Brain Activity After Concussions -Condition May Last Months

By Lois Baker

Release Date: November 19, 1996

BUFFALO, N.Y. ­ Researchers at the University at Buffalo have shown that a concussion results in abnormal brain activity within the first few weeks post-injury, and that the abnormality can last for months. This activity correlates with patient complaints of physical and emotional discomfort early on, and later with various cognitive impairments, researchers found.

A multidisciplinary research team headed by Richard Linn, Ph.D., assistant professor of rehabilitation medicine, uncovered the abnormal brain activity in a small group of patients with recent concussion, using positron emission tomography, or PET, scans.

This ultra-sensitive imaging technology allows researchers to witness the brain's activity, such as its use of oxygen or glucose, as it is taking place, rather than showing its structure, as with magnetic resonance imaging (MRI) scans.

Linn, program director of the UB Traumatic Brain Injury Rehabilitation System and a specialist in the evaluation and treatment of persons recovering from serious head injury, is one of the few researchers using PET scanning to understand mild traumatic brain injury, the medical term for concussion.

"In most instances, a concussion is not going to cause significant disability," Linn said. "The question is, 'Are these people thinking less clearly?' 'Yes.' 'Are these changes in thinking related to brain abnormalities?' 'Yes.' 'Does the condition persist for several months?' Again, the answer is 'Yes.'"

"The amount of disability depends to some extent on the type of day-to-day activity the individual performs," he stated. "A person whose job requires quick reflexes, focused concentration and good coordination may be more affected than someone performing less demanding work."

Linn's research is funded by the National Institute of Disability and Rehabilitation Research.

Concussion traditionally has not been considered a significant medical problem. If patients don't have a fracture or other complications, and they respond normally during neurological examination in the emergency room, they are sent home.

"In the first few weeks post-injury, some may experience headache, irritability, dizziness or fuzzy thinking," Linn said. "They may have an MRI scan, which typically shows no abnormalities. Many may come away still feeling that their thinking isn't right, but they don't know why. We now are able to show that these symptoms are related to a definite change in brain activity, and that these patients are not merely imagining their symptoms."

PET scans of six people who had sustained a mild traumatic brain injury administered during the first two to three weeks after injury and again three to four months later revealed small but significant areas of increased glucose metabolism in a region of the cerebrum called the anterior cingulate, more pronounced in the right hemisphere than the left.

All patients in the study with abnormal PET scans had had normal MRI scans, and showed few outward signs of injury. PET scans appear to be more sensitive than MRI scans or other techniques in detecting these changes, Linn said.

The increased use of glucose may be a sign that the cells are repairing themselves after injury, or that their ability to function is diminished and they need more energy to perform the same work, Linn said. Regardless of the mechanism, they are behaving abnormally, he noted.

In the early stages after injury, this abnormal activity correlated with patient complaints, such as headache, irritability, anxiety, depression, dizziness and lack of concentration, symptoms so common to concussion sufferers that, if they persist, are dubbed collectively "post-concussive syndrome."

After three to four months, the areas of abnormal activity had enlarged somewhat and were correlated with impaired attention span, verbal memory, motor function and information processing, but not with post-concussion symptoms, findings showed.

"The abnormalities in the brain reflected how well patients performed on cognitive tests," Linn said. "The greater the abnormality, the worse the patient's performance."

Linn said the only treatment for mild traumatic brain injury is education and patience. "People just have to wait it out. More than 50 percent of patients are back to normal by six months; more than 95 percent are fully recovered in a year."

Patients and health-care professionals need to be educated that mild brain injuries definitely produce brain abnormalities that lead to cognitive and emotional symptoms, Linn said.

"Patients need to know they aren't going crazy, and that what they are experiencing may be a normal part of the recovery process."

The researchers currently are conducting further research using PET scans to study brain function following brain injury.