Helping stroke patients to recover

Strokes are the primary cause of adult mobility impairment, the second-leading cause of dementia and the third most common cause of death in France. They represent one of the most resource-intensive emergency hospital admissions. Around 500 000 patients in France today suffer as a result of a stroke (with about 130 000 new cases each year)*.  Centrale Nantes researchers, in collaboration with Nantes University Hospital, are contributing to efforts to improve the rehabilitation of stroke patients, a major issue in healthcare today.

WHAT IS A STROKE?

Also known as a cerebrovascular accident, a stroke is when blood ceases to flow to part of the brain, most commonly as the result of a clot obstructing a blood vessel. The brain ceases to receive its normal oxygen supply leading to brain cell death in the affected area. A less frequent cause of stroke is when a blood vessel bursts resulting in a cerebral haemorrhage. The extent of the damage caused by a stroke depends on which area of the brain was affected.

WHAT'S THE LINK WITH ENGINEERING?

Four years ago, Centrale Nantes researcher Marie-Françoise Lucas began to work with Dr. Vincent Roualdes, Neurosurgeon at Nantes University Hospital, studying the Brain Computer Interface (BCI) for therapeutic purposes. Saïd Moussaoui, researcher and head of the specialisation Signals, Images and biomedical and audio applications' at Centrale Nantes, took over from Marie-Françoise Lucas after her retirement in 2015. He is continuing the research focussing in particular on functional - mainly motor - rehabilitation of stroke patients through the use of electroencephalographic (EEG) signals (recorded via electrodes placed on the scalp) or electrocorticographic (ECoG) signals (recorded via electrodes placed on the cerebal cortex). His expertise in signal and image processing is useful for the hospital team. The aim is to combine medical knowledge with that of the researchers and engineers to develop new techniques to help stroke patients recover.

HOW CAN PATIENTS BE HELPED?

The research undertaken by the two teams concerns patients presenting with partial paralysis after one or more strokes and for whom conventional rehabilitation methods have reached their limits. The objective is to promote recovery of the damaged parts of the brain by guiding the natural brain plasticity with a brain computer interface (BCI), so that the patient can regain some control of movement. This involves the analysis of electrical signals in the brain (EEG) which are recorded and analysed in real time by the brain computer interface. The computer provides the patient with a visual feedback of neural activity during the imposed exercise (e.g. attempt to move or imagine moving his/her paralysed hand). This visual feedback encourages the patient and enhances his/her ability to control his/her brain. A special helmet is used to detect the electrical signals. It is also possible to place electrodes, which are connected to the computers, directly on the surface of the brain. Astonishing, but effective! Results indicate improved mobility for some patients.

In other cases, where the patient presents with paralysis caused by nerve damage, BCI can be used to analyse and transmit an intended movement directly to a prosthetic limb or to a muscle simulation device.

All the data generated by this research is precious and valuable for Centrale Nantes and Nantes University Hospital, who are working together to collect and process it. To this end, an engineer by the name of Aurélien Van Langhenhove acts as an interface working daily alongside Dr Roualdes. He is developing the processing software and partially supervising Centrale Nantes student projects.

The Centrale Nantes team - in particular, the researcher Eric Le Carpentier - is also working on the analysis of electrical muscle signals produced during movement. This involves electromyography (EMG). Electrodes and prostheses create movement generated from these signals and can be combined with BCI to remedy numerous handicaps.

Two final-year Centrale Nantes students and an Erasmus Mundus post-doc are currently interning for six months each in Dr Roualdes' team.

This collaboration between Centrale Nantes and Nantes University Hospital is still in its early stages, but is set to develop into larger-scale projects.


* Source: fondacoeur.com


Students from the SIGMA specialisation following a class on BCI given by Dr Vincent Roualdes and Aurélien Van Langhenhove (24 February 2016).