As we attempt to navigate our world among all the commotion and noise, there are plenty of simple, unconscious parts of our life we never stop to appreciate or even think about. In trying to move through the world, we often take for granted just that: movement. However, nearly 5.4 million Americans living with paralysis cannot move. According to the American Journal of Public Health, paralysis has a variety of causes such as stroke accounting for the largest portion of cases (33.7%), with spinal cord injury accounting for 27.3% of cases and multiple sclerosis following with 18.6% (Armour, 2016). For those affected by paralysis, navigating through the world becomes an even bigger challenge, yet current rehabilitation and treatments to regain movement have been limited, especially with severe paralysis.
One novel technology developed recently
attempts to help patients gain back movement through direct brain stimulation of
the motor cortex and computer machine learning. In the article, “The mind-reading
devices that can free paralysed muscles”, researchers implanted electrodes in
the motor cortex and subcutaneously in the arm to stimulate and coordinate
movement from the brain to the arm. They did this by recording the patient’s brain
activity when he tried to move or thought about moving into a computer and then
used machine learning to decipher the type of movement he wanted to make. The computer
then sent a specific pattern of stimuli that allowed him to move. However, despite
this amazing progress, there are limitations in applying this treatment outside
of a laboratory setting (i.e. in their own home) as well as in the bulkiness of
these kinds of prosthetics which are often physically linked to a computer. The
implanted electrodes also do not usually last for more than a few years
(Savage, 2018).
The research done by Dr. Perez and
Dr. Jo in their paper, “Corticospinal-motor neuronal plasticity promotes
exercise-mediated recovery in humans with spinal cord injury” embarks on a non-invasive
strategy combined with exercise to not only assist movement but establish
long-term improvement in mobility. And it seems more research in spinal cord
injury (SCI) treatments and paralysis is headed towards this less invasive
direction. Instead of stimulating the neurons on the motor cortex and the limbs
and using an external computer to coordinate movement, these methods rely more on
the neuroplasticity of the remaining motor neurons to induce movement.
One similar study by Gad et. al. attempted
to improve the ability of patients with severe paralysis such as tetraplegics. This
paper perhaps perfectly states the ideal goal of these non-invasive strategies
in saying, “we refer to the neuromodulatory method used as transcutaneous
enabling motor control to emphasize that the stimulation parameters used are
designed to avoid directly inducing muscular contractions, but to enable task
performance according to the subject’s voluntary intent” (Gad, 2018). In combing
transcutaneous stimulation of the cervical spinal cord with training, they
found improvements by 325% in hand grip forces with stimulation and about 225%
without stimulation (Gad, 2018) as well as some additional benefits for certain
patients such as improved autonomic function, reorganization of supraspinal-spinal
networks, and some sensation before the level of lesion (Gad, 2018). With hand movement
and grasping being one of the top functions tetraplegics seek to regain, this
study provides a significant technique to improving the lives of patients with
severe paralysis.
A similar clinical trial utilized non-invasive
cerebellar stimulation to improve gait and balance in patients who had suffered
from hemiparetic stroke. Gait and balance are functions important to movement associated
with the cerebellum. In this clinical trial conducted by Koch et. al. cerebellar
intermittent θ-burst stimulation (CRB-iTBS) was paired with physiotherapy and
resulted in significant improvements in balance three weeks after treatment as
well as three weeks after the end of treatment (Koch, 2019).
Moving forward, non-invasive stimulation
is beginning to be utilized as a means of treating non-movement related issues
often present along with paralysis such as paralyzed patients with aphasia
caused by stroke. The study “Transcranial direct current stimulation effects on
neural processing in post-stroke aphasia” by Darkow et. al. found an improvement
in aphasic language after the stimulation. They also found that anodal transcranial
direct current stimulation (tDCS) indicated increase within-network
communication, an overall “normalization” of brain functions in patients, and showed
selectively increased language network activity (Darkow, 2017).
Taken together, these studies
provide a promising outlook for substantial recovery for the millions of
Americans living with paralysis, particularly those with severe paralysis. However,
there is much work still needed to be done. Advancements in neuroengineering
and robotics focusing on less bulky and more natural moving prosthetics could improve
the daily application of these lab models. Further studies and techniques are
necessary to look at the long-term efficacy of non-invasive techniques as only
a few followed up with patients after treatment, and future directions need to
address treatments for patients who have been paralyzed for more than 6 months
to a year. Paralysis can have severe impacts economically, socially, and mentally,
and as it affects a larger portion of the American population than what I would
have originally thought, paralysis research and treatment is critical to not
only improving the individual lives of patients affected by paralysis but also
to improving the lives of those around them.
Armour, B. S.,
Courtney-Long, E. A., Fox, M. H., Fredine, H., Cahill, A. (2016, Oct. 1). Prevalence
and Causes of Paralysis—United States, 2013. American Journal of Public
Health.106(10):1855-1857. https://ajph.aphapublications.org/doi/10.2105/AJPH.2016.303270
Darkow, R.,
Martin, A., Würtz, A., Flöel, A., Meinzer, M. (2017, Mar). Transcranial direct
current stimulation effects on neural processing in post-stroke aphasia. Hum
Brain Mapp. 38(3):1518-1531.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6119225/
Gad, P., Lee, S.,
Terrafranca, N., Zhong, H., Turner, A., Gerasimenko, Y., Edgerton, V.R. (2018,
Sep. 15). Non-Invasive Activation of Cervical Spinal Networks after Severe
Paralysis. J Neurotrauma. 35(18):2145-2158. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6119225/
Koch G, Bonnì S,
Casula EP, Iosa M, Paolucci S, Pellicciari MC, Cinnera AM, Ponzo V, Maiella M,
Picazio S, Sallustio F, Caltagirone C. (2019, Feb. 1). Effect of Cerebellar
Stimulation on Gait and Balance Recovery in Patients With Hemiparetic Stroke: A
Randomized Clinical Trial. JAMA Neurol. 76(2):170-178. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6439971/
Savage, N. (2018,
Mar. 7). The mind-reading devices that can free paralysed muscles. Nature
555, S12-14. https://www.nature.com/articles/d41586-018-02478-0
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