The interpretation of the EEG in stupor and coma

This review discusses a variety of causes of stupor and coma and associated electroencephalographic (EEG) findings. These include metabolic disturbances such as hepatic or renal dysfunction, which are often characterized by slowing of background rhythms and triphasic waves. Hypoxia and drug intoxications can produce a number of abnormal EEG patterns such as burst suppression, alpha coma, and spindle coma. Structural lesions, either supra- or infratentorial, are reviewed. EEGs in the former may show focal disturbances such as delta and theta activity, epileptiform abnormalities, and attenuation of faster frequencies. In infratentorial lesions, the EEG may appear normal, particularly with a pontine lesion. Some patients may be encephalopathic because of ongoing epileptic activity with minimal or no motor movements. This entity, nonconvulsive status epilepticus (NCSE), is difficult to diagnose in obtunded/comatose patients, and an EEG is required to verify the diagnosis and to monitor treatment. Several EEG patterns and their interpretation in suspected cases of NCSE such as periodic lateralized epileptiform discharges (PLEDs), bilateral independent periodic lateralized epileptiform discharges (BIPLEDs), generalized periodic epileptiform discharges (GPEDs), and triphasic waves are reviewed. Other entities discussed include the locked-in syndrome, neocortical death, persistent vegetative state, brainstem death, and brain death.     

Clinical correlates and prognosis in early spindle coma.

OBJECTIVE: To determine the prognostic significance of spindle coma (SC) according to etiology and EEG reactivity.METHODS: We reviewed 15 patients with SC due to various causes within 8 days of coma to determine the prognostic significance of this EEG pattern.RESULTS: The outcome among survivors was favorable: among 13 survivors, 9 were independent in all activities of daily living (ADLs) at 6 months; 3 were dependent in all ADLs; and one remained in coma. EEG reactivity to noxious stimuli best predicted outcome: All patients (whatever the coma etiology) with EEG reactivity survived; conversely, not all patients without EEG reactivity died.CONCLUSION: In our patients, EEG reactivity independent of etiology predicted survival, neurological examination did not predict outcome. Most SC survivors had a meaningful recovery achieving all ADLs. From the literature, the cause of SC was predictive of outcome: encephalopathy, seizures and trauma had the best prognosis while hypoxia, CRA and structural lesions carried the worst. Literature review revealed that 23% of patients [56/242] died or remained in a persistent vegetative state (PVS). Best outcomes occurred when SC was due to drugs, encephalopathy or seizures: (0/14 died or were in a PVS). With trauma 15% [25/169] died or were in a PVS). Intermediate outcomes occurred with hypoxia and cardio-respiratory arrest (CRA): 33% [7/21] died or were in a PVS. The gravest outcomes occurred with brain-stem and cerebral infarctions, and tumors: 73% [22/30] died or were in a PVS.     

Information processing in severe disorders of consciousness: vegetative state and minimally conscious state.

OBJECTIVE: To study the presence of electrophysiological indicators of remaining cortical functions in patients with persistent vegetative state (PVS) and minimally conscious state (MCS). Previous electrophysiological and PET data indicated that some PVS patients have partially intact cortical processing functions. However, it remains unclear whether the reported patients were representative for PVS population or just some exceptional cases. Methods: Event-related brain responses to stimuli of different complexity levels, recorded in 98 patients with extremely severe diffuse brain injuries, 50 of which in PVS. Four main indicators of cortical functions were: (i) N1-P2 complex as an index of simple, undifferentiated cortical processing; (ii) mismatch negativity as an index of pre-attentive, probably unconscious, cortical orientation; (iii) P3 wave as an index of deep cortical analysis of physical stimuli, and (iv) brain responses to semantic stimuli. RESULTS: Cortical responses were found in all PVS patients with a background EEG activity > 4 Hz. All responses investigated, including those to semantic stimuli that indicated comprehension of meaning, occurred significantly above chance, though less frequently than in patients with severe brain injuries who were conscious. CONCLUSIONS: Cortical responses were lacking in most patients with severe EEG slowing (< 4 Hz). Follow-up data revealed that the presence of a mismatch negativity, a short disease duration, and the traumatic etiology were related to a better outcome. SIGNIFICANCE: The data show that in a subpopulation of PVS patients with preserved thalamocortical feedback connections, remaining cortical information processing is a consistent finding and may even involve semantic levels of processing.     

Serial EEG in intractable epilepsy

We compared serial EEGs performed at admission, discharge, and follow-up (mean, 25 months) to clinical outcome in 70 patients with intractable epilepsy. The diagnosis in each case was confirmed by intensive monitoring. EEG features evaluated were background slowing, focal slowing, and focal, bilateral, or generalized epileptiform discharges. Clinical measures were seizure frequency and medication toxicity. No statistically significant correlations were found between improvement in any EEG feature and any clinical measure. EEG did not predict which patients would benefit from intensive monitoring. Serial EEGs may be of little value in assessing the results of treatment in patients with severe epilepsy.     

Pyridoxine-dependent epilepsy: EEG investigations and long-term follow-up.

The EEG features and clinical correlates were investigated before, directly after, and on long-term follow-up after initiation of pyridoxine therapy in 6 patients with B6-dependent epilepsy. At each phase, the EEG provided important diagnostic and prognostic information. Pre-B6 3 neonates manifested a unique EEG pattern of generalized bursts of 1-4 Hz sharp and slow activity. This pattern has not been previously described in neonates with B6 dependency and in this age group appears to be highly suggestive of the diagnosis. Five patients experienced an apparent initial response to traditional antiepileptics. The parenteral pyridoxine test, performed in all 5, and repeated in 3, proved to be a highly reliable and reproducible diagnostic test. After 50-100 mg of B6 there was cessation of clinical seizures within minutes and of paroxysmal discharges within hours. On long-term follow-up (3-28 years) all 6 patients were seizure free on B6 (10-100 mg/day) monotherapy. Recurrences of seizures and of specific sequential EEG changes (background slowing, photoparoxysmal response, spontaneous discharges, stimulus-induced myoclonus, generalized seizures) occurred upon B6 withdrawal. Long-term prognosis correlated with the EEG. Two patients had persistently abnormal EEG backgrounds and were moderately to severely retarded, while 4 had normal EEGs with normal or near normal development.     

Seizure outcomes of posterior reversible encephalopathy syndrome and correlations with electroencephalographic changes

RationaleSeizures are among the most common clinical presentations of posterior reversible encephalopathy syndrome (PRES). This syndrome has rarely been reported to cause chronic epilepsy or persistent cortical dysfunction. The prognostic value of EEG findings during PRES is unknown. We retrospectively evaluated EEG characteristics in patients with PRES in a single medical center. We also evaluated the long-term outcome regarding seizure occurrence beyond the acute phase in these patients.MethodsWe searched a radiology database at the University of Minnesota from 1997 to 2012 to identify patients with clinically and radiologically diagnosed PRES. Among the patients with PRES, we reviewed MRI images, EEG findings, clinical manifestations including seizure occurrences, and clinical outcomes beyond the acute phase.ResultsSeventy-five patients were included in the study. Fifty-eight out of seventy-five (77.3%) patients with PRES had seizures. A total of 48 EEG studies were performed in 38 patients. Generalized slowing was the most common EEG pattern. Among the 38 patients who had EEGs, 37 (97.3%) patients had diffuse or focal slowing of the background, and 11 (28.9%) patients had IEDs. Four out of seventy-five (5.3%) patients had seizures later than one month beyond their hospitalization for PRES. None of these 4 patients had seizures before the episode of PRES. Two patients developed chronic epilepsy, with seizures occurring later than one year after the PRES.ConclusionMost patients who had seizures or who had epileptiform activities in EEG during PRES did not subsequently develop chronic epilepsy. No patient developed chronic epilepsy in the absence of clinical seizures during PRES. Posterior reversible encephalopathy syndrome may infrequently be associated with subsequent development of symptomatic epilepsy.     

Neurophysiological abnormalities in adolescents with type I Crigler-Najjar syndrome.

We report neurophysiological abnormalities in two adolescents with type I Crigler-Najjar syndrome, an autosomal recessive disorder characterized by severe unconjugated hyperbilirubinemia. Electroencephalograms (EEGs) demonstrated frequent generalized single and polyspikes, and background slowing. Normal pattern reversal evoked responses (PRVERs) and normal central brain-stem auditory evoked responses (BAERs) were recorded in both patients. These findings differ from the EEG triphasic wave pattern seen in the EEG in hepatic encephalopathy and the central BAER abnormalities seen in many infants with kernicterus. Thus these findings most likely result from complex multifactorial processes and are not simply the result of the hyperbilirubinemia which is common to all 3 conditions.     

The use of routine EEG in acute ischemic stroke patients without seizures: generalized but not focal EEG pathology is associated with clinical deterioration

Purpose: Specialized electroencephalography (EEG) methods have been used to provide clues about stroke features and prognosis. However, the value of routine EEG in stroke patients without (suspected) seizures has been somewhat neglected. We aimed to assess this in a group of acute ischemic stroke patients in regard to short-term prognosis and basic stroke features. Methods: We assessed routine (10–20) EEG findings in 69 consecutive acute ischemic stroke patients without seizures. Associations between EEG abnormalities and NIHSS scores, clinical improvement or deterioration as well as MRI stroke characteristics were evaluated. Results: Mean age was 69 ± 18 years, 43 of the patients (62.3%) were men. Abnormal EEG was found in 40 patients (58%) and was associated with higher age (p = 0.021). The most common EEG pathology was focal slowing (30; 43.5%). No epileptiform potentials were found. Abnormal EEG in general and generalized or focal slowing in particular was significantly associated with higher NIHSS score on admission and discharge as well as with hemorrhagic transformation of the ischemic lesion. Abnormal EEG and generalized (but not focal) slowing were associated with clinical deterioration (?p = 0.036, p = 0.003). Patients with lacunar strokes had no EEG abnormalities. Conclusions: Abnormal EEG in general and generalized slowing in particular are associated with clinical deterioration after acute ischemic stroke. The study demonstrates the value of routine EEG as a simple diagnostic tool in the evaluation of stroke patients especially with regard to short-term prognosis.     

Utility of Neurodiagnostic Studies in the Diagnosis of Autoimmune Encephalitis in Children

BackgroundAutoimmune encephalitis is currently a clinical diagnosis without widely accepted diagnostic criteria, often leading to a delay in diagnosis. The utility of magnetic resonance imaging (MRI) and electroencephalography (EEG) in this disease is unknown. The objective of this study was to identify disease-specific patterns of neurodiagnostic studies (MRI and EEG) for autoimmune encephalitis in children.MethodsWe completed a retrospective chart review of encephalopathic patients seen at a large pediatric hospital over a four year interval. Clinical presentation, autoantibody status, and MRI and EEG findings were identified and compared. Individuals with autoantibodies were considered “definite” cases, whereas those without antibodies or those with only thyroperoxidase antibodies were characterized as “suspected.”ResultsEighteen patients met the inclusion criteria and autoantibodies were identified in nine of these. The patients with definite autoimmune encephalitis had MRI abnormalities within limbic structures, most notably the anteromedial temporal lobes (56%). Only individuals with suspected disease had nontemporal lobe cortical lesions. Sixteen patients had an EEG and 13 (81%) of these were abnormal. The most common findings were abnormal background rhythm (63%), generalized slowing (50%), focal slowing (43%), and focal epileptiform discharges (31%). Sleep spindle abnormalities occurred in 38% of patients. There were no specific differences in the EEG findings between the definite and suspected cases. Focal EEG findings only correlated with a focal lesion on MRI in a single definite case.ConclusionsPediatric patients with definite autoimmune encephalitis have a narrow spectrum of MRI abnormalities. Conversely, EEG abnormalities are mostly nonspecific. All patients in our cohort had abnormalities on one or both of these neurodiagnostic studies.     

Clinical and electrographic features of epileptic spasms persisting beyond the second year of life

PURPOSE: Few reports detailing the electroclinical features of epileptic spasms persisting beyond infancy have been published. We sought to characterize this unique population further. METHODS: We retrospectively reviewed the clinical and video-EEG data on 26 patients (4-17 years; mean, 93 months) with a confirmed diagnosis of epileptic spasms and who were evaluated at our tertiary referral center between 1993 and 2000. RESULTS: In half of our cases, epileptic spasms were associated with disorders of neuronal migration, severe perinatal asphyxia, and genetic anomalies. Interictal EEGs showed generalized slowing in the majority of patients, and a slow-wave transient followed by an attenuation of the background amplitude was the most common ictal EEG pattern associated with an epileptic spasm (19 cases). Other seizure types (number of cases in parentheses) included tonic seizures with or without a preceding spasm (13), partial seizures (11), myoclonic seizures (11), generalized tonic-clonic seizures (six), atypical absence seizures (two), and atonic seizures (one). Cases with a more organized EEG background (especially with frequencies > or =7 Hz) were more likely to have better cognition. Continued disorganization of the EEG background and persistence of hypsarrhythmia were associated with poor developmental outcome. CONCLUSIONS: Patients with epileptic spasms persisting beyond age 2 years constitute a truly refractory population, one that should be better recognized by clinicians. Interestingly, although many therapies resulted in a >50% reduction in seizures, neither neurocognitive function nor quality of life was substantially improved with intervention. The interictal EEG background is the most helpful in predicting neurologic outcome.     

The persistent vegetative state in children: report of the Child Neurology Society Ethics Committee.

Increasing concern about children in a persistent vegetative state (PVS) prompted a survey of members of the Child Neurology Society regarding aspects of the diagnosis and management of this disorder. Major findings of those responding to this survey (26% response rate) were as follows: (1) 93% believed that a diagnosis of PVS can be made in children, but only 16% believed that this applied to infants younger than 2 months and 70% in the 2-month to 2-year group; (2) a period of 3 to 6 months was believed to be the minimum observation period required before a diagnosis of PVS could be made; (3) 86% believed that the age of the patient would affect the duration of time needed to make the diagnosis of PVS; (4) 78% thought a diagnosis of PVS could be made in children with severe congenital brain malformations; (5) 75% believed that neurodiagnostic studies would be of value and supportive of the clinical diagnosis of PVS; (6) members' opinions as to the average life expectancy (in years) for the following age groups after the patients were considered vegetative were: newborn to 2 months, 4.1; 2 months to 2 years, 5.5; 2 to 7 years, 7.3; and more than 7 years, 7.4; (7) 20% believed that infants and children in a PVS experience pain and suffering; and (8) 75% "never" withhold fluid and nutrition from infants and children in a PVS and 28% "always" give medication for pain and suffering.(ABSTRACT TRUNCATED AT 250 WORDS)     

Vestibular neuronitis; a neurological and neurophysiological evaluation

ABSTRACT- Neurological and neurophysiological findings were retrospectively reviewed in a group of 50 patients with vestibular neuronitis (VN). The onsets of VN were found to be clustered in the period from August to January. A preceding infection was reported by 36% of the patients. Neurological examinations did not reveal any other relevant signs than a spontaneous nystagmus during the acute phase. The results of routine laboratory tests and cerebrospinal fluid tests were within normal limits. EEG was recorded in 37 patients; 15 patients had a definitely abnormal EEG, with a slowing of the dominant occipital rhythm or more generalized diffuse slowing in 12 cases. 5 patients, 3 of them without slowing of the background activity, had a distinct focal disturbance of intermittent slow activity in the temporal region. In control recordings, an improvement was seen in the slowing of the background activity but not in the focal disturbances. Brain-stem auditory evoked responses (BSER) were recorded in 12 patients, 5 of whom had abnormal responses. The seasonal clustering of VN onsets and the association of VN with overt infections further suggest its infectious pathogenesis. The observed EEG and BSER disturbances suggest a sub-clinical brainstem involvement in some cases of VN.     

Persistent vegetative state. Extension of the syndrome to include chronic disorders

Twenty-nine institutionalized patients had the vegetative state as a sequela of chronic progressive neurologic disorders. During three years, the state was persistent; none improved, ten died. Eight similar patients were reviewed retrospectively post mortem. Eight patients with severe dementia, while acutely ill or sedated, temporarily met the criteria for persistent vegetative state (PVS) but improved when the underlying condition was treated. Abnormalities on electroencephalography or computed tomographic scan are not specific for the PVS. Electroencephalograms were normal in three patients with PVS. The computed tomographic scans showed extensive destruction of the brain parenchyma but were not different from those of severely demented patients without the PVS. The PVS is a feature of the terminal phase of several progressive neurologic disorders. Patients should be treated without excessive intervention.     

Interictal EEG changes in eclampsia

The pathogenesis of seizures and encephalopathy in eclampsia remains obscure even today. There are only a few reports on EEG findings in eclampsia. This is a report of the interictal EEG changes in 8 patients with eclampsia who were evaluated prospectively. The major EEG changes observed were (1) slowing of the background activity (generalized slowing in 4 patients and focal slowing in 3 patients) and (2) intermittent spike and sharp wave transients (5 patients). These abnormalities had disappeared in all except 2 patients when the EEG was repeated on the seventh day. A comparison is drawn between eclampsia and hypertensive encephalopathy for the clinical, EEG and CT/MRI findings. The pathogenesis of seizures and encephalopathy could be similar in these two conditions. It is worth while considering then; EEG changes while planning the treatment of eclampsia.     

Electroencephalographic findings in Kufs disease.

OBJECTIVE: To characterize the electroencephalographic (EEG) findings in patients with Kufs disease, the adult autosomal recessive form of neuronal ceroid-lipofuscinosis. METHODS: We reviewed the EEG findings in 5 patients with biopsy-proven Kufs disease from our institution and 14 case reports of Kufs disease in the literature. The criteria used for patient inclusion were clinical evidence of a progressive neurodegenerative disorder, biopsy-proven evidence of Kufs disease, and EEG recordings during the course of the illness. RESULTS: One patient had phenotype A with generalized atypical spike and slow wave complexes and marked photoparoxysmal responses, particularly at low flash frequencies. Three patients had phenotype B with generalized slowing. One patient in the miscellaneous category showed focal sharp and spike waves and quasi-periodic slow waves maximal over anterior regions of the head. Review of the literature identified 14 case reports that met the inclusion criteria. CONCLUSIONS: The inheritance, mechanism, and manifestations of Kufs disease are not well understood. EEG findings may guide clinicians toward a confirmatory pathological diagnosis and distinguish various phenotypes of this disorder. SIGNIFICANCE: The EEG may assist in the diagnosis of Kufs disease.     

EEG features in idiopathic generalized epilepsy: clues to diagnosis

PURPOSE: To investigate the EEG profile and its contribution for diagnosis and management in a group of patients with a clinical diagnosis of idiopathic generalized epilepsy (IGE) who were referred to a tertiary hospital. METHODS: We retrospectively studied clinical and EEG features of 180 consecutive patients with IGE. Eighty patients were diagnosed with juvenile myoclonic epilepsy (JME), 35 had absence epilepsy (AE), 13 had generalized tonic-clonic seizures on awakening (GTCS-A), 28 had generalized tonic-clonic seizures only (TCS), and 24 had adult-onset idiopathic generalized epilepsy (AIGE). The EEGs were classified in typical (synchronous generalized spike or polyspikes-and-wave discharges with normal background), atypical (with clear focalities or asymmetries), and normal. RESULTS: The 493 EEG exams were analyzed. The first EEG was normal in 45% of the 180 patients, and only 33% had typical abnormalities. AE had a higher proportion of typical examinations and needed fewer sequential examinations to register a typical abnormality compared with the other groups. By contrast, the serial EEG profile of TCS and AIGE showed a higher proportion of normal and atypical EEG findings. CONCLUSIONS: These findings support previous recommendations that IGE patients should be treated with appropriate therapy based on clinical history. Waiting for a typical abnormal EEG pattern can generate an unacceptable delay in the correct diagnosis and treatment of these patients. In patients with long-term epilepsy, the diagnosis may be difficult. Furthermore, serial EEGs can help to elucidate the syndromic diagnosis, especially in patients with TCS and AIGE.     

Concomitant administration of sodium dichloroacetate and thiamine in west syndrome caused by thiamine-responsive pyruvate dehydrogenase complex deficiency

IRDA (intermittent rhythmic delta activity) is an abnormal generalized EEG pattern that is not specific to any single etiology and can occur with diffuse or focal cerebral disturbances. To determine whether different electrographic features of IRDA and associated EEG findings can differentiate underlying focal from diffuse brain disturbances, we performed a blind analysis of 58 consecutive EEGs with an IRDA pattern, recorded from 1993 until 1996, in which we evaluated posterior background activity, focal slowing and IRDA characteristics (frequency, distribution, duration, symmetry and abundance). The clinical diagnosis, state of consciousness and CT brain findings were retrieved from the patients' hospital records. There were 58 patients (33 females; mean age, 58+/-21 years). Twelve (21%) had only focal brain lesions, while 46 (79%) had diffuse brain abnormalities, (15 diffuse structural, 19 metabolic abnormalities, 12 postictal). Normal consciousness and focal EEG slowing were more frequent in patients with focal abnormalities, however, this was not statistically significant. Of the patients with focal abnormality, 11 (92%) had normal posterior background activity either bilaterally (n=4) or contralateral to the focal lesion (n=7). Bilaterally normal posterior background activity was observed in about 30% in both groups. Bilaterally abnormal posterior background activity was apparent in one patient (8%) with focal brain lesion and in 31 patients (67%) with diffuse brain abnormalities (P<0.0001). There were no significant differences in IRDA electrographic features between the focal group and the group with diffuse brain disturbances. We conclude that IRDA morphology cannot distinguish between focal and diffuse brain abnormalities.     

The EEG in the diagnosis of subdural empyema

The EEG findings in 9 patients with a subdural empyema are reported. In all cases the EEG, recorded before the diagnosis had been established, contained focal zeta waves, extensive unilateral depression of cortical activity and, in all but one, a diffuse slowing of the background activity. This combination has not been reported before in the literature and it is concluded that in its presence the existence of a subdural empyema should be seriously considered. Comparison with CT scan findings in 3 cases indicated that sometimes EEG may be more sensitive than CT scanning in the diagnosis of subdural empyema. The value of EEG and CT scan in the diagnosis of patients presenting with an acute or subacute bacterial meningo-encephalitis is briefly discussed.     

Clinicophysiological study of multimodality evoked potentials and computed tomographic findings in persistent vegetative state

The auditory brainstem response (ABR), short latency somatosensory evoked potential (SSEP) and visual evoked potential (VEP) of patients in the persistent vegetative state (PVS) are reported, and the correlations between the electrophysiological findings and the CT scan findings with the three clinical grades of the PVS (transitional, incomplete and complete vegetative syndromes) are discussed. Twenty two patients in a vegetative state caused by subarachnoid hemorrhage (3), hypertensive intracerebral hemorrhage (5), cerebral infarction (6), head injury (3), cerebral anoxia (4) and brain tumor (1). Each evoked response was evaluated for the presence or absence of abnormalities and assigned a grade ranked I to III. Briefly an evoked response was assigned a grade I, II, III if it satisfied the respective criteria of normal, moderately abnormal and severely abnormal or absent electrical activity. On the other hand CT scan findings in the PVS were evaluated for abnormal low density areas, ventricular dilatation and enlargement of the sulci and cisterns indicative of atrophy of the brain parenchyma. SSEP and VEP were better correlated with the clinical grade than ABR, and upper brainstem atrophy and abnormal low density area in CT scan findings were more valuable as an index to expresses the clinical features than ventricular dilatation. On the basis of these results, it is concluded that studies of ABR, SSEP and VEP associated with CT scan findings in the PVS could be a useful diagnostic aid to evaluate the lesions of these patients.     

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.