Cooling the Nervous System to Protect it
At some point, you’ve probably heard about hypothermia treatment, this case cooling the nervous system, being used in people with new spinal cord injuries (SCI). Mild hypothermia treatment involves cooling a person’s body temperature by just a few degrees, immediately after injury, which appears to protect the nervous system from secondary damage caused by bleeding, swelling, and the body’s natural inflammatory responses to trauma. Scientists at The Miami Project, led by Dr. Allan Levi, Professor and Chairman of The Department of Neurological Surgery, have been evaluating hypothermia in participants with acute SCI for over 10 years. His team is currently conducting a multi-center clinical trial to further investigate the effects of hypothermia treatment in people with cervical-level SCI. Results from this study should be able to provide data to determine whether systemic hypothermia should be implemented as part of the new standard of care treatment for cervical SCI.
Small variations in body and brain temperature can have a major effect on how much damage occurs in traumatic brain injury (TBI), as well. Hypothermia treatment has also been shown to help protect the nervous system after TBI, by minimizing the cascade of temperature-sensitive secondary injury mechanisms. At the other end of the spectrum, Miami Project scientists have also been looking at what happens when body temperature is elevated or “hyperthermic”. Since many TBIs occur while people are playing sports or exercising (think concussions in football players), during which time brain temperature becomes elevated, this topic is extremely relevant. Researchers in the laboratories of Dr. W. Dalton Dietrich, Dr. Helen Bramlett, and Dr. Coleen Atkins are using various pre-clinical models of TBI to evaluate the effects of hyperthermia before TBI. They are actually seeing that higher temperatures in the brain before TBI significantly increases damage when compared to TBIs that occur at normal temperatures.
Based on the promising results of cooling the nervous system in SCI and TBI, Miami Project scientists are exploring additional applications where hypothermia’s neuroprotective effects may be beneficial. Dr. Dietrich, in collaboration with Dr. Suhrud Rajguru, Associate Professor of Biomedical Engineering and Otolaryngology, are evaluating the effects of cooling during implantation of cochlear implants, electronic devices that can restore hearing in people with severe hearing loss. The trauma caused during cochlear implant insertion using current methods can result in cell death and damage, leading to loss of residual hearing. In an experimental model, the researchers inserted a cooling probe into the inner ear and reduced the temperature of the cochlea by 5-6 degrees Celsius for 20 minutes before and after implantation of the hearing device. The found that cooling resulted in significantly less damage, which may lead to less loss of residual hearing. They also tested their approach in human cadaveric temporal bones to show that controlled and effective cooling could be applied and maintained. Based on these results, localized application of hypothermia during cochlear implantation may have a future in human clinical applications.
Dididze M, Green BA, Dietrich WD, Vanni S, Wang MY, Levi AD. Systemic hypothermia in acute cervical spinal cord injury: a case-controlled study. Spinal Cord. 2013 May;51(5):395-400.
Atkins CM, Bramlett HM, Dietrich WD. Is temperature an important variable in recovery after mild traumatic brain injury? F1000Res. 2017 Nov 20;6:2031.
Tamames I, King C, Bas E, Dietrich WD, Telischi F, Rajguru SM. A cool approach to reducing electrode-induced trauma: Localized therapeutic hypothermia conserves residual hearing in cochlear implantation. Hear Res. 2016 Sep;339:32-9.