DTI Shows Post-concussion Damage to Brain's White Matter
By Richard S. Dargan
People who suffer concussions may have damage to the white matter (WM) of their brains that corresponds with specific post-injury symptoms like depression and neck pain, according to results from two studies presented Monday.
Previous research has shown that mild traumatic brain injury (mTBI)—more commonly referred to as a concussion—can cause lasting damage to the brain's signal-carrying WM. The development of the MRI technique diffusion tensor imaging (DTI) has enabled researchers to look for damage all the way down to individual WM tracts.
"Often, conventional MRI results are normal in these patients," said Joseph Delic M.D., from the University of Pittsburgh Medical Center. "DTI is more sensitive to white matter and allows us to see specific regions corresponding to injuries that present as a specific symptom."
In the first study, Dr. Delic and colleagues looked at associations between WM injury patterns and neuropsychiatric symptoms like depression and anxiety in subjects with mTBI. The 74 subjects with post-concussion symptoms were compared with 36 mTBI patients who were free from the corresponding symptoms. The researchers used DTI to create fractional anisotropy (FA) maps, a reflection of how easily water moves along WM tracts. Lower FA values correspond to a greater degree of damage.
Patients with mTBI and depression had decreased FA values in three areas of the brain: the superior longitudinal fasciculus; the white matter around the nucleus accumbens; and the anterior limb of the internal capsule. Patients with anxiety had diminished FA values in the cerebellum.
"We saw central white matter injury in people with post-traumatic depression as well as anxiety, and the regions that were damaged corresponded to regions we already know are associated with non-traumatic depression," said Dr. Delic.
Intracranial Injuries May be Source of Post-traumatic Neck Pain
Dr. Delic also presented results from a study of the association between WM injury and peripheral symptoms like cervicalgia and parathesias. Researchers reviewed DTI results from 19 mTBI patients with cervicalgia and nine with peripheral paresthesias and compared them with 55 mTBI patients without cervicalgia and 65 mTBI patients without paresthesias.
Patients with post-traumatic neck pain had decreased FA values in a white matter tract known as the right superior longitudinal fasciculus, suggesting that their pain may be at least partly related to intracranial, or within the skull, injuries.
"The intracranial aspect may cause problems with spatial orientation," said Dr. Delic. "This suggests that post-traumatic neck pain may result not from direct injury to the cervical region, but from attempts at compensation for spatial orientation insufficiencies after mTBI."
Further, the results show that the diagnosis and treatment of patients with post-traumatic neck pain should not merely be focused on the cervical region, but also extend to possible intracranial injuries, Dr. Delic said.
The two studies highlight the potential for WM injury patterns to provide new targets for therapeutic interventions, Dr. Delic said. "The ultimate goal is to develop techniques to identify injuries in patients, determine if those injuries are predictive of specific symptoms and tailor treatments for each patient," he said.