Neural correlates of malingering in mild traumatic brain injury: A positron emission tomography study

Toward a global and reproducible science for brain imaging in neurotrauma: the ENIGMA adult moderate/severe traumatic brain injury working group

The global burden of mortality and morbidity caused by traumatic brain injury (TBI) is significant, and the heterogeneity of TBI patients and the relatively small sample sizes of most current neuroimaging studies is a major challenge for scientific advances and clinical translation. The ENIGMA (Enhancing NeuroImaging Genetics through Meta-Analysis) Adult moderate/severe TBI (AMS-TBI) working group aims to be a driving force for new discoveries in AMS-TBI by providing researchers world-wide with an effective framework and platform for large-scale cross-border collaboration and data sharing. Based on the principles of transparency, rigor, reproducibility and collaboration, we will facilitate the development and dissemination of multiscale and big data analysis pipelines for harmonized analyses in AMS-TBI using structural and functional neuroimaging in combination with non-imaging biomarkers, genetics, as well as clinical and behavioral measures. Ultimately, we will offer investigators an unprecedented opportunity to test important hypotheses about recovery and morbidity in AMS-TBI by taking advantage of our robust methods for large-scale neuroimaging data analysis. In this consensus statement we outline the working group's short-term, intermediate, and long-term goals.

Neuroimaging and Psychometric Assessment of Mild Cognitive Impairment After Traumatic Brain Injury

Traumatic brain injury (TBI) can be serious partly due to the challenges of assessing and treating its neurocognitive and affective sequelae. The effects of a single TBI may persist for years and can limit patients’ activities due to somatic complaints (headaches, vertigo, sleep disturbances, nausea, light or sound sensitivity), affective sequelae (post-traumatic depressive symptoms, anxiety, irritability, emotional instability) and mild cognitive impairment (MCI, including social cognition disturbances, attention deficits, information processing speed decreases, memory degradation and executive dysfunction). Despite a growing amount of research, study comparison and knowledge synthesis in this field are problematic due to TBI heterogeneity and factors like injury mechanism, age at or time since injury. The relative lack of standardization in neuropsychological assessment strategies for quantifying sequelae adds to these challenges, and the proper administration of neuropsychological testing relative to the relationship between TBI, MCI and neuroimaging has not been reviewed satisfactorily. Social cognition impairments after TBI (e.g., disturbed emotion recognition, theory of mind impairment, altered self-awareness) and their neuroimaging correlates have not been explored thoroughly. This review consolidates recent findings on the cognitive and affective consequences of TBI in relation to neuropsychological testing strategies, to neurobiological and neuroimaging correlates, and to patient age at and assessment time after injury. All cognitive domains recognized by the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) are reviewed, including social cognition, complex attention, learning and memory, executive function, language and perceptual-motor function. Affect and effort are additionally discussed owing to their relationships to cognition and to their potentially confounding effects. Our findings highlight non-negligible cognitive and affective impairments following TBI, their gravity often increasing with injury severity. Future research should study (A) language, executive and perceptual-motor function (whose evolution post-TBI remains under-explored), (B) the effects of age at and time since injury, and (C) cognitive impairment severity as a function of injury severity. Such efforts should aim to develop and standardize batteries for cognitive subdomains—rather than only domains—with high ecological validity. Additionally, they should utilize multivariate techniques like factor analysis and related methods to clarify which cognitive subdomains or components are indeed measured by standardized tests.

Neural correlates of response bias: Larger hippocampal volume correlates with symptom aggravation in combat-related posttraumatic stress disorder

The diagnosis of posttraumatic stress disorder (PTSD) is vulnerable to the simulation or exaggeration of symptoms as it depends on the individual's self-report of symptoms. The use of symptom validity tests is recommended to detect malingering in PTSD. However, in neuroimaging research, PTSD diagnosis is often taken at face validity. To date, no neuroimaging study has compared credible PTSD patients with those identified as malingering, and the potential impacts of including malingerers along with credible patients on results is unclear. We classified male patients with combat-related PTSD as either credible (n = 37) or malingerers (n = 9) based on the Morel Emotional Numbing Test and compared structural neuroimaging and psychological questionnaire data. Patients identified as malingerers had larger gray matter volumes in the hippocampus, right inferior frontal gyrus and thalamus, and reported higher PTSD symptoms than credible PTSD patients. This is the first structural neuroimaging study to compare credible PTSD patients and malingerers. We find evidence of structural differences between these groups, in regions implicated in PTSD, inhibition and deception. These results emphasize the need for the inclusion of SVTs in neuroimaging studies of PTSD to ensure future findings are not confounded by an unknown mix of valid PTSD patients and malingerers.

Concussion and the autonomic nervous system: An introduction to the field and the results of a systematic review

BACKGROUND

Recent evidence suggests that autonomic nervous dysfunction may be one of many potential factors contributing to persisting post-concussion symptoms.

OBJECTIVE

This is the first systematic review to explore the impact of concussion on multiple aspects of autonomic nervous system functioning.

METHODS

The methods employed are in compliance with the American Academy of Neurology (AAN) and PRISMA standards. Embase, MEDLINE, PsychINFO, and Science Citation Index literature searches were performed using relevant indexing terms for articles published prior to the end of December 2016. Data extraction was performed by two independent groups, including study quality indicators to determine potential risk for bias according to the 4-tiered classification scheme of the AAN.

RESULTS

Thirty-six articles qualified for inclusion in the analysis. Only three studies (one Class II and two Class IV) did not identify anomalies in measures of ANS functioning in concussed populations.

CONCLUSIONS

The evidence supports the conclusion that it is likely that concussion causes autonomic nervous system anomalies. An awareness of this relationship increases our understanding of the physical impact of concussion, partially explains the overlap of concussion symptoms with other medical conditions, presents opportunities for further research, and has the potential to powerfully inform treatment decisions.

Neural differences underlying face processing in veterans with TBI and co-occurring TBI and PTSD

BACKGROUND

Traumatic brain injury (TBI) is common in military personnel and associated with high rates of posttraumatic stress disorder (PTSD). TBI impacts widely-distributed neural patterns, some of which influence affective processing. Better understanding how TBI and PTSD/TBI alters affective neural activity may improve our understanding of comorbidity mechanisms, but to date the neural correlates of emotional processing in these groups has been relatively understudied.

METHODS

Military controls, military personnel with a history of TBI, and military personnel with both TBI and PTSD (N = 53) completed an emotional face processing task during fMRI. Whole-brain activation and functional connectivity during task conditions were compared between groups.

RESULTS

Few whole-brain group differences emerged in planned pairwise contrasts, though the TBI group showed some areas of hypoactivation relative to other groups during processing of faces versus shapes. The PTSD/TBI group compared to the control and TBI groups demonstrated greater connectivity between the amygdala and insula seed regions and a number of prefrontal and posterior cingulate regions.

LIMITATIONS

Generalizability to other patient groups, including those with only PTSD, has not yet been established.

CONCLUSION

TBI alone was associated with hypoactivation during a condition processing faces versus shapes, but PTSD with TBI was associated altered functional connectivity between amygdala and insula regions and cingulate and prefrontal areas. Altered connectivity patterns across groups suggests that individuals with PTSD/TBI may need to increase frontal connectivity with the insulae in order to achieve similar task-based activity.

Symptom overreporting and dissociative experiences: A qualitative review

We discuss a phenomenon that has received little attention to date in research on dissociative phenomena, namely that self-reports of these phenomena overlap with the tendency to overendorse eccentric items. We review the literature documenting the dissociation-overreporting link and then briefly discuss various interpretations of this link: (1) overreporting is an artifact of measuring dissociative symptoms; (2) dissociative psychopathology engenders overreporting of eccentric symptoms through fantasy proneness or impairments in internal monitoring; (3) an overreporting response style as is evident in malingerers, for example, promotes reports of dissociative symptoms. These three interpretations are not mutually exclusive. Also, the dissociation-overreporting link may have different origins among different samples. Because overreporting may introduce noise in datasets, we need more research specifically aimed at disentangling the dissociation-overreporting link. We suggest various avenues to accomplish this goal.