Post-cardiorespiratory arrest beta-alpha coma: an unusual electroencephalographic phenomenon

The presence of frontally-dominant alpha pattern in the EEG is common in patients with coma due to trauma, toxic-metabolic causes and following cardiorespiratory arrest. Diffuse beta activity following resuscitation after a cardiac arrest is not well recognized. We report a case of coma in a 3-year-old girl who had a cardiac arrest from which she was revived. Initial EEG showed diffuse beta activity, which later evolved to predominantly alpha activity. The possible mechanisms involved in the generation of such rhythms are discussed. Transition of EEG activity from faster to slower frequencies is suggested as an adverse prognostic factor in post-cardiorespiratory arrest coma.     

A case of area-specific stimulus-sensitive postanoxic myoclonus.

The authors report a case of area-specific stimulus-sensitive postanoxic myoclonus and discuss possible pathophysiology. A 71-year-old man sustained cardiorespiratory arrest that lasted 10 minutes and remained unresponsive. On the first EEG obtained 8 hours after the arrest there was no cerebral electrical activity before stimulation of the trigeminal-innervated areas. Periorbital stimulation was associated with bursts of spike-wave activity and generalized myoclonic jerks, whereas other types of stimulation did not elicit any response. A second EEG obtained 32 hours later showed a nonreactive alpha coma pattern. The patient died 7 days after the arrest. Area-specific stimulus-sensitive postanoxic myoclonus is very rare. The regularity of generalized bursts of spike-wave activity (cortical response) in response to stimulation of trigeminal-innervated areas suggests that the resting EEG electrocerebral silence may have been a result of cortical suppression with disinhibition of stimulus-sensitive brainstem-generated myoclonus.     

Prognostic significance of alpha frequency EEG rhythm in coma after cardiac arrest.

Sixty-five patients who remained in coma for more than 24 hours after resuscitation from cardiac arrest were divided into two groups according to their EEGs. Thirteen patients were found to have rhythm of alpha frequency while 52 had the usual EEG findings after cerebral anoxia. Three patients from the group with alpha frequency EEG rhythms regained full consciousness but showed severe sequelae. Our results suggest that the prognosis of comatose patients with EEG rhythm of alpha frequency is no poorer than that of other individuals who are comatose after cardiac arrest.     

Alpha rhythm and alpha-like activity in coma

A normal waking EEG was obtained on a 22 year old man four days prior to cardiopulmonary arrest. Three days after resuscitation the EEG showed the pattern of alpha-like activity while the patient remained in deep coma. Since the EEGs were recorded by the same technician using the same 16 channel electroencephalograph and montages, it is possible to compare in the same individual these alpha-frequency activities before and after arrest. The alpha-like activity of coma does not resemble the waking alpha rhythm in amplitude, frequency, spatial distribution, variability and reactivity.     

"Theta pattern coma" occurring in younger adults

Since our previous report, where "theta pattern coma" was described in 2 elderly patients as an EEG pattern with a grave prognosis, we have had the opportunity to see another 9 affected patients. In this article, 3 men with a mean age of 36 years who died after cardiorespiratory arrest presented a "theta coma pattern." The EEG activity was initially reactive to and attenuated by external stimulation in 2, but prior to death the pattern became arreactive. This article shows that "theta pattern coma" is not an age related phenomenon as previously considered. So far, 11 patients with this type of EEG abnormality have been seen in our department; all have died, and all were over 30 years of age. An expanded definition of "theta pattern coma" is given in the discussion. The pathophysiological mechanisms involved in generation of this abnormality are not known. This abnormality, when seen in the unconscious patient, should be classified as a grade 4 abnormality on the EEG coma scale and should be differentiated from rather diffuse theta activity in coma. The prognostic significance of "theta pattern coma" appears to be similar to that of "alpha pattern coma."     

Value of a revised EEG coma scale for prognosis after cerebral anoxia and diffuse head injury

The prognostic validity for survival of a recently devised EEG grading scale was tested in anoxic and post-traumatic coma. This scale divides EEG in coma into five major grades and ten subdivisions with emphasis on the presence of dominant activities, their amplitude, persistence, distribution and reactivity. In this scale, patterns previously not allocated, such as "spindle pattern coma," "alpha pattern coma," and "theta pattern coma" are also included. The prognostic power of the revised scale was tested retrospectively without knowledge of clinical data in a group of patients with cerebral anoxia after cardiac arrest lasting more than seven minutes and in a group of diffuse head injuries. The validity of the scale was found to be higher than those used in previously published studies, reaching 98.4% prognostic accuracy in anoxic encephalopathies and was very high in head injuries.     

Anoxic-ischemic alpha coma: prognostic significance of the incomplete variant

Abstract. The prognostic significance of post-anoxic-ischemic alpha coma (AC) is controversial. We recorded somatosensory evoked potentials (SEPs) and performed serial electroencephalography (EEG) in a 60-year-old woman in coma after cardiac arrest. The first EEG was recorded after 48 hours (GCS=5; E1-V1-M3); brain-stem reflexes were preserved. The EEG pattern showed monotonous alpha frequencies (10–11 Hz) with posterior predominance; acoustic and noxious stimuli evoked EEG reactivity. Early cortical SEPs (72 h) were normal. On the fifth day (GCS=8; E4-V1-M3), the EEG alpha pattern was replaced by a diffuse delta activity; rhythmic theta changes appeared spontaneously or in response to stimuli. The patient regained consciousness on the tenth day and EEG showed posterior theta activity (6–7 c/s) partially reactive to stimuli. At the 6-month follow-up, cognitive evaluation showed mild dementia. Recent studies identified two forms of AC. Patients with complete AC have an outcome that is almost invariably poor. Conversely, incomplete AC (posteriorly accentuated alpha frequency, reactive and with SEPs mostly normal) reflects a less severe degree of anoxic-ischemic encephalopathy. The case we report should be classified, according to the SEPs and EEG features, as incomplete AC. The fact that the patient has regained consciousness, even if with residual cognitive impairment, confirms the need to distinguish this variant from complete AC.     

Falsely pessimistic prognosis by EEG in post-anoxic coma after cardiac arrest: the borderland of nonconvulsive status epilepticus

Background. Prognostication following anoxic coma relies on clinical assessment and is assisted by neurophysiology. A non-evolving EEG spike burst/isoelectric suppression pattern after the first 24 hours almost invariably indicates poor outcome, while an evolving pattern implies nonconvulsive status epilepticus (NCSE) that may "hide" surviving brain activity and is amenable to treatment. Case study. We present the case of a 53-year-old woman who had a witnessed out-of-hospital ventricular fibrillation cardiac arrest, was resuscitated by paramedics, but remained comatose. An EEG, performed 36 hours post-insult, showed an unremitting, non-evolving, unresponsive 2-6?Hz high-voltage spike burst/isoelectric suppression pattern, which remained unchanged at 96 hours post-insult, following therapeutic hypothermia. During this period, she was completely off sedation and taking triple antiepileptic treatment, without systemic confounding disorders. Although the initial pattern was indicative of poor neurological outcome, she eventually made meaningful functional recovery; the last EEG showed satisfactory background rhythms and stimulus-induced epileptiform discharges without seizures. Conclusion. In post-anoxic coma, non-evolving >2?Hz spike burst/isoelectric suppression pattern may still reflect NCSE and therefore should be considered in the diagnostic EEG criteria for NCSE. Such borderline patterns should not dissuade physicians from intensifying treatment until more confident prognostication can be made.     

Clinical neurophysiologic monitoring and brain injury from cardiac arrest

Electrophysiologic testing continues to play an important role in injury stratification and prognostication in patients who are comatose after cardiac arrest. As discussed previously, however, the adage about treating whole patients, not just the numbers, is relevant in this situation. EEG and SSEP can offer high specificity for discerning poor prognosis as long as they are applied to appropriate patient populations. As discussed previously, EEG and SSEP patterns change during the first hours to days after cardiac arrest and negative prognostic information should not be based solely on studies performed during the first 24 hours. Both electrophysiologic techniques also are susceptible to artifacts that may worsen the electrical patterns artificially and suggest a falsely poor prognosis. EEG is suppressed by anesthetic agents and hypothermia, both of which may produce ECS and burst suppression. Patients who experience respiratory arrest from a toxic ingestion of narcotics or barbiturates, in particular, may present with high-grade EEG patterns initially. Many patients also receive anesthetic medications at the time of tracheal intubation, which may linger beyond their normal half-life in patients who have hepatic or renal insufficiency or concurrent use of interacting medications. SSEP is much less susceptible to sedative anesthetic agents, but hypothermia is demonstrated to prolong evoked potential latencies. As therapeutic hypothermia becomes more common after cardiac arrest, the effect of temperature on electrophysiologic testing needs to be taken into account. The publications discussed previously also emphasize the need to adjust the prognostic value of electro-physiologic tests to the pretest probability of meaningful neurologic recovery in individual patients. Clearly, grade I EEG patterns and normal N20 potentials indicate a much better prognosis in patients who have a short du-ration of cardiac arrest, short duration of coma after resuscitation, and when the studies are performed within the first few days. In patients who remain in coma days after resuscitation and lack appropriate brainstem reflexes, however, even the most normal appearing electrophysiologic patterns do little to change the overall prognosis. Aside from prognostication, electrophysiologic testing holds great promise in defining the basic anatomy and physiology of coma emergence after cardiac arrest. In addition, quantitative EEG and automated evoked potentials have the potential to render these tools less subjective and arcane and more applicable for monitoring patients in the period during and immediately after resuscitation. Quantitative EEG also has great potential asa tool to define the time window for neuroprotective intervention and the means to track the response to such therapies in real time.     

Brain death in secondary brain lesion

The criteria of brain death established by Japanese Society of EEG in 1974, necessitates a prerequisite; be applicable only to "acute destructive, primary gross lesion of brain". Namely, because of insufficient clinical data, secondary brain lesion such as post-anoxia, intoxication, metabolic coma and some kinds of CNS infection were excluded for the object to determine brain death. The criteria published by others also describe that etiology of coma should be clarified, and that careful measures are necessary to diagnose brain death if the cause of coma is unknown. In the present study, it was investigated that whether a clinico-pathological entity of brain death could exist universally regardless of the etiology, and by what means it could be defined clinically. The patients suffering from nondestructive, secondary brain lesions and who showed "brain death-like state" were selected for the study. ("Brain death-like state" requires coma, dilated nonreactive pupis and arrest of respiration concomitantly for more than 6 hours.) And 25 patients were collected, whose underlying diseases were post-anoxia or shock, CO intoxication, Paraquat poisoning, near-drowning or suffocation, hepatic coma, accidental hypothermia and sepsis, with or without the episode of cardiac arrest. Though all the patients died from 1 to 13 days after the insult, clinical signs of brain death-like state were not always irreversible. Isoelectric EEG was obtained on that state in 11 patients and repeated EEG revealed no return on those patients. But another 5 patients showed EEG activity when brain death was strongly suspected clinically.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prognostically important EEG coma patterns in diffuse anoxic and traumatic encephalopathies in adults

Because of the paucity in the English literature of a detailed and universally accepted EEG grading scale relating to survival after diffuse traumatic and anoxic brain insults, prognostically oriented EEG patterns including recently described abnormalities are presented and discussed. The significance of these patterns may also apply in cases of coma of other etiologies, which can present morphologically similar features. EEG patterns have been classified into five major grades based on an internationally accepted scale. Individual patterns have been more clearly defined on the basis of the morphology of dominant activities, their distribution, persistence, and reactivity to external stimulation. Favorable outcome with survival seems to occur with both grade 1 and the "reactive type" of grade 2 abnormalities, with preservation of normal sleep features, and with frontal monorhythmic delta activity. Prognostically uncertain patterns are "nonreactive" grade 2 abnormalities, diffuse delta activity with grade 3 abnormality, and the "reactive type of alpha pattern coma." The following patterns are suggested to be prognostically malignant if persistent: grade 3 abnormality with small amplitude, diffuse, irregular delta activity; grade 4 ("burst suppression pattern"), in particular when epileptiform discharges are present and with "low-output EEG"; and grade 5 ("isoelectric EEG"). Fatal outcome is also common with the "nonreactive type of alpha pattern coma" and the recently reported "theta pattern coma." These patterns are presented in the illustrations. It is intended that this more detailed subdivision will promote understanding between electroencephalographers using visual EEG assessment in cases of coma.     

Unusual EEG patterns in coma, and their evolution.

A 23-year-old chronic asthmatic patient is reported who showed successively four different EEG patterns within a 7 day period of unconsciousness following cardio-respiratory arrest. The initial record was dominated by alpha activity, then beta activity supervened, to be followed by spindle components. Finally an isoelectric tracing occurred before death. A computer file search for all cases of unusual EEG coma patterns was carried out. It failed to reveal any other patient with a similar sequence, but various types of evolution were noted. Such features are seen in only a very small percentage of comatose patients, and in the context of cardio-respiratory arrest are almost invariably fatal.     

Epileptiform discharges in presence of continuous background activity in anoxic coma

The EEGs of a group of patients in anoxic coma following cardiorespiratory arrest were retrospectively studied. Twelve of 70 patients had at least one EEG recorded during the acute period which consisted of epileptiform discharges in the presence of continuous diffuse background activity. Nine of the patients died while three made a generally favorable recovery. The analysis confirms the prediction of a recent revision of EEG grades in coma that this particular pattern of activity is of uncertain prognostic significance. This is in contrast to the occurrence of epileptiform discharges during discontinuous "burst suppression" activity which generally indicates a fatal outcome.     

Alpha-pattern coma in a 2-year-old child.

An EEG of a two-year-old child with Reye's syndrome complicated by prolonged hypoglycemia showed continuous, diffusely distributed, 8- to 9-Hz, well-modulated alpha activity while the patient was comatose. Continuous monitoring of EEG showed gradual reduction of alpha activity and the appearance of moderate-amplitude delta waves within the next 18 hours. Subsequent EEGs showed electrocerebral silence. The EEG features and their evolution resembled those described in postanoxic "alpha-pattern coma" in adults. A diffuse cortical-subcortical insult, possibly due to hypoglycemia, may be responsible for the generation of diffuse alpha activity in our case. Because of its transient nature, immediate and serial EEG studies following the acute cerebral insult may be necessary to demonstrate this pattern in children.     

Hanging survivor showing alpha coma--a case report

A case of a survivor who showed alpha coma after an attempted suicide by hanging was reported. A 19 years old woman was admitted to the hospital because of respiratory arrest following a hanging attempt on October 10, 1987. She was found pendent completely. On admission she was comatose and the pupils were not reactive to light. The systolic blood pressure was 60 mmHg and immediately an endotracheal intubation was instituted. After six hours from the onset, the spontaneous respiration was restored and the pupils reacted briskly to light. At 48 hours later she was still comatose, presenting flaccid quadriplegia with no responses to stimulations. An EEG showed a moderate amount of regular, 8 approximately 10 Hz, 10 approximately 50 microV potentials distributed predominantly on the centro-parieto-occipital regions. This alpha rhythm had persisted until 72 hours from the onset, and subsequently diffuse 5 approximately 7Hz, 10 approximately 40 microV slow activity replaced the alpha frequency at 120 hours after the attempt. On the 5th hospital day the hyperbaric oxygen therapy was given and on the 7th day she had become conscious, but showed the apallic syndrome. The both auditory and somatosensory evoked potentials were normal. On the 45th day the brain MRI revealed diffuse cerebral cortical atrophy, although no lesions were visualized in the brain stem. She showed gradual progress towards neurologic recovery. This is the first presentation of a survivor from alpha coma caused by anoxic encephalopathy following a hanging attempt.     

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.     

Alpha coma

Six personal cases of alpha coma are reported: 3 following a cerebrovascular accident and 3 resulting from cerebral concussion. Two patients survived. On the basis of differences in pathogenesis, EEG characteristics and prognosis, the following classification is proposed: alpha coma resulting from brain stem vascular accident; cerebral concussion; diffuse cerebral hypoxia; drug intoxication. The clinical course of each of the classes of alpha coma is outlined. The alpha coma state is not restricted to cases with structural brain stem lesions c.q. lesions of the pontomesencephalic region.     

Visual evoked potentials during hypothermia and prolonged circulatory arrest.

Visual evoked potentials were recorded in eight children during hypothermia and circulatory arrest. The potentials were lost in all children recorded in late arrest. The evoked potential is a more sensitive indicator of CNS stress as provoked by combined hypothermia and hypoxia than is the EEG. EEG activity persisted in six of the eight children in this series even during circulatory arrest. The EEG had been seen to do the same in more than half of a larger series of children recorded at that stage. The results suggest that evoked potentials may be a sensitive indicator of early impairment of cerebral function and may demonstrate useful change sooner than the EEG. The examination may be useful in following children with illnesses producing hypoxia or anoxia. The N1 component was as easily and as frequently identifiable as the P2 component. Under the stress of this procedure, the latency of the P2 component became more variable than the N1 peak. The results suggest the N1 component may be as useful and perhaps more useful than the P2 wave in following the effect of some CNS stresses in children.     

Quantitative EEG during progressive hypocarbia and hypoxia. Hyperventilation-induced EEG changes reconsidered.

To investigate the role of cerebral hypoxia as a causative factor in the alteration of the qEEG during hyperventilation, qEEG changes caused by progressive hypocapnia were compared with qEEG changes due to progressive normobaric hypoxia in two parallel groups of 12 and 10 healthy male subjects (age 20-27 years), respectively. In the first group, qEEG records were obtained before and during hyperventilation to pCO2 levels of 4.0, 3.0 and 2.0 kPa. In the second group, the qEEG samples were taken before and during hypoxia with hemoglobin oxygen saturations of 80, 70 and 60%. In both groups, blood flow velocity in the middle cerebral artery was also recorded. Hyperventilation caused an exponential increase in slow activity and a decrease in alpha power. No shift in the alpha mean frequency and alpha peak frequency was observed, except with the pCO2 level of 4.0 kPa, which caused an increase in both variables. Hypoxia with a hemoglobin oxygen saturation of 60% caused a much less pronounced increase in slow activity. No change in total power in the alpha band was found, but both the alpha peak frequency and alpha mean frequency decreased. Lesser degrees of hypoxia caused only minimal EEG changes. Blood flow velocity was decreased by hyperventilation but increased by hypoxia. It is concluded that the EEG changes observed during hyperventilation must mainly or totally be attributed to factors other than cerebral hypoxia.     

Electroencephalographic findings in coma caused by fatal chloroquine poisoning

A 19-year-old patient in deep anoxic coma after cardiopulmonary arrest due to suicidal acute overdosage of chloroquine was resuscitated at the intensive care unit. An EEG starting about 12 hours later and lasting for 93 minutes showed a rapid succession of diffuse ectopic rhythms, diffuse slow output, generalized periodic slow waves in paroxysmal episodes which preceded burst suppression patterns and definite establishment of electrocerebral silence. All these EEG patterns indicating a poor prognosis were registered about three hours before the patient died during irreversible ventricular fibrillation.