A physiological coma scale: grading of coma by combined use of brain-stem trigeminal and auditory evoked potentials and the Glasgow Coma Scale

The Clinical Effect of Repetitive Transcranial Magnetic Stimulation on the Disturbance of Consciousness in Patients in a Vegetative State

Objective

To explore the effect of combining repetitive transcranial magnetic stimulation (rTMS) and conventional rehabilitation on the recovery of consciousness in patients in a persistent vegetative state (PVS).

Methods

A total of 48 patients in a PVS were randomly divided into a treatment and control group. Patients in the treatment group were treated with rTMS to stimulate the dorsolateral prefrontal cortex, and patients in the control group were treated with false stimulation. All patients were evaluated using scales and neuroelectrophysiological assessment before treatment, after 30 days of treatment, and following 60 days of treatment.

Results

Based on the Coma Recovery Scale-Revised (CRS-R) and electroencephalogram (EEG) grading indexes, the treatment group was significantly higher than those of the control group after 30 and 60 days of treatment. The average difference in the three measurements between the two groups before treatment, at 30 days, and 60 days was 0.04, 1.54, and 2.09 for CRS-R and 0.08, −0.83, and −0.62 for EEG indexes, respectively. The latency periods of each wave of the brainstem auditory evoked potentials (BAEPs) in the treatment group were shorter than those in the control group after 30 and 60 days of treatment. In both groups, the BAEP scores after 30 days of treatment were significantly higher than the scores before treatment, and the scores after 60 days of treatment were higher than the scores after 30 days.

Conclusion

In patients in a PVS, rTMS assists in the recovery of consciousness function.

Brainstem Monitoring in the Neurocritical Care Unit: A Rationale for Real-Time, Automated Neurophysiological Monitoring

Patients with severe traumatic brain injury or large intracranial space-occupying lesions (spontaneous cerebral hemorrhage, infarction, or tumor) commonly present to the neurocritical care unit with an altered mental status. Many experience progressive stupor and coma from mass effects and transtentorial brain herniation compromising the ascending arousal (reticular activating) system. Yet, little progress has been made in the practicality of bedside, noninvasive, real-time, automated, neurophysiological brainstem, or cerebral hemispheric monitoring. In this critical review, we discuss the ascending arousal system, brain herniation, and shortcomings of our current management including the neurological exam, intracranial pressure monitoring, and neuroimaging. We present a rationale for the development of nurse-friendly-continuous, automated, and alarmed-evoked potential monitoring, based upon the clinical and experimental literature, advances in the prognostication of cerebral anoxia, and intraoperative neurophysiological monitoring.

Prognostic Value of Evoked Responses and Event-Related Brain Potentials in

The behaviourally unresponsive patient, unable to exhibit the presence of cognition, constitutes a conundrum for health care specialists. Prognostic uncertainty impedes accurate management decisions and the application of ethical principles. An early, reliable prognosis is highly desirable. In this review investigations studying comatose patients with coma of different etiologies were selected. It is concluded that objective prognostication is enhanced by the use of electrophysiological tests. Persistent abnormalities of brainstem auditory evoked potentials and short-latency somatosensory evoked potentials reliably indicate the likelihood of irreversible neurological deficit or death. Meanwhile, the presence of “cognitive” event-related brain potentials (e.g., P300 and mismatch negativity) reflects the functional integrity of higher level information processing and, therefore, the likelihood of capacity for cognition. An approach that combines clinical and electrophysiological values provides optimal prediction of outcome and level of disability.

Over-Complete Discrete Wavelet Transformation of the Normal Auditory Brainstem Response Improves Prediction of Outcome following Severe Acute Closed Head Injury

Previous research has shown that complex statistical analysis (discriminant function analysis) of a 'normal' auditory brainstem response (ABR) result can improve this measure's ability to predict subject outcome following severe acute closed head injury (ACHI). We hypothesized that adding the ABR's time-frequency information to such an analysis would improve this predictive value even further. 'Normal' ABR results were sampled from 69 severe ACHI subjects (22 of whom died and 47 of whom lived) and their time-frequency information extracted using an over-complete discrete wavelet transformation (OCDWT). A series of logistic regression analyses then showed correct predictions of death and survival as follows: ABR measures only 72 and 89% (respectively), ABR OCDWT measures only 82 and 89% (respectively), and ABR and ABR OCDWT measures combined 86 and 93% (respectively). These results showed that the addition of time-frequency information can improve the ability of the 'normal' ABR result to predict outcome following severe ACHI.

The neurophysiology of brain injury

OBJECTIVE

This article reviews the mechanisms and pathophysiology of traumatic brain injury (TBI).

METHODS

Research on the pathophysiology of diffuse and focal TBI is reviewed with an emphasis on damage that occurs at the cellular level. The mechanisms of injury are discussed in detail including the factors and time course associated with mild to severe diffuse injury as well as the pathophysiology of focal injuries. Examples of electrophysiologic procedures consistent with recent theory and research evidence are presented.

RESULTS

Acceleration/deceleration (A/D) forces rarely cause shearing of nervous tissue, but instead, initiate a pathophysiologic process with a well defined temporal progression. The injury foci are considered to be diffuse trauma to white matter with damage occurring at the superficial layers of the brain, and extending inward as A/D forces increase. Focal injuries result in primary injuries to neurons and the surrounding cerebrovasculature, with secondary damage occurring due to ischemia and a cytotoxic cascade. A subset of electrophysiologic procedures consistent with current TBI research is briefly reviewed.

CONCLUSIONS

The pathophysiology of TBI occurs over time, in a pattern consistent with the physics of injury. The development of electrophysiologic procedures designed to detect specific patterns of change related to TBI may be of most use to the neurophysiologist.

SIGNIFICANCE

This article provides an up-to-date review of the mechanisms and pathophysiology of TBI and attempts to address misconceptions in the existing literature.

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.

Classification of brain-stem trigeminal evoked potentials in multiple sclerosis, minor head injuries and post-concussion syndrome pathologies by similarity measurements

In this study measurements obtained from brain-stem trigeminal evoked potentials (BTEP) are applied to the problem of diagnosing Multiple Sclerosis (MS) and Post-concussion syndrome (PCS). We present a simplistic model that depicts the BTEP waveform as the linear combination of a set of filters excited by a short stimulus. The relation between the BTEP latencies and the 1st to 4th harmonic components is shown. The performance of a fuzzy similarity measure based classifier is compared with that of human experts. The efficiency of the proposed classifier in conjunction with delay time and amplitude features is examined. Using this novel approach, a classification rate of 93.55% and 84.1% for MS and PCS pathologies, respectively, was achieved. This performance compares favorably to the classification rates of 84.28% for MS and 70.47% for PCS pathologies achieved by human experts.

Trigeminal somatosensory evoked potentials before, during and after an inferior alveolar nerve block in normal subjects

The changes of the trigeminal somatosensory evoked potential (TSEP) before, during and after inferior alveolar nerve block were serially recorded in six healthy subjects (33-43 years of age; mean age 38.0 years). In four subjects in whom successful nerve block was achieved, TSEP showed linear flattening of the wave form. The recovery of TSEP slightly preceded the recovery of threshold of the sensation to electrical stimulation and that of two-point discrimination on the skin. In the remaining two subjects, in whom effective nerve block failed, TSEP showed no change in the wave form but did show slight prolongation of the latencies. We conclude that TSEP can be used as a method to confirm whether conduction anesthesia has been successful or unsuccessful.

A comparison of neural network and Bayes recognition approaches in the evaluation of the brainstem trigeminal evoked potentials in multiple sclerosis

This article describes the application of Multi-Layer Perceptron (MLP), Probabilistic Neural Network and Kohonen's Learning Vector Quantization to the problem of diagnosing Multiple Sclerosis. The classification information is obtained from brainstem trigeminal evoked potential. The performance of the neural networks based classifiers is compared with that of the human experts and the Bayes classifier. The ability of the MLP classifier to generalize is far better than that of the Bayes classifier. The efficiency of the neural network based classifiers in conjunction with several types of well-known evoked potential features, such as Fourier transform space, latency and temporal wave, is examined. Although a large clinical data base would be necessary, before this approach can be fully validated, the initial results are promising.

Quantitative EEG analysis as a supplement to the clinical coma scale RLS85

BACKGROUND

The aim of the study was to investigate the correlation between EEG indicators and clinical scores based on the RLS85 (Reaction Level Scale 85) in comatose patients. The results of a simple visual assessment of the EEG, using an arbitrary scale with typical EEG patterns, were compared with those obtained by quantitative electroencephalography (qEEG).

METHOD

The RLS85 scores were examined in 34 patients with impaired consciousness due to brain tumours, vascular lesions or head injuries. The EEG was recorded shortly before or after the clinical examination. The semiquantitative assessment was made by visual inspection of the tracings, using an arbitrary scale where 12 EEG patterns with increasing proportion of slow activity were displayed. Parallel to the visual analysis, the EEGs were processed by means of EEG spectrum analysis and the power/amplitude in slow frequency bands was used as an indicator. The results were based on correlation between various types of EEG variables and the RLS scores which were obtained in the same patients.

RESULTS

The correlation between the visual EEG indicators and coma scores ranged between 0.53 and 0.57 (P < 0.01). As regards the computerised EEG analysis, the correlation between the clinical scores and various EEG spectrum values did not exceed 0.45 (P < 0.01). A higher correlation could be obtained by combining eight EEG variables; the multiple correlation coefficient was then 0.68.

CONCLUSIONS

The amount of EEG slow activity is significantly correlated to the RLS85 score. This means that the EEG also provides information on the level and not only on the changes of the coma degree. Surprisingly, the indicators based on quantitative EEG, as used in commercially available instruments, did not give better results than the visual assessment. However, the results of the computerised analysis could be improved using multivariate statistical methods. The study also showed a way to improve communication between the neurophysiologist and clinician by presenting the EEG findings in terms similar to those used in the clinical scales. However, the clinician should be aware of the fact that the "EEG score" and the clinical score is not the same: the intention is to supplement rather than to simulate the clinical observation.

Brain-stem trigeminal and auditory evoked potentials in multiple sclerosis: physiological insights

Thirty-six patients with multiple sclerosis were evaluated by means of brain-stem trigeminal and auditory evoked potentials. The brain-stem auditory evoked potentials (BAEPs) were abnormal in 26 patients (72.2%). Brain-stem trigeminal evoked potentials (BTEPs) yielded similar results, showing distorted waveforms and/or prolonged latencies in 25 patients (69.4%). As expected, the MRI proved to be the most efficient single test, revealing plaques in 86.4% of the patients evaluated. However, the diagnostic accuracy of MRI was lower than that provided by the combination of the BTEP and BAEP (88.9%). Moreover, in patients having signs of brain-stem involvement, the BTEP, alone and in combination with the BAEP, proved to be more sensitive than the MRI in revealing brain-stem lesions. Correlation between clinical and BTEP findings could be found only in those patients who presented with signs of trigeminal involvement such as trigeminal neuralgia or dysesthesiae. The analysis of the BTEP waveforms showed two distinct types of abnormality-a peripheral type and a central type-suggesting plaques in distinct locations. Both the BTEP and the BAEP demonstrated a correlation with the clinical course of the disease and the condition of the patient at the time of the evaluation. Relapse of the disease was associated with a marked prolongation of the central conduction time in the BTEP and in the BAEP, suggesting the application of such studies to the monitoring of unstable patients in the evaluation of new therapeutic protocols.

Trigeminal and auditory evoked responses in minor head injuries and post-concussion syndrome

Forty patients who sustained minor head trauma were investigated by brainstem trigeminal and auditory evoked potentials (BTEP, BAEP) and middle-latency auditory evoked potentials (MLAEP). The patients were evaluated within the first 48 h following their admission and at 3 months after the injury. Outcome was scored at the follow-up examination according to six complaints: failure to resume previous professional activity, headache, memory disorders, dizziness and vertigo, behavioural and emotional disturbances, and other symptoms of a neurological nature. Post-concussion syndrome (PCS) was defined by the presence of four or more of the listed features. All three evoked potential modalities showed significantly increased latencies at the initial assessment, disclosing disseminated axonal damage. Unlike the BTEPs and the BAEPs, the MLAEPs proved to correlate to outcome at 3 months, especially in its psychocognitive aspects. These findings suggest that organic diencephalic-paraventricular primary damage may account for the occurrence of PCS.