VNS 'Wakes' Patient After 15 Years in a Vegetative State

Use of vagus nerve stimulation (VNS) may modulate brain activity and improve disorders of consciousness, a new case report suggests.

A case report of a male patient, who was in a vegetative state for 15 years after a traumatic brain injury (TBI) due to an automobile accident was surgically implanted with a VNS device. After 1 month of increasing stimulation, when the intensity level was at 1 mA, the patient showed improvement in arousal, attention, and spontaneous movement.

Improved scores on the Coma Recovery Scale-Revised (CRS-R) over baseline also suggested "a transition from a vegetative to minimally conscious state," report the investigators, led by Martina Corazzol, Centre National de la Recherche Scientifique, Bron, France.

In addition, scalp electroencephalography (EEG) data showed an increase in theta band power, and 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) readings showed increased activity in basal ganglia and occipito-parieto-frontal regions.

Overall, the results "show that stimulation of the vagus nerve promoted the spread of cortical signals and caused an increase of metabolic activity leading to behavioral improvement, as measured with the CRS-R...and as reported by clinicians and family members," write the researchers.

These improvements also question "the belief that disorders of consciousness persisting after 12 months are irreversible," they add.

The findings are published in the September 25 issue of Current Biology.

Novel Treatments Needed

As reported by Medscape Medical News, VNS has been shown to provide pain relief for patients with episodic cluster headaches. Other research has suggested that it improves arm function after stroke, lowers risk for sudden unexpected death in epilepsy, and offers hope for treatment-resistant depression.

For patients in a vegetative state, there is significant debate about why some recover while others do not.

"The neural signature of spontaneous recovery is linked to increased thalamo-cortical activity and improved fronto-parietal functional connectivity," write the investigators.

"The likelihood of consciousness recovery depends on the extent of brain damage and patients' etiology, but after one year of unresponsive behavior, chances become low. There is thus a need to explore novel ways of repairing lost consciousness."

For the study, they sought to use VNS to activate the thalamo-cortical network.

This process not only increases metabolism in the thalmus and forebrain but also "enhances neuronal firing in the locus coeruleus which leads to massive release of norepinephrine," which is important for arousal and alertness, note the researchers.

After the family granted permission, the patient was surgically implanted with a VNS device in his chest. Preimplantation (baseline) and postimplantation EEG and 18F-FDG PET recordings were conducted. VNS was increased gradually up to 1.5 mA, and monitoring continued up to 6 months.

Therapeutic Potential

Results showed consistent improvements at 1 month in general arousal, visual pursuit, body motility, and sustained attention. According to a press release, the man's family reported that he was able to turn his head upon request and follow an object with his eyes.

The baseline CRS-R score of 5 improved to 10 when the stimulation's intensity level was at 1.0 to 1.25 mA, with the improvement mostly concentrated in the test's visual domain.

Theta band power, "a brain signal found to reliably distinguish minimally conscious patients from vegetative ones," increased significantly from 4 Hz at baseline to 7 Hz after implantation (P < .001), the researchers note.

Activity increases in the occipito-parieto-frontal and basal ganglia regions were shown, via 18F-FDG PET recordings, by the 3-month assessment. In addition, the thalamus' metabolic signal was enhanced.

"Our study demonstrates the therapeutic potential of vagus nerve stimulation to modulate large-scale human brain activity and alleviate disorders of consciousness," summarize the investigators.

Because the patient didn't completely "wake up" but was in a state of minimal consciousness, principal investigator, Angela Sirigu, PhD, also from the Centre National de la Recherche Scientifique, has been getting questions about whether the patient really is better off.

"It is always better to understand than not be aware of what others are doing to you or telling you," Dr Sirigu said in an article published by National Geographic.

"I would prefer to be aware, in any case."

Curr Biol. 2017;27:R994-R996. Full text

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