Jamshid Ghajar, MD, PhD, FACS

All Publications

• Clinical evaluation of concussion: the evolving role of oculomotor assessments. Neurosurgical focus Sussman, E. S., Ho, A. L., Pendharkar, A. V., Ghajar, J. 2016; 40 (4): E7-?

  Abstract

  Sports-related concussion is a change in brain function following a direct or an indirect force to the head, identified in awake individuals and accounting for a considerable proportion of mild traumatic brain injury. Although the neurological signs and symptoms of concussion can be subtle and transient, there can be persistent sequelae, such as impaired attention and balance, that make affected patients particularly vulnerable to further injury. Currently, there is no accepted definition or diagnostic criteria for concussion, and there is no single assessment that is accepted as capable of identifying all patients with concussion. In this paper, the authors review the available screening tools for concussion, with particular emphasis on the role of visual function testing. In particular, they discuss the oculomotor assessment tools that are being investigated in the setting of concussion screening.

  View details for DOI 10.3171/2016.1.FOCUS15610

  View details for PubMedID 27032924

• Filling in the gaps: Anticipatory control of eye movements in chronic mild traumatic brain injury NEUROIMAGE-CLINICAL Diwakar, M., Harrington, D. L., Maruta, J., Ghajar, J., El-Gabalawy, F., Muzzatti, L., Corbetta, M., Huang, M., Lee, R. R. 2015; 8: 210-223

  Abstract

  A barrier in the diagnosis of mild traumatic brain injury (mTBI) stems from the lack of measures that are adequately sensitive in detecting mild head injuries. MRI and CT are typically negative in mTBI patients with persistent symptoms of post-concussive syndrome (PCS), and characteristic difficulties in sustaining attention often go undetected on neuropsychological testing, which can be insensitive to momentary lapses in concentration. Conversely, visual tracking strongly depends on sustained attention over time and is impaired in chronic mTBI patients, especially when tracking an occluded target. This finding suggests deficient internal anticipatory control in mTBI, the neural underpinnings of which are poorly understood. The present study investigated the neuronal bases for deficient anticipatory control during visual tracking in 25 chronic mTBI patients with persistent PCS symptoms and 25 healthy control subjects. The task was performed while undergoing magnetoencephalography (MEG), which allowed us to examine whether neural dysfunction associated with anticipatory control deficits was due to altered alpha, beta, and/or gamma activity. Neuropsychological examinations characterized cognition in both groups. During MEG recordings, subjects tracked a predictably moving target that was either continuously visible or randomly occluded (gap condition). MEG source-imaging analyses tested for group differences in alpha, beta, and gamma frequency bands. The results showed executive functioning, information processing speed, and verbal memory deficits in the mTBI group. Visual tracking was impaired in the mTBI group only in the gap condition. Patients showed greater error than controls before and during target occlusion, and were slower to resynchronize with the target when it reappeared. Impaired tracking concurred with abnormal beta activity, which was suppressed in the parietal cortex, especially the right hemisphere, and enhanced in left caudate and frontal-temporal areas. Regional beta-amplitude demonstrated high classification accuracy (92%) compared to eye-tracking (65%) and neuropsychological variables (80%). These findings show that deficient internal anticipatory control in mTBI is associated with altered beta activity, which is remarkably sensitive given the heterogeneity of injuries.

  View details for DOI 10.1016/j.nicl.2015.04.011

  View details for Web of Science ID 000373187100022

• Executive summary of concussion guidelines step 1: systematic review of prevalent indicators. Neurosurgery Carney, N., Ghajar, J., Jagoda, A., Bedrick, S., Davis-O'Reilly, C., du Coudray, H., Hack, D., Helfand, N., Huddleston, A., Nettleton, T., Riggio, S. 2014; 75: S1-2

  View details for DOI 10.1227/NEU.0000000000000434

  View details for PubMedID 24867198

• Concussion guidelines step 1: systematic review of prevalent indicators. Neurosurgery Carney, N., Ghajar, J., Jagoda, A., Bedrick, S., Davis-O'Reilly, C., du Coudray, H., Hack, D., Helfand, N., Huddleston, A., Nettleton, T., Riggio, S. 2014; 75: S3-S15

  Abstract

  Currently, there is no evidence-based definition for concussion that is being uniformly applied in clinical and research settings.To conduct a systematic review of the highest-quality literature about concussion and to assemble evidence about the prevalence and associations of key indicators of concussion. The goal was to establish an evidence-based foundation from which to derive, in future work, a definition, diagnostic criteria, and prognostic indicators for concussion.Key questions were developed, and an electronic literature search from 1980 to 2012 was conducted to acquire evidence about the prevalence of and associations among signs, symptoms, and neurologic and cognitive deficits in samples of individuals exposed to potential concussive events. Included studies were assessed for potential for bias and confound and rated as high, medium, or low potential for bias and confound. Those rated as high were excluded from the analysis. Studies were further triaged on the basis of whether the definition of a case of concussion was exclusive or inclusive; only those with wide, inclusive case definitions were used in the analysis. Finally, only studies reporting data collected at fixed time points were used. For a study to be included in the conclusions, it was required that the presence of any particular sign, symptom, or deficit be reported in at least 2 independent samples.From 5437 abstracts, 1362 full-text publications were reviewed, of which 231 studies were included in the final library. Twenty-six met all criteria required to be used in the analysis, and of those, 11 independent samples from 8 publications directly contributed data to conclusions. Prevalent and consistent indicators of concussion are (1) observed and documented disorientation or confusion immediately after the event, (2) impaired balance within 1 day after injury, (3) slower reaction time within 2 days after injury, and/or (4) impaired verbal learning and memory within 2 days after injury.The results of this systematic review identify the consistent and prevalent indicators of concussion and their associations, derived from the strongest evidence in the published literature. The product is an evidence-based foundation from which to develop diagnostic criteria and prognostic indicators.GCS, Glasgow Coma ScaleLOC, loss of consciousnessPCE, potential concussive eventPTA, posttraumatic amnesiaSOT, Sensory Organization TestSSD, signs, symptoms, neurologic deficits, and cognitive deficits.

  View details for DOI 10.1227/NEU.0000000000000433

  View details for PubMedID 25006974

• Predictive Visual Tracking: Specificity in Mild Traumatic Brain Injury and Sleep Deprivation MILITARY MEDICINE Maruta, J., Heaton, K. J., Mau, A. L., Ghajar, J. 2014; 179 (6): 619-625

  Abstract

  We tested whether reduced cognitive function associated with mild traumatic brain injury (mTBI) and sleep deprivation can be detected and distinguished using indices of predictive visual tracking. A circular visual tracking test was given to 13 patients with acute mTBI (recruited within 2 weeks of injury), 127 normal control subjects, and 43 healthy subjects who were fatigued by 26-hour sleep deprivation. Eye movement was monitored with video-oculography. In the mTBI-related portion of the study, visual tracking performance of acute mTBI patients was significantly worse than normal subjects (p < 0.001). In the sleep-deprivation-related portion of the study, no change was detected between the two baseline measures separated by 2 to 3 weeks, but the 26-hour sleep deprivation significantly degraded the visual tracking performance (p < 0.001). The mTBI subjects had substantially worse visual tracking than sleep-deprived subjects that could also be identified with different visual tracking indices, indicating possible different neurophysiological mechanisms. Results suggest that cognitive impairment associated with mTBI and fatigue may be triaged with the aid of visual tracking measures.

  View details for DOI 10.7205/MILMED-D-13-00420

  View details for Web of Science ID 000340806500006

  View details for PubMedID 24902128

• Detecting eye movement abnormalities from concussion. Progress in neurological surgery Maruta, J., Ghajar, J. 2014; 28: 226-233

  Abstract

  An attention-based biomarker may be useful for concussion screening. A key role of attention is to generate time-based expectancies of specific sensory information, and it is postulated that postconcussion cognitive impairments and symptoms may stem from a primary deficit in this predictive timing mechanism. There is a close relationship between gaze and attention, but in addressing predictive timing, there is a need for an appropriate testing paradigm and methods to quantify oculomotor anomalies. We have utilized a continuous predictive visual tracking paradigm because human visual tracking requires predicting the temporal course of a stimulus and dynamically synchronizing the required action with the stimulus. We have shown that concussion patients often show disrupted gaze-target synchronization characterized by large gaze position error variability and overall phase advancement. Various attention components interact with visual tracking, and thus there is a possibility that different neurological and physiological conditions produce identifiable visual tracking characteristics. Analyzing neuromotor functions, specifically oculomotor synchronization, can provide a fast, accurate, and reliable assessment of cognitive functions. © 2014 S. Karger AG, Basel.

  View details for DOI 10.1159/000358786

  View details for PubMedID 24923406

• Chronic Post-Concussion Neurocognitive Deficits. II. Relationship with Persistent Symptoms FRONTIERS IN HUMAN NEUROSCIENCE Maruta, J., Spielman, L. A., Yarusi, B. B., Wang, Y., Silver, J. M., Ghajar, J. 2016; 10

  Abstract

  Individuals who sustain a concussion may continue to experience problems long after their injury. However, it has been postulated in the literature that the relationship between a concussive injury and persistent complaints attributed to it is mediated largely by the development of symptoms associated with posttraumatic stress disorder (PTSD) and depression. We sought to characterize cognitive deficits of adult patients who had persistent symptoms after a concussion and determine whether the original injury retains associations with these deficits after accounting for the developed symptoms that overlap with PTSD and depression. We compared the results of neurocognitive testing from 33 patients of both genders aged 18-55 at 3 months to 5 years post-injury with those from 140 control subjects. Statistical comparisons revealed that patients generally produced accurate responses on reaction time-based tests, but with reduced efficiency. On visual tracking, patients increased gaze position error variability following an attention demanding task, an effect that may reflect greater fatigability. When neurocognitive performance was examined in the context of demographic- and symptom-related variables, the original injury retained associations with reduced performance at a statistically significant level. For some patients, reduced cognitive efficiency and fatigability may represent key elements of interference when interacting with the environment, leading to varied paths of recovery after a concussion. Poor recovery may be better understood when these deficits are taken into consideration.

  View details for DOI 10.3389/fnhum.2016.00045

  View details for Web of Science ID 000370120800001

  View details for PubMedID 26912999

• Chronic Post-Concussion Neurocognitive Deficits. I. Relationship with White Matter Integrity FRONTIERS IN HUMAN NEUROSCIENCE Maruta, J., Palacios, E. M., Zimmerman, R. D., Ghajar, J., Mukherjee, P. 2016; 10

  Abstract

  We previously identified visual tracking deficits and associated degradation of integrity in specific white matter tracts as characteristics of concussion. We re-explored these characteristics in adult patients with persistent post-concussive symptoms using independent new data acquired during 2009-2012. Thirty-two patients and 126 normal controls underwent cognitive assessments and MR-DTI. After data collection, a subset of control subjects was selected to be individually paired with patients based on gender and age. We identified patients' cognitive deficits through pairwise comparisons between patients and matched control subjects. Within the remaining 94 normal subjects, we identified white matter tracts whose integrity correlated with metrics that indicated performance degradation in patients. We then tested for reduced integrity in these white matter tracts in patients relative to matched controls. Most patients showed no abnormality in MR images unlike the previous study. Patients' visual tracking was generally normal. Patients' response times in an attention task were slowed, but could not be explained as reduced integrity of white matter tracts relating to normal response timing. In the present patient cohort, we did not observe behavioral or anatomical deficits that we previously identified as characteristic of concussion. The recent cohort likely represented those with milder injury compared to the earlier cohort. The discrepancy may be explained by a change in the patient recruitment pool circa 2007 associated with an increase in public awareness of concussion.

  View details for DOI 10.3389/fnhum.2016.00035

  View details for Web of Science ID 000369850900001

  View details for PubMedID 26903842