Prospects for CNS treatment with electrode-based neural prostheses

The use of neural prosthetics is surprisingly widespread. For example, according to the FDA, as of Dec ’10 more than 200,000 patients have received cochlear implants for hearing impairments. A summer ’11 report indicates that over 70,000 patients have been treated with deep brain stimulation (DBS) for movement disorders such as Parkinson’s.

DBS has also been used experimentally. A Mar ’10 review summarizes its effects on more than 200 patients with treatment resistant depression and/or OCD. And an Aug ’10 review refers to studies of its efficacy on around 200 patients with various forms of epilepsy.

A review from the beginning of this year, which just came to my attention, discusses some of the challenges involved in making neural prostheses robust over several decades. Three of the problems they mention are:

• electrode encapsulation, whereby native tissue forms a glial scar and renders the electrode non-functional
• motion of the surrounding tissue relative to the stationary electrode, due to head movements or pressure changes during respiration
• material or engineering failures, which would presumably decrease in frequency with more widespread use

One of the other problems that the authors discuss is electrical interference, which causes artifacts and thus occasional blackout periods of the electrode’s ability to record signals. The lack of continuous recording would hinder bidirectional feedback.

It remains to be seen whether these problems in endurance and capacity can be overcome with the electrode approach, and, perhaps more realistically, over what timescale they can be addressed.

Reference

Gilja V, et al. 2011 Challenges and Opportunities for Next-Generation Intracortically Based Neural Prostheses. IEEE TBE. doi:  10.1109/TBME.2011.2107553.