Implanted device predicts epilepsy seizures

For the first time, a small device implanted in the brain has accurately predicted the onset of seizures in some adults who have epilepsy and do not respond to drugs.

The small proof-of-concept study is published today in The Lancet Neurology.

‘Knowing when a seizure might happen could dramatically improve the quality of life and independence of people with epilepsy and potentially allow them to avoid dangerous situations such as driving or swimming, or to take drugs to stop seizures before they start, rather than continuously as at present,’ said lead author Mark Cook from the University of Melbourne in Australia.

The technology, developed by Seattle-based NeuroVista, is designed to detect abnormal electrical activity in the brain that precedes a seizure using electrodes implanted between the skull and brain surface which constantly monitor electrical activity (electroencephalography or EEG) data.

The electrodes are connected to a second device implanted under the skin of the chest which transmits this information wirelessly to a hand-held device that calculates the probability of a seizure.

Three coloured lights warn patients of the high (red), moderate (white), or low (blue) risk of an impending seizure.

The Australian feasibility study included 15 people with focal epilepsy, a condition where seizures start in a specific part of the brain.  Aged between 20–62 years, they experienced between two and 12 seizures per month and had not had their seizures controlled despite use of at least two anti-epileptic drugs.

During the first month after surgical implant, the system was set for detection only while EEG data containing a minimum of five seizures was collected and analysed to construct an individualised algorithm to predict the likelihood of a seizure.

The researchers measured the system’s performance, clinical effectiveness, and safety for four months after implant and four months following activation.

During the initial data collection, the system correctly predicted seizures with a ‘high warning’ sensitivity (the proportion of actual positives which were correctly identified) greater than 65 per cent, and worked to a level better than chance in 11 of the 15 adults. In eight of the 11 patients who went on to have the device activated and to use the system for four months, sensitivity ranged from 56 per cent to 100 per cent.

The technology is said to appear relatively safe, with a similar safety profile to other implanted devices such as deep brain stimulators for Parkinson’s disease. Three patients experienced serious device-related adverse events, with two requiring the device to be removed.

The study revealed disparities between reported and detected events, with most participants underestimating the number of their seizures. One patient who reported having 11 seizures per month actually had 102.

According to a statement, Cook is optimistic that if the findings are replicated in larger, longer studies, this technology will improve management strategies including developing methods of preventing seizures using direct electrical stimulation or fast-acting drug therapies.