post-concussive symptoms

Increased Gray Matter Diffusion Anisotropy in Patients with Persistent Post-Concussive Symptoms following Mild Traumatic Brain Injury

Authors: Bouix S, Pasternak O, Rathi Y, Pelavin PE, Zafonte R, Shenton ME.

A significant percentage of individuals diagnosed with mild traumatic brain injury (mTBI) experience persistent post-concussive symptoms (PPCS). Little is known about the pathology of these symptoms and there is often no radiological evidence based on conventional clinical imaging. We aimed to utilize methods to evaluate microstructural tissue changes and to determine whether or not a link with PPCS was present. A novel analysis method was developed to identify abnormalities in high-resolution diffusion tensor imaging (DTI) when the location of brain injury is heterogeneous across subjects. A normative atlas with 145 brain regions of interest (ROI) was built from 47 normal controls. Comparing each subject's diffusion measures to the atlas generated subject-specific profiles of injury. Abnormal ROIs were defined by absolute z-score values above a given threshold. The method was applied to 11 PPCS patients following mTBI and 11 matched controls. Z-score information for each individual was summarized with two location-independent measures: "load" (number of abnormal regions) and "severity" (largest absolute z-score). Group differences were then computed using Wilcoxon rank sum tests. Results showed statistically significantly higher load (p = 0.018) and severity (p = 0.006) for fractional anisotropy (FA) in patients compared with controls. Subject-specific profiles of injury evinced abnormally high FA regions in gray matter (30 occurrences over 11 patients), and abnormally low FA in white matter (3 occurrences over 11 subjects). Subject-specific profiles provide important information regarding the pathology associated with PPCS. Increased gray matter (GM) anisotropy is a novel in-vivo finding, which is consistent with an animal model of brain trauma that associates increased FA in GM with pathologies such as gliosis. In addition, the individualized analysis shows promise for enhancing the clinical care of PPCS patients as it could play a role in the diagnosis of brain injury not revealed using conventional imaging.

Abnormal whole-brain functional networks in homogeneous acute mild traumatic brain injury

Authors: Shumskaya E, Andriessen TM, Norris DG, Vos PE.

OBJECTIVES: To evaluate the whole-brain resting-state networks in a homogeneous group of patients with acute mild traumatic brain injury (MTBI) and to identify alterations in functional connectivity induced by MTBI.
METHODS: Thirty-five patients with acute MTBI and 35 healthy control subjects, matched in age, gender, handedness, and education, underwent resting-state fMRI, susceptibility weighted imaging, neuropsychological, and postconcussive symptom assessments. We ensured the homogeneity of the patient group by limiting the injury mechanism to fronto-occipital impacts. Alterations in functional connectivity were analyzed by using data-driven independent component analysis, which is not biased by a priori region selection.
RESULTS: We found a decrease in functional connectivity within the motor-striatal network in the MTBI group. At the same time, patients showed deficits in psychomotor speed as well as in speed of information processing. We propose that although disorders in motor function after MTBI are rarely reported, injury still has an effect on motor functioning, which in its turn may also explain the reduction in speed of information processing. Further, we found a cluster of increased functional connectivity in the right frontoparietal network in the MTBI group. We suggest that this abnormal increased connectivity might reflect increased awareness to external environment and explain excessive cognitive fatigue reported by patients with MTBI. It might also underlie the physical postconcussive symptoms, such as headache and increased sensitivity to noise/light.
CONCLUSIONS: We proved that whole-brain functional connectivity is altered early (within 4 weeks) after MTBI, suggesting that changes in functional networks underlie the cognitive deficits and postconcussive complaints reported by patients with MTBI.

Postconcussion symptoms in patients with injury-related chronic pain

Author: Stålnacke BM.

Background. Postconcussion symptoms (PCSs)-such as fatigue, headache, irritability, dizziness, and impaired memory-are commonly reported in patients who have mild traumatic brain injuries (MTBIs). Evaluation of PCS after MTBI is proposed to have a diagnostic value although it is unclear whether PCS are specific to MTBI. After whiplash injuries, patients most often complain of headaches and neck pain; the other PCS are not as closely evaluated. In patients with chronic pain because of other injuries, the presence of PCS is unclear. This study aimed to describe the frequency of PCS in patients with injury-related pain and to examine the relationships between PCS, pain, and psychological factors. Methods. This study collected data using questionnaires addressing PCS (Rivermead Postconcussion Questionnaire, RPQ), pain intensity (Visual Analogue Scale), depression, anxiety (Hospital, Anxiety, and Depression Scale), and posttraumatic stress (Impact of Event Scale). Results. Fatigue (90.7%), sleep disturbance (84.9%), headache (73.5%), poor concentration (88.2%), and poor memory (67.1%) were some of the most commonly reported PCS. Significant relationships were found between PCS and posttraumatic stress, depression, and anxiety. Conclusion. To optimize treatment, it is important to assess each patient's PCS, the mechanism of injury, and factors such as posttraumatic stress and depression.

Cerebrocerebellar hypometabolism associated with repetitive blast exposure mild traumatic brain injury in 12 Iraq war Veterans with persistent post-concussive symptoms

Authors: Elaine R. Peskind a c, Eric C. Petrie a c, Donna J. Cross d, Kathleen Pagulayan ac, Kathleen McCraw a, David Hoffa, Kim Hart a, Chang-En Yu b, e, Murray A. Raskind a, c, David G. Cook b, e and Satoshi Minoshima d

Disagreement exists regarding the extent to which persistent post-concussive symptoms (PCS) reported by Iraq combat Veterans with repeated episodes of mild traumatic brain injury (mTBI) from explosive blasts represent structural or functional brain damage or an epiphenomenon of comorbid depression or posttraumatic stress disorder (PTSD). Objective assessment of brain function in this population may clarify the issue. To this end, twelve Iraq war Veterans (32.0 ± 8.5 years of age) reporting one or more blast exposures meeting American Congress of Rehabilitation Medicine criteria for mTBI and persistent PCS and 12 cognitively normal community volunteers (53.0 ± 4.6 years of age) without history of head trauma underwent brain fluorodeoxyglucose positron emission tomography (FDG-PET) and neuropsychological assessments and completed PCS and psychiatric symptom rating scales. Compared to controls, Veterans with mTBI (with or without PTSD) exhibited decreased cerebral metabolic rate of glucose in the cerebellum, vermis, pons, and medial temporal lobe. They also exhibited subtle impairments in verbal fluency, cognitive processing speed, attention, and working memory, similar to those reported in the literature for patients with cerebellar lesions. These FDG-PET imaging findings suggest that regional brain hypometabolism may constitute a neurobiological substrate for chronic PCS in Iraq combat Veterans with repetitive blast-trauma mTBI. Given the potential public health implications of these findings, further investigation of brain function in these Veterans appears warranted.

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