Comprehensive predictions of outcome in closed head-injured patients. The development of prognostic equations

Quantitative Electroencephalography Objectivity and Reliability in the Diagnosis and Management of Traumatic Brain Injury: A Systematic Review

Background. Persons with a history of traumatic brain injury (TBI) may exhibit short- and long-term cognitive deficits as well as psychiatric symptoms. These symptoms often reflect functional anomalies in the brain that are not detected by standard neuroimaging. In this context, quantitative electroencephalography (qEEG) is more suitable to evaluate non-normative activity in a wide range of clinical settings. Method. We searched the literature using the "Medline" and "Web of Science" online databases. The search was concluded on February 23, 2023, and revised on July 12, 2023. It returned 134 results from Medline and 4 from Web of Science. We then applied the PRISMA method, which led to the selection of 31 articles, the most recent one published in March 2023. Results. The qEEG method can detect functional anomalies in the brain occurring immediately after and even years after injury, revealing in most cases abnormal power variability and increases in slow (delta and theta) versus decreases in fast (alpha, beta, and gamma) frequency activity. Moreover, other findings show that reduced beta coherence between frontoparietal regions is associated with slower processing speed in patients with recent mild TBI (mTBI). More recently, machine learning (ML) research has developed highly reliable models and algorithms for the detection of TBI, some of which are already integrated into commercial qEEG equipment. Conclusion. Accumulating evidence indicates that the qEEG method may improve the diagnosis and management of TBI, in many cases revealing long-term functional anomalies in the brain or even neuroanatomical insults that are not revealed by standard neuroimaging. While FDA clearance has been obtained only for some of the commercially available equipment, the qEEG method allows for systematic, cost-effective, non-invasive, and reliable investigations at emergency departments. Importantly, the automated implementation of intelligent algorithms based on multimodally acquired, clinically relevant measures may play a key role in increasing diagnosis reliability.

Recovery of Theta Frequency Oscillations in Rats Following Lateral Fluid Percussion Corresponds With a Mild Cognitive Phenotype

Whether from a fall, sports concussion, or even combat injury, there is a critical need to identify when an individual is able to return to play or work following traumatic brain injury (TBI). Electroencephalogram (EEG) and local field potentials (LFP) represent potential tools to monitor circuit-level abnormalities related to learning and memory: specifically, theta oscillations can be readily observed and play a critical role in cognition. Following moderate traumatic brain injury in the rat, lasting changes in theta oscillations coincide with deficits in spatial learning. We hypothesized, therefore, that theta oscillations can be used as an objective biomarker of recovery, with a return of oscillatory activity corresponding with improved spatial learning. In the current study, LFP were recorded from dorsal hippocampus and anterior cingulate in awake, behaving adult Sprague Dawley rats in both a novel environment on post-injury days 3 and 7, and Barnes maze spatial navigation on post-injury days 8–11. Theta oscillations, as measured by power, theta-delta ratio, peak theta frequency, and phase coherence, were significantly altered on day 3, but had largely recovered by day 7 post-injury. Injured rats had a mild behavioral phenotype and were not different from shams on the Barnes maze, as measured by escape latency. Injured rats did use suboptimal search strategies. Combined with our previous findings that demonstrated a correlation between persistent alterations in theta oscillations and spatial learning deficits, these new data suggest that neural oscillations, and particularly theta oscillations, have potential as a biomarker to monitor recovery of brain function following TBI. Specifically, we now demonstrate that oscillations are depressed following injury, but as oscillations recover, so does behavior.

Investigating the validity and reliability of Electrovestibulography (EVestG) for detecting post-concussion syndrome (PCS) with and without comorbid depression

Features from Electrovestibulography (EVestG) recordings have been used to classify and measure the severity of both persistent post-concussion syndrome (PCS) and major depressive disorder. Herein, we examined the effect of comorbid depression on the detection of persistent PCS using EVestG. To validate our previously developed EVestG classifier for PCS detection, the classifier was tested with a new blind dataset (N = 21). The unbiased accuracy for identifying the new PCS from controls was found to be >90%. Next, the PCS group (N = 59) was divided into three subgroups: PCS with no-depression (n = 18), PCS with mild-depression (n = 27) and PCS with moderate/severe-depression (n = 14). When moderate/severe depression was present, PCS classification accuracy dropped to 83%. By adding an EVestG depression feature from a previous study, separation accuracy of each PCS subgroup from controls was >90%. A four and three-group (excluding mild-depression subgroup) classification, achieved an accuracy of 74% and 81%, respectively. Correlation analysis indicated a significant correlation (R = 0.67) between the depression feature and the MADRS depression score as well as between the PCS-specific feature and Rivermead Post-Concussion Questionnaire (RPQ) (R = −0.48). No significant correlation was found between the PCS-specific feature and the MADRS score (R = 0.20) or between RPQ and the depression feature (R = 0.12). The (PCS-specific and depression-specific) EVestG features used herein have the potential to robustly detect and monitor changes, relatively independently, in both persistent PCS and its depression comorbidity. Clinically, this can be particularly advantageous.

Quantitative EEG Parameters for Prediction of Outcome in Severe Traumatic Brain Injury: Development Study

Monitoring of quantitative EEG (QEEG) parameters in the intensive care unit (ICU) can aid in the treatment of traumatic brain injury (TBI) patients by complementing visual EEG review done by an expert. We performed an explorative study investigating the prognostic value of 59 QEEG parameters in predicting the outcome of patients with severe TBI. Continuous EEG recordings were done on 28 patients with severe TBI in the ICU of Turku University Hospital. We computed a set of QEEG parameters for each patient, and correlated these to patient outcome, measured by dichotomized Glasgow Outcome Scale (GOS) at a follow-up visit between 6 and 12 months, using area under receiver operating characteristic curve (AUC) as a nonlinear correlation measure. For 17 of the 59 QEEG parameters (28.8%), the AUC differed significantly from 0.5, most of these parameters measured EEG power or variability. The best QEEG parameters for outcome prediction were alpha power (AUC = 0.87, P < .01) and variability of the relative fast theta power (AUC = 0.84, P < .01). The results of this study indicate that QEEG parameters provide useful information for predicting outcome in severe TBI. Novel QEEG parameters with potential in outcome prediction were found, the prognostic value of these parameters should be confirmed in later studies. The results also provide further evidence of the usefulness of parameters studied in preexisting studies.

Quantitative EEG Neurometric Analysis-Guided Neurofeedback Treatment in Postconcussion Syndrome (PCS): Forty Cases. How Is Neurometric Analysis Important for the Treatment of PCS and as a Biomarker?

Postconcussion syndrome (PCS) has been used to describe a range of residual symptoms that persist 12 months or more after the injury, often despite a lack of evidence of brain abnormalities on magnetic resonance imaging and computed tomography scans. In this clinical case series, the efficacy of quantitative EEG-guided neurofeedback in 40 subjects diagnosed with PCS was investigated. Overall improvement was seen in all the primary (Symptom Assessment-45 Questionnaire, Clinical Global Impressions Scale, Hamilton Depression Scale) and secondary measures (Minnesota Multiphasic Personality Inventory, Test of Variables for Attention). The Neuroguide Traumatic Brain Index for the group also showed a decrease. Thirty-nine subjects were followed up long term with an average follow-up length of 3.1 years (CI = 2.7-3.3). All but 2 subjects were stable and were off medication. Overall neurofeedback treatment was shown to be effective in this group of subjects studied.

Early Brain Edema is a Predictor of In-Hospital Mortality in Traumatic Brain Injury

BACKGROUND

Identifying patients who may progress to a poor clinical outcome will encourage earlier appropriate therapeutic interventions. Brain edema may contribute to secondary injury in traumatic brain injury (TBI) and thus, may be a useful prognostic indicator.

OBJECTIVE

We determined whether the presence of brain edema on the initial computed tomography (CT) scan of TBI patients would predict poor in-hospital outcome.

METHODS

We performed a retrospective review of all trauma patients with nonpenetrating head trauma at a Level I Trauma Center. International Classification of Diseases, Ninth Revision codes indicated the presence of brain edema and we evaluated the validity of this pragmatic assessment quantitatively in a random subset of patients. In-hospital mortality was the primary outcome variable. Univariate analysis and logistic regression identified predictors of mortality in all TBI patients and those with mild TBI.

RESULTS

Over 7200 patients were included in the study, including 6225 with mild TBI. Measurements of gray and white matter CT density verified radiological assessments of brain edema. Patients with documented brain edema had a mortality rate over 10 times that of the entire study population. With logistic regression accounting for Injury Severity Score, Glasgow Coma Scale score, other CT findings, and clinical variables, brain edema predicted an eightfold greater mortality rate in all patients (odds ratio 8.0, 95% confidence interval 4.6-14.0) and fivefold greater mortality rate for mild TBI patients (odds ratio 4.9, 95% confidence interval 2.0-11.7).

CONCLUSIONS

Brain edema is an independent prognostic variable across all categories of TBI severity. By alerting emergency physicians to patients with poor predicted clinical outcomes, this finding will drive better resource allocation, earlier intervention, and reduced patient mortality.

Increased gamma connectivity during working memory retention following traumatic brain injury

PRIMARY OBJECTIVE

Alterations to functional connectivity following a traumatic brain injury (TBI) may lead to impaired cognitive performance and major depressive disorder (MDD). In particular, functional gamma band connectivity is thought to reflect information binding important for working memory. The objective of this study was to determine whether altered functional gamma connectivity may be a factor in MDD following TBI (TBI-MDD).

RESEARCH DESIGN

This study assessed individuals with TBI-MDD, as well as individuals with TBI alone and MDD alone using electroencephalographic recordings while participants performed a working memory task to assess differences in functional connectivity between these groups.

METHODS AND PROCEDURES

Functional connectivity was compared using the debiased weighted phase lag index (wPLI). wPLI was measured from a group of healthy controls (n = 31), participants with MDD (n = 17), participants with TBI (n = 20) and participants with TBI-MDD (n = 15).

MAIN OUTCOMES AND RESULTS

Contrary to the predictions, this study found both the groups with TBI and TBI-MDD showed higher gamma connectivity from posterior regions during WM retention.

CONCLUSIONS

This may reflect dysfunctional functional connectivity in these groups, as a result of maladaptive neuroplastic reorganization.

Making Waves in the Brain: What Are Oscillations, and Why Modulating Them Makes Sense for Brain Injury

Traumatic brain injury (TBI) can result in persistent cognitive, behavioral and emotional deficits. However, the vast majority of patients are not chronically hospitalized; rather they have to manage their disabilities once they are discharged to home. Promoting recovery to pre-injury level is important from a patient care as well as a societal perspective. Electrical neuromodulation is one approach that has shown promise in alleviating symptoms associated with neurological disorders such as in Parkinson’s disease (PD) and epilepsy. Consistent with this perspective, both animal and clinical studies have revealed that TBI alters physiological oscillatory rhythms. More recently several studies demonstrated that low frequency stimulation improves cognitive outcome in models of TBI. Specifically, stimulation of the septohippocampal circuit in the theta frequency entrained oscillations and improved spatial learning following TBI. In order to evaluate the potential of electrical deep brain stimulation for clinical translation we review the basic neurophysiology of oscillations, their role in cognition and how they are changed post-TBI. Furthermore, we highlight several factors for future pre-clinical and clinical studies to consider, with the hope that it will promote a hypothesis driven approach to subsequent experimental designs and ultimately successful translation to improve outcome in patients with TBI.

May clinical neurophysiology help to predict the recovery of neurological early rehabilitation patients?

BACKGROUND

So far, the role of clinical neurophysiology in the prediction of outcome from neurological and neurosurgical early rehabilitation is unclear.

METHODS

Clinical and neurophysiological data of a large sample of 803 early rehabilitation cases of the BDH-Clinic Hessisch Oldendorf in Northern Germany have been carefully reviewed. Most patients (43.5%) were transferred to rehabilitation after stroke, mean age was 66.6 (15.5) years. Median somatosensory (SEP), auditory (AEP) and visual evoked potentials (VEP) along with EEG recordings took place within the first two weeks after admission. Length of stay (LOS) in early rehabilitation was 38.3 (37.2) days.

RESULTS

Absence of SEP on one or both sides was associated with poor outcome, χ2 = 12.98 (p = 0.005); only 12.5% had a good outcome (defined as Barthel index, BI ≥50) when SEP were missing on both sides. In AEP, significantly longer bilateral latencies III were observed in the poor outcome group (p < 0.05). Flash VEP showed that patients in the poor outcome group had a significantly longer latency III on both sides (p < 0.05). The longer latency III, the smaller BI changes (BI discharge minus admission) were observed (latency III right r = -0.145, p < 0.01; left r = -0.206, p < 0.001). While about half of the patients with alpha EEG activity belonged to the good outcome group (80/159, 50.3%), only 39/125 (31.2%) with theta and 5/41 (12.2%) with delta rhythm had a favourable outcome, χ2 = 24.2, p < 0.001.

CONCLUSIONS

Results from this study suggest that loss of median SEP, prolongation of wave III in AEP and flash-VEP as well as theta or delta rhythms in EEG are associated with poor outcome from neurological early rehabilitation. Further studies on this topic are strongly encouraged.

A Review of the Effectiveness of Neuroimaging Modalities for the Detection of Traumatic Brain Injury

The incidence of traumatic brain injury (TBI) in the United States was 3.5 million cases in 2009, according to the Centers for Disease Control and Prevention. It is a contributing factor in 30.5% of injury-related deaths among civilians. Additionally, since 2000, more than 260,000 service members were diagnosed with TBI, with the vast majority classified as mild or concussive (76%). The objective assessment of TBI via imaging is a critical research gap, both in the military and civilian communities. In 2011, the Department of Defense (DoD) prepared a congressional report summarizing the effectiveness of seven neuroimaging modalities (computed tomography [CT], magnetic resonance imaging [MRI], transcranial Doppler [TCD], positron emission tomography, single photon emission computed tomography, electrophysiologic techniques [magnetoencephalography and electroencephalography], and functional near-infrared spectroscopy) to assess the spectrum of TBI from concussion to coma. For this report, neuroimaging experts identified the most relevant peer-reviewed publications and assessed the quality of the literature for each of these imaging technique in the clinical and research settings. Although CT, MRI, and TCD were determined to be the most useful modalities in the clinical setting, no single imaging modality proved sufficient for all patients due to the heterogeneity of TBI. All imaging modalities reviewed demonstrated the potential to emerge as part of future clinical care. This paper describes and updates the results of the DoD report and also expands on the use of angiography in patients with TBI.

Traumatic brain injury detection using electrophysiological methods

Measuring neuronal activity with electrophysiological methods may be useful in detecting neurological dysfunctions, such as mild traumatic brain injury (mTBI). This approach may be particularly valuable for rapid detection in at-risk populations including military service members and athletes. Electrophysiological methods, such as quantitative electroencephalography (qEEG) and recording event-related potentials (ERPs) may be promising; however, the field is nascent and significant controversy exists on the efficacy and accuracy of the approaches as diagnostic tools. For example, the specific measures derived from an electroencephalogram (EEG) that are most suitable as markers of dysfunction have not been clearly established. A study was conducted to summarize and evaluate the statistical rigor of evidence on the overall utility of qEEG as an mTBI detection tool. The analysis evaluated qEEG measures/parameters that may be most suitable as fieldable diagnostic tools, identified other types of EEG measures and analysis methods of promise, recommended specific measures and analysis methods for further development as mTBI detection tools, identified research gaps in the field, and recommended future research and development thrust areas. The qEEG study group formed the following conclusions: (1) Individual qEEG measures provide limited diagnostic utility for mTBI. However, many measures can be important features of qEEG discriminant functions, which do show significant promise as mTBI detection tools. (2) ERPs offer utility in mTBI detection. In fact, evidence indicates that ERPs can identify abnormalities in cases where EEGs alone are non-disclosing. (3) The standard mathematical procedures used in the characterization of mTBI EEGs should be expanded to incorporate newer methods of analysis including non-linear dynamical analysis, complexity measures, analysis of causal interactions, graph theory, and information dynamics. (4) Reports of high specificity in qEEG evaluations of TBI must be interpreted with care. High specificities have been reported in carefully constructed clinical studies in which healthy controls were compared against a carefully selected TBI population. The published literature indicates, however, that similar abnormalities in qEEG measures are observed in other neuropsychiatric disorders. While it may be possible to distinguish a clinical patient from a healthy control participant with this technology, these measures are unlikely to discriminate between, for example, major depressive disorder, bipolar disorder, or TBI. The specificities observed in these clinical studies may well be lost in real world clinical practice. (5) The absence of specificity does not preclude clinical utility. The possibility of use as a longitudinal measure of treatment response remains. However, efficacy as a longitudinal clinical measure does require acceptable test-retest reliability. To date, very few test-retest reliability studies have been published with qEEG data obtained from TBI patients or from healthy controls. This is a particular concern because high variability is a known characteristic of the injured central nervous system.

Dissociation of vegetative and minimally conscious patients based on brain operational architectonics: factor of etiology

Discrimination between patients in vegetative (VS) and minimally conscious state (MCS) is currently based upon the behavioral gold standard. Behavioral assessment remains equivocal and difficult to interpret as evidence for the presence or absence of consciousness, resulting in possible clinical misdiagnosis in such patients. Application of an operational architectonics (OA) strategy to electroencephalogram (EEG) analysis reveals that absence of consciousness in patients in VS is paralleled by significant impairment in overall EEG operational architecture compared to patients in MCS: neuronal assemblies become smaller, their life span shortened, and they became highly unstable and functionally disconnected (desynchronized). However, in a previous study, patients with different brain damage etiologies were intermixed. Therefore, the goal of the present study was to investigate whether the application of OA methodology to EEG could reliably dissociate patients in VS and MCS independent of brain damage etiology. We conclude that the observed EEG OA structure impairment in patients in VS and partial preservation in patients in MCS is a marker of consciousness/unconsciousness rather than physiological damage. Results of this study may have neuroscientific, clinical, and ethical implications.

Smartphone Household Wireless Electroencephalogram Hat

Rudimentarybrain machine interfacehas existed for the gaming industry. Here, we propose a wireless, real-time, and smartphone-based electroencephalogram (EEG) system for homecare applications. The system uses high-density dry electrodes and compressive sensing strategies to overcome conflicting requirements between spatial electrode density, temporal resolution, and spatiotemporal throughput rate.Spatial sparsenessis addressed by close proximity between active electrodes and desired source locations and using an adaptive selection ofNactive among10Npassive electrodes to formm-organized random linear combinations of readouts,m≪N≪10N.Temporal sparsenessis addressed via parallel frame differences in hardware. During the design phase, we took tethered laboratory EEG dataset and applied fuzzy logic to compute (a) spatiotemporal average of larger magnitude EEG data centers in 0.3 second intervals and (b) inside brainwave sources by Independent Component Analysis blind deconvolution without knowing the impulse response function. Our main contributions are the fidelity of quality wireless EEG data compared to original tethered data and the speed of compressive image recovery. We have compared our recovery of ill-posed inverse data against results using Block Sparse Code. Future work includes development of strategies to filter unwanted artifact from high-density EEGs (i.e., facial muscle-related events and wireless environmental electromagnetic interferences).

Clinical electrophysiologic assessments and mild traumatic brain injury: state-of-the-science and implications for clinical practice

Conventional and quantitative electroencephalography (EEG and qEEG, respectively) may enhance clinical diagnosis and treatment planning provided to persons with mild traumatic brain injury (mTBI) and postconcussive symptoms. Effective and appropriate use of EEG and qEEG in this context requires expert-level knowledge of these technologies, mTBI, and the differential diagnosis for postconcussive symptoms. A practical and brief review from the perspective of a clinician-scientist engaged principally in the care and study of persons with mTBI therefore may be of use and value to other clinicians and scientists interested in these matters. Toward that end, this article offers an overview of the current applications of conventional EEG and qEEG to the study and clinical evaluation of persons with mTBI. The clinical case definition of TBI, the differential diagnosis of post-injury neuropsychiatric disturbances, and the typical course of recovery following mTBI are reviewed. With this background and context, the strengths and limitations of the literature describing EEG and qEEG studies in this population are considered. The implications of this review on the applications of these electrophysiologic assessments to the clinical evaluation of persons with mTBI and postconcussive symptoms are then considered. Finally, suggestions are offered regarding the design of future studies using these technologies in this population. Although this review may be of interest and value to professionals engaged in clinical or research electrophysiology in their daily work, it is intended to serve more immediately the needs of clinicians less familiar with these types of clinical electrophysiologic assessments.

A preliminary investigation of motor evoked potential abnormalities following sport-related concussion

BACKGROUND

Assessment of concussion is primarily based on self-reported symptoms, neurological examination and neuropsychological testing. The neurophysiologic sequelae and the integrity of the corticomotor pathways could be obtained by evaluating motor evoked potentials (MEPs).

OBJECTIVES

To compare MEPs obtained through transcranial magnetic stimulation (TMS) in acutely concussed and non-concussed collegiate athletes.

METHODS

Eighteen collegiate athletes (12 males, six females, aged 20.4 +/- 1.3 years) including nine subjects with acute concussion (<or=24 hours) matched to nine control subjects. TMS was applied over the motor cortex and MEP responses were recorded from the contralateral upper extremity. MEP thresholds (%), latencies (milliseconds per metre) and amplitudes were assessed. Central motor conduction time (CMCT) was calculated from MEP, M response and F wave latencies. Testing was performed on days 1, 3, 5 and 10 post-concussion.

RESULTS

Ulnar MEP amplitudes were significantly different between post-concussion days 3 and 5 (F(3,48) = 3.13, p = 0.041) with smaller amplitudes recorded on day 3 (0.28 +/- 0.10 ms m(-1)). Median MEP latencies were significantly longer (F(3,48) = 4.53, p = 0.023) 10 days post-concussion (27.1 +/- 1.4 ms m(-1)) compared to day 1 (25.7 +/- 1.5 ms m(-1)). No significant differences for motor thresholds or CMCTs were observed (p > 0.05).

CONCLUSION

MEP abnormalities among acutely concussed collegiate athletes provide direct electrophysiologic evidence for the immediate effects of concussion.

Prognostic value of the Glasgow Coma Scale and pupil reactivity in traumatic brain injury assessed pre-hospital and on enrollment: an IMPACT analysis

We studied the prognostic strength of the individual components of the Glasgow Coma Scale (GCS) and pupil reactivity to Glasgow Outcome Score (GOS) at 6 months post-injury. A total of 8721 moderate or severe traumatic brain injury (TBI) patient data from the IMPACT database on traumatic brain injury comprised the study cohort. The associations between motor score and pupil reactivity and 6-month GOS were analyzed by binary logistic regression and proportional odds methodology. The strength of prognostic effects were expressed as the unadjusted odds ratios presented for all individual studies as well as in meta-analysis. We found a consistent strong association between motor score and 6-month GOS across all studies (OR 1.74-7.48). The Eye and Verbal components were also strongly associated with GOS. In the pooled population, one or both un-reactive pupils and lower motor scores were significantly associated with unfavorable outcome (range 2.71-7.31). We also found a significant change in motor score from pre-hospital direct to study hospital enrollment ( p < 0.0001) and from the first in-hospital to study enrollment scores (p < 0.0001). Pupil reactivity was more robust between these time points. It is recommended that the study hospital enrollment GCS and pupil reactivity be used for prognostic analysis.

Neurophysiological correlates of persistent vegetative and minimally conscious states

The evaluation of patients after severe brain injury is a complex process for the clinician, even with the information provided by a detailed neurological examination. The clinical examination often does not provide sufficient information to fully evaluate these patients due to several factors. Limited and inconsistent motor responses may obscure expression of greater cognitive capacities. More importantly, evaluation of the functional integrity of the cerebral cortical, thalamic and basal ganglia system is poorly indicated by the clinical examination in many patients. Neurophysiological studies provide a complementary set of objective data for evaluating brain-injured patients, as well as predicting and following the course of their recovery. This additional information can be of great importance since vegetative patients may be difficult to distinguish clinically from those in the minimally conscious state. This is important because the latter category of patients may have a significantly better prognosis for recovery in the initial phase of injury. Electrodiagnostic and imaging studies can help the practitioner to determine the degree of preserved and recovering neurological function. In this review we will assess the various neurophysiological studies currently at our disposal to evaluate and follow the clinical course of patients who have suffered severe brain injuries.

The usefulness of quantitative EEG (QEEG) and neurotherapy in the assessment and treatment of post-concussion syndrome

Mild traumatic brain injury (TBI) is associated with damage to frontal, temporal and parietal lobes. Post-concussion syndrome has been used to describe a range of residual symptoms that persist 12 months or more after the injury, often despite a lack of evidence of brain abnormalities on MRI and CT scans. The core deficits of post-concussion syndrome are similar to those of ADHD and mood disorders, and sufferers often report memory, socialization problems and frequent headaches. While cognitive rehabilitation and psychological support are widely used, neither has been shown to be effective in redressing the core deficits of post-concussion syndrome. On the other hand, quantitative EEG has been shown to be highly sensitive (96%) in identifying post-concussion syndrome, and neurotherapy has been shown in a number of studies to be effective in significantly improving or redressing the symptoms of post-concussion syndrome, as well as improving similar symptoms in non-TBI patients.

[Prognostic factors in severe head injury]

The knowledge of the so called prognostic factors or indicators involved in severe head injury (SHI) is an issue of great interest to make predictions about the future of patients with this pathology. Those indicators constitute the basic elements of the different prognostic formulas or models carried out in order to make predictions in SHI. The mentioned models, therefore, will be constructed by a group of variables (prognostic indicators or factors) and several scales (prognostic scales) that are useful for measuring the final outcome of these patients. In this paper we resume, after an exhaustive review of the literature, the knowledge about the prognostic factors related to SHI. These indicators have been classified as follows: clinical, radiological, physiological, and biochemical. Moreover, we have briefly described the prognostic scales more commonly used in SHI.

Quantitative EEG and the Frye and Daubert standards of admissibility

The 70-year-old Frye standards of "general acceptance" were replaced by the Supreme Court's 1993 Daubert criteria of the scientific method, which established the standards for admissibility of evidence in Federal Court. The four Daubert criteria were: 1- Hypothesis testing, 2- Estimates of error rates, 3- Peer reviewed publication and 4- General acceptance (Daubert v. Merrell Dow Pharmaceuticals, 61 U.S.LW 4805 (U.S. June 29, 1993)). The present paper starts with the Daubert four factors and then matches them, step by step, to the scientific peer reviewed literature of quantitative EEG (QEEG) in relation to different clinical evaluations. This process shows how the peer reviewed science of the Digital EEG and the Quantitative EEG (QEEG) meet all of the Daubert standards of scientific knowledge. Furthermore, the science and technical aspects of QEEG in measuring the effects of neurological and psychiatric dysfunction also match the recent Supreme Court standards of "technical" and "other specialized" knowledge (General Electric Co v. Joiner, 1997, Kumho Tire Company, Ltd. v. Carmichael, 1999). Finally, it is shown that QEEG scientific knowledge and QEEG "technical" and "other specialized" knowledge meet the trilogy standards of the Supreme Court rulings in support of QEEG's admissibility as a clinically valid method in the evaluation of the nature and extent of neurological and psychiatric disorders.

Improving the prediction of outcome in severe acute closed head injury by using discriminant function analysis of normal auditory brainstem response latencies and amplitudes

OBJECT

The auditory brainstem response (ABR) is a useful addition to standard medical measures for predicting outcome in patients with severe acute closed head injury (ACHI). Limiting this success, however, is the poor predictive value of a so-called "normal" ABR. In this study the authors used discriminant function analysis (DFA) of ABR Wave I, III, and V latencies and amplitudes to improve the predictive accuracy of the normal ABR, both as a single measure and in combination with other standard medical measures.

METHODS

The DFAs were conducted using the ABR and medical results in 68 patients with severe ACHI (30 who died [ACHI-died], and 38 who survived [ACHI-lived]) who presented with normal ABR responses in the neurosurgical intensive care unit of the authors' hospital in Johannesburg. All patients had undergone surgery to remove an intracranial hematoma. Correct predictions of outcome by ABR DFA measures were 83% for the ACHI-died group (48% at > or = 90% confidence level) and 87% for the ACHI-lived group (71% at > or = 90% confidence level); by medical DFA measures the correct predictions were 83% for the ACHI-died group (96% at >; or = 90% confidence level) and 95% for the ACHI-lived group (94% at > or = 90% confidence level); and by combined ABR and medical DFA measures correct predictions were 100% for the ACHI-died group (100% at > or = 90% confidence level) and 97% for the ACHI-lived group (100% at > or = 90% confidence level).

CONCLUSIONS

The DFA of ABR Wave I, III, and V latencies and amplitudes improved the predictive ability of normal ABR results to rates similar to those obtained using DFA for the medical measures, although at lower confidence levels. The DFA of the combined ABR and medical measures improved correct predictions to rates significantly higher than for either of the measures on its own.

Early and persistent impaired percent alpha variability on continuous electroencephalography monitoring as predictive of poor outcome after traumatic brain injury

OBJECT

Early prediction of outcomes in patients after they suffer traumatic brain injury (TBI) is often nonspecific and based on initial imaging and clinical findings alone, without direct physiological testing. Improved outcome prediction is desirable for ethical, social, and financial reasons. The goal of this study was to determine the usefulness of continuous electroencephalography (EEG) monitoring in determining prognosis early after TBI, while the patient is in the intensive care unit.

METHODS

The authors hypothesized that the reduced percentage of alpha variability (PAV) in continuous EEG tracings indicates a poor prognosis. Prospective continuous EEG monitoring was performed in 89 consecutive patients with moderate to severe TBI (Glasgow Coma Scale [GCS] Scores 3-12) from 0 to 10 days after injury. The PAV was calculated daily, and the time course and trends of the PAV were analyzed in comparison with the patient's Glasgow Outcome Scale (GOS) score at the time of discharge. In patients with GCS scores of 8 or lower, a PAV value of 0.1 or lower is highly predictive of a poor outcome or death (positive predictive value 86%). The determinant PAV value was obtained by Day 3 after injury. Persistent PAV values of 0.1 or lower over several days or worsening of the PAV to a value of 0.1 or lower indicated a high likelihood of poor outcome (GOS Scores 1 and 2). In comparison with the combination of traditional initial clinical indicators of outcome (GCS score, pupillary response to light, patient age, results of computerized tomography scanning, and early hypotension or hypoxemia), the early PAV value during the initial 3 days after injury independently improved prognostic ability (p < 0.01).

CONCLUSIONS

Continuous EEG monitoring performed with particular attention paid to the PAV is a sensitive and specific method of prognosis that can indicate outcomes in patients with moderate to severe TBI within 3 days postinjury.

Estimation of the EEG power spectrum using MRI T(2) relaxation time in traumatic brain injury

OBJECTIVES

To study the relationship between magnetic resonance imaging (MRI) T(2) relaxation time and the power spectrum of the electroencephalogram (EEG) in long-term follow up of traumatic brain injury.

METHODS

Nineteen channel quantitative electroencephalograms or qEEG, tests of cognitive function and quantitative MRI T(2) relaxation times (qMRI) were measured in 18 mild to severe closed head injured outpatients 2 months to 4.6 years after injury and 11 normal controls. MRI T(2) and the Laplacian of T(2) were then correlated with the power spectrum of the scalp electrical potentials and current source densities of the qEEG.

RESULTS

qEEG and qMRI T(2) were related by a frequency tuning with maxima in the alpha (8-12Hz) and the lower EEG frequencies (0.5-5Hz), which varied as a function of spatial location. The Laplacian of T(2) acted like a spatial-temporal "lens" by increasing the spatial-temporal resolution of correlation between 3-dimensional T(2) and the ear referenced alert but resting spontaneous qEEG.

CONCLUSIONS

The severity of traumatic brain injury can be modeled by a linear transfer function that relates the molecular qMRI to qEEG resonant frequencies.

A history and review of quantitative electroencephalography in traumatic brain injury

The electroencephalogram (EEG) is a physiologic measure of cerebral function that has been used by some to assess coma and prognosticate survival and global outcome after traumatic brain injury (TBI). Surface recordings of the brain's electrical activity reveal distinct patterns that indicate injury severity, depth of unconsciousness, and patient survival. The data produced with traditional qualitative studies, however, does not allow resolution and quantification of the wave frequency spectrum present in the brain. As a result, conventional EEG typically has only been used for gross and qualitative analyses and is not practical for use in long-term patient monitoring or as a sophisticated prognostic tool. One area of investigation that is working to address the limitations of conventional EEG has been the development and implementation of Fourier Transform (FT) EEG which resolves and quantifies frequency bands present in the brain. When FT analysis is applied to EEG, it provides concurrent and continuous monitoring, resolution, and quantification of all frequencies emitted. This review discusses the history and significance of conventional EEG and provides a review of how FT-EEG, commonly referred to as Quantitative EEG (QEEG), is being used in the clinical setting. The specific applications and significance of QEEG methods regarding treatment of patients with TBI are discussed in detail. The advantages, disadvantages, and future directions of QEEG in TBI are also discussed.

Early recovery after closed traumatic head injury: Somatosensory evoked potentials and clinical findings

OBJECTIVE

To determine the ability of somatosensory evoked potentials (SEP) compared with clinical findings to monitor and predict recovery in patients suffering from closed head injury with predominantly diffuse axonal injury (DAI).

DESIGN

Prospective cohort study.

SETTING

Neurologic intensive care unit (ICU) of a university hospital.

PATIENTS

Serial SEP recordings were obtained from 31 consecutive patients with closed head injury. The first SEP was recorded within 48 hrs after trauma, followed by recordings after another 2 days, after which the time interval for each consecutive recording was doubled. Clinical examinations were performed every 6 hrs during the ICU stay and daily after transfer to a general neurologic ward.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Twenty-three of 31 patients demonstrated pathologic SEP findings at initial examination. Of these patients, 11 recovered clinically, two remained vegetative, and ten died. In all 11 patients with clinical recovery, SEP also recovered. In 8 of 31 patients, initial SEPs were normal and remained normal until discharge, all eight had a good outcome. Initial SEP findings were related with outcome at 6 months (p = .02), and follow-up studies increased the predictive value of SEP studies (p = .009). Other factors related to outcome included age, severity of DAI, and length of ICU/hospital stay. In the 11 patients with SEP and clinical recovery, early (day 2) and late (>or=2 months) recovery was documented. Early and reliable SEP indicators of improvement included N20-P25-Amplitudes (mean recovery, 8.5 days) and central conduction time (9.6 days). Pupillary light reaction (6.4 days), Babinski reflex (12.4 days), and Glasgow Coma Score (9.6 days) were the most valuable clinical findings. Recovery of the Glasgow Coma Score frequently coincided with reduction of sedatives. In most patients, recovery was detected with SEP before clinical recovery (7/11 patients, time difference 1 wk).

CONCLUSIONS

Initial SEP findings correlate with long-term outcome in patients with closed head injury with DAI. Initial bilaterally absent cortical responses in the SEP reliably predicted death, whereas completely normal SEP findings predicted good long-term outcome. Early recovery after DAI can be detected with serial SEP recordings despite sedative medications. Electrophysiologic recovery frequently precedes clinical recovery.

Power spectra and coherence in the EEG of a vegetative patient with severe asymmetric brain damage

OBJECTIVES

To examine differences in power spectra and intra-hemispheric coherence between the left and right hemispheres in the presence of severe asymmetric brain damage.

METHODS

Power spectra and coherence functions were computed for a patient with severe damage to subcortical gray matter structures on the right side but relative preservation on the left.

RESULTS

Power spectra differed modestly over the hemispheres, with greater low frequency power and less high frequency power over the more damaged right hemisphere. Coherence differed dramatically, with marked reduced coherence over the right hemisphere, particularly frontally where the damage was most extensive.

CONCLUSIONS

Damage to subcortical structures of one hemisphere may result in a marked reduction in coherence in the ipsilateral EEG with only a modest change in the power spectrum. We speculate that the physiologic basis of this selective change is damage to structures mediating communication between cortical areas.

Electroencephalogram silence ratio for early outcome prognosis in severe head trauma

OBJECTIVE

To introduce the electroencephalogram silence-ratio (ESR) as a variable derived from mathematically processed electroencephalogram for early outcome prognosis in patients with severe head trauma and to comparatively assess sensitivity, specificity and predictive value vs. somatosensory evoked potentials and brainstem auditory evoked potentials.

DESIGN

Prospective, interventional study.

SETTING

Intensive care unit of a university hospital.

PATIENTS

A total of 32 adults with severe acute head trauma (Glasgow Coma Scale score < or = 8).

METHODS AND MAIN RESULTS

In all patients, electroencephalographic recording was continuously performed by frontomastoid electrode montage for 24-96 hrs after admission to the ICU. The data were subsequently computed by fast Fourier analysis and the ESR (intervals of suppression as periods >240 msecs during which the electroencephalographic voltage did not exceed 5 microV) was displayed and recorded on a computer for further evaluation. Somatosensory evoked potentials and brainstem auditory evoked potentials were elicited during the first 2 days after admission. Outcome evaluation was performed 6 months after trauma using the Glasgow Outcome Scale and the Rappaport Disability Rating Scale. After careful artifact exclusion, the ESR depicted the highest sensitivity, specificity, and positive predictive value compared with evoked potentials. Even a highly significant correlation between outcome and ESR was found (p < .0001).

CONCLUSION

The ESR is a valuable variable showing a high reliability with respect to outcome prediction in severe head trauma with a higher predictive value than short latency somatosensory evoked potentials. Evidence exists that the ESR provides at least partial information regarding adequate cerebral oxygen delivery.

Functional neuroimaging and quantitative electroencephalography in adult traumatic head injury: clinical applications and interpretive cautions

Functional neuroimaging and quantitative electroencephalographic procedures are being used increasingly in brain injury research and clinical care. These procedures are also seeing increased use in the context of forensic evaluations, particularly in cases of mild head trauma. This article provides an overview of the use of procedures such as positron emission tomography, single photon emission computed tomography, and quantitative electroencephalogram in adults. Also discussed are the clinical limitations of each procedure within the context of myriad interpretive confounds that can interfere with accurate differential diagnosis of mild head trauma.

EEG operant conditioning (biofeedback) and traumatic brain injury

A review is presented of the currently sparse literature about EEG operant conditioning or biofeedback as a treatment to reduce symptomology and patient complaints following a traumatic brain injury. The paper also evaluates the general use of quantitative EEG (QEEG) to assess traumatic brain injury and to facilitate EEG biofeedback treatment. The use of an age matched reference normative QEEG database and QEEG discriminant function are presented as a method to evaluate the nature or neurological basis of a patient's complaints as well as to individualize an efficient and optimal feedback protocol and to help evaluate the efficacy of the biofeedback therapy. Univariate and multivariate statistical issues are discussed, different classes of experimental designs are described and then a "double blind" research study is proposed in an effort to encourage future research in the area of EEG biofeedback for the treatment and rehabilitation of traumatic brain injury.

Functional outcome of individuals with traumatic brain injury and lower extremity deep venous thrombosis

OBJECTIVE

To determine the impact of acute lower extremity (LE) deep venous thrombosis (DVT) on functional outcome after traumatic brain injury (TBI).

SETTING

Tertiary university medical center rehabilitation unit.

SUBJECTS

Ninety-two TBI rehabilitation patients (46 patients with DVT and 46 patients without DVT). Forty-six TBI patients with a diagnosis of LE DVT were 1:1 matched with non-DVT TBI patients. Matching criteria included: primary diagnosis of TBI, admission Functional Independence Measure (FIM), Glasgow Coma Scale (GCS), and age.

OUTCOME MEASURES

FIM (admission, discharge, change, and efficiency), FIM subscores (activities of daily living [ADL], mobility, cognition), length of stay ([LOS] acute and rehabilitation), and discharge living disposition.

DESIGN

Cohort study utilizing prospectively collected data. DVT diagnoses were made upon rehabilitation admission using color flow duplex Doppler ultrasonography. Descriptive statistics were run on demographic variables. Analyses of variance (ANOVAs) were performed on the sample with regard to outcome measures, including FIM scores, FIM subscores, and LOS (acute and rehabilitation).

RESULTS

No significant between-group differences were found concerning LOS, rehabilitation costs, FIM total, or FIM subgroup scores. Chi-squared analyses revealed significant differences between groups with regard to discharge living disposition (chi(2) = 4.7, P <.03).

CONCLUSION

Lower extremity DVT does not appear to interfere with functional outcome after TBI. The data suggest that this patient population is appropriate for admission or continued participation in acute inpatient rehabilitation, despite the presence of LE DVT.

Biophysical linkage between MRI and EEG amplitude in closed head injury

Nuclear magnetic resonance of brain water proton (1H) T2 relaxation times and measures of absolute amplitude of EEG were obtained from 19 closed head injured patients. The relationship between EEG and T2 relaxation time differed as a function of both EEG frequency and gray matter versus white matter. White matter T2 relaxation time was positively correlated with increased EEG amplitude in the delta frequency band (0.5-3.5 Hz). In contrast, lengthened gray matter T2 relaxation time was inversely correlated with EEG amplitude in the alpha and beta frequency bands (7-22 Hz). These findings are consistent with clinical EEG studies in which white matter lesions are related to increased EEG delta amplitude and gray matter lesions are related to decreased EEG alpha and beta frequency amplitude. Estimates of the severity of injury were obtained by neuropsychological measurements, in which lengthened T2 relaxation times in both the neocortical gray and white matter were correlated with diminished cognitive function. Decreased EEG beta and alpha amplitude and increased EEG delta amplitude were also correlated with diminished cognitive function. The findings imply a biophysical linkage between the state of protein-lipid structures of the brain as measured by the MRI and the scalp-recorded EEG.

Quantitative electroencephalographic evaluation of non-fatal and fatal traumatic coma

Diffuse axonal injury (DAI) is an important cause of morbidity and mortality after traumatic brain injury (TBI), and its severity is therefore a major determinant of outcome. There have been suggestions that the extent of DAI may be reflected in quantitative measures of cerebral function, including the electroencephalogram (EEG) and brain-stem auditory evoked potentials (BAEPs). It has therefore been proposed that these quantitative methods of analysis may provide objective predictors of outcome following TBI. We prospectively investigated the relationship between quantitative EEG and BAEP measures and outcome, in 60 comatose patients (47 male and 13 female; age range 1-80 years, mean 36.4) after severe, closed head injury (post-resuscitation Glasgow Coma Scale (GCS) of 8). The Spearman correlation coefficients (rs) have been calculated for quantitative EEG measures (mean regional power and interhemispheric coherence) and BAEPs with patient outcome on the Glasgow Outcome and Disability Rating Scales at 6 months and 1 year. The measures most significantly correlated with outcome (P < 0.001) are over the left hemisphere, beta activity power (amplitude squared) in the fronto-central and centro-temporal regions, and alpha activity power in the centro-temporal region. We found no correlation between interhemispheric coherence (a statistical measure of cross-correlation in the frequency domain) and outcome at either 6 months or 1 year post-injury. In 10 fatalities, we examined the relationship between interhemispheric EEG coherence prior to deaths and the histopathological severity of DAI, in concordant regions. The only significant correlation between DAI and interhemispheric coherence is seen in the alpha band at the temporo-occipital site (rs = -0.79, P = 0.007). Our data indicate that there is regional information in EEG power spectra over the left hemisphere, which could be used in prognostic predictions for patients in coma after severe TBI. We were unable to demonstrate a correlation between interhemispheric coherence and outcome, or any clear and consistent evidence of a relationship between interhemispheric coherence and the severity of DAI.

Monitoring severe head injury: a comparison of EEG and somatosensory evoked potentials

We report on our experience with long-term monitoring of the EEG power spectrum and somatosensory evoked potentials (SSEPs) in 103 patients with severe closed head injury (Glasgow Coma Scale-GCS < or = 8). Patients were monitored for an average of 5 days post injury and monitoring was terminated when they died, regained consciousness or their intracranial physiologic parameters (primarily intracranial pressure-ICP) were stable for 2-3 days. Patients were treated according to a standard protocol that included mechanical ventilation, sedation, and neuromuscular blockade. At 7 of 9 twelve hour time intervals post injury, SSEPs were significantly (p < .05) different between outcome groups using the Glasgow Outcome Score collapsed to 3 categories. The percent slow (delta) activity in the EEG was not significantly different between outcome groups at any time point, post injury. The total power in the EEG power spectrum differed only at the last time epoch post injury (108 hr.). Based on the superior prognostic capabilities of the SSEP, we routinely base critical management decisions on SSEP values. We have not been able to rely on EEG parameters for these same decisions due to the lack of clear distinction between good and poor prognosis groups based on common EEG parameters.

Prognostic indicators in medical rehabilitation of traumatic brain injury: a commentary and review

The National Information System (NIS) project is developing consensus opinion regarding a proposed structural framework for the prognostic data to be collected as part of this proposed multicenter research effort on severe traumatic brain injury (TBI). This article provide a brief history of the process, examines challenges facing rehabilitation research in this particular area, discusses reasons for identifying prognostic data within the research context of the NIS project, and describes methodologies for use of mathematical models in predicting outcome from TBI. The literature regarding prognostic parameters in severe TBI is briefly reviewed, utilizing three broad parameter categorizations: preinjury, injury, and postinjury. The implications of this research and directions for further study within the NIS project are discussed.

Kernohan-Woltman notch phenomenon: an unusual cause of ipsilateral motor deficit

Posttraumatic ipsilateral motor deficits are rare and raise etiologic and prognostic concerns for the rehabilitation team. We present two cases with an unusual central neurologic cause of ipsilateral weakness. The first patient was assaulted, with a resultant severe traumatic brain injury. Initial computed tomography showed a large right subdural hematoma (SDH) with significant mass effect. Following a craniotomy for evacuation of the SDH, the patient was noted to have paradoxical right-sided (ipsilateral) motor deficits. Postoperative magnetic resonance imaging (MRI) showed compression of the contralateral (left) cerebral peduncle against the tentorium, thus resulting in ipsilateral (right-sided) motor weakness (the Kernohan-Woltman notch phenomenon). Prior limited reports carried a grave prognosis for these patients. On discharge from inpatient rehabilitation, the patient was functioning at a Rancho Los Amigos Scale VI. The second patient was involved in a motor vehicle accident and was found to have a large left frontotemporal subdural hematoma with shift. A dense left hemiplegia was noted after hematoma evacuation. MRI also showed a right cerebral peduncle hypointensity. At discharge, the patient was rated a Rancho Los Amigos Scale VI. Physiatrists need to be aware of the causes of ipsilateral motor weakness as well as the limitations of prognostic data.

Epidemiologic aspects of brain injury

Approximately 2 million head injuries occur each year in the United States, producing a brain injury rate of 175 to 200 per 100,000 population and causing as many as 56,000 deaths per year. The economic and emotional toll of this public health burden is staggering. By identifying risk factors, perhaps effective legislation and environmental and educational intervention strategies can be developed to prevent brain injury.

Post-traumatic apallic syndrome following head injury. Part 1: clinical characteristics

Epidemiological studies made within the western countries indicate an incidence of 200-300 traumatic head injuries per 100 000 residents each year. Severe head injuries account for 5-25% of all head injuries; 10-14% of all severe head-injured patients develop into a vegetative state, in which a sleep-wake rhythm is apparent, but however in which there is no evidence of awakeness or reactivity to the environment. The most commonly used labels, in the German and international literature, for these patients are 'vegetative state', 'apallic syndrome' and 'coma vigile'. This clinical characterization is not sufficient. It is necessary to employ additional criteria to distinguish subsets of vegetative patients e.g. computerized tomography, magnetic resonance imaging, single photon emission tomography, electroencephalography, brainstem reflexes, evoked potentials, assessment scales, age, premorbid brain disorders. Diagnostic and prognostic parameters must form the basis for various decisions relating to patients' care and intervention.