OCT 02, 2017 01:54 PM PDT
Vegetative Patient Shows Signs of Consciousness After Vagus Nerve Stimulation
WRITTEN BY: Carmen Leitch
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It has long been thought that not much hope remains for people that fall into a persistent vegetative state, but scientists have not given up. A recent success was reported when neurosurgeons implanted a device that stimulates the vagus nerve into a man that had been left vegetative after a car accident 15 years ago. After implantation, the 35-year-old man began to show signs of consciousness. It’s been reported in Current Biology and is outlined in the first half of the following video.

Vagus nerve stimulation (VNS) is already being used in the clinic to treat epilepsy and depression. Now it may help restore consciousness to those that have been vegetative for many years. There is a medical belief that after twelve months in such a state, the condition is irreversible; this report challenges that assumption, said the investigators.

Stimulation of the vagus nerve, has shown that "it is possible to improve a patient's presence in the world," commented the corresponding author of the work, Angela Sirigu of Institut des Sciences Cognitives Marc Jeannerod in Lyon, France.

Many parts of the body are connected to the brain by the vagus nerve, like the gut and heart. It has roles in modulating heart rate, wakefulness, and stress, among many other critical functions. In order to see whether consciousness might be restored through stimulation of the vagus nerve, the scientists looked for a particularly tough case. For this work, they selected a patient who had been determined to have no sign of improvement for ten years. 

The patient received one month of VNS, after which the movement, attention, and brain activity of the patient improved significantly. The researchers reported that the man began to respond to simple orders, something that was not previously possible. For example, after stimulation, his eyes followed, and upon request, he turned his head. His mother observed an improvement in his ability to stay awake as his therapist read a book.

Other changes were seen as well in the so-called threat response. Once absent, the patient exhibited new reactions, such as widening his eyes after an examiner suddenly approached. He had regained minimal consciousness, though he spent over a decade in a vegetative state.

This figure shows information sharing across all electrodes before and after vagus nerve stimulation (VNS). On the right, the warmer colors (yellow/orange) indicate an increase of connectivity among posterior parietal regions. / Credit: Corazzol et al.

 

Brain activity recordings confirmed that major changes were taking place in the patient. PET scans indicated that metabolic activity was rising in cortical and subcortical regions of his brain. Functional connectivity in the brain was increased. Theta EEG signals, which distinguish between minimal consciousness and vegetative states indicated a significant improvement in brain regions that control awareness, sensation, and movement.

The researchers are confident that the work shows how the proper intervention strategies can yield improvements in the most serious cases.

"Brain plasticity and brain repair are still possible even when hope seems to have vanished," Sirigu said.

Next, a large collaborative study is planned so that the scientists can confirm the findings and extend the therapeutic application of VNS for those stuck in a vegetative or minimally conscious state. Not only can this assist patients, said Sirigu, the findings will also expand our understanding of "this fascinating capacity of our mind to produce conscious experience."

 

Sources: AAAS/Eurekalert! via Cell Press, Current Biology


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