"Alpha-pattern coma" in high voltage electrical injury.

Two cases are reported in which reversible deep coma subsequent to high voltage electrical injury occurred in association with alpha frequencies in the EEG. The EEG pattern differs from the alpha rhythm of the normal awake patient by its diffuse distribution and unresponsiveness to a variety of stimulation. The term "alpha-pattern coma" is introduced to designate the occurrence of this pattern in comatose patients. The EEG in the cases described initially demonstrated activity in the alpha frequency which occurred in a generalized distribution and was unresponsive to stimulation. During the early stages of recovery an increased incidence of theta and delta activity was observed. The recovery records contained a low voltage alpha rhythm and responded to photic stimulation. The literature on this subject is reviewed and the possible modes of pathogenesis are discussed. The authors conclude that such examples of alpha-pattern coma are the result of diffuse cerebral damage and might be detected more frequently in comatose patients who survive if these patients are studied earlier in their clinical course with EEGs.     

高颈段脊髓电刺激促醒颅脑创伤昏迷一例并文献复习

目的 研究高颈段脊髓电刺激对颅脑创伤昏迷的促醒作用.方法 观察1例重型颅脑创伤患者高颈段脊髓电刺激术后清醒时间、脑电图、诱发电位及脑血流的变化.结果 患者术后2个月逐渐清醒,脑电图逐渐转为正常α节律,诱发电位潜伏期延长逐渐改善,脑血流明显增加.结论 高颈段脊髓电刺激可能通过增加脑血流、恢复正常的神经电生理活动促醒颅脑创伤昏迷患者.

Abstract：

Objective To study the awoking effect of high cervical spinal cord stimulation on comatose patients with traumatic brain injury.Methods Recovery time,electroencephalogram(EEG),evoked patentials,cerebral blood perfusion after cervical spinal cord stimulation in a comatose patient were investigated.Results The patient emerged form conla at 2 months after spinal cord stimulation treatment.EEG gradually turned into a normal(rhythm,evoked potentials latency improved,and cerebral blood perfusion increased significantly.Conclusions High cervical spinal cord stimulation exerts its beneficial effects to comatose patients with traumatic brain injury by increasing cerebral blood perfusion and restoring normal cerebral electrical activity.     

Failure of electroencephalography to diagnose brain death in comatose children.

Two isoelectric electroencephalograms obtained 24 hours apart support a clinical diagnosis of brain death in prolonged coma. Without documentation of electrocerebral silence, physicians are reluctant to discontinue vital support systems. A radionuclide bolus technique has been developed that documents the absence of cerebral blood flow in suspected brain death and supplements the flat EEG. In a recent review of this technique, all 27 adults who had EEG activity maintained the integrity of their cerebral blood flow. This contrasts to our studies of 5 children, all of whom demonstrated persistent EEG activity but had no evidence of cerebral blood flow by either the isotope bolus technique (5 patients) or cerebral angiography (4 patients). These children (mean age, 7 months) lacked cephalic reflexes and were maintained on assisted ventilation for an average of 15 days. Multiple electroencephalographic tracings persistently demonstrated low-voltage cortical activity over this time. Despite the lack of cerebral blood flow, all patients were continued on respiratory support. At autopsy, extensive brain liquefaction necrosis was noted. In comatose children, EEG monitoring may be of limited value while cerebral blood flow measurements can provide more practical and prognostic information.     

Atlas of Electroencephalography, 3rd Edition

Electroencephalography (EEG) is the recording of the electrical activity of the brain. EEG is a reliable test to assess cerebral function. It aids in diagnosis, classification, and management of patients with epilepsy. It also has practical uses in conditions other than epilepsy. Moreover, it is harmless and inexpensive. EEG is an important tool for evaluating patients with epilepsy. It may help classify the syndrome, identify the likely source of focal seizures, and confirm a diagnosis of status epilepticus. EEG is therefore helpful when selecting appropriate antiepileptic drugs for patients with epilepsy, is valuable for diagnosis and management of status epilepticus as well as predicting the prognosis in epilepsy syndromes, and, is finally useful when localizing an area for resection in surgery candidates. In addition, despite advances in neuroimaging, EEG remains a valuable tool in the evaluation of stuporous and comatose patients. A systematic approach is essential for EEG interpretation, and when combined with good clinical judgment, it will improve diagnostic sensitivity and specificity and may improve therapeutic outcomes. This EEG atlas is designed as a practical guide for neurology residents, neurologists, and epileptologists, so that they may appropriately identify normal and abnormal findings, while reading an EEG. By reading and reviewing the relevant chapter of this well‐organized atlas, that includes many EEG images, the reader will also learn how to report an EEG finding. We hope that this atlas fills an unmet need, and leads to improved patient care.     

Quantified EEG analysis monitoring in a novel model of general anaesthesia in rats

The aim of this research was to evaluate the safety and reliability of an anaesthetic mixture (Equitensine: pentobarbital, chloral hydrate, dihydroxypropane, ethanol) which, unlike other 'classic' anaesthetics, such as ketamine [The Electroencephalogram in Anaesthesia, Springer, Berlin, 1984], has been demonstrated not to induce alterations in the extracellular concentrations of cerebral excitatory amino acids. Quantified EEG analysis monitoring and behavioural observation were used to quantify the degree and the time course of the changes in cerebral electrical activity, analgesia and sedation induced, in rats, by the compound under investigation. Equitensine (0.33 ml/100 g), administered intraperitoneally, induced analgesia (monitored by the tail flick method) for 60-70 min and a pattern of behavioural sedation (loss of the righting reflex) lasting, on average, 130-150 min. The EEG monitoring revealed a pattern typical of burst suppression which lasted 15-20 min, followed by another, lasting 270-300 min, characterized by slow waves of high amplitude. The quantified EEG analysis demonstrated that the changes in cerebral electrical activity lasted longer than behavioural observation suggested. The compound under examination was found to be safe, reliable and non-invasive to administer and sustain in all the animals, and quantified EEG analysis proved to be a very sensitive method for highlighting the functional changes in the central nervous system.     

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.     

Prevalence of nonconvulsive status epilepticus in comatose patients

BACKGROUND: Nonconvulsive status epilepticus (NCSE) is a form of status epilepticus (SE) that is an often unrecognized cause of coma. OBJECTIVE: To evaluate the presence of NCSE in comatose patients with no clinical signs of seizure activity. METHODS: A total of 236 patients with coma and no overt clinical seizure activity were monitored with EEG as part of their coma evaluation. This study was conducted during our prospective evaluation of SE, where it has been validated that we identify over 95% of all SE cases at the Medical College of Virginia Hospitals. Only cases that were found to have no clinical signs of SE were included in this study. RESULTS: EEG demonstrated that 8% of these patients met the criteria for the diagnosis of NCSE. The study included an age range from 1 month to 87 years. CONCLUSION: This large-scale EEG evaluation of comatose patients without clinical signs of seizure activity found that NCSE is an underrecognized cause of coma, occurring in 8% of all comatose patients without signs of seizure activity. EEG should be included in the routine evaluation of comatose patients even if clinical seizure activity is not apparent.     

Usefulness of intracranial pressure monitoring and EEG analysis in a child with acute encephalitis

The usefulness of continuous intracranial pressure (ICP) monitoring and the correlation between ICP and electroencephalographic findings were investigated in a 6-year-old boy with acute encephalitis. On admission he was comatose in a decerebrate posture. ICP was continuously monitored by the epidural transducer and controlled with hyperventilation, fluid restriction and administration of mannitol, glycerol and pentobarbital to keep below 20 mm Hg. The inotropic agents such as dopamine and dobutamine were also given to maintain the cerebral perfusion pressure (CPP) at 50 mm Hg or greater. At the same time with ICP monitoring, EEG records were obtained with scalp electrodes at monopolar T3-A1 and T4-A2 regions according to the 10-20 international system on an analog tape simultaneously with a data recorder. The records were digitized at 50 samples/sec, and the high-order auto-regressive (AR) power spectrum was calculated with a minicomputer PFU-1200 (Fujitsu Co Ltd.). At pressures greater than 25 mm Hg in ICP, the total power of the high-order AR activity of EEG was apparently decreased. The results indicated that the AR power spectral analysis of EEG is sensitive method for obtaining valuable information regarding the electrical brain activity and intracranial pressure.     

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.     

The usefulness of EEG, exogenous evoked potentials, and cognitive evoked potentials in the acute stage of post-anoxic and post-traumatic coma

Three-modality evoked potentials (TMEPs) have been used for several years in association with the EEG as a diagnostic and prognostic tool in acute anoxic or traumatic coma. Cognitive EPs have been recently introduced. EEG and cognitive EPs provide functional assessment of the cerebral cortex. TMEP parameters can be described by two indices: the index of global cortical function (IGCF) and the index of brainstem conduction (IBSC). Although it remains a unique tool for epilepsy assessment, the value of EEG is largely limited by its high sensitivity to the electrical environmental noise, its dependence on sedative drugs, and its inability to test the brainstem. Major TMEP alterations (absence of cortical activities more than 24 hours after the onset of post-anoxic coma, major pontine involvement in head trauma) are associated in all cases with an ominous prognosis (death or vegetative state). However, even if mild TMEP changes are associated with a good prognosis in 65% (post-anoxic coma) to 90% (head trauma) of cases, some patients never recover despite exogenous TMEPs that are only mildly altered in the acute stage. Thus, cognitive EPs can usefully complement exogenous EPs as a prognostic tool in coma. Indeed, even if the absence of cognitive EPs in comatose patients does not have any prognostic value, their presence implies a very high (more than 90%) probability of consciousness recovery. The major technical challenge for the future will be the development of reliable tools for continuous EEG and TMEP monitoring.     

Long term EEG analytical and neurological follow-up study in completed stroke patients after extra-intracranial vascular anastomosis

In 33 chronic stroke patients, who had internal carotid or middle cerebral artery occlusion that resulted in neurological deficit persisting for an average of more than 10 weeks, it was possible toperform a postoperative follow-up study for aperiod of six to eight years after extraintracranial vascular anastomosis.

Serial neurological examinations with grading of motor deficit and EEG analyses were performed to assess the clinical course of the cerebral lesion.

These long term examinations showed a postoperative continuing improvement of electrical brain activity in nearly two thirds of the patients, nine patients showed no significant changes and three worsened. The EEG analytical findings correlated well to the neurological findings. An increase of electrical brain activity was bilateral with accentuation over the affected hemisphere, a phenomenon known from follow-up nrCBF measurements after anastomosis. During the follow-up one patient died five years, one six years following stroke under signs of cardiovascular disease, and one after six years suffering from a recurrent stroke opposite to the side of anastomosis.

In conclusion the findings indicate that EEG analysis is of value for assessment of long term follow-up of cerebral ischaemic lesions, chronic ischaemic alterations of the brain can be improved by anastomosis, and especially in comparison to a non-operated group of stroke patients, the course of the operated one seemed to be more advantageous, as the five-year survival rate of the Framingham study for stroke victims is 69%.     

Mu and alpha rhythm in comatose children

Three anoxic comatose children had EEG alpha-like activity and in two of them mu rhythm was recorded. The paradoxical appearance of these electrical activities in comatose children seems to indicate a grave prognosis. A possible role for barbiturate treatment in this phenomenon is not excluded.     

Early electroencephalography in acute ischemic stroke: Prediction of a malignant course?

OBJECTIVE: In patients with large middle cerebral artery (MCA) infarction space occupying brain edema may lead to a malignant course with up to 80% mortality under conservative treatment. As interventional treatment strategies must be started before the deterioration occurs predictors of a malignant course are necessary. PATIENTS AND METHODS: This study reports on the results of early electroencephalography (EEG) within 24h after onset of stroke in 25 patients suffering a large MCA infarct (12 patients with a malignant and 13 with a non-malignant course). EEG analysis was performed according well-established indicators for focal as well as global changes. RESULTS: Our findings indicate that the absence of delta activity and the presence of theta and fast beta frequencies within the focus predict a benign course (p < 0.05), whereas diffuse generalized slowing and slow delta activity in the ischemic hemisphere may point to a malignant course. CONCLUSION: This study shows that in patients suffering from large MCA infarction early EEG delivers useful information to select those patients who develop malignant edema.     

Nasal Air Puff Promotes Default Mode Network Activity in Mechanically Ventilated Comatose Patients: A Noninvasive Brain Stimulation Approach

ObjectivesComa state and loss of consciousness are associated with impaired brain activity, particularly gamma oscillations, that integrate functional connectivity in neural networks, including the default mode network (DMN). Mechanical ventilation (MV) in comatose patients can aggravate brain activity, which has decreased in coma, presumably because of diminished nasal airflow. Nasal airflow, known to drive functional neural oscillations, synchronizing distant brain networks activity, is eliminated by tracheal intubation and MV. Hence, we proposed that rhythmic nasal air puffing in mechanically ventilated comatose patients may promote brain activity and improve network connectivity.Materials and MethodsWe recorded electroencephalography (EEG) from 15 comatose patients (seven women) admitted to the intensive care unit because of opium poisoning and assessed the activity, complexity, and connectivity of the DMN before and during the nasal air-puff stimulation. Nasal cavity air puffing was done through a nasal cannula controlled by an electrical valve (open duration of 630 ms) with a frequency of 0.2 Hz (ie, 12 puff/min).ResultsOur analyses demonstrated that nasal air puffing enhanced the power of gamma oscillations (30–100 Hz) in the DMN. In addition, we found that the coherence and synchrony between DMN regions were increased during nasal air puffing. Recurrence quantification and fractal dimension analyses revealed that EEG global complexity and irregularity, typically seen in wakefulness and conscious state, increased during rhythmic nasal air puffing.ConclusionsRhythmic nasal air puffing, as a noninvasive brain stimulation method, opens a new window to modifying the brain connectivity integration in comatose patients. This approach may potentially influence comatose patients’ outcomes by increasing brain reactivity and network connectivity.     

Neurophysiological identification of a late infantile form of 'neuronal lipidosis'

In the past, the classification of progressive neurological diseases in childhood has been based on either clinical or histological criteria. More recently biochemical aspects have been included and the resulting terminology has become very complex. As the electrical activity of the brain is a sensitive indicator of altered cerebral metabolism, the EEG has added further parameters in the study of neurometabolic disorders. In the present study 30 children were selected on the basis of an unusual combination of EEG features: excess of irregular slow activity, spikes, often polyphasic, and very large amplitude discharges in response to low rates of photic stimulation. All these children suffered from a disease which after an insidious onset progressed with a fairly uniform clinical course leading to death in a few years. The histological diagnosis was that of `Batten''s disease'', but other patients with the same histological diagnosis did not show either the same EEG features or a similar clinical picture. It is suggested that the EEG features make it possible to identify at an early stage, a disease entity within the wider range of conditions sometimes called `Batten''s disease''.     

Generalized Convulsive Status Epilepticus in the Adult

Summary: Status epilepticus (SE) is denned as recurrent epileptic seizures without full recovery of consciousness before the next seizure begins, or more-or-less continuous clinical and/or electrical seizure activity lasting for more than 30 min whether or not consciousness is impaired. Three presentations of SE are now recognized: recurrent generalized tonic and/or clonic seizures without full recovery of consciousness between attacks, nonconvulsive status where the patient appears to be in a prolonged "epileptic twilight state," and continuous/repetitive focal seizure activity without alteration of consciousness. Generalized convulsive status epilepticus (GCSE) encompasses a broad spectrum of clinical presentations from repeated overt generalized tonic-clonic seizures to subtle convulsive movements in a profoundly comatose patient. Thus, GCSE is a dynamic state that is characterized by paroxysmal or continuous tonic and/or clonic motor activity, which may be symmetrical or asymmetrical and overt or subtle but which is associated with a marked impairment of consciousness and with bilateral (although frequently asymmetrical) ictal discharges on the EEG. Just as there is a progression from overt to increasingly subtle clinical manifestations of GCSE, there is also a predictable sequence of progressive EEG changes during untreated GCSE. A sequence of five patterns of ictal discharges has been observed: discrete electrographic seizures, waxing and waning, continuous, continuous with flat periods, and periodic epileptiform discharges on a relatively flat background. A patient actively having seizures or comatose who exhibits any of these patterns on EEG should be considered to be in GCSE and should be treated aggressively to stop all clinical and electrical seizure activity to prevent further neurological morbidity and mortality.     

脑死亡—4例临床和电生理报告

报告4例脑死亡患者,病因:2例为脑出血,1例为癫痫连续状态,1例为脑肿瘤,分别于发病后1.5h、50h、48h、72h进入脑死亡状态。临床特点为深昏迷、呼吸停止和脑干反射消失。电生理表现为脑电图(EEG)呈平直线,脑干听觉诱发电位(BAEP)无波形,体感诱发电位(SEP)示头皮无电位,说明电生理检查是判断脑死亡的重要辅助手段。     

Functional coupling of simultaneous electrical and metabolic activity in the human brain

The relationships between brain electrical and metabolic activity are being uncovered currently in animal models using invasive methods; however, in the human brain this relationship remains not well understood. In particular, the relationship between noninvasive measurements of electrical activity and metabolism remains largely undefined. To understand better these relations, cerebral activity was measured simultaneously with electroencephalography (EEG) and positron emission tomography using [(18)f]-fluoro-2-deoxy-D-glucose (PET-FDG) in 12 normal human subjects during rest. Intracerebral distributions of current density were estimated, yielding tomographic maps for seven standard EEG frequency bands. The PET and EEG data were registered to the same space and voxel dimensions, and correlational maps were created on a voxel-by-voxel basis across all subjects. For each band, significant positive and negative correlations were found that are generally consistent with extant understanding of EEG band power function. With increasing EEG frequency, there was an increase in the number of positively correlated voxels, whereas the lower alpha band (8.5-10.0 Hz) was associated with the highest number of negative correlations. This work presents a method for comparing EEG signals with other more traditionally tomographic functional imaging data on a 3-D basis. This method will be useful in the future when it is applied to functional imaging methods with faster time resolution, such as short half-life PET blood flow tracers and functional magnetic resonance imaging.     

Spatial pattern of cerebral glucose metabolism (PET) correlates with localization of intracerebral EEG-generators in Alzheimer's disease.

BACKGROUND: Since the measurement of human cerebral glucose metabolism (GluM) by positron emission tomography (PET) and that of human cerebral electrical activity by EEG reflect synaptic activity, both methods should be related in their cerebral spatial distribution. Healthy subjects do indeed demonstrate similar metabolic and neuroelectric spatial patterns. OBJECTIVE: The aim of the study was to show that this similarity of GluM and EEG spatial patterns holds true in a population with a high variability of glucose metabolism. METHODS: We investigated healthy control subjects and patients with varying degrees of cognitive dysfunction and varying GluM patterns by applying [18F]FDG PET and EEG. RESULTS: We demonstrated that the localization of intracerebral generators of EEG correlates with spatial indices of GluM. CONCLUSION: These results indicates that EEG provides similar spatial information about brain function as GluM-PET. Since EEG is a non-invasive technique, which is more widely available and can be repeated more often than PET, this may have important implications both for neuropsychiatric research and for clinical diagnosis. However, further studies are required to determine whether equivalent EEG dipole generators can yield a diagnostic specificity and sensitivity similar to that of GluM-PET.     

Prognostic value of electroencephalography and evoked potentials in the early course of malignant middle cerebral artery infarction

Space-occupying brain edema may lead to a malignant course in patients with large middle cerebral artery infarction. Decompressive hemicraniectomy has to be initiated early to prevent further tissue damage. In this retrospective study, we analyzed electroencephalography (EEG) and evoked potentials (EPs), obtained within 24 h after onset of stroke, in 22 patients suffering from a large middle cerebral artery infarction. Our findings indicate a prognostic value of EEG and brainstem auditory EP (BAEP): the absence of delta activity and the presence of theta and fast beta frequencies within EEG-focus predicted a non-malignant course. In contrast, diffuse generalized slowing and slow delta activity in the ischemic hemisphere pointed to a malignant course. Likewise, pathological BAEP were correlated with a malignant course. The coexistence of background slowing and pathological BAEP showed the highest level of significance. In conclusion, our findings implicate an additional early application of electrophysiological methods in stroke patients. EEG and EP deliver useful information to select those patients who develop malignant edema.