Brain implants help people to recover after severe head injury
A coloured MRI scan of a healthy human brain. When the brain is injured, neural circuits involved in cognition and memory are damaged. Credit: K H Fung/Science Photo Library
The technique known as deep brain stimulation (DBS) has improved cognition in people with traumatic brain injuries, a small clinical trial has found.
The trial data, published in Nature Medicine on 4 December1, show that the five participants had a 15–52% improvement in their processing speed in a cognitive test after three months compared to their performance before the DBS implants.
“For some participants, the improvements have been transformative, even many years after the injury,” says study co-author Jaimie Henderson, a neurosurgeon at Stanford University in California.
Medium to severe traumatic brain injury (msTBI), often a result of wounds or trauma to the head, causes neurons to die and brain circuits to disconnect, leading to long-term cognitive difficulties. People who have this type of injury — of which there are more than 5 million in the United States — often cannot resume their pre-injury life and work.
How deep brain stimulation is helping people with severe depression
MsTBI is thought to affect neural circuits in the thalamus, a structure near the centre of the brain involved in attention, decision-making and working memory. Henderson and his colleagues hoped that applying an electrical current — a technique shown to activate and restore connections among damaged neurons — to key parts of the thalamus could lead to improvements in cognitive functioning in people with msTBI.
To precisely target neurons in the thalamus, the research team designed personalized treatment approaches for the four men and one woman who took part in the study, using individuals’ brain imaging data and specialized anatomical atlases.
The participants, all of whom had experienced msTBI for at least two years, had surgery to implant electrodes near the lateral side of their thalamus in both brain hemispheres. After the surgery, the researchers spent 14 days fine-tuning the stimulation parameters for each participant. Then, they used the implants to apply an electrical current at a frequency of 150–185 hertz for 12 hours a day for three months.
To test the participants’ cognitive functioning, the researchers used a test that assesses task switching, attention and working memory. Participants had to connect consecutive numbers or letters arranged in a specific geometric pattern.
At the end of the three months, participants showed an average improvement of 30.7% in the attention task compared to their performance before the surgery, and their speed at completing the cognitive test improved by 32%.
The team hopes to carry on this work by running larger trials, says study co-author Nicholas Schiff, a neurologist at Cornell University in Ithaca, New York. They would also like to develop a reliable protocol to train other centres to deliver the treatment.