Just like anyone else, stroke survivors can benefit from the attributes of their enormous neuroplastic brains. The stakes may be higher but just like any great journey, the first step is often the most challenging. That is where we, as therapists armed with scientifically proven neuroplastic therapies, can help with the first step and as guides for the rest of the journey.
The human brain has been described as the most complicated structure in the universe. It has 100 billion neurons, but the actual number of neurons pales in comparison to the number of connections between neurons.
Each neuron connects to between 10,000 and 100,000 other neurons. Do the math and you'll find, very conservatively, that the adult human brain has at least 100 trillion neuronal connections. It has long been known that children who have stroke before 7 years of age have a remarkable ability to reconfigure their brains, automatically, without help from any outside influence.
This often results in complete recovery relative to the lesion size. Could the same process happen in the brains of older stroke survivors? There is now ample evidence that, given the proper therapeutic intervention and a lot of hard work, stroke survivors can reconfigure their neurons to offset the loss of neurons created by their stroke. This process is called neuroplasticity, and it is the foundation of all lasting recovery from stroke.
Neuroplasticity, broadly speaking, is the ability of the brain to reconfigure itself in response to challenges that beset it. This reconfiguration of the brain requires development of new neuronal connections and, through repeated use, strengthening of these new connections.
With the proper intervention and training, the pathways these newly tethered neurons form wind their way through the brains of stroke survivors in new combinations. It is a rewiring, if you will, and what makes neuroplasticity so intriguing is that neuroplastic rewiring of the human brain is simply an act of will.
As Aristotle eloquently articulated, "We are what we repeatedly do." As clinicians, we assist stroke survivors in their effort to change neuronal connections and forge new pathways. But therapists don't need to know an amygdala from a dendrite to have their patients realize the benefits of the neuroplastic process. It is enough to view the brain as a "neuroplastic black box" in which a particular stimulus (treatment or modality) produces a particular response (improved movement or function).
But what tools are available to therapists to facilitate neuroplastic changes in stroke survivors? There are several emerging therapies that have a proven track record of providing neuroplastic change. The granddaddy is constraint-induced therapy, including Dr. Edward Taub's constraint-induced movement therapy (CIMT) and Dr. Stephen Page's modified constraint-induced therapy (mCIT).
Included in the continuum of therapies that provide therapeutic benefit through neuroplastic change are: EMG-based bio- feedback coupled and uncoupled with electrical stimulation (i.e., Neuromove, Mentamove), virtual reality (IREX VR), robot therapy (i.e., MIT's MANUS), and Whitall's bilateral arm training with rhythmic auditory cuing (BATRAC).
One of the most intriguing and potentially promising of the emerging neuroplastic facilitation therapies has been developed by Northstar Neuroscience, based in Seattle. Northstar has developed an elegant fusion of therapist and patient within a therapy that may allow enhanced and more exacting development of neuronal pathways.
Northstar doctors, scientists and engineers first experimented in animal models to develop techniques and technologies that provided the foundational knowledge needed to translate the concept into human study participants. Northstar is currently conducting an FDA-approved pivotal study involving 150-plus participants at 18 centers across the United States. Northstar has conducted previous animal and human studies suggesting that sub-threshold electrical stimulation of the cortex, near the region affected by stroke, may make the neurons in the area hypersensitive to neuroplastic change.
Northstar has developed procedures and an investigational device to provide a precise type (short train, asymmetric) and amount of stimulation required to elicit an actual movement of stimulation to the motor cortex. Using functional magnetic resonance imaging (fMRI), neurosurgeons locate a precise area adjacent to the infarcted motor cortex that has the potential to facilitate the greatest neuroplastic effect. A thumbnail-sized electrode is then implanted on dura mater overlying the targeted portion of the brain. Stimulation of this target creates susceptibility within stimulated neurons. But having neurons sensitive to change is only half the equation.
The role of the therapist-directed skilled therapy is the fuel in Northstar's high-tech "priming" of the patient's motor neurons. A short review of what neurons within the brain do is essential to understanding the therapist's contribution in choreographing this complex dance of neuronal interaction.
Neurons vary in size from fractions of a millimeter to a meter. The higher one goes on the evolutionary ladder the more abundant the tiniest of these neurons are. This is because humans do much more processing of gathered internal and external information and these small neurons are used to disperse information through our relatively enormous brains.
In humans, a movement may have an emotional content (i.e., dancing, gesturing, hugging); an instinctual (autonomic) content; a memory component (i.e., previous, similar movements, as well as storing the proprioceptive feeling of a novel movement for future reference); and a sensory component, as well as the required motor planning needed to perform the desired movement. So a relatively simple multi-joint movement requires a complex electrochemical dance between many neurons that span multiple portions of our brains.
Once a movement is practiced repeatedly, the neurons involved tend to develop into chains that process information necessary to carry out that movement. As electrochemical signals are sent through individual neurons, across neural junctions (synapses) and to adjacent neurons, more permanent connections can, with force of attention and will, allow for a tightening of these connections.
There is a saying, "Neurons that fire together, wire together" and this is the crux of neuroplasticity. Imagine neurons that are needed for movement as water. With each subsequent effort, the patient forges a bit more of a creek through which subsequent water can easily flow. With each dedicated effort of the patient toward a movement goal, new connections are made and strengthened.
Within cortical stimulation treatment, the role of the therapist is to help the patient develop the neural pathways needed to move better. In clinical trials, both physical and occupational therapists provide guidance in the development and strengthening of these neural pathways. The patient receives the cortical stimulation only during therapy sessions. The stimulation is programmed, remotely through a hand-held computer, to coincide with the movement being worked on.
For instance, if shoulder flexion is the movement the patient and therapist are working on, the electrodes on the dura mater overlying the neurons that have most opportunity to take up the slack of the infarcted area, are stimulated while the therapist guides the patient through shoulder flexion exercises.
Beyond the Plateau
New and strengthened connections can initiate a positive spiral of neuroplastic events, which can advance patients enough to involve them in other therapies that allow for the promise of further recovery. Just as an athlete who uses a new training regimen discovers increased athletic performance, so the stroke survivor can use the initiation of the neuroplastic process to allow for involvement in other appropriate therapies.
Take, for instance, the stroke survivor who is two years post-stroke and has "plateaued" with a nominal amount of hand and finger movement. The standard medical model suggests that this patient will have to live with this diminished level of movement. But what if, for instance, EMG-based electrical stimulation or an electrical stimulation orthotic could be used to coax just a few degrees of wrist and finger extension? This could provide enough movement to justify entrance into a "constraint-induced" type therapy that could lead not only to further extension in the wrist and fingers but also gains in rotation of the forearm, elbow extension and increased shoulder complex movement.
One attribute that defines us as inextricably human and that separates us from other life forms is our ability to reconfigure our brains as we see fit. It is simply want that changes us. As our societies and physical culture advance it is, more and more, force of will and not habit, environmental need or instinct that defines what sort of tool our minds become. We choose what sort of masterful instrument our brains become and we decide to what level of expertise we develop that instrument.
People often ask: But what of folks who have lower IQs or have lost brain neurons to stroke or other acquired brain injury? Surely some people are better suited than others for certain skills. We can speak of talented musicians or gifted athletes and say, well, they have an IQ of 150 or they are "natural athletes." But the ability to reconfigure our brains is not a competition. The competition is against our "former" selves. We train to be better than we were yesterday. And we plan for tomorrow's training with an eye on how we, and our patients, can become better than today.
Pete Levine, PTA, is a senior research assistant in the University of Cincinnati Department of Physical Medicine and Rehabilitation and co-director of the Neuromotor Recovery and Research Laboratory at the Drake Center, Cincinnati, OH. Reach him at email@example.com. If you are interested in the Northstar stroke recovery trial, call 888-546-9779.