Electroencephalography research

A brain-monitoring system such as this one has been used to assess cognitive activity in people with brain injuries. Credit: Amelie Benoist/BSIP/Getty

Medical research

Hidden brain activity revealed in people with coma

Hospital patients who appear unresponsive after commands show evidence of brain activity.

Fifteen per cent of hospital patients with severe brain injuries exhibited cognitive activity in response to commands — even though they did not react visibly.

Jan Claassen at Columbia University in New York and his colleagues studied 104 ‘clinically unresponsive’ patients whose brains had been damaged by a stroke or other trauma. None showed a visible response to verbal instructions; some were in a coma.

The researchers used a technique called electroencephalography (EEG) to study electrical activity in the patients’ brains. When asked to move one hand, 15% of patients showed brain patterns similar to those of healthy volunteers responding to the same instructions.

A year after their injury, 44% of patients whose brains responded to commands could look after themselves for at least 8 hours, compared with only 14% of those whose brains did not respond. Larger trials are needed to test the value of EEG for prognosis, the authors say.