Clinical correlation of occipital intermittent rhythmic delta activity

Pretreatment electroencephalographic features in patients with childhood absence epilepsy

OBJECTIVE

To analyze the ictal and interictal electroencephalographic (EEG) features in newly diagnosed childhood absence epilepsy (CAE) and determine the association between seizure onset topography, interictal focal spike-wave discharges (FSWDs) and accompanying clinical features of absence seizures.

METHODS

The authors searched the EEG database for a definite diagnosis of CAE according to ILAE 2017 criteria. Video-EEGs of untreated pediatric patients during sleep and wakefulness were evaluated retrospectively.

RESULTS

The study included 47 patients (25 males, 22 females). Interictal FSWDs were observed in 49% of patients with CAE during wakefulness and in 85.1% during sleep (p = 0.001). Interictal FSWDs were most frequently observed in the frontal regions (awake: 34%; asleep: 74.5%), followed by the posterior temporoparietooccipital region (awake: 21.2%; asleep: 36.1%), and the centrotemporal region (awake: 6.4%; asleep: 8.5%). Eleven patients (23.4%) had polyspikes during sleep. Both bilateral symmetric and asymmetric seizure onset were noted in 32%, whereas focal seizure onset was observed in 14.9% of the patients. Absence seizures with and without motor components were seen in 72.3% and 61.7% of patients, respectively, and in 33% of patients both occurred. There were no associations between the existence of interictal FSWDs, focal/asymmetric seizure onset, and absence seizures with and/or without motor components.

CONCLUSION

Asymmetric and/or focal seizure onset, interictal FSWDs, and absence seizures with motor components are commonly observed in drug-naive CAE. This study found no association between seizure onset topography, interictal FSWDs, and semiological features of absence seizures.

Brainwaves beyond diagnosis: Wider applications of electroencephalography in idiopathic generalized epilepsy

Electroencephalography (EEG) has long been used as a versatile and noninvasive diagnostic tool in epilepsy. With the advent of digital EEG, more advanced applications of EEG have emerged. Compared with technologically advanced practice in focal epilepsies, the utilization of EEG in idiopathic generalized epilepsy (IGE) has been lagging, often restricted to a simple diagnostic tool. In this narrative review, we provide an overview of broader applications of EEG beyond this narrow scope, discussing how the current clinical and research applications of EEG may potentially be extended to IGE. The current literature, although limited, suggests that EEG can be used in syndromic classification, guiding antiseizure medication therapy, predicting prognosis, unraveling biorhythms, and investigating functional brain connectivity of IGE. We emphasize the need for longer recordings, particularly 24-h ambulatory EEG, to capture discharges reflecting circadian and sleep-wake cycle-associated variations for wider EEG applications in IGE. Finally, we highlight the challenges and limitations of the current body of literature and suggest future directions to encourage and enhance more extensive applications of this potent tool.

Occipital intermittent rhythmic delta activity (OIRDA) in pediatric focal epilepsies: A case series

In this case series, we have identified an atypical pattern of OIRDA (Occipital intermittent rhythmic delta activity) on the electroencephalograms (EEGs) of three pediatric patients with self-limited focal epilepsies, including Childhood Epilepsy with Centrotemporal Spikes (CECTS), and Panayiotopoulos syndrome (PS). Previously, OIRDA was described as a symmetric sinusoidal occipital-maximal activity, often associated with childhood idiopathic generalized epilepsies, although it was also reported among other physiologic or pathological entities including focal epilepsy. We have observed in our case series that OIRDA, without prominent field effect, is lateralized or maximal on the hemispheric side ipsilateral to the more defining epileptiform discharges in these focal epilepsies. They also exhibit a notched morphology due to the intermixed sharp wave activities, although the sharp waves are not occurring repetitively. This report provides additional evidence that OIRDA can be associated with a spectrum of idiopathic focal epilepsies and may suggest a cortical origin of OIRDA in these patients as opposed to a hypothesized subcortical generator in patients with primary generalized absence epilepsy, even though further investigation is warranted for either hypothesis.

The Relationship between Carotid Doppler Ultrasound and EEG Metrics in Healthy Preschoolers and Adults

Despite widespread using electroencephalography (EEG) and Doppler ultrasound in pediatric neurology clinical practice, there are still no well-known correlations between these methods that could contribute to a better understanding of brain processes and development of neurological pathology. This study aims to reveal relationship between EEG and Doppler ultrasound methods. We compared two cohorts of adults and preschool children with no history of neurological or mental diseases. The data analysis included investigation of EEG and carotid blood flow indexes, which are significant in neurological diagnosis, as well as calculation of linear and non-linear EEG parameters and ratios between the systolic peak velocities of carotid arteries and carotid blood asymmetry. We have found age-dependent correlations between EEG and power Doppler ultrasound imaging (PDUI) data. Carotid blood flow asymmetry correlated with delta-rhythm power spectral density only in preschoolers. The ratios of blood flow velocities in the internal carotid arteries to those in the common carotid arteries correlated with higher peak alpha frequency and lower fractal dimension; moreover, they were associated with lower Epworth sleepiness scale scores. The study revealed significant correlations between EEG and PDUI imaging indexes, which are different for healthy children and adults. Despite the fact that the correlations were associated with non-clinical states such as overwork or stress, we assumed that the investigated parameters could be applicable for clinical trials.

Electroencephalographic features associated with intermittent rhythmic delta activity

OBJECTIVE

To investigate the clinical importance of intermittent rhythmic delta activity (IRDA) in terms of accompanying electrophysiological findings on EEG and their association with IRDA.

METHODS

We retrospectively assessed all EEG studies recorded in our institution from 2011 to 2017. Patients with intermittent rhythmic delta activity (IRDA) in EEGs were included. Clinical data were collected from charts of the patients with IRDA.

RESULTS

We identified 69 EEGs with IRDA in 58 patients from a total of 18,625 EEG recordings. The most common IRDA type was frontal IRDA (FIRDA; 55%), followed by temporal IRDA (TIRDA; 28.9%). Unilateral (UL) distribution was present in 36.8% of FIRDAs and 95% of TIRDAs. The frequency of focal epileptiform discharges (FED) was 78.5% in UL FIRDA group and 89.4% in UL TIRDA group. Among the EEGs with FEDs, in UL FIRDA group 90.9% and in UL TIRDA group 70.5% of the FEDs were ipsilateral. Concordance of focal structural brain lesions and FEDs with UL TIRDA was 30.7%, and with UL FIRDA was 50%. UL FIRDA had a 71.4% positive predictive value for ipsilateral focal epileptic focus and UL TIRDA had 63.1%. The frequency of focal structural lesions and FEDs were significantly higher in the UL FIRDA group than bilateral FIRDA group (P=0.03; P=0.01). Among the patients with focal structural lesions, ipsilateral FED association is significantly higher in the UL FIRDA group than BL FIRDA group (P=0.03).

CONCLUSIONS

UL FIRDA is more likely to indicate a focal lesion and a focal epileptic focus compared to bilateral FIRDA, and it had similar characteristics to UL TIRDA. It can be considered that UL FIRDA has as good a lateralizing value for ipsilateral focal epileptic focus and focal lesion as UL TIRDA.

Prognosis of Periodic and Rhythmic Patterns in Adult and Pediatric Populations

Although electrographic seizures are known to have an outcome on clinical prognosis, the implications of periodic and rhythmic patterns are less clear. The outcomes of adults with these patterns have been reported and are often poor; however, the outcomes in pediatric populations are less well characterized and may be different than in the adult population, as the etiologies of periodic and rhythmic patterns may differ in children and adults. In adults, generalized periodic discharges are highly associated with toxic-metabolic disturbances, infection, and anoxic injury; 30% to 64% of patients have poor outcomes. By contrast, in pediatric patients, generalized periodic discharges are more commonly associated with refractory status epilepticus, with good outcomes in 50% to 77%. The underlying etiology of the periodic or rhythmic pattern has a large influence on overall morbidity and mortality.

Generalized and Lateralized Rhythmic Patterns

The relationship between generalized and lateralized rhythmic delta activity (RDA) and seizures is more ambiguous than the relationship between periodic discharges and seizures. Although frontally predominant generalized RDA is not associated with seizures, occipitally predominant RDA may be associated with the absence of seizures. Lateralized RDA seems to be more strongly associated with the presence of seizure activity. Appropriate recognition of generalized RDA and lateralized rhythmic delta activity may be confounded by benign etiologies of RDA, such as phi rhythm, slow alpha variant, subclinical rhythmic electrographic discharges of adults, or hyperventilation-induced high-amplitude rhythmic slowing. Angelman syndrome and NMDA-receptor antibody encephalitis can also produce morphologically distinct patterns of RDA.

Clinical associations of occipital intermittent rhythmic delta activity

Association of occipital intermittent rhythmic delta activity with absence seizures has been well documented in the published literature. Two recent studies have also described an association with focal seizures. After obtaining approval from our Institutional Review Board, all electroencephalograms with occipital intermittent rhythmic delta activity at our institution between July 1, 2006 and December 31, 2009 were identified. Charts of these patients were reviewed to collect clinical data. A matched comparison group was assembled. Thirty-one of the patients who met criteria had evaluable clinical data. Fifteen had generalized seizures (9 absence; 2 tonic-clonic; 3 absence and tonic-clonic; 1 absence, tonic-clonic, myoclonic, and atonic). Eleven had focal seizures. One had both generalized tonic-clonic and focal seizures. Events in 1 were nonepileptic in nature. Documentation was inadequate for seizure classification in 3. There was a statistically significant difference between the study and comparison groups for absence seizures, but not for focal seizures.

Age- and genotype-related neurophysiologic reactivity to oxidative stress in healthy adults

The epsilon4 allele of the apolipoprotein E gene (ApoE), as well as aging increase the risk of Alzheimer's and vascular diseases. Electroencephalogram (EEG) reactivity to hyperventilation (HV) depends on hypocapnia-induced cerebral vasoconstriction, which may be impaired in subjects with subclinical cerebrovascular disease. Quantitative EEG at rest and under 3-minute HV was examined in 125 healthy subjects divided into younger (age range 28-50) and older (age range 51-82) cohorts and stratified by ApoE genotype. The younger ApoE-epsilon4 carriers had excessive EEG reactivity to HV characterized by the manifestation of high-voltage delta, theta activity and sharp waves, and larger HV-induced changes in EEG relative powers than in the younger ApoE-epsilon4 noncarriers. EEG reactivity to HV decreased with aging, and in the ApoE-epsilon4 carriers the decrease was more pronounced than in the ApoE-epsilon4 noncarriers. The older ApoE-epsilon4 carriers had smaller HV-induced changes in EEG relative powers than the older ApoE-epsilon4 noncarriers. A marked decline of EEG reactivity to HV in the older ApoE-epsilon4 carriers suggests the possible impact of vascular factors on the pathogenesis of ApoE-induced Alzheimer disease.

Intermittent rhythmic delta activity patterns

Intermittent rhythmic delta activity is a typical EEG pattern that was originally described by W.A. Cobb in 1945 (J Neurol Neurosurg Psychiatr 1945;8:65-78). It may be classified into three distinct forms according to the main cortical region involved on the EEG: frontal (FIRDA), temporal (TIRDA), and occipital (OIRDA) intermittent delta activity. This article is a review of the main aspects of these patterns, with a special focus on EEG features and problems that may be encountered during interpretation of these patterns. In contrast to FIRDA and OIRDA, TIRDA is highly indicative of ipsilateral pathology. OIRDA and TIRDA are highly correlated with epilepsy, whereas FIRDA is a rather nonspecific EEG pattern.

Endogenous adenosine A1 receptor activation underlies the transient post-ischemic rhythmic delta EEG activity

OBJECTIVE

Emergence of slow EEG rhythms within the delta frequency band following an ischemic insult of the brain has long been considered a marker of irreversible anatomical damage. Here we investigated whether ischemic adenosine release and subsequent functional inhibition via the adenosine A(1) receptor (A(1)R) contributes to post-ischemic delta activity.

METHODS

Rats were subjected to episodes of non-injuring transient global cerebral ischemia (GCI) under chloral hydrate anesthesia.

RESULTS

We found that a GCI lasting only 10s was enough to induce a brief discharge of rhythmic delta activity (RDA) with a peak frequency just below 1 Hz quantified as an increase by twofold of the 0.5-1.5 Hz spectral power. This post-ischemic RDA did not occur following administration of the A(1)R antagonist 8-cyclopentyl-1,3-dipropylxanthine. Nevertheless, a similar RDA could be induced in rats not subjected to GCI, by systemic administration of the A(1)R agonist N(6)-cyclopentyladenosine.

CONCLUSIONS

Our data suggest that A(1)R activation at levels that occur following cerebral ischemia underlies the transient post-ischemic RDA.

SIGNIFICANCE

It is likely that the functional, thus potentially reversible, synaptic disconnection by A(1)R activation promotes slow oscillations in the cortical networks. This should be accounted for in the interpretation of early post-ischemic EEG delta activity.

EEG alterations in non-demented individuals related to apolipoprotein E genotype and to risk of Alzheimer disease

Identification of preclinical markers is required for early diagnosis of Alzheimer's disease (AD) and cognitive dysfunction in advancing age. Quantitative EEG was examined in 145 individuals with AD, their unaffected relatives and unrelated individuals. The AD patients and their relatives were stratified by ApoE genotype. The resting EEG parameters were severely changed in AD patients, and in patients carrying the ApoE epsilon4 allele the decrease in alpha power was higher than in epsilon4 non-carriers. The resting EEG parameters were indistinguishable in AD relatives with different ApoE genotypes and similar to EEG pattern in common population. Under hyperventilation the presence of the epsilon4 allele in AD relatives was associated with the manifestation of synchronous high-voltage delta-, theta-activity and sharp-waves, pronounced decrease in alpha and increase in delta and theta relative powers. The data suggest that neurophysiological endophenotype of non-demented individuals at genetic risk for AD, characterized by increased excitability and dysfunction of deep brain and alpha rhythm-generating structures, may be revealed decades before the first clinical symptoms of presumable dementia.

Clinical Correlates of Occipital Intermittent Rhythmic Delta Activity (OIRDA) in Children

PURPOSE

The clinical significance of occipital intermittent rhythmic delta activity (OIRDA) on the electroencephalogram has not been fully established. Recent studies suggest that this pattern occurs almost exclusively in children and is probably of epileptic origin in most cases. We sought to characterize the electrographic features and clinical correlates of occipital intermittent rhythmic delta activity.

METHODS

A review of 697 consecutive pediatric electroencephalograms detected occipital intermittent rhythmic delta activity in 24 studies. Mean patient age was 7.96 years.

RESULTS

Recent convulsions and absence seizures constituted the main indications for the study. Concomitant, independent epileptiform activity was noted in half of the cases. This activity was focal in all but one case. Conversely, in most cases of absence seizures, epileptiform activity intermixed with occipital intermittent rhythmic delta activity. Furthermore, the frequency of the occipital rhythmic discharges in studies of children with absences was generally faster (3-4 Hz) than in localization-related epilepsy (2-3 Hz). Most patients were awake when occipital intermittent rhythmic delta activity occurred. Chronic encephalopathy was seen in one child only. Analysis of neuroimaging studies in eight cases revealed no structural pathology associated with occipital intermittent rhythmic delta activity.

CONCLUSIONS

Occipital intermittent rhythmic delta activity is probably an epileptiform pattern, although it is noted occasionally in encephalopathic children. Its electrographic characteristics appear to differ between localization-related epilepsy and primary generalized epilepsy, particularly absence seizures.

Occipital intermittent rhythmic delta activity in absence epilepsy

Occipital intermittent rhythmic delta activity (OIRDA) is considered good prognostic factor in typical absences (TA). We report electroclinical evolution in 14 patients with TA and OIRDA, which performed video-EEG. Seven patients were female; 9 had childhood absence epilepsy and the others did not present electroclinical characteristics for syndromic classification according to ILAE's classification (1989). Pyknolepsy was referred to in 13; TA was the only seizure type in 13; one had generalized tonic-clonic seizures (GTCS) and three had myoclonic jerks during TA. VPA monotherapy controlled seizures in 11, diVPA and ESM, in one each. After seizure control EEG normalized in 10 while in three, spike-wave complexes (SWC) persisted, accompanied by OIRDA in one. Finally in another, seizures were not controlled and SWC and OIRDA persisted. In conclusion, we observed in this series of TA and OIRDA with onset before 10 years, pyknolepsy as common finding and few GTCS. VPA controlled seizures in most cases and EEG normalized in 76.92%. We suggest that OIRDA could be considered good prognostic factor in TA associated with SWC and of epileptiform nature leading to appropriate investigation.

Electroencephalographic Assessment of Coma

SUMMARY

Altered mental status ranging from confusion to deep unresponsiveness can be described as coma. Electroencephalography is an important tool in assessing comatose patients. Some EEG patterns are seen with lighter stages of coma and have a good prognosis, whereas others are seen in deep, often irreversible coma. These EEG patterns carry a much more grave prognosis. This paper discusses the various EEG features seen in coma, ranging from intermittent rhythmic delta activity to electrocerebral inactivity. A discussion regarding etiology and prognosis is presented after the EEG pattern is described in detail. Special EEG features, such as alpha coma, beta coma, spindle coma, etc., are discussed toward the end.

Occipital intermittent rhythmic delta activity only following eye closure in atypical CNS Salmonellosis

OBJECTIVE

A statement recently published on the base of a large retrospective analysis, report that the occipital intermittent rhythmic delta activity (OIRDA) "is associated with epilepsy but not acute encephalopathy" [Gullapalli and Fountain. J Clin Neurophysiol 2003;20:35-41]. Our aim is to report, the exception from a child with an intermittent fever, in which the finding of an occipital intermittent rhythmic delta activity (OIRDA) following the eye closure in the EEG recording was the first clinical sign addressing to a CNS involvement.

METHODS

To review the record from a five-year-old girl with a normal basal electroencephalogram and OIRDA that only appeared following eye closure.

RESULTS

We found OIRDA associated with atypical CNS Salmonellosis. Brain MRI and CSF examination confirmed an acute encephalopathy, which was due to Salmonella infection. The only symptoms of the infection were episodes of nightly fever that had lasted for four weeks, sometimes associated with headache and vomiting. Both OIRDA only induced by eye closing and other symptoms disappeared after starting antimicrobial therapy.

CONCLUSIONS

OIRDA only following eye closure is a non-specific abnormality and the present findings, based on a single case, merely indicate that intracranial infection is among the possible causes.

SIGNIFICANCE

The new clinical association is certainly worth recording, as the presence of this electrophysiological sign may provoke clinicians to then delve further into a diagnostic work up.

BOLD-contrast functional MRI signal changes related to intermittent rhythmic delta activity in EEG during voluntary hyperventilation-simultaneous EEG and fMRI study

Differences in the blood oxygen level dependent (BOLD) signal changes were studied during voluntary hyperventilation (HV) between young healthy volunteer groups, (1) with intermittent rhythmic delta activity (IRDA) (N = 4) and (2) controls (N = 4) with only diffuse arrhythmic slowing in EEG (normal response). Subjects hyperventilated (3 min) during an 8-min functional MRI in a 1.5-T scanner, with simultaneous recording of EEG (successful with N = 3 in both groups) and physiological parameters. IRDA power and average BOLD signal intensities (of selected brain regions) were calculated. Hypocapnia showed a tendency to be slightly lighter in the controls than in the IRDA group. IRDA power increased during the last minute of HV and ended 10-15 s after HV. The BOLD signal decreased in white and gray matter after the onset of HV and returned to the baseline within 2 min after HV. The BOLD signal in gray matter decreased approximately 30% more in subjects with IRDA than in controls, during the first 2 min of HV. This difference disappeared (in three subjects out of four) during IRDA in EEG. BOLD signal changes seem to depict changes, which precede IRDA. IRDA due to HV in healthy volunteers represent a model with a clearly defined EEG pattern and an observable BOLD signal change.