Restoring Reach and Grasp in a Patient with Tetraplegia

A case report demonstrates that brain–machine interfaces can allow intuitive control over a complex prosthetic device with reaching and grasping functionality.

Brain–machine interfaces (BMIs) may eventually allow patients with severe disabilities to exert direct neural control of assistive devices in a manner analogous to our natural effortless control of movement. Growing efforts are aimed at clinically translating BMIs (JW Neurol Sep 5 2006 and Sep 15 2009). However, the degree of movement complexity that a patient can stably control using a BMI has been uncertain.

In this short-term study, researchers assessed whether a patient with tetraplegia could control a robotic arm to perform tasks. The researchers surgically implanted two 96-electrode arrays into motor areas in one hemisphere to record action potentials. Using an innovative algorithm developed using a nonhuman primate model, the authors translated the patient's movement intentions into signals that could directly control the robotic arm. Over several months, they tested control of the robotic arm, including the ability to complete tasks measured by a validated clinical scale.

The patient reliably completed a range of reaching and grasping tasks (e.g., picking up blocks varying in size from 2.5 to 7.5 cm). An example of a task that the patient could not perform reliably was pouring water from one glass to another. The authors conclude that brain-controlled prostheses that use their model might allow clinically significant restoration of upper limb function.

Comment: These authors take an important step toward the long-term goal of restoring motor function in patients with severe disabilities. They specifically show that complex reaching and grasping actions can be generated reliably via direct neural control of a robotic arm. Although numerous obstacles, such as achieving long-term neuronal recording stability, remain, this report offers a framework for pursuing long-term restoration of clinically meaningful function.

— Karunesh Ganguly, MD, PhD

Dr. Ganguly is a Staff Neurologist, San Francisco Veterans Affairs Medical Center, and Assistant Professor, Department of Neurology, University of California, San Francisco.

Published in Journal Watch Neurology February 12, 2013

Citation(s):

http://dx.doi.org/10.1016/S0140-6736(12)61816-9)