Somatosensory evoked potentials for prediction of outcome in acute severe brain injury

Neuromonitoring after Pediatric Cardiac Arrest: Cerebral Physiology and Injury Stratification

BACKGROUND

Significant long-term neurologic disability occurs in survivors of pediatric cardiac arrest, primarily due to hypoxic-ischemic brain injury. Postresuscitation care focuses on preventing secondary injury and the pathophysiologic cascade that leads to neuronal cell death. These injury processes include reperfusion injury, perturbations in cerebral blood flow, disturbed oxygen metabolism, impaired autoregulation, cerebral edema, and hyperthermia. Postresuscitation care also focuses on early injury stratification to allow clinicians to identify patients who could benefit from neuroprotective interventions in clinical trials and enable targeted therapeutics.

METHODS

In this review, we provide an overview of postcardiac arrest pathophysiology, explore the role of neuromonitoring in understanding postcardiac arrest cerebral physiology, and summarize the evidence supporting the use of neuromonitoring devices to guide pediatric postcardiac arrest care. We provide an in-depth review of the neuromonitoring modalities that measure cerebral perfusion, oxygenation, and function, as well as neuroimaging, serum biomarkers, and the implications of targeted temperature management.

RESULTS

For each modality, we provide an in-depth review of its impact on treatment, its ability to stratify hypoxic-ischemic brain injury severity, and its role in neuroprognostication.

CONCLUSION

Potential therapeutic targets and future directions are discussed, with the hope that multimodality monitoring can shift postarrest care from a one-size-fits-all model to an individualized model that uses cerebrovascular physiology to reduce secondary brain injury, increase accuracy of neuroprognostication, and improve outcomes.

The Prognostic Value of Somatosensory Evoked Potentials in Children After Cardiac Arrest: The SEPIA Study

PURPOSE

Absent cortical somatosensory evoked potentials (SSEPs) reliably predict poor neurologic outcome in adults after cardiac arrest (CA). However, there is less evidence to support this in children. In addition, targeted temperature management, test timing, and a lack of blinding may affect test accuracy.

METHODS

A single-center, prospective cohort study of pediatric (aged 24 hours to 15 years) patients in which prognostic value of SSEPs were assessed 24, 48, and 72 hours after CA. Targeted temperature management (33-34°C for 24 hours) followed by gradual rewarming to 37°C was used. Somatosensory evoked potentials were graded as present, absent, or indeterminate, and results were blinded to clinicians. Neurologic outcome was graded as "good" (score 1-3) or "poor" (4-6) using the Pediatric Cerebral Performance Category scale 30 days after CA and blinded to SSEP interpreter.

RESULTS

Twelve patients (median age, 12 months; interquartile range, 2-150; 92% male) had SSEPs interpreted as absent (6/12) or present (6/12) <72 hours after CA. Outcome was good in 7 of 12 patients (58%) and poor in 5 of 12 patients (42%). Absent SSEPs predicted poor outcome with 88% specificity (95% confidence interval, 53% to 98%). One patient with an absent SSEP had good outcome (Pediatric Cerebral Performance Category 3), and all patients with present SSEPs had good outcome (specificity 100%; 95% confidence interval, 51% to 100%). Absence or presence of SSEP was consistent across 24-hour (temperature = 34°C), 48-hour (t = 36°C), and 72-hour (t = 36°C) recordings after CA.

CONCLUSIONS

Results support SSEP utility when predicting favorable outcome; however, predictions resulting in withdrawal of life support should be made with caution and never in isolation because in this very small sample there was a false prediction of unfavorable outcome. Further prospective, blinded studies are needed and encouraged.

Defining catastrophic brain injury in children leading to coma and disorders of consciousness and the scope of the problem

PURPOSE OF REVIEW

Severe brain injury in children resulting in coma and disorders of consciousness (DOC) is a catastrophic event for the life and function of children and their families. The present article summarizes the recently published pediatric literature on validated diagnostic assessments, potential predictors of recovery, and outcome measures used in children with catastrophic brain injury (CBI). Literature search terms included variants of consciousness, diagnostic tests, predictors of outcome, and outcome measures.

RECENT FINDINGS

Developmentally appropriate diagnostic tools, outcome predictors, and outcome measures are lacking for children with CBI leading to coma and DOC. Individual case prognosis relies on serial clinical examinations and experience. Evidence regarding optimal diagnosis of the highest level of consciousness and management of children with CBI is needed. Global efforts through the ongoing Curing Coma Campaign are aimed at: developing common data elements for information capture; streamlining the classification of coma endotypes; describing trajectories with biomarkers to monitor recovery or disease progression; and devising effective treatments for adults and children.

SUMMARY

Standardized, developmentally appropriate diagnostic and outcome assessments for CBI in children are needed. Future research should use these content standards to update our understanding of children with CBI leading to coma and DOC, and evaluate effective practices using acute adjunctive and rehabilitation therapies.

Somatosensory evoked potentials after decompressive craniectomy for traumatic brain injury

Somatosensory evoked potentials (SSEPs) are used for neuroprognosis after severe traumatic brain injury (TBI). However decompressive craniectomy (DC), involving removal of a portion of the skull to alleviate elevated intracranial pressure, is associated with an increase in SSEP amplitude. Accordingly, SSEPs are not available for neuroprognosis over the hemisphere with DC. We aim to determine the degree to which SSEP amplitudes are increased in the absence of cranial bone. This will serve as a precursor for translation to clinically prognostic ranges. Intra-operative SSEPs were performed before and after bone flap replacement in 22 patients with severe TBI. SSEP measurements were also performed in a comparison non-traumatic group undergoing craniotomy for tumor resection. N20/P25 amplitudes and central conduction time were measured with the bone flap in (BI) and out (BO). Linear regressions, adjusting for skull thickness and study arm, were performed to evaluate the contribution of bone presence to SSEP amplitudes. Latencies were not different between BO or BI trials in either group. Mean N20/P25 amplitudes recorded with BO were statistically different (p = 0.0001) from BI in both cohorts, showing an approximate doubling in BO amplitudes. For contralateral-ipsilateral montages r² was 0.28 and for frontal pole montages r² was 0.62. Cortical SSEP amplitudes are influenced by the presence of cortical bone as is particularly evident in frontal pole montages. Larger, longitudinal trials to assess feasibility of neuroprognosis over the hemisphere with DC in severe TBI patients are warranted.

Pediatric Head Injury: A Study of 403 Cases in a Tertiary Care Hospital in a Developing Country

INTRODUCTION

Traumatic brain injury (TBI) in children is a significant cause of morbidity and mortality worldwide. Falls are the most common type of injury, followed by motor vehicle-related accidents and child abuse.

AIMS AND OBJECTIVES

The aim and objective of this study was to elucidate the various modes of injury, prognostic factors, complications, incidence of various modes of injury, and outcome in TBI in pediatric population.

MATERIALS AND METHODS

Patients with TBI, 18 years or less in age, managed in our Department of Neurosurgery, over a period of 2 years, were studied prospectively. Detailed history, general physical examination, systemic examination, and central nervous system examination including assessment of Glasgow Coma Scale score (GCS) and pupillary size and reaction were noted in every patient. Based on GCS, patients were divided into mild head injury (GCS 13-15), moderate head injury (GCS 9-12), and severe head injury (GCS ≤8) categories. All the patients were subjected to plain computed tomography (CT) scan head, and CT findings were noted. Patients were managed conservatively or surgically as per the standard indications. The outcome of all these patients was assessed by Glasgow outcome scale and divided into good (normal, moderate disability) and poor (severe, vegetative, dead) outcome. Outcome was assessed in relation to age, sex, GCS, pupil size and reaction, CT scan features, intervention, and associated injuries.

RESULTS

A total of 403 patients aged between 1 day and 18 years were included in the study comprising 252 males (63%) and 151 females (37.75%). The common modes of injury were fall 228 (56.6%) followed by road traffic accidents 138 (34.2%), assault 10 (2.5%), and others 27 (6.7%) which include sports injury, hit by some object on head, and firearm injury. Majority of our patients had a GCS of 13-15 (mild head injury), 229 (57.3%), followed by 9-12 (moderate head injury) 119 (29.8%), followed by 8 or less (severe head injury) 52 (13%). In group of patients in the category of GCS ≤ 8, poor outcome was seen in 65.3%, followed by patients in group GCS 9-12 at 2.45% succeeded by group of patients with GCS 13-15 at 2.6%, which was statistically significant (P < 0.0001). A total of 354 (87.8%) patients had normal pupils, 37 (9.2%) had anisocoria, and 12 (3%) patients had fixed dilated pupils. Fixed dilated pupil had poor outcome (100%) followed by anisocoria (40.5%) and normal pupils (16%), which was statistically significant (P < 0.0001).

CONCLUSION

Majority of children who suffer from TBI do well although it still continues to be a significant cause of morbidity and mortality in them. The outcome is directly related to the neurological status in which they present to the hospital.

A Critical Review for Developing Accurate and Dynamic Predictive Models Using Machine Learning Methods in Medicine and Health Care

Recently, Artificial Intelligence (AI) has been used widely in medicine and health care sector. In machine learning, the classification or prediction is a major field of AI. Today, the study of existing predictive models based on machine learning methods is extremely active. Doctors need accurate predictions for the outcomes of their patients' diseases. In addition, for accurate predictions, timing is another significant factor that influences treatment decisions. In this paper, existing predictive models in medicine and health care have critically reviewed. Furthermore, the most famous machine learning methods have explained, and the confusion between a statistical approach and machine learning has clarified. A review of related literature reveals that the predictions of existing predictive models differ even when the same dataset is used. Therefore, existing predictive models are essential, and current methods must be improved.

Phase synchronization in electroencephalographic recordings prognosticates outcome in paediatric coma

Brain injury from trauma, cardiac arrest or stroke is the most important cause of death and acquired disability in the paediatric population. Due to the lifetime impact of brain injury, there is a need for methods to stratify patient risk and ultimately predict outcome. Early prognosis is fundamental to the implementation of interventions to improve recovery, but no clinical model as yet exists. Healthy physiology is associated with a relative high variability of physiologic signals in organ systems. This was first evaluated in heart rate variability research. Brain variability can be quantified through electroencephalographic (EEG) phase synchrony. We hypothesised that variability in brain signals from EEG recordings would correlate with patient outcome after brain injury. Lower variability in EEG phase synchronization, would be associated with poor patient prognosis. A retrospective study, spanning 10 years (2000-2010) analysed the scalp EEGs of children aged 1 month to 17 years in coma (Glasgow Coma Scale, GCS, <8) admitted to the paediatric critical care unit (PCCU) following brain injury from TBI, cardiac arrest or stroke. Phase synchrony of the EEGs was evaluated using the Hilbert transform and the variability of the phase synchrony calculated. Outcome was evaluated using the 6 point Paediatric Performance Category Score (PCPC) based on chart review at the time of hospital discharge. Outcome was dichotomized to good outcome (PCPC score 1 to 3) and poor outcome (PCPC score 4 to 6). Children who had a poor outcome following brain injury secondary to cardiac arrest, TBI or stroke, had a higher magnitude of synchrony (R index), a lower spatial complexity of the synchrony patterns and a lower temporal variability of the synchrony index values at 15 Hz when compared to those patients with a good outcome.

Prognosis in prolonged coma patients with diffuse axonal injury assessed by somatosensory evoked potentia

A total of 43 prolonged coma patients with diffuse axonal injury received the somatosensory evoked potential examination one month after injury in the First Affiliated Hospital, School of Medicine, Zhejiang University in China. Somatosensory evoked potentials were graded as normal, abnormal or absent (grades I–III) according to N20 amplitude and central conduction time. The outcome in patients with grade III somatosensory evoked potential was in each case unfavorable. The prognostic accuracy of grade III somatosensory evoked potential for unfavorable and non-awakening outcome was 100% and 80%, respectively. The prognostic accuracy of grade I somatosensory evoked potential for favorable and wakening outcome was 86% and 100%, respectively. These results suggest that somatosensory evoked potential grade is closely correlated with coma severity and degree of recovery. Somatosensory evoked potential is a valuable diagnostic tool to assess prognosis in prolonged coma patients with diffuse axonal injury.

Outcome prediction by motor and pupillary responses in children treated with therapeutic hypothermia after cardiac arrest

OBJECTIVE

Clinical neurologic signs considered predictive of adverse outcome after pediatric cardiac arrest may have a different prognostic value in the setting of therapeutic hypothermia. We aimed to determine the prognostic value of motor and pupillary responses in children treated with therapeutic hypothermia after cardiac arrest.

DESIGN

Prospective cohort study.

SETTING

Pediatric intensive care unit in tertiary care hospital.

PATIENTS

Children treated with therapeutic hypothermia after cardiac arrest.

MEASUREMENTS AND MAIN RESULTS

Thirty-five children treated with therapeutic hypothermia after cardiac arrest were prospectively enrolled. Examinations were performed by emergency medicine physicians and intensive care unit bedside nurses. Examinations were performed after resuscitation, 1 hr after achievement of hypothermia, during the last hour of hypothermia, 1 hr after achievement of normothermia, after 24 hrs of normothermia, and after 72 hrs of normothermia. The primary outcome was unfavorable outcome at intensive care unit discharge, defined as a pediatric cerebral performance category score of 4-6 at hospital discharge. The secondary outcome was death (pediatric cerebral performance category = 6). The associations between exam responses and unfavorable outcomes (as both pediatric cerebral performance category 4, 5, 6 and pediatric cerebral performance category 6) are presented as positive predictive values, for both all subjects and subjects not receiving paralytics. Statistical significance for these comparisons was determined using Fisher's exact test. At all examination times and examination categories, positive predictive values were higher for the unfavorable outcome pediatric cerebral performance category 4, 5, 6 than the pediatric cerebral performance category 6. By normothermia hour 24, absent motor and pupil responses were highly predictive of unfavorable outcome (pediatric cerebral performance category 4, 5, 6) (positive predictive value 100% and p < .03 for all categories), while at earlier times the predictive value was lower.

CONCLUSIONS

Absent motor and pupil responses are more predictive of unfavorable outcome when defined more broadly than when defined as only death. Absent motor and pupil responses during hypothermia and soon after return of spontaneous circulation were not predictive of unfavorable outcome while absent motor and pupil responses once normothermic were predictive of unfavorable short-term outcome. Further study is needed using more robust short-term and long-term outcome measures.

Prognostic value of somatosensory evoked potentials in comatose children: a systematic literature review

PURPOSE

To review the predictive powers of SEPs in comatose children after acute brain injury.

METHODS

MEDLINE, EMBASE, OVID, ISI Web of Knowledge, BIOMED Central and the Cochrane Library (1981-2007) were searched. First, predictive values were calculated for each primary study. Second, we analysed effects of different factors on the SEP diagnostic odds ratio by meta-regression. Third, we compared SEP predictive values in children and in adults.

RESULTS

We selected 14 studies covering 732 patients; analysis was conducted in 11, while the other 3 were used for simple qualitative examination. In individual papers, the presence of SEP predicted favourable outcomes as shown by the area under both sROC curves being 0.958. The same value was shown by SEP absence for predicting unfavourable outcomes. All covariates showed no significant effects on diagnostic accuracy, but only a slight non-significant trend. For SEP grading, a simple sub-group analysis showed a high predictive value for non-awakening for absence of SEPs (PPV 97.0%) and a high prognostic power to predict awakening for normal SEPs (PPV 92.2%). Pathological SEPs did not show reliable predictivity. In children, the presence of SEPs showed a high prognostic power similar to that in adults.

CONCLUSION

This study supports the use of SEPs in the integrated process of outcome prediction after acute brain injury in children. Caution is recommended in predicting unfavourable outcomes in patients with an absence of SEPs in both TBI and HIE comas. Future studies are needed to resolve the issue of the effect of aetiology and age on SEP's predictive power.

Somatosensory and visual evoked potentials in children with cerebral palsy: Correlations and discrepancies with MRI findings and clinical picture

PURPOSE

To determine if there is any association between the findings of visual evoked potentials (VEPs), somatosensory evoked potentials (SEPs), and magnetic resonance imaging (MRI) findings with the neurodevelopment and severity in children with cerebral palsy (CP).

METHODS

The present study included 15 children with spastic diplegic CP and five children with spastic hemiplegic CP and 42 healthy children as controls. The number of the controls was two-times greater than the study group to increase statistical power of this study. VEPs and SEPs were recorded in the CP children and compared with healthy controls. All MR scans were obtained using a 1.5 T MR scanner.

RESULTS

A significant difference was found in the latencies P100 (VEP) between the CP and controls. No correlations between increased P100 latencies and asphyxia, prematurity, the CP severity, MRI findings and mental retardation were noted. A significant difference in N13-N20 conductions (SEPs) between the subjects with CP and the control group was found. SEPs were positively correlated with mental retardation in CP children. The brain lesions in MRI showed a significant correlation with the CP severity scores and mental retardation.

CONCLUSION

The differences in VEPs and SEPs were determined between CP children and healthy children. The MRI findings were positively correlated with the CP severity and mental retardation.

Outcome following cardiopulmonary arrest

This article summarizes the current state of outcomes and outcome predictors following pediatric cardiopulmonary arrest with special emphasis on neurologic outcome. The authors briefly describe the factors associated with outcome and review clinical signs, electrophysiology, neuroimaging, and biomarkers used to predict outcome after cardiopulmonary arrest. Although clinical signs, imaging, and somatosensory evoked potentials are best associated with outcome, there are limited data to guide clinicians. Combinations of these predictors will most likely improve outcome prediction, but large-scale outcome studies are needed to better define these predictors.

Predicting outcome in children with hypoxic ischemic encephalopathy

OBJECTIVE

Hypoxic ischemic encephalopathy (HIE) is common in children, and providing accurate and timely prognostic information is important in determining the appropriate level of care. While practice parameters are available for prognostication in adults, similar reviews are not available for children. This article reviews the current evidence in domains used to provide prognostic information in children with coma due to HIE. These include historical features of the event; physical exam signs; neurophysiologic studies, such as electroencephalogram and evoked potentials; and neuroimaging.

DATA SOURCE

A literature search of MEDLINE was performed using the search terms HIE and prognosis cross-referenced in series with specific domains used to provide prognostic information, including physical examination, electroencephalogram, evoked potentials, neuroimaging, and magnetic resonance imaging. The results of these searches were scanned by the authors to identify articles pertaining to children (nonneonates). Further literature was identified from the reference lists of the literature identified by MEDLINE search. Clinical, preclinical, and review articles were identified that were related to the current understanding of prognosis in pediatric HIE. Only literature in English was reviewed.

RESULTS

When performed at least 24 hrs after the inciting event, abnormal exam signs (pupil reactivity and motor response), absent N20 waves bilaterally on somatosensory evoked potentials, electrocerebral silence or burst suppression patterns on electroencephalogram (not due to metabolic or medication etiology), and abnormal magnetic resonance imaging with diffusion restriction in the cortex and basal ganglia are each highly predictive of poor outcome. Combining these modalities improves the overall predictive value.

CONCLUSIONS

All testing provides the best prognostic information several days after hypoxic-ischemic injury, and often multiple tests are required to improve prognostic ability and rule out potentially confounding conditions. Thus, when decisions can be postponed several days, neurologic consultation and testing can provide the best prognostic information to families.

Prognosis Following Severe Head Injury: Development and Validation of a Model for Prediction of Death, Disability, and Functional Recovery

BACKGROUND

A prognostic model for head trauma patients is useful only if it predicts clinically relevant outcomes accurately on new subjects in various settings. Most existing models consider only dichotomous outcome and have not been tested externally. We developed and validated a rule for prediction of three functional outcome states after severe head injury, using information from day 1.

METHODS

The model was developed in a cohort of 304 adults who were admitted to a Dutch trauma center and had survived and remained comatose for >24 hours following severe head injury. We used ordinal logistic regression analysis to predict the extended Glasgow Outcome Scale after > or =12 months, merged into three categories. We preselected five known predictors of outcome and used bootstrapping techniques to avoid statistical overfitting. The performance of the model was subsequently tested in a cohort of 122 patients from an unrelated hospital.

RESULTS

The model contained age (p < 0.0001), best motor response on day 1 (p = 0.002), pupil response after resuscitation (p = 0.005), computed tomography findings (p = 0.004), and presence of arterial hypotension (p = 0.37) as predictor variables. In the external validation cohort, the model showed adequate agreement between observed and predicted outcome probabilities (calibration). The model had a good ability to discriminate patients with different outcomes (c-statistic 0.808). The predictive accuracy was 66% when the model was used to classify patients across the three outcome categories.

CONCLUSIONS

We have developed a practical model for predicting the probability of death, survival with major disability, and functional recovery in patients who are comatose 24 hours after severe head injury. The model performed well in an external setting, indicating that measures to avoid statistical overfitting were successful.

Koma

BACKGROUND

The prognosis after traumatic coma is often unclear. We investigated the prognostic value of somatosensory (SSEP) and early acoustic (EAEP) evoked potentials on comatose patients in the intensive care unit regarding long-term outcome. Different evaluation systems were investigated.

METHODS

This was a retrospective analysis of 100 patients. SSEP and EAEP were examined at different times and analysed according to the Riffel score. Combinations of the different types of potentials were evaluated regarding possible improvement of outcome prediction.

RESULTS

The positive predictive value of at least one missing peak V of the EAEP regarding a fatal prognosis was 83%. The negative predictive value of the EAEP was 96%. A good outcome (GOS 4+5) could be predicted by bilateral normal SSEP and EAEP with a positive predictive value of 98%.

CONCLUSIONS

Early evaluation of SSEP and EAEP allows reliable prognostic predictions regarding a later outcome in patients with severe traumatic brain injury and should therefore be used more often for intensive care patients.

Quantitative multichannel EEG measure predicting the optimal weaning from ventilator in ICU patients with acute respiratory failure

OBJECTIVE

The objective of this study was to develop a novel quantitative multichannel EEG (qEEG) based analysis method, called Global Field Damping Time (GFDT), in order to detect potential EEG changes of patients admitted to the ICU with acute respiratory failure, and correlate them to the patients' recovery outcome predicting the optimal time-point to disconnect the patient from mechanical ventilation.

METHODS

Twenty-nine adult patients with acute respiratory failure out of 98 admitted to the Intensive Care Unit of Saint Paul General Hospital were enrolled, and among them only 15 completed the study. The patients were classified in 3 groups according to their outcome after 3 months follow-up. The patients were intubated with fraction of inspired oxygen (FiO2) of 100%. Neurological Deficit Scores (NDS) were measured 24 h after intubation to assess patients' neurological condition. Twenty-four hours after patient's intubation, FiO2 was decreased to 40% (weaning session), followed by a 5 min early recovery session, a 5 min recovery 1 session and a 5 min recovery 2 session. EEG recordings were performed during this experimental procedure. Multichannel EEG segments were processed and fitted into a multivariate autoregressive (mAR) model, and single channel EEG segments into a scalar autoregressive (sAR) model. The mAR and the sAR models of arbitrary order p were decomposed into mp and p oscillators and relaxators, respectively. Damping time of each oscillator and each relaxator, and the Global Field Damping Time (GFDT) as a weighted damping time were estimated for both mAR and sAR models.

RESULTS

A statistically significant increase of mAR model's GFDT during the weaning session was observed in the subjects of all groups. Comparing the 3 patients' groups, statistically significant differences for mAR model's GFDT were observed for the weaning and early recovery session. Linear regression analysis between NDS and mean mAR model's GFDT showed statistical significance during weaning session, early recovery session, and recovery 1 session. There was no statistical significance for SaO2 in the regression analysis with NDS. The sAR model's GFDT presented worst results in comparison with the mAR modelling GFDT in the identification of hypoxic conditions during weaning session and in the discrimination of patients with acute respiratory failure according to their neurological outcome.

CONCLUSIONS

Global Field Damping Time as correlated to the patients' neurological outcome appears to be a simple, compact, and substantial novel indicator of cerebral hypoxia and a potential predictor of the optimal time-point to disconnect the patient from the ventilator.

SIGNIFICANCE

Quantitative EEG seems to be an important tool for ICU clinicians assisting them to decide for the patients' optimal time-point to disconnect the patient from the ventilator.

Amantadine to enhance readiness for rehabilitation following severe traumatic brain injury

PRIMARY OBJECTIVE

To evaluate the association between amantadine and recovery of consciousness from prolonged traumatic coma.

RESEARCH DESIGN

A retrospective cohort study.

METHODS

Subjects included 123 adults with severe traumatic brain injury (TBI) admitted over a 10-year period who remained in coma despite becoming medically stable.

EXPERIMENTAL INTERVENTIONS

Cases received 100-200 mg of amantadine twice daily.

MAIN OUTCOMES AND RESULTS

46.4% (13/28) of cases emerged from coma compared to 37.9% (36/95) of controls (p = 0.42). Somatosensory evoked potential (SSEP) was the only significant predictor of emergence from coma (p = 0.02), while SSEP, age and Glasgow Coma Score (GCS) significantly predicted time to emerge from coma (p < 0.05).

CONCLUSIONS

Although the study and its design do not support the view that amantadine has an effect on recovery of consciousness; it remains safe, inexpensive and has few side effects. The lack of treatment alternatives and anecdotal support for its use may warrant further study. Prospective controlled trials would yield more definitive results.

Reactive EEG patterns in pediatric coma

This study was designed to determine whether the observed reactive electroencephalographic patterns in comatose children were associated with a better outcome. All electroencephalograms performed in comatose children aged 2 months to 18 years during the period 1996-2003 were retrospectively analyzed and classified according to modified Young's classification. Reactivity to painful/auditory stimuli and passive eye closure (at least two modalities) was checked in all electroencephalograms. The clinical outcome at 1 year or during the last clinic/inpatient follow-up was scored according to the Pediatric Cerebral and Overall Performance Category Scale. Outcomes were then compared using Fisher exact test and the Mann-Whitney test. Thirty-three patients had electroencephalography within 72 hours after the onset of coma. Fourteen of 33 electroencephalograms revealed reactive patterns. Outcome was unfavorable in 4 (28.6%) of these patients. Three children had no residual neurologic impairment. Among the 19 children with nonreactive electroencephalogram, 13 (65%) had unfavorable outcome, which included 10 deaths. All the survivors had residual neurologic impairment. Outcome was better in children with reactive electroencephalographic patterns (Fisher exact test; P = 0.023). Comatose children with reactive electroencephalographic patterns have better clinical outcome in terms of morbidity and mortality. A careful assessment of electroencephalographic reactive patterns in all comatose children is required for better understanding of the clinical outcome.

Somatosensory evoked potentials in children with severe head trauma

We evaluated the predictive value of somatosensory evoked potentials (SEP) in a series of children with severe traumatic brain injury (TBI). The prospective clinical investigation was performed in a Level I paediatric trauma centre. We included 26 consecutive comatose paediatric patients aged from 1 month to 17 years (median age 11 years) following severe TBI (initial Glasgow Coma Score (GCS) 8 or below). Besides SEP recordings, the intracranial pressure and the results of an initial cranial CT scan were filed. The Glasgow Outcome Scale (GOS) was used to assess outcome at discharge. Thirteen children had normal SEP measurements, three patients had abnormal SEP recordings and a cortical response was bilaterally absent in ten children. Out of 26 children, 10 died whereas two remained in a persistent vegetative state. Only one child suffered from significant neurological deficits (GOS 3) at discharge. Seven patients survived with a GOS of 4 and six children survived without neurological impairment (GOS 5). Normal SEP indicated a favourable outcome in most children but did not rule out the occurrence of death, while absence of SEP was related to unfavourable outcome in all cases.

CONCLUSION

Measurement of somatosensory evoked potentials provides valuable data for determining the prognosis at early coma stages. Our data show that an unfavourable outcome can be predicted with higher precision than a favourable outcome.

A prospective study of outcome predictors after severe brain injury in children

OBJECTIVE

To directly compare the predictive powers of somatosensory evoked potentials (SEPs) to those of motor and pupillary responses.

DESIGN AND SETTING

Prospective clinical study in a paediatric intensive care unit.

PATIENTS AND PARTICIPANTS

102 severely brain-injured children less than 15 years of age.

MEASUREMENTS AND RESULTS

SEPs and motor and pupillary responses were serially recorded during the first 9 days after admission. Initial, last and those tests performed on or after day 2 were analysed. Outcome was assessed 5 years after injury. SEPs had equal or superior predictive statistics and ROC curves compared to the other tests with few exceptions. Pupillary responses had higher sensitivity for favourable outcome prediction while for unfavourable outcome prediction the last motor responses had higher sensitivity, and the last pupillary responses had slightly higher specificity. Combining SEPs and motor responses provided the best combination for predicting unfavourable outcome.

CONCLUSIONS

SEPs are the best overall predictor of outcome while motor and pupillary responses have advantages in some specific areas. The routine use of SEPs should be considered in the prediction of outcome of severely brain-injured patients.

Are somatosensory evoked potentials the best predictor of outcome after severe brain injury? A systematic review

OBJECTIVE

Many tests have been used to predict outcome following severe brain injury. We compared predictive powers of clinical examination (pupillary responses, motor responses and Glasgow Coma Scale, GCS), electroencephalography (EEG) and computed tomography (CT) to that of somatosensory evoked potentials (SEPs) in a systematic review.

MATERIALS AND METHODS

Medline (1976-2002) and Embase (1980-2002) were searched, manual review of article reference lists was conducted, and authors were contacted. We selected 25 studies addressing the prediction of outcome after severe brain injury using SEPs and either GCS, EEG, CT, pupillary or motor responses. Outcomes were determined for patients with normal or bilaterally absent SEPs and graded measures of GCS, EEG, CT, pupillary responses or motor responses. For favourable outcome prediction SEPs were superior in sensitivity, specificity and positive and negative predictive values, except for pupillary responses which had superior sensitivity and GCS which had higher specificity. SEPs had superior summary receiver operating characteristic curves, with the exception of motor responses, and superior ratio of odds ratios. For unfavourable outcome prediction SEPs were superior to the other tests in sensitivity, specificity and positive and negative predictive values, except for motor and pupillary responses, GCS and CTs which had superior sensitivity. All SEP summary receiver operating characteristic curves and pooled ratio of odds ratios were superior.

CONCLUSIONS

Although imperfect, SEPs appear to be the best single overall predictor of outcome. There is sufficient evidence for clinicians to use SEPs in the prediction of outcome after brain injury.

Evoked potentials in severe brain injury

Three-modality evoked potentials (EPs) have been used for several years in association with the electroencephalogram (EEG) as a diagnostic and prognostic tool in acute traumatic or nontraumatic coma. In 1993 we proposed to combine these in two indices: the index of global cortical function (IGCF) and the index of brain-stem conduction (IBSC). Four EP patterns based on both indices emerge at the acute stage of severe head trauma. These are easily explainable by pathophysiology. Pattern 1 corresponds to alterations in the index of global cortical function without changes in the index of brain-stem conduction. Its prognosis is good (80 to 90% of these patients recover). Pattern 2 is characterized by alterations of somatosensory EPs that are suggestive of midbrain dysfunction. The prognosis depends both on the reversibility of the midbrain dysfunction and on the extent of associated diffuse axonal lesions, whose evaluation requires MRI. Patients who recovered from Pattern 2 sometimes did so after a long interval during which they remained vegetative. Pattern 3 is characterized by alterations of brain-stem auditory EPs that are suggestive of pontine involvement. It usually follows uncontrolled intracranial hypertension and corresponds to evolving transtentorial herniation. All patients with that transient pattern eventually died. Pattern 4 is categorized by the disappearance of all activities of intracranial origin, contrasting with the preservation of all activities of retinal, spinal-cord, and peripheral-nerve origin. This pattern corresponds to brain death. In our experience, three-modality EPs are currently the best bedside brain-death confirmatory tool.

Proton MRS in Acute Traumatic Brain Injury: Role for Glutamate/Glutamine and Choline for Outcome Prediction

Proton magnetic resonance spectroscopy (MRS) is being used to evaluate individuals with acute traumatic brain injury and several studies have shown that changes in certain brain metabolites (N-acetylaspartate, choline) are associated with poor neurologic outcomes. The majority of previous MRS studies have been obtained relatively late after injury and none have examined the role of glutamate/ glutamine (Glx). We conducted a prospective MRS study of 42 severely injured adults to measure quantitative metabolite changes early (7 days) after injury in normal appearing brain. We used these findings to predict long-term neurologic outcome and to determine if MRS data alone or in combination with clinical outcome variables provided better prediction of long-term outcomes. We found that glutamate/glutamine (Glx) and choline (Cho) were significantly elevated in occipital gray and parietal white matter early after injury in patients with poor long-term (6-12-month) outcomes. Glx and Cho ratios predicted long-term outcome with 94% accuracy and when combined with the motor Glasgow Coma Scale score provided the highest predictive accuracy (97%). Somatosensory evoked potentials were not as accurate as MRS data in predicting outcome. Elevated Glx and Cho are more sensitive indicators of injury and predictors of poor outcome when spectroscopy is done early after injury. This may be a reflection of early excitotoxic injury (i.e., elevated Glx) and of injury associated with membrane disruption (i.e., increased Cho) secondary to diffuse axonal injury.

Evaluation of coma and brain death

Coma is a nonspecific sign of widespread central nervous system impairment resulting from various metabolic and structural etiologies. The rapid recognition of this neurologic emergency and results from the history, physical examination, and early investigative studies are key to the identification and treatment of its underlying cause. The prognosis for recovery depends greatly on the underlying etiology as well as on its optimal treatment, which seeks to preserve neurologic function and maximize the potential for recovery by reversing the primary cause of brain injury, if known, and preventing secondary brain injury from anoxia, ischemia, hypoglycemia, cerebral edema, seizures, infections, and electrolyte and temperature disturbances. Brain death must be diagnosed with similar care and precision, and families approached compassionately about the diagnosis and their decisions regarding organ donation.

Somatosensory evoked potentials in coma prognosis

SEPs provide useful prognostic information regarding outcome after coma. Use of the summary data presented here should allow clinicians caring for these patients to provide families with a greater degree of certainty regarding outcome than previously has been available.

Medical aspects of the minimally conscious state in children

The minimally conscious state is a condition of severely altered consciousness in which minimal but definite behavioral evidence of self or environmental awareness is demonstrated. This must be established on a reproducible or sustained basis by one or more of four types of behaviors including simple command-following, gestural or verbal 'yes/no' responses, intelligible verbalizations, or purposeful behaviors. The minimally conscious state can occur in children and usually is due to acquired brain injuries (traumatic and non-traumatic), central nervous system degenerative and neurometabolic disorders or congenital or developmental disorders. It is assumed that the lower limit of the minimally conscious state occurs when patients emerge from a vegetative state. What remains uncertain is how we can assess the upper limits, that is the degree of improvement that indicates that an individual is no longer minimally conscious. It also is unknown if, when and to what extent children can emerge from a minimally conscious state and whether their prognosis is better than children who are vegetative. It is assumed that the minimally conscious state may become 'permanent' 12 months after traumatic brain injury and 3 months after non-traumatic injury although there have been no studies that have examined this issue. Medical and rehabilitative treatment of children in a minimally conscious state should be provided to maintain comfort, reduce complications, and optimize functional recovery.

Outcome of coma in children

Coma following a hypoxic-ischemic event is a serious condition and common reason for admission to the pediatric intensive care unit. Because coma has a high rate of mortality and morbidity in children, and the clinician may be unsure of the outcome very early in the course, it is important to have strategies to define prognosis. Although most studies have been conducted in adults, we review factors predicting outcome from coma of nontraumatic causes in infants and children. We consider the relation between physical findings, commonly accessible laboratory tools, and outcome, and comment on some newer techniques that may become more available for clinical purposes.

Vulnerability of the thalamic somatosensory pathway after prolonged global hypoxic-ischemic injury

The aim of this study was to test the hypothesis that under prolonged global ischemic injury, the somatosensory thalamus and the cortex would manifest differential susceptibility leading to varying degrees of thalamo-cortical dissociation. The thalamic electrical responses displayed increasing suppression with longer durations of ischemia leading to a significant thalamo-cortical electrical dissociation. The data also point to a selective vulnerability of the network oscillations involving the thalamic relay and reticular thalamic neurons. An adult rat model of asphyxial cardiac arrest involving three cohorts with 3 min (G1, n=5), 5 min (G2, n=5) and 7 min (G3, n=5) of asphyxia respectively was used. The cortical evoked response, as quantified by the peak amplitude at 20 ms in the cortical evoked potential, recovers to more than 60% of baseline in all the cases. The multi-unit responses to the somatosensory stimuli recorded from the thalamic ventral posterior lateral (VPL) nuclei consists typically of three components: (1). the ON response (<30 ms after stimulus), (2). the OFF response (period of inhibition, from 30 ms to 100 ms after stimulus) and (3). rhythmic spindles (beyond 100 ms after stimulus). Asphyxia has a significant effect on the VPL ON response at 30 min (P<0.025), 60 min (P<0.05) and 90 min (P<0.05) after asphyxia. Only animals in G3 show a significant suppression (P<0.05) of the VPL ON response when compared to the sham group at 30 min, 60 min and 90 min after asphyxia. There was no significant reduction in somatosensory cortical N20 (negative peak in the cortical response at 20 ms after stimulus) amplitude in any of the three groups with asphyxia indicating a thalamo-cortical dissociation in G3. Further, rhythmic spindle oscillations in the thalamic VPL nuclei that normally accompany the ON response recover either slowly after the recovery of ON response (in the case of G1 and G2) or do not recover at all (in the case of G3).We conclude that there is strong evidence for selective vulnerability of thalamic relay neurons and its network interactions with the inhibitory interneurons in the somatosensory pathway leading to a thalamo-cortical dissociation after prolonged durations of global ischemia.

Predictive value of somatosensory evoked potentials for awakening from coma

OBJECTIVES

A systematic review of somatosensory evoked potentials performed early after onset of coma, to predict the likelihood of nonawakening. The pooled results were evaluated for rates of awakening, confidence intervals, and the possibility of rare exceptions.

DATA SOURCES

Forty-one articles reporting somatosensory evoked potentials in comatose patients and subsequent outcomes, from 1983 to 2000.

STUDY SELECTION

Studies were included if they reported coma etiology, age group, presence or absence of somatosensory evoked potentials, and coma outcomes.

DATA EXTRACTION

We separated patients into four groups: adults with hypoxic-ischemic encephalopathy, adults with intracranial hemorrhage, adults and adolescents with traumatic brain injury, and children and adolescents with any etiologies. Somatosensory evoked potentials were categorized as normal, abnormal, or bilaterally absent. Outcomes were categorized as persistent vegetative state or death vs. awakening.

DATA SYNTHESIS

For each somatosensory evoked potential result, rates of awakening (95% confidence interval) were calculated: adult hypoxic-ischemic encephalopathy: absent 0% (0%-1%), abnormal 22% (17%-26%), normal 52% (48%-56%); adult intracranial hemorrhage: absent 1% (0%-4%), present 38% (27%-48%); adult-teen traumatic brain injury: absent 5% (2%-7%), abnormal 70% (64%-75%), normal 89% (85%-92%); child-teen: absent 7% (4%-10%), abnormal 69% (61%-77%), normal 86% (80%-92%).

CONCLUSIONS

Somatosensory evoked potential results predict the likelihood of nonawakening from coma with a high level of certainty. Adults in coma from hypoxic-ischemic encephalopathy with absent somatosensory evoked potential responses have <1% chance of awakening.

Use of somatosensory-evoked potentials and cognitive event-related potentials in predicting outcomes of patients with severe traumatic brain injury

OBJECTIVE

This study was performed to evaluate the usefulness of somatosensory-evoked potentials (SEPs) and cognitive event-related potentials (ERPs) in predicting functional outcomes of severe traumatic brain injury patients.

DESIGN

Prospective study of 22 patients with severe traumatic brain injury. Demographic information, Glasgow Coma Scale, and electrophysiologic measurements were recorded. Functional outcomes, as quantified by the Glasgow Outcome Scale-Extended, were obtained.

RESULTS

Bilateral absence of median nerve SEP was strongly predictive of the worst functional outcome. The specificity and positive predictive value of absent SEP for predicting death or persistent vegetative state at 6 mo after traumatic brain injury were as high as 100%. If the definition of unfavorable outcome was expanded to include Glasgow Outcome Scale-Extended 1-4, absence of ERP was equivalent to the absence of SEP in specificity and positive predictive value. On the other hand, normal ERPs showed higher sensitivity and negative predictive value for prognosticating the best outcomes compared with normal SEPs. If the definition of favorable outcome was expanded to include Glasgow Outcome Scale-Extended 5-8, ERP was still superior to SEP for prognosticating good outcome. Interestingly, the highest sensitivity and negative predictive value for favorable outcomes were associated with the presence of any discernible waveform.

CONCLUSIONS

Although median nerve SEP continues to make reliable prediction of ominous outcome in severe traumatic brain injury, the addition of the speech-evoked ERPs may be helpful in predicting favorable outcomes. The strength of the latter test seems to complement the weakness of the former.

Critical care management of head trauma in children

Trauma is the leading cause of both morbidity and mortality in the pediatric population, and traumatic injury causes > 50% of all childhood deaths. Significant mortality rates have been reported for children with traumatic brain injury. Although children have better survival rates as compared with adults with traumatic brain injury, the long-term sequelae and consequences are often more devastating in children due to their age and developmental potential. The costs involved in the care of a child with severe traumatic brain injury, extended over that child's lifetime, are significant. It is unfortunate that despite preventive measures, traumatic brain injury remains the major morbidity and mortality factor for children.

Prediction of outcome after hypoxic-ischemic encephalopathy: a prospective clinical and electrophysiologic study

OBJECTIVES

To evaluate and compare the predictive value of history, clinical examination, and biologic and electrophysiologic data regarding the prognosis of children with acute hypoxic-ischemic encephalopathy (HIE).

STUDY DESIGN

Prospective cohort of 57 consecutive children who were mechanically ventilated for HIE throughout a 3-year period in a tertiary pediatric intensive care unit at a university hospital in France.

RESULTS

At 24 hours after admission, 12 patients had died, 3 were awake and 42 showed impaired consciousness or were in a coma, of whom 38% had a favorable outcome. In this group, an initial cardiopulmonary resuscitation duration longer than 10 minutes and a Glasgow Coma Scale <5 at 24 hours after admission were associated with an unfavorable outcome (positive predictive value [PPV] 91%, 100%; sensitivity 50%, 54%). A discontinuous electroencephalogram (EEG), the presence of spikes or epileptiform discharges were associated with an unfavorable outcome (PPV 100% for the 2 criteria; sensitivity 27%, 54%). The bilateral absence of the N20 wave on short-latency sensory evoked potentials (SEPs) had a PPV for unfavorable outcome of 100% (sensitivity 63%).

CONCLUSIONS

The clinical assessment combined with EEG and SEPs allow an early prediction of the prognosis of children with HIE.

[Multimodal monitoring of head injuries in children]

As in the case of adults, there are three main goals in the monitoring of severe head trauma in children: to prevent or minimize the apparition of secondary lesions, to optimize treatment, to help make precise prognosis. The basic monitoring is composed of repeated clinical examinations, brain radiological imaging and control of vital parameters (blood pressure, temperature, PaO2 (SpO2), PaCO2 (FETCO2), haemoglobin, haematocrit. On the other hand, during specific brain monitoring, the brain perfusion (TCD, intracranial pressure), the electrical activity of the brain and sometimes the brain oxygenation (SvjO2) are controlled. The data obtained from the brain monitoring must always be interpreted carefully. A child with a severe head trauma, in ICU, always requires constant and competent medical attention.

Prognostic value of evoked potentials and sleep recordings in the prolonged comatose state of children. Preliminary data

OBJECTIVES

Sleep recordings and evoked potentials (EPs) were used in five comatose children to evaluate their predictive value for outcome following a severe comatose state.

METHODS AND SUBJECTS

The protocol included EEG, Brainstem Evoked Responses (BERs), Somatosensory Evoked Potentials (SEPs) and polysomnography. From 10 to 15 days post-coma (D10 to D15), EEG and clinical examinations were carried out every second day, then one day in four from 15 to 30 days post-coma (D15 to D30), and one day in seven from D30 to six months (M6). Evoked potentials and Polysomnography were recorded on D10-D15 or D30 in the second month (M2) and in M6. Of the five children, three were in anoxic coma and two in traumatic coma. All had extensive lesions and a Glasgow Coma Scale (GCS) score of less than five. The results of the EEG, polysomnographic and EP recordings were compared to the clinical outcome.

RESULTS AND CONCLUSION

In the three anoxic comas we observed BER abnormalities and the absence of SEP N20 associated with wide cortical lesions with brainstem extension. Sleep recordings showed major alterations of the wake-sleep cycle without any improvement in M6. Abnormalities included loss of the normal REM-sleep pattern associated with alteration of NREM sleep and periods of increase in motor activity without EEG arousal. This sleep pattern appeared to be associated with involvement of the brainstem. In the two traumatic comas, alterations of the early cortical SEP responses were less severe and the BERs were normal. Some sleep spindles were observed as well as the persistence of sleep cycles in the first weeks post-coma. The combined use of EEG, EPs and polysomnography improved the outcome prediction in comparison with the use of just one modality. EPs and sleep recordings were far superior to clinical evaluation and to GCS in the appreciation of the functional status of comatose children. The reappearance of sleep patterns is considered to be of favorable prognosis for outcome of the coma state, as is the presence of sleep spindles in post-trauma coma. This study showed that EPs and sleep recordings help to further distinguish between patients with good or bad outcomes.

Denver developmental screening test II for early identification of the infants who will develop major neurological deficit as a sequalea of hypoxic-ischemic encephalopathy

BACKGROUND

The primary aim of this study was to find widely available, inexpensive, and non-invasive parameters for early identification or prediction of the infants with hypoxic-ischemic encephalopathy (HIE) who will have a severe adverse outcome (classified as death or a major neurological deficit).

METHODS

Fifty-seven full-term or near-term newborn infants with a diagnosis of HIE were consecutively admitted to the neonatal intensive care unit and studied. Occurrence of seizures during the first 24 h, cranial ultrasonography (US) findings within the first 5 days of life, and Denver developmental screening test II (DDST II) at 6 months of age, were analyzed in relation to mortality and neurological status at 2 years of age.

RESULTS

Of the 57 infants, 10 were lost to follow-up. Twenty of the remaining 47 infants had a severe adverse outcome. Among the predictors of severe adverse outcome, occurrence of seizures was found to have a poor predictive accuracy. Cranial US had 100% sensitivity, however with a rather low specificity (55%). However, DDST II at 6 months of age, yielded a very high predictive accuracy (sensitivity=100%, specificity=95%).

CONCLUSION

We conclude that DDST II at 6 months of age could be used in predicting severe neurological outcome in infants with HIE.

Review of the use of somatosensory evoked potentials in the prediction of outcome after severe brain injury

OBJECTIVE

Review the predictive powers of somatosensory evoked potentials (SEPs) in severe brain injury.

DATA SOURCES

Publications in the scientific literature, manual review of article bibliographies, and questioning workers in the field.

STUDY SELECTION

Studies addressing the prediction of outcome after severe brain injury using SEPs.

DATA EXTRACTION

To determine the outcome of patients with either normal or bilaterally absent SEPs as categorized using the Glasgow Outcome Scale into favorable outcomes (good or moderate disability) or unfavorable outcomes (severe disability, vegetative, or dead). Studies were included if they were in English and allowed the determination of outcomes for all patients with normal or bilaterally absent SEPs. Papers were not considered if subjects were neonates, consisted of abstracts where all necessary details were unavailable, were case reports or duplications of other published studies, or dealt only with brain dead subjects.

DATA SYNTHESIS

For all studies (n = 44), positive likelihood ratio, positive predictive value, and sensitivity were 4.04, 71.2%, and 59.0%, respectively, for normal SEPs (predicting favorable outcome) and 11.41, 98.5%, and 46.2%, respectively, for bilaterally absent SEPs (predicting unfavorable outcome). Summary receiver operating characteristic curve analysis detected a cut-off criterion effect for only blinded studies of bilaterally absent SEPs. Twelve patients (12/777) were identified with bilaterally absent SEPs who had favorable outcomes. These false positives are typically pediatric patients or have suffered traumatic brain injuries. We suggest criteria for the use of bilaterally absent SEPs in the prediction of poor outcome, which include absence of focal lesions, subdural or extradural fluid collections, and no decompressive craniotomy in previous 48 hrs. Using these criteria the data suggest that the false-positive rate is <0.5% for bilaterally absent SEPs.

CONCLUSIONS

SEPs are powerful predictors of outcome, particularly poor outcome, if patients with focal lesions, subdural effusions, and those who have had recent decompressive craniotomies are excluded.

Coma prognosis in children. Part I: definitional and methodological challenges

Prediction of outcome from coma is a frequent and important task of neurologists. It is difficult enough in adult patients and even more difficult in children. Part I of this review considers some of the methodological problems and caveats besetting clinical research in this field: the very definition of coma, definition of the study population and outcome variables, study design, the fallacy of self-fulfilling prophecy, early death rate from nonneurologic causes resulting in low statistical power, and invalid attempts to compensate for that by combining outcome categories, lumping together age groups, short and inhomogeneous follow-up, and failure to provide confidence intervals. Part II reviews the clinical pediatric coma-prognosis literature, first according to etiology and then according to electrodiagnostic tests.

Predictive value of proton magnetic resonance spectroscopy in pediatric closed head injury

We studied 26 infants (1-18 months old) and 27 children (18 months or older) with acute nonaccidental (n = 21) or other forms (n = 32) of traumatic brain injury using clinical rating scales, a 15-point MRI scoring system, and occipital gray matter short-echo proton MRS. We compared the differences between the acutely determined variables (metabolite ratios and the presence of lactate) and 6- to 12-month outcomes. The metabolite ratios were abnormal (lower NAA/Cre or NAA/Cho; higher Cho/Cre) in patients with a poor outcome. Lactate was evident in 91% of infants and 80% of children with poor outcomes; none of the patients with a good outcome had lactate. At best, the clinical variables alone predicted the outcome in 77% of infants and 86% of children, and lactate alone predicted the outcome in 96% of infants and 96% of children. No further improvement in outcome prediction was observed when the lactate variable was combined with MRI ratios or clinical variables. The findings of spectral sampling in areas of brain not directly injured reflected the effects of global metabolic changes. Proton MRS provides objective data early after traumatic brain injury that can improve the ability to predict long-term neurologic outcome.

The Brain Trauma Foundation. The American Association of Neurological Surgeons. The Joint Section on Neurotrauma and Critical Care. Glasgow coma scale score

When considering the use of the initial GCS for prognosis, the two most important problems are the reliability of the initial measurement, and its lack of precision for prediction of a good outcome if the initial GCS is low. If the initial GCS is reliably obtained and not tainted by prehospital medications or intubation, approximately 20% of the patients with the worst initial GCS will survive and 8-10% will have a functional survival (GOS 4-5).

Somatosensory evoked potentials in severe traumatic brain injury: a blinded study

OBJECT

Beginning in 1979, the results of somatosensory evoked potential (SSEP) monitoring have been used to predict outcome in patients who have suffered severe brain trauma. The data indicate that if the cortical components of the SSEPs were bilaterally absent, the outcome was always death or a vegetative state, but previous studies have not been blinded. The aims of this study were to correlate the results of SSEP recordings with the outcome in a prospectively blinded manner and to assess whether monitoring of SSEPs was a useful adjunct to clinical judgment in the prediction of outcome.

METHODS

The authors studied 105 severely head injured patients (median Glasgow Coma Scale score of 6) who were admitted to the Waikato Intensive Care Unit. The upper limb SSEPs were classified according to the central conduction time (CCT) as normal, of increased latency, or absent. The outcome as assessed using the Glasgow Outcome Scale (GOS) score was evaluated 12 months after the injury.

CONCLUSIONS

Of 51 patients with a bilaterally normal CCT, 29 (57%) had a good outcome (GOS Score 5). Any delay in CCT was associated with a decreased incidence of good outcome (30%). Unilateral absence of the cortical component of the SSEP was usually associated with a poor outcome (death or severe disability), and bilateral absence was always associated with a poor outcome. The authors conclude that SSEPs correlate well with outcome and that this is not the result of investigator bias.

Medical technology assessment EEG and evoked potentials in the intensive care unit

We review the principal aspects of EEG and evoked potential (EP) neuromonitoring in the intensive care unit. The electrophysiological methods allow functional assessment of comatose patients and can be used (a) as a help to diagnose the origin of coma, (b) as a means to predict outcome, and (c) for monitoring purposes. The combination of the EEG and long-, middle-, and short-latency EPs allows widespread assessment of the cerebral cortex, the brain-stem, and the spinal cord. The EEG and the EP interpretation first requires taking into account non-neurological factors that may interfere with the recorded activities (sensory pathologies, toxic or metabolic problems, body temperature). The sensitivity and the specificity of any neurophysiological technique depend on the etiology of coma. Anoxic comas are associated with a predominantly cortical involvement, while the cortical and brain-stem functions are to be taken into account to interpret the EEG and the EPs in head trauma. The EEG and the EPs can be used to differentiate the comas due to structural lesions from those of metabolic origin, to confirm brain death and help to diagnose psychogenic unresponsiveness or a de-efferented state. While the prognostic value of the EEG is markedly hampered by the widespread use of sedative drugs, it has been possible to design efficient systems based on early- and middle-latency multimodality evoked potentials in anoxic and traumatic comas and, more generally, in all comas associated with an increase of the intracranial pressure. Continuous neuromonitoring techniques are currently under development. They have already been proven useful for the early detection and for the prevention of subclinical seizures, transtentorial herniation, vasospasm, and other causes of brain or spinal-cord ischemia.

Evaluation and prognostication in coma

Electroencephalography (EEG) and evoked potential (EP) studies are neurophysiologic techniques which provide information on physiological state and response to therapy, and may aid diagnosis and prognosis. Serial studies or continuous monitoring may enable changes to be detected prior to irreversible deterioration in the patient's condition. Current computer technology allows simultaneous display and correlation of electrophysiologic parameters, cardiovascular state and ICP. Continuous EEG monitoring in the ICU has been shown to have a decisive or contributing impact on medical decision making in more than three-quarters of patients. In addition, continuous EEG monitoring has revealed previously unsuspected non-convulsive seizures in two-thirds of patients. Somatosensory and auditory EPs can provide useful prognostic information in coma patients, however, these tests are etiologically non-specific and must be carefully integrated into the clinical situation. Motor EPs offer a potentially useful tool for evaluating motor system abnormalities in the ICU. Thus, neurophysiologic tests are established monitoring tools in the neurological intensive care unit.