Defining prognosis in medical coma

Distinct Spectral Profiles of Awake Resting EEG in Disorders of Consciousness: The Role of Frequency and Topography of Oscillations

The prolonged disorders of consciousness (PDOC) pose a challenge for an accurate clinical diagnosis, mainly due to patients' scarce or ambiguous behavioral responsiveness. Measurement of brain activity can support better diagnosis, independent of motor restrictions. Methods based on spectral analysis of resting-state EEG appear as a promising path, revealing specific changes within the internal brain dynamics in PDOC patients. In this study we used a robust method of resting-state EEG power spectrum parameter extraction to identify distinct spectral properties for different types of PDOC. Sixty patients and 37 healthy volunteers participated in this study. Patient group consisted of 22 unresponsive wakefulness patients, 25 minimally conscious patients and 13 patients emerging from the minimally conscious state. Ten minutes of resting EEG was acquired during wakefulness and transformed into individual power spectra. For each patient, using the spectral decomposition algorithm, we extracted maximum peak frequency within 1-14 Hz range in the centro-parietal region, and the antero-posterior (AP) gradient of the maximal frequency peak. All patients were behaviorally diagnosed using coma recovery scale-revised (CRS-R). The maximal peak frequency in the 1-14 Hz range successfully predicted both neurobehavioral capacity of patients as indicated by CRS-R total score and PDOC diagnosis. Additionally, in patients in whom only one peak within the 1-14 Hz range was observed, the AP gradient significantly contributed to the accuracy of prediction. We have identified three distinct spectral profiles of patients, likely representing separate neurophysiological modes of thalamocortical functioning. Etiology did not have significant influence on the obtained results.

EEG pattern predicts awakening of comatose patients after cardiopulmonary resuscitation

OBJECTIVE

To explore the value of electroencephalogram (EEG) pattern in predicting awakening of comatose patients after cardiopulmonary resuscitation (CPR).

METHODS

A retrospective cohort study was conducted on comatose patients after CPR in the neuro-critical care unit of Xuanwu Hospital, Capital Medical University, from 2002 to 2018. The included patients received clinical evaluation, and the Glasgow coma scale (GCS) score was recorded. Bedside EEG monitoring was performed for visual grading and reactivity detection. The 3-month prognostic assessment was performed using the Glasgow outcome scale (GOS). The patients were dichotomized into the awakening group (GOS 3-5) and the unawakening group (GOS 1-2).

RESULTS

A total of 160 patients were included. There was no significant difference in the baseline data between the two groups except that the GCS score of the awakening group was higher (P = 0.000). Different EEG patterns were used to predict awakening from coma. As a result, the slow wave pattern showed the highest accuracy (73.1%, 95% CI: 0.66-0.79), and the sensitivity and specificity reached 61.3% (95% CI: 0.48-0.73) and 80.6% (95% CI: 0.71-0.88), respectively. Compared with EEG reactivity, the slow wave pattern was more sensitive in predicting awakening. It was also more specific than GCS in predicting awakening. The slow wave pattern within different time frame after coma was used to predict the prognosis of awakening, suggesting that the accuracy (100%, 95% CI: 0.75-1.00), sensitivity (100%, 95% CI: 0.46-1.00), and specificity (100%, 95% CI: 0.63-1.00) of predicting awakening within 8-14 days were the highest.

CONCLUSIONS

The slow wave pattern of EEG had a good predictive value for awakening in comatose patients after CPR, and the highest accuracy occurred within 8-14 days from coma.

PET in coma and in vegetative state

Advances in resuscitation and critical care management have resulted in the survival of many patients despite severe brain damage. These patients may remain in coma or in vegetative state. The probability of recovery of conscious function is dependent on the extent of structural brain damage, which is difficult to assess by clinical, laboratory or functional tests. Positron emission tomography (PET) of 18F-fluordeoxyglucose (FDG) can be used to investigate metabolic and functional impairment of the brain. In acute vegetative state (AVS, duration <1 month), overall glucose utilization was significantly reduced in comparison with age-matched controls. In a few cases with locked-in syndrome, cortical metabolism was in the normal range. 11C-Flumazenil (FMZ) measures the density of benzodiazepine receptors (BZRs) and thereby furnishes an estimate of neuronal integrity. PET with this tracer demonstrated a considerable reduction in BZRs in cortical areas, but indicated that the cerebellum was spared from neuronal loss. The comparison of FDG- and FMZ-PET findings in AVS demonstrates that alterations of cerebral glucose consumption do not represent mere functional inactivation, but also irreversible structural damage. In some cases with minimally conscious state, auditory stimuli with emotional valence induced more brain activation (investigated by H215O-PET) than meaningless noise; such studies can be used to detect residual cortical function. To improve prognostication of chances for recovery, a combination of functional activation studies and assessment of the extent of neuronal damage might be the optimal procedure and should be tested in larger cohorts of patients with comatose states of different severity.

Epidemiology and prognosis of coma in daytime television dramas

OBJECTIVE

To determine how soap operas portray, and possibly misrepresent, the likelihood of recovery for patients in coma.

DESIGN

Retrospective cohort study.

SETTING

Nine soap operas in the United States reviewed between 1 January 1995 and 15 May 2005.

SUBJECTS

64 characters who experienced a period of unconsciousness lasting at least 24 hours. Their final status at the end of the follow-up period was compared with pooled data from a meta-analysis.

RESULTS

Comas lasted a median of 13 days (interquartile range 7-25 days). Fifty seven (89%) patients recovered fully, five (8%) died, and two (3%) remained in a vegetative state. Mortality for non-traumatic and traumatic coma was significantly lower than would be predicted from the meta-analysis data (non-traumatic 4% v 53%; traumatic 6% v 67%; Fisher's exact test both P < 0.001). On the day that patients regained consciousness, most (49/57; 86%) had no evidence of limited function, cognitive deficit, or residual disability needing rehabilitation. Compared with meta-analysis data, patients in this sample had a much better than expected chance of returning to normal function (non-traumatic 91% v 1%; traumatic 89% v 7%; both P < 0.001).

CONCLUSIONS

The portrayal of coma in soap operas is overly optimistic. Although these programmes are presented as fiction, they may contribute to unrealistic expectations of recovery.

The correlation between cerebral glucose metabolism and benzodiazepine receptor density in the acute vegetative state

This paper compares the results of parallel positron emission tomography (PET) studies of regional cerebral glucose metabolism with the radiotracer 18F-fluorodeoxyglucose (FDG) and benzodiazepine receptor (BZR) density by PET using the BZR ligand 11C-flumazenil (FMZ), a tracer of neuronal integrity, in nine patients with acute vegetative state (AVS, duration <1 month). Overall glucose utilization was significantly reduced in AVS in comparison with age-matched controls (global metabolic rate for glucose 26 micromol/100 g/min in AVS vs. 31 micromol/100 g/min in controls). FMZ-PET demonstrated a considerable reduction of BZR binding sites in all cortical regions that grossly corresponded to the extent of reduction of cerebral glucose metabolism assessed with FDG-PET, whilst the cerebellum was spared from neuronal loss. In controls, cortical relative flumazenil binding was not lower than five times the average white matter activity, whilst in AVS, nearly all values were below this threshold. There was no relevant overlap of the data of relative flumazenil binding between both groups. The comparison of FDG- and FMZ-PET findings in AVS demonstrates that alterations of cerebral glucose consumption do not represent mere functional inactivation, but irreversible structural brain damage.

Preliminary outcome analysis of a long-term rehabilitation program for severe acquired brain injury

OBJECTIVES

To describe the general characteristics and functional outcomes of individuals treated in a publicly funded, long-term, acquired brain injury rehabilitation program and investigate variables affecting functional outcomes in this patient population.

DESIGN

Retrospective database review of demographic, descriptive, and functional outcome assessment data.

SETTING

Publicly funded, comprehensive, multidisciplinary, long-term, residential brain injury rehabilitation program in Alberta, Canada (64 beds).

PATIENTS

All rehabilitation patients admitted to and discharged from the brain injury program from February 1991 to March 1999 (n = 349).

INTERVENTIONS

Multidisciplinary rehabilitation program.

MAIN OUTCOME MEASURES

Demographic and descriptive information included sex, age at admission, type and severity of injury, time from injury to long-term program admission, and length of stay (LOS). Functional outcome information included level of care required at admission and discharge, admission and discharge Rappaport disability rating scale scores, and admission and discharge FIM instrument and Functional Assessment Measure scores for a subset of patients.

RESULTS

Fifty-nine percent of the subjects had severe traumatic brain injuries (TBI) and 41% had severe nontraumatic brain injuries (NTBI) of various causes. Mean age at admission was older and LOS was longer for NTBI compared with TBI; there were no other differences between the groups in demographic or descriptive measures. The TBI group had significantly lower admission motor subscale scores than the NTBI group, but the groups did not differ on cognitive scores. All functional assessment measures showed statistically significant improvement from admission to discharge, and 85.6% of patients were discharged to community living after a mean LOS of 359.5 days. Functional status at admission, age at admission, length of time between injury and admission, and LOS in the rehabilitation program significantly correlated with functional improvement.

CONCLUSIONS

Patients with severe TBI and NTBI who were not candidates for other more conventional forms of rehabilitation showed significant improvement in functional outcomes after extended program admissions. Consideration was also given to the potential insensitivity of commonly used outcome assessment measures in this population.

Ethics in the intensive care unit with emphasis on medical futility in comatose survivors of cardiac arrest

Medical futility refers to situations or cases in which treatment offers no meaningful benefit to the patient. Brain death does not pose a management problem because patients are considered to be dead. Management of other cases requires sequential considerations. First, the prognosis must be established with certainty. Then, if it is determined that there is no possibility of the patient regaining conscious awareness, a level of care should be decided through discussions involving the physician and significant others. Usually there is a consensus that high-level intensive care is not justified to maintain such a low quality of life. When the patient's advance directives or the substitute decision maker's request differs from the physician's recommendations, there are methods of resolving the issues that respect ethical and legal principles.

[Prediction by means of endogenous and exogenous evoked potentials of the favorable evolution of a prolonged coma]

A neurophysiological follow-up (EEG, exogenous and endogenous evoked potentials--EP) was performed over a 4-month period in a patient who presented a long-lasting coma following a cardiac arrest and an amniotic embolism. A pure anoxic aetiology was ruled out starting from the second day on the basis of a dissociation between mildly altered flash visual EP and markedly altered somatosensory EP, indicating focal brain-stem pathology. Endogenous EP reappeared after 12 days. This patient recovered consciousness after 51 days. Despite the absence of MRI abnormalities, we put forward the hypothesis that a brain-stem embolism had, in fact, worsened the clinical picture of an actually moderate anoxia. This case exemplifies the interest of an integrated neurophysiological approach (EEG, exogenous three-modality EP and endogenous EP) in the early evaluation of coma. It also illustrates the complement between structural imaging and functional assessment of the nervous system.

Increased serum levels of the S-100 protein are associated with hypoxic brain damage after cardiac arrest

BACKGROUND AND PURPOSE

Patients resuscitated from cardiac arrest have a high early mortality rate. Prognostic evaluation based on clinical observations is uncertain and would benefit from the use of biochemical markers of hypoxic brain damage. The astroglial protein S-100 is an established biochemical marker of central nervous system injury. The purpose of the present study was to validate the use of serum determinations of S-100 with regard to outcome after cardiac arrest.

METHODS

Levels of serum S-100 were measured with a radioimmunoassay in 41 patients the first 3 days after out-of-hospital cardiac arrest. The main outcome variable was fatal outcome within 14 days.

RESULTS

S-100 levels were increased after cardiac arrest compared with controls with the highest levels observed the first day. S-100 levels day 1 and 2 correlated to the degree of coma as well as to the time of anoxia. Seventeen patients died within 14 days after the cardiac arrest. The deceased patients had increased S-100 levels on days 1 through 3 compared with survivors. All patients (100%) with an S-100 level of > or =0.2 on day 2 after the cardiac arrest died within 14 days, and 89% of the patients with levels below this limit value survived (positive and negative predictive values). The corresponding predictive values on day 1 were 71% and 85%, respectively.

CONCLUSIONS

The present study shows that hypoxic brain damage after cardiac arrest can be estimated by measurement of serum S-100 concentrations. The method can be used in early prognostic evaluation of short-term outcome after cardiac arrest.

Early prognosis in coma after cardiac arrest: a prospective clinical, electrophysiological, and biochemical study of 60 patients

BACKGROUND

The univariate study of clinical, electrophysiological, or biochemical variables has been shown to predict the outcome in postanoxic coma in about 50% of patients for each type of variable. Previous studies did not, however, consider the prognostic accuracy of a multivariate approach.

METHODS

Sixty patients in coma for more than six hours after cardiac arrest were prospectively examined by means of repeated clinical examinations (including Glasgow coma score (GCS)), EEG, and medianus nerve somatosensory evoked potentials (SEPs). In 16 patients, the early concentrations of serum neuron specific enolase and ionised calcium were also measured.

RESULTS

Within the first year after cardiac arrest, 20% of patients made a good neurological recovery; 80% remained in a vegetative state or died. Clinical examination correctly predicted outcome in 58% of patients, SEP in 59%, and EEG in 41%. The combination of clinical examination, SEP, and EEG raised the percentage of correct predictions to 82%, without false pessimistic predictions. Concentrations of serum neuron specific enolase and ionised calcium were of no additional prognostic help. Multivariate regression analysis identified the association of GCS < 8 at 48 hours with abnormal or absent early cortical SEPs as highly predictive of a bad outcome (risk = 97%, 95% confidence interval = 86-99%).

CONCLUSION

The combination of GCS at 48 hours, SEP, and if these are non-conclusive, EEG, permits a more reliable prediction of outcome in postanoxic coma than clinical examination alone.

Proton magnetic resonance spectroscopy in children with acute central nervous system injury

Single voxel proton magnetic resonance spectroscopy (1H-MRS) was used in 30 infants and children with acute central nervous system injuries to determine the value of changes in specific metabolite ratios in predicting outcome. The mean age of all patients was 38 +/- 52 months and the mean time of study after insult was 7 +/- 5 days. 1H-MRS was determined in the occipital gray and parietal white matter (8 cm3 volume, STEAM sequence with TE = 20 ms, TR = 3,000 ms). Data were expressed as ratios of different metabolite peak areas including N-acetylaspartate (NA), choline-containing compounds (Ch), creatine and phosphocreatine (Cr), and lactate (Lac). Statistically significant differences were observed when patients with good/moderate (G/M) outcomes (n = 17; mean age: 46 months) were compared to patients with bad outcomes (n = 10; mean age: 26 months). NA/Cr and NA/Ch were significantly lower in the bad outcome group (NA/Cr = 1.15 +/- 0.38; NA/Ch = 1.18 +/- 0.52) compared to the G/M group (NA/Cr = 1.41 +/- 0.28, P < .05; NA/Ch = 1.98 +/- 0.81, P < .01). Lactate was present in 80% of bad outcome patients and in none of the G/M group (P < .0001). Using a linear discriminant analysis and combining 4 clinical variables (Glasgow Coma Scale score, initial pH and glucose, number of days unconscious at time of 1H-MRS) allows classification of 94% of patients into their correct outcome group. Use of spectroscopy variables (NA/Cr, NA/Ch, Ch/Cr, presence of lactate) alone correctly classified 81% of patients. The combination of clinical and 1H-MRS variables correctly classified 100% of patients. Our findings suggest that 1H-MRS adds information which, in combination with clinical examination, may be useful in outcome assessment in children with serious acute central nervous system injury.

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

The purpose of this study was to evaluate prospectively short-latency somatosensory evoked potentials (SEPs) as a predictor of outcome in acute, severe brain injury, and to compare this with the predictive power of the motor component of the Glasgow Coma Scale score and computed tomographic scan. Outcome was measured with the Glasgow Outcome Scale at a minimum of 6 months after injury. We studied 109 patients (aged 0.1 to 16.8 years) with SEPs within 4 days of the onset of coma. Four patients had absent SEPs and a favorable outcome by the Glasgow Outcome Scale (full recovery or moderate disability); two of these patients had meningitis with bilateral subdural effusions, one had a midbrain hemorrhage, and one had a decompressive craniectomy for uncontrolled intracranial hypertension. Normal SEPs had a positive predictive value for favorable outcome of 93% (95% confidence interval (CI), 77% to 99%), and absent SEPs had a positive predictive value for unfavorable outcome by the Glasgow Outcome Scale (severe disability, survival in a persistent vegetative state, or death) of 92% (95% CI, 80% to 98%). If the above identifiable clinical situations in which a physical barrier existed to impede cutaneous reception of the electrical impulse were excluded, the positive predictive value of absent SEPs for poor outcome reached 100% (95% CI, 92% to 100%). An absent motor response to painful stimulus also had 100% positive predictive value (95% CI, 84% to 100%) for unfavorable outcome; however, 23% of patients could not be evaluated because of the effects of muscle relaxants or sedatives. In patients with traumatic brain injury, results of computed tomography did not reliably predict outcome. Of the 59 patients with unfavorable outcome, 76% could be identified with SEPs compared with 36% with examination of motor function. We suggest that SEPs be performed in children with acute severe brain injury because they add an important tool to the physician's prognostic armamentarium. We conclude that in the absence of the above mentioned identifiable clinical situations, absent SEPs predict 100% unfavorable outcome, and this finding may warrant consideration of withdrawal of treatment in children with brain injuries.

Medical aspects of the persistent vegetative state (1)

This consensus statement of the Multi-Society Task Force summarizes current knowledge of the medical aspects of the persistent vegetative state in adults and children. The vegetative state is a clinical condition of complete unawareness of the self and the environment, accompanied by sleep-wake cycles, with either complete or partial preservation of hypothalamic and brain-stem autonomic functions. In addition, patients in a vegetative state show no evidence of sustained, reproducible, purposeful, or voluntary behavioral responses to visual, auditory, tactile, or noxious stimuli; show no evidence of language comprehension or expression; have bowel and bladder incontinence; and have variably preserved cranial-nerve and spinal reflexes. We define persistent vegetative state as a vegetative state present one month after acute traumatic or nontraumatic brain injury or lasting for at least one month in patients with degenerative or metabolic disorders or developmental malformations. The clinical course and outcome of a persistent vegetative state depend on its cause. Three categories of disorder can cause such a state: acute traumatic and non-traumatic brain injuries; degenerative and metabolic brain disorders, and severe congenital malformations of the nervous system. Recovery of consciousness from a posttraumatic persistent vegetative state is unlikely after 12 months in adults and children. Recovery from a nontraumatic persistent vegetative state after three months is exceedingly rare in both adults and children. Patients with degenerative or metabolic disorders or congenital malformations who remain in a persistent vegetative state for several months are unlikely to recover consciousness. The life span of adults and children in such a state is substantially reduced. For most such patients, life expectancy ranges from 2 to 5 years; survival beyond 10 years is unusual.

Predictive value of P300 event-related potentials compared with EEG and somatosensory evoked potentials in non-traumatic coma

Developments in ethical decision making are increasing demand for more accurate predictions of outcome in coma. New neurophysiologic tests are needed to improve the ability to predict awakening as well as poor outcome. We have recently reported that the P300 event-related potential (P300) correlates with awakening and depth of nontraumatic coma. In this companion study, the predictive value of the P300 was compared with median nerve somatosensory evoked potentials (SEP) and EEG in 20 patients in non-traumatic coma. We also evaluated the predictive value of a simplified grading scale for both the EEG and SEP (the USC SEP scale and USC EEG scale). The presence of a P300 was significantly associated with higher Glasgow coma scores (GCS) and awakening. Severe abnormalities of the somatosensory evoked potentials significantly correlated with the absence of awakening and a low GCS. Moderate abnormalities of the SEP were significantly associated with awakening and higher GCS scores. The EEG was significantly associated with GCS score and severe abnormalities of the EEG were predictive of the absence of awakening and very low GCS scores. The data indicates that the P300 and SEP are more effective than the EEG in predicting awakening, and that the SEP and EEG are more effective than the P300 in predicting poor outcome. We conclude that, in addition to EEG and SEP, the P300 should be considered in the prognostic evaluation of patients in nontraumatic coma. Further, simplified scales for the EEG and SEP are predictive of depth of coma and outcome.