Minah Suh, PhD, Ranjeeta Sarkar, Rachel Kolster, Pamela Drexel, Jamshid Ghajar, MD, PhD

Explosive devices directed against both civilian and military targets are often employed in acts of terrorism throughout the world, with the incidence of blast injuries on the rise [1]. In war zones, it is estimated that as many as 47% of all blast injuries affect the head [2]. Increased prevalence underscores the need for researching innovative assessment methods in detecting blast-related brain injury, since many brain injuries may have no external marker of injury. Blast injuries often produce symptoms similar to those found in classical traumatic brain injury (TBI) [3], thereby making detection, diagnosis, and treatment exceedingly complex and variable [4].

Relationship between Blast Injury and TBI

TBI can be mild, moderate, or severe, depending on the extent of damage to the brain and a patient’s subsequent level of wakefulness. The damage sustained can be confined to one area of the brain, making it focal, or it can involve more than one area of the brain, thereby making it diffuse [5]. Blast related TBI shares these features, but can also include additional considerations, such as blast impact, propulsion of the patient due to the force of the blast, possible burns, and inhalation of toxic substances [1].

Approximately twenty percent of mild TBI patients develop a number of persistent symptoms post-injury. These symptoms are collectively labeled post concussive syndrome (PCS). Such behavioral, cognitive, and psychological symptoms vary greatly in both severity and onset, and are also evident in patients who have suffered blast related TBI [6]. Many patients experience cognitive deficits including problems with concentration and attention, as well as difficulties with higher level executive functions, such as planning, organization, and decision making. Critical life outcomes such as vocational success, community reintegration and social autonomy have been linked with executive functioning following brain injury [7].

Web-based Neuropsychological Measures

Several studies have examined the efficacy of web-based support for both patients and family members. Wade, et al [8] suggest that a computer-based pediatric intervention may be utilized in an effort to improve children’s emotional and cognitive outcomes following TBI, as well as ameliorate injury-related burden, psychiatric symptoms, and depression in parents of children with TBI. A similar study in adults used a website to provide in-home adjunctive and supportive services to TBI patients and their families [9], with family caregivers using web-based interventions for social support and guidance following the return home of family members who had suffered a TBI.

Web-based neuropsychological measures are aimed at offering a more accessible alternative to traditional paper-based cognitive batteries. Such tools include the online version of the Glasgow Coma Scale, as well as the Orientation Log [10], a measure of one’s awareness and orientation similar to the popular paper-based Galveston Orientation and Amnesia Test (GOAT), along with the Rancho Los Amigos Scale, an outcome assessment form delineating ten descriptive levels of cognitive function that range from “modified independent” to “total assistance” [11]. Websites such as the one from the Center for Outcome Measurement in Brain Injury (COMBI), are geared toward current researchers, and offer detailed explanations of scales, along with specific administration protocols for researchers to employ (www.tbims.org/combi).

Although not identical, the sports model of rapid, effective cognitive assessment could be applied to blast related TBI in an effort to provide an index of a patient’s cognitive functioning post-injury. For instance, the Concussion Resolution Index (CRI), based largely on the well-known Reliable Change Index (RCI) has been developed as an online assessment tool that, following sports-related concussion, tracks the resolution of symptoms in patients [12], and is largely geared toward determining if an athlete is well enough to return to competitive play. Similarly, the CSI, or Cognitive Stability Index, is a web-based system that attempts routine monitoring of cognitive function in TBI patients [12]. The variable nature of existing neuropsychological evaluations of TBI make results hard to interpret and codify, highlighting the need for a sensitive, straightforward assessment of post-injury cognitive function.

Existing neuropsychological measures used to examine the cognitive implications of brain injury are numerous. Some of the most widely used measures include the California Verbal Learning Test (CVLT), a standardized measure of working memory [13], and the Wechsler Abbreviated Scale of Intelligence (WASI), a measure of both verbal and quantitative abilities [14], the Center for Epidemiological Studies Depression Scale (CES-D), a commonly used metric of depression/anxiety [15], and the Glasgow Outcome Scale (GOS), an interview addressing gross physical and mental functionality post-injury [16]. However, some of these tests depend on lengthy testing sessions, making the assessment of brain injury inefficient for researchers, clinicians, and patients alike.

Eyetracking Advantages and Sensitivity

Since neural pathways in eye movements and higher cognitive functions [17] are similar, it has been suggested that oculomotor testing may be a promising and sensitive marker for attentional deficits in TBI patients. The utilization of oculomotor testing with high temporal resolution (500Hz) enables researchers to collect hundreds of data points in a short amount of time. Previous studies [18, 19] have shown that mild TBI patients showed reduced target anticipation, increased oculomotor error, and increased variability of oculomotor error during predictive target tracking, and these deficits were correlated with deficits in the California Verbal Learning Test (CVLT-II) measures related to working memory, learning, and executive attention [13]. Furthermore, when the target is temporarily extinguished during predictive target tracking, the smooth pursuit system relies on cortical input in order to extrapolate the virtual trajectory [17, 20], necessitating the need of anticipatory eye movement. Such paradigms may be an especially sensitive indicator of the integrity of cerebellar-cortical pathways after mild TBI [19].

With greater sensitivity than traditional neuropsychological tests, eyetracking has the potential to be an effective tool for the precise and rapid diagnosis of deficits in cognitive functioning following blast injury. Furthermore, eyetracking equipment can be developed to be portable, so that it could be brought to the injury site, thereby allowing for a rapid, effective assay of cognitive abilities post-injury.

About The Author

Minah Suh, PhD, is Assistant Professor of Neuroscience in the Department of Neurological Surgery at Cornell University Medical College, where she has been actively conducting various clinically oriented neuroscience projects, such as optical imaging of epilepsy & synchronization in the olivo-cerebellar system and cognitive deficits in traumatic brain injury (TBI).

Ranjeeta Sarker graduated from Barnard College in 2004 with a BA in Neuroscience, and has been a research assistant at the Brain Trauma Foundation for three years. She is currently working on longitudinal studies of cognitive deficits and their relationship to white matter tract integrity in mild TBI patients.
Rachel Kolster graduated from Columbia University in 2004 with a BA in Neuroscience, and has been a research assistant at the Sackler Institute of Cornell Medical College and the Brain Trauma Foundation for two years. She is currently working on studies of the relationship between eye movement deficits and white matter tract integrity in mild TBI patients.

Pamela Drexel trained as a clinical psychologist, and she has served as Executive Director of the Brain Trauma Foundation since 2001.

Jamshid Ghajar, MD, PhD, is Chief of Neurosurgery at NewYork’s Jamaica Hospital-Cornell Trauma Center and is a practicing neurosurgeon at New York Presbyterian Hospital. He is currently President of the Brain Trauma Foundation, whose mission is to improve the outcome of patients with traumatic brain injury.

REFERENCES