Deep Brain Stimulation and Traumatic Brain Injury

By Dr. Clausyl J. Plummer II

Traumatic brain injury (TBI) is the disruption of brain function as a result of external forces, which can include closed head injuries (blunt force trauma to the head by or against an object) or penetrating head injuries. According to the Centers for Disease Control and Prevention (CDC), approximately 1.5 million individuals in the United States survive a traumatic brain injury annually, and many develop both short-term and long-term disabilities related to wakefulness, cognition, behavior, and movement.

Managing Care

Healthcare professionals have traditionally recommended medication to manage negative outcomes, but the efficacy has been limited. This is especially evident in post-traumatic neuro-psychiatric derangement and post- traumatic movement disorders. When pharmacologic interventions are not an adequate treatment, healthcare professionals may consider options in the form of neuromodulation.

Neuromodulation is the process of inhibition, stimulation, or modification of electrical and chemical activity in the nervous system. It can involve both the central and peripheral nervous system and is further classified as non-invasive and invasive modalities.

• Non-invasive neuromodulation examples include transcranial stimulation and transcranial direct current stimulation. These methods are currently being studied for efficacy in the brain injury population.
• Invasive neuromodulation examples include deep brain stimulation (DBS), which is being studied for use in a variety of ailments.

Of note, there have been multiple studies that have demonstrated efficacy in the treatment of depression, PTSD, and anxiety with trans-cranial stimulation and direct current stimulation, but far fewer studies assessing deep brain stimulation in the TBI population.

Deep Brain Stimulation (DBS)

DBS is a surgical treatment option that involves the use of constant or intermittent electrical stimulation through the placement of electrodes into specific areas of the brain that assist with movement and cognitive behavioral function. These areas are also referred to as subcortical regions of the brain and include structures like the thalamus and the globus pallidus in the basal ganglia.

DBS was first approved by the United States Food and Drug Administration (FDA) for treatment of essential tremors in 1997 and was later approved for the treatment of Parkinson’s disease in 2002. Since then, there have been multiple studies demonstrating its efficacy in these patient populations and as a result, indications for deep brain stimulation have been expanded to include refractory depression, post-traumatic stress disorder (PTSD), obsessive compulsive disorder (OCD), and are also being investigated in the TBI population.

Studying the Effects of DBS Among TBI Survivors

There are an increasing number of studies being done to evaluate DBS among TBI survivors.

Minimally Conscious States (MCS)

One study looked to investigate the potential therapeutic use of DBS of patients in a minimally conscious state or vegetative state caused by traumatic brain injury or hypoxic encephalopathy. Fourteen out of 49 patients met inclusion criteria for the study, and they underwent surgical placement of electrodes into the thalamic centromedian/parafascicular (CM-Pf) complex for deep brain stimulation.

Four of the selected patients showed functional improvement within 38 to 60 months after implantation with three of those previously being at a minimally conscious level and one at a vegetative state level. Two of the patients in a MCS regained consciousness and progressed to functional improvement in ability to ambulate, speak fluently, and live independently. One of the patients in a MCS also regained consciousness and was still utilizing a wheelchair at the time of the study’s publishing.

This small study was able to demonstrate possible benefits to the utilization of DBS for patients who are suffering from disorders of consciousness.

Behavioral Challenges

Another study done by Rezai et al. (2016) investigated the safety and effectiveness of DBS for individuals with chronic TBI coupled with behavioral challenges, including impulsivity issues and reduced initiation. This study included four patients who had sustained severe TBIs from motor vehicle collisions and were six to 21 years post-injury. These patients underwent DBS bilaterally into the nucleus accumbens in addition to the anterior limb of the internal capsules and were tracked with serial assessments for two years.

After two years of serial assessments, three of the four patients demonstrated functional improvement as measured by the Mayo-Portland Adaptability Inventory-4 assessment and demonstrated improvement in impulsivity, initiation, and ability to perform activities of daily living. Several of the patients involved also tolerated weaning various atypical antipsychotics and benzodiazepines that were previously being used for behavioral problems prior to DBS implantation.

Though this study had several limitations, it provides additional insight into potential areas in which DBS can be considered in the chronic TBI population.

Post-Traumatic Dystonia

A more recent case series done by Li et al. (2019) looked to highlight the efficacy of DBS for post-traumatic dystonia (PTD) in five patients that demonstrated improvement in function. These patients were considered to have disabling PTD and underwent DBS implantation in the globus pallidus internus, the subthalamic nucleus, or the ventral intermediate nucleus. They were assessed using the Burke-Fahn-Marsden dystonia rating scale (BFMDRS) at baseline and then again at the last follow-up appointment over 12 months after implantation.

All five of the patients demonstrated improvement ranging from 65.9% on the BFMDRS movement assessment and by 68.6% on the disability score. This functional improvement also resulted in all five patients demonstrating improvement in quality of life as illustrated on the Short Form health survey (SF-36). This small case series provides another example of the potential for DBS to help facilitate functional recovery for PTD after a TBI.

In all, there have been studies that demonstrate some potential for efficacy with DBS in the TBI population, but larger randomized trials are needed to better demonstrate effectiveness in treatment of behavioral disturbances and movement disorders in this population. It remains a more invasive form of treatment and there must be continued attention to the mitigation of surgical complications. Not all studies on DBS and TBI have demonstrated efficacy and there needs to be more robust research to further explore those differences in results.

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This article originally appeared in Volume 16, Issue 2 of THE Challenge! published in 2022.