Structural lesions in periodic lateralized epileptiform discharges (PLEDs)

Lateralized Periodic Discharges During Remifentanil Infusion

Lateralized periodic discharges (LPDs) are a common electroencephalographic (EEG) pattern in the neurointensive care unit setting. LPDs are typically observed in association with acute structural lesions of the brain with different etiologies. There are no reports describing a link between the occurrence of LPDs and the administration of remifentanil. Remifentanil is a rapid-acting pure μ-opioid receptor agonist, which is indicated to provide analgesia and sedation in mechanically ventilated patients in intensive care units. We present a case of an 84-year-old man with neuroglycopenia who developed LPDs while sedated with remifentanil. We report, for the first time, a potential relationship between remifentanil and the induction of LPDs.

Etiology and Clinical Impact of Interictal Periodic Discharges on the Routine Outpatient Scalp EEG

PURPOSE

Periodic discharges (PDs) are common in acute structural or metabolic brain lesions, but their occurrence during follow-up of epileptic patients in an outpatient setting is rare. Aim of this article was to study whether PDs on the routine outpatient scalp EEG of patients with epilepsy, as compared with nonperiodic epileptiform discharges, are associated with drug refractoriness and the decompensation of epilepsy and particular etiologies.

METHODS

A retrospective case-control study. EEG reports were screened for PDs and their variants. The inclusion criteria were as follows: a diagnosis of epilepsy, epileptogenic lesion on imaging, or a normal 3-T MRI. Inpatient EEGs or EEGs performed in patients with acute cerebral lesions were excluded. Age- and sex-matched controls presenting with other epileptiform EEG abnormalities were selected, and similar selection criteria were applied.

RESULTS

Forty-one patients with PDs and 82 controls were selected. There were no significant differences between the cases and controls in the rates of epilepsy decompensation at the time of EEG collection or drug refractoriness. Stroke, hippocampal sclerosis, and malformations of cortical development were the most frequent etiologies, without significant differences between the groups.

CONCLUSIONS

By performing a case-control study, the authors have shown that PDs are not a marker of epilepsy decompensation and drug refractoriness and that the finding of PDs is not suggestive of particular epilepsy etiologies, when compared with other epileptiform abnormalities.

Neuroimaging Correlates of Lateralized Rhythmic Delta Activity, Lateralized Periodic Discharges, and Generalized Rhythmic Delta Activity on EEG in Critically Ill Patients

PURPOSE

The neuroimaging correlates of lateralized rhythmic delta activity (LRDA) are not well defined, and imaging findings between different epileptiform patterns have seldom been compared directly.

METHODS

Patients were retrospectively selected from a critical care EEG database between December 2014 and December 2017. Patients were included if they had greater than 6 hours of continuous EEG that contained LRDA, lateralized periodic discharges LPDs), or generalized rhythmic delta activity (GRDA) and had an MRI within 48 hours of the EEG. Clinical, EEG, and MRI characteristics were collected and compared.

RESULTS

All the following results showed statistical significance between the groups: Patients with GRDA were more likely to have a normal MRI (LRDA, 0%; LPDs, 0.8%; GRDA, 17.3%), although the majority were abnormal. In patients with LRDA and LPDs, the MRI abnormalities were much more likely lateralized to one side, whereas in those with GRDA, they were more likely to have bilateral or multifocal abnormalities. Across all groups most abnormalities were acute, although this proportion was higher in patients with LRDA and LPDs compared with that in those with GRDA (LRDA, 91.3%; LPDs, 86.0%; GRDA, 70.4%). An MRI abnormality that was concordant with the side of LRDA was present in 66.3%, with 17.3% having discordant findings. These were similar in patients with LPDs (concordant 67.4%; discordant 11.6%).

CONCLUSIONS

Patients with LRDA had a similarly high rate of acute focal abnormalities ipsilateral to the EEG pattern compared with those with LPDs. Patients with GRDA were more likely to have a normal MRI, but the majority of patients with GRDA still had acute focal findings.

Clinical neurophysiology of altered states of consciousness: Encephalopathy and coma

The neurophysiologist will commonly encounter patients with encephalopathy/delirium (altered consciousness with impaired cognition, usually with sleep-wake cycle alteration and lethargy) or coma (an eyes-closed state of unresponsiveness) in the hospital setting. Assessing the background frequency of the EEG, as well as the presence or absence of other features (reactivity, periodic discharges such as triphasic waves), can provide insight into the patient's underlying condition and in some cases may provide prognostic information. The literature of postanoxic arrest EEG patterns continues to expand. Other neurophysiologic tests, such as somatosensory evoked potentials, auditory mismatch negativity, and even EMG, may also play a role in assessing brain function; distinguishing among a locked-in state, minimally conscious state, persistent vegetative state, and waking/unresponsive states; and assessing the potential for recovery after brain injury.

Neuroimaging Correlates of Periodic Discharges

Despite being first described over 50 years ago, periodic discharges continue to generate controversy as to whether they are always, sometimes, or never "ictal." Investigators and clinicians have proposed adjunctive markers to help clarify this distinction-in particular measures of perfusion and metabolism. Here, we review the growing number of neuroimaging studies using Fluorodeoxyglucose-PET, MRI diffusion, Magnetic resonance perfusion, Single Photon Emission Computed Tomography, and Magnetoencepgalography to gain further insight into the physiology and clinical significance of periodic discharges. To date, however, no definitive consensus exists regarding the features of periodic discharges that warrant treatment intensification. However, an emerging consilience among neuroimaging modalities suggests that periodic discharges can induce a hyperexcitatory state with associated hypermetabolism and hyperperfusion, which may result in local metabolic failure.

Ictal-Interictal Continuum

The term "ictal-interictal" continuum has seen wide adoption in the critical care EEG domain, referring to the presence of abnormal periodic activity on the scalp EEG variably associated with seizures. The historical origin of the ictal-interictal continuum concept is discussed with a review of known and surmised physiological mechanisms for their origin and relationship to seizures. Therapeutic approaches to patients exhibiting ictal-interictal continuum EEG patterns are reviewed, and some open scientific questions highlighted. Further understanding of the ictal-interictal continuum is likely to significantly improve the care of the critically ill neurological patient.

Lateralized Periodic Discharges: A Literature Review

The purpose of this article is to provide a comprehensive review of the literature about a particular EEG pattern, lateralized periodic discharges (LPDs), or periodic lateralized epileptiform discharges (PLEDs). The review will discuss the history and terminology of LPDs and provide a detailed summary of the etiologies, pathophysiology, clinical symptoms, and imaging studies related to LPDs. Current controversies about the association of LPDs with seizures and their management will be reviewed. Finally, some unanswered questions and suggestions for future research on LPDs will be discussed.

Electrographic Features of Lateralized Periodic Discharges Stratify Risk in the Interictal-Ictal Continuum

PURPOSE

To risk-stratify electrographic features of lateralized periodic discharges (LPDs) in acute structural brain lesions for predictors of electrographic seizures.

METHODS

This is a retrospective review of 100 consecutive patients with LPDs. Epileptiform features of LPDs were described based on electrographic features: blunt delta morphology, sharply contoured, overlying fast frequencies, and/or rhythmicity (loss of interdischarge interval lasting ≥1 second). EEG seizures were defined as evolving in frequency, distribution, or morphology at ≥2 Hz for ≥10 seconds.

RESULTS

Overall, electrographic seizures occurred in 55% of patients with LPDs. Lateralized periodic discharges with rhythmicity (odds ratio 13.91) were most significant for predicting status epilepticus and/or seizures. This was followed by LPDs with overlying faster frequencies (odds ratio 5.16) and then sharply contoured morphology (odds ratio 4.09). Blunt delta morphology (0.24) had the lowest risk for seizures.

CONCLUSIONS

Electrographic features of LPDs may help determine seizure risk in patients with acute structural lesions. Sharply contoured morphology, overlying fast frequencies, or rhythmicity, showed progressively higher risk of seizures on continuous electroencephalography, whereas blunt delta morphology had the lowest risk of seizures.

Population of the ictal-interictal zone: The significance of periodic and rhythmic activity

Seizures contribute to patient mortality and are usually treated aggressively. Rhythmic and periodic patterns - the "ictal-interictal continuum" - are often associated with seizures, yet the optimum method of treating these patterns is not known: should they be aggressively suppressed, or monitored without treatment? Understanding which patterns are more strongly associated with seizures and which are highly associated with mortality is important to help the clinician decide how to treat these findings. We present an overview of the etiologies, association with seizures, and mortality of periodic and rhythmic patterns, and one approach to treatment.

Periodic Lateralized Epileptiform Discharges can Survive Anesthesia and Result in Asymmetric Drug-induced Burst Suppression

Drug-induced burst suppression (DIBS) is bihemispheric and bisymmetric in adults and older children. However, asymmetric DIBS may occur if a pathological process is affecting one hemisphere only or both hemispheres disproportionately. The usual suspect is a destructive lesion; an irritative or epileptogenic lesion is usually not invoked to explain DIBS asymmetry. We report the case of a 66-year-old woman with new-onset seizures who was found to have a hemorrhagic cavernoma and periodic lateralized epileptiform discharges (PLEDs) in the right temporal region. After levetiracetam and before anesthetic antiepileptic drugs (AEDs) were administered, the electroencephalogram (EEG) showed continuous PLEDs over the right hemisphere with maximum voltage in the posterior temporal region. Focal electrographic seizures also occurred occasionally in the same location. Propofol resulted in bihemispheric, but not in bisymmetric, DIBS. Remnants or fragments of PLEDs that survived anesthesia increased the amplitude and complexity of the bursts in the right hemisphere leading to asymmetric DIBS. Phenytoin, lacosamide, ketamine, midazolam, and topiramate were administered at various times in the course of EEG monitoring, resulting in suppression of seizures but not of PLEDs. Ketamine and midazolam reduced the rate, amplitude, and complexity of PLEDs but only after producing substantial attenuation of all burst components. When all anesthetics were discontinued, the EEG reverted to the original preanesthesia pattern with continuous non-fragmented PLEDs. The fact that PLEDs can survive anesthesia and affect DIBS symmetry is a testament to the robustness of the neurodynamic processes underlying PLEDs.

Periodic Lateralized Epileptiform Discharges and Afterdischarges: Common Dynamic Mechanisms

PURPOSE

No neurophysiological hypothesis currently exists addressing how and why periodic lateralized epileptiform discharges (PLEDs) arise in certain types of brain disease. Based on spectral analysis of clinical scalp EEG traces, the authors formulated a general mechanism for the emergence of PLEDs.

METHODS

The authors retrospectively analyzed spectra of PLED time series and control EEG segments from the opposite hemisphere in 25 hospitalized neurological patients. The observations led to the development of a phenomenological model for PLED emergence.

RESULTS

Similar to that observed in our previous work with afterdischarges, an analytic relationship is found between the spectrum of the baseline EEG and the PLED EEG, characterized by "condensation" of the main baseline spectral cluster, with variable inclusion of higher harmonics of the condensate.

CONCLUSIONS

Periodic lateralized epileptiform discharges may arise by synchronization of preexisting local field potentials, through a variable combination of enhancement of excitatory neurotransmission and inactivation of inhibitory neurotransmission provoked by the PLED-associated disease process. Higher harmonics in the PLED spectrum may arise by recurrent feedback, possibly from entrained single units. A mechanism is suggested for PLED emergence in certain diseased brain states and the association of PLEDs with EEG seizures. The framework is a spatially extended version of that, which the authors proposed, underlies afterdischarge and analogous to the cooperative behavior seen in a variety of natural multi-oscillator systems.

PLEDS : corrélations cliniques

Objective:

We reviewed our experience in 96 consecutive patients exhibiting periodic lateralized epileptiform discharges (PLEDs) on EEG.

Methods:

EEG reports from January 1, 1999 to September 30, 2006 were screened for the term ‘PLEDs’ and its variants. A retrospective chart review, including examination of neuroimaging and other investigations, was conducted on each patient identified.

Results:

Acute stroke, tumor and central nervous system infection were the most common etiologies, accounting for 26%, 12% and 12% of cases respectively. Acute hemorrhage and traumatic brain injury combined accounted for another 12%. Previously unreported etiologies included posterior reversible encephalopathy syndrome (PRES), familial hemiplegic migraine and cerebral amyloidosis. There were 9 cases of chronic PLEDs attributable to underlying cortical dysplasia or severe remote cerebral injury, all with an accompanying partial seizure disorder. A prominent role for alcohol withdrawal was noted, and in 6 cases was the sole etiological factor. Fever was present as a potential contributing factor in 40% of cases, and significant metabolic abnormalities in 35%. Seizure activity occurred in 85% of patients overall, but in 100% of patients with PLEDs Plus and BiPLEDs Plus. The overall mortality rate was 27%. Mortality among patients with BiPLEDs however was almost twice that, at 52%.

Conclusions:

This case series demonstrates the wide variety of potential PLED etiologies. It also emphasizes that despite advances in neurocritical care, the morbidity and mortality associated with PLEDs has changed little since their recognition four decades ago.

Periodic Lateralized Epileptiform Discharges Associated With Irreversible Hyperglycemic Hemichorea-Hemiballism

Periodic lateralized epileptiform discharges (PLEDs) on electroencephlography (EEG) usually indicate an acute, diffuse, and severe cerebral insult. Although hyperglycemic hemichorea-hemiballisum (HCHB) and striatal hyperintensity on T1-weighted magnetic resonance (MR) images is an accepted clinical entity, PLEDs have not previously been reported. Herein, we report a 74-year-old man with hyperglycemic HCHB, hyperintense putamen on T1-MR images and PLEDs on EEG. Aggressive sugar control with neuroleptic treatment only slightly improved the severity of HCHB. We also tried titrated oral and intravenous haloperidol, clonazepam, and propranolol sequentially and in combination; however, the effects were poor. Unlike the generally reversibility of hyperglycemic HCHB, the condition was still present 6 months later. Hyperglycemia can cause HCHB and produce subcortical type-PLEDs, which may explain the findings in our patient. In conclusion, PLEDs can be found in patients with hyperglycemic HCHB and striatal hyperintensity on T1-weighted MR images, and the appearance of PLEDs may indicate an irreversible outcome. EEG should be considered in such circumstances.

Periodic Epileptiform Discharges Clarified for the Nonneurologist Intensivist: Clinical Implications and Current Management

Periodic epileptiform discharges (PEDs) are frequently encountered during continuous electroencephalography monitoring in the intensive care unit. Their implications and management are variable and highly dependent on the clinical context. This article is intended for the nonneurologist intensivist, reviews basic terminology and clinical implications (including causes, prognosis, and association with seizures), and suggests an approach to management. Several case vignettes are included to illustrate the clinical variability associated with PEDs.

Periodic epileptiform discharges in mesial temporal lobe epilepsy with hippocampal sclerosis

PURPOSE

Periodic epileptiform discharges (PEDs) are an uncommon, abnormal EEG pattern seen usually in patients with acute diseases and less frequently in chronic conditions, such as mesial temporal lobe epilepsy (mTLE). Evaluate the clinical histories, neuroimaging findings, and serial electrophysiological studies prior to the appearance of PEDs in patients with mTLE secondary to hippocampal sclerosis (HS).

METHODS

We searched 19, 375 EEGs (2006-2012) for the presence of PEDs secondary to mTLE due to HS.

RESULTS

12 patients were included. The patients with PEDs had a high prevalence of psychiatric comorbilities, including major depression (50%), interictal psychosis (16%) and dementia (8%). All of the patients had intractable epilepsy with similar clinical findings. We observed a sequential neurophysiological worsening of the EEG patterns prior to the appearance of PEDs. Five patients with PEDs underwent epilepsy surgery and four were seizure free at follow-up 15 (±9) months.

CONCLUSIONS

PEDs are rare in patients with mTLE and HS and their presence in these cases could reflect clinical severity and neurophysiologic worsening, clinically manifested by intractable epilepsy and severe psychiatric comorbidities. The presence of PEDs in EEGs of patients with mTLE, however, was not associated with poor postsurgical seizure-freedom.

Periodic lateralized epileptiform discharges (PLEDs) in cerebral lupus correlated with white-matter lesions in brain MRI and reduced cerebral blood flow in SPECT

This is a case report on an uncommon correlation between periodic lateralized epileptiform discharges (PLEDs) and white-matter lesions in cerebral lupus, and with a reduced cerebral blood flow (CBF) in single-photon emission computed tomography (SPECT). A 47-year-old woman with a long-term history of systemic lupus erythematosus (SLE) presented with a seizure followed by frontal lobe dysfunction clinically. An electroencephalogram (EEG) showed bilateral independent PLEDs in the frontal region. A magnetic resonance image of the brain showed white-matter changes in the frontal periventricular region. Cerebral angiogram did not reveal any evidence of vasculitis. A cerebral SPECT with tracer injected during the EEG showing PLEDs showed a reduction in CBF in the frontal regions. Clinical recovery was observed with intravenous immunoglobulin. This case shows that PLEDs can be seen with white-matter changes in SLE.

Ictal sensory periodic lateralized epileptiform discharges

We describe the case of a 74-year-old man with left parietal arteriovenous malformation (AVM) and cerebral white matter radiation necrosis who developed persistent subjective right-sided groin pulsations. The EEG revealed left parietal periodic lateralized epileptiform discharges (PLEDs) time-locked to these sensations, confirming that the patient's symptoms represented sensory seizures with ictal PLEDs as the electrographic correlate. To our knowledge, this is the first reported case of ictal PLEDs manifesting as sensory seizures.

Periodic lateralized epileptiform discharges: Do they represent an ictal pattern requiring treatment?

The goal of this report is to review periodic lateralized epileptiform discharges (PLEDs), particularly their associated symptoms, the possibility that the pattern represents a focal status epilepticus, and finally the usefulness of antiepileptic drugs (AEDs). The associated symptoms often include an "altered state of consciousness" or "confusional state," but also more specific symptoms have been noted, such as nystagmus retractorius, cortical blindness, depression, apraxia, amnesia, hemianopsia, hemiparesis, gaze preference or deviation, dysphasia, and speech impediment. PLEDs have often been referred to as an ictal pattern, and many investigators have viewed the condition an example of subclinical status epilepticus. The intense hypermetabolism and increased blood flow revealed by PET and SPECT scans have been considered to support the ictal nature of this waveform. Although the pattern is difficult to treat, the AEDs that have been reported as successful include carbamazepine, midazolam, pentobarbital, sodium valproate, and felbamate. As only subtle symptoms are, at times, present and therefore may be missed and the pattern is known to be difficult to treat, epileptologists who view the PLED pattern as only an EEG curiosity and decide against treatment may wish to reevaluate the electroclinical evidence related to this interesting and significant pattern.

Nonconvulsive status epilepticus

Nonconvulsive status epilepticus (NCSE) is a heterogeneous disorder with multiple subtypes. Although attempts have been made to define and classify this disorder, there is yet no universally accepted definition or classification that encompasses all subtypes or electroclinical scenarios. Developing such a classification scheme is becoming increasingly important, because NCSE is more common than previously thought, with a bimodal peak, in children and the elderly. Recent studies have also shown a high incidence of NCSE in the critically ill. Although strong epidemiological data are lacking, NCSE constitutes about 25-50% of all cases of status epilepticus. For the purposes of this review, we propose an etiological classification for NCSE including NCSE in metabolic disorders, NCSE in coma, NCSE in acute cerebral lesions, and NCSE in those with preexisting epilepsy with or without epileptic encephalopathy. NCSE is still underrecognized, yet potentially fatal if untreated. Diagnosis can be established using an electroencephalogram (EEG) in most cases, sometimes requiring continuous monitoring. However, in comatose patients, diagnosis can be difficult, and the EEG can show a variety of rhythmic or periodic patterns, some of which are of unclear significance. Although some subtypes of NCSE are easily treatable, such as absence status epilepticus, others do not respond well to treatment, and debate exists over how aggressively clinicians should treat NCSE. In particular, the appropriate treatment of NCSE in patients who are critically ill and/or comatose is not well established, and large-scale trials are needed. Overall, further work is needed to better define NCSE, to determine which EEG patterns represent NCSE, and to establish treatment paradigms for different subtypes of NCSE.

Pathological effect of homeostatic synaptic scaling on network dynamics in diseases of the cortex

Slow periodic EEG discharges are common in CNS disorders. The pathophysiology of this aberrant rhythmic activity is poorly understood. We used a computational model of a neocortical network with a dynamic homeostatic scaling rule to show that loss of input (partial deafferentation) can trigger network reorganization that results in pathological periodic discharges. The decrease in average firing rate in the network by deafferentation was compensated by homeostatic synaptic scaling of recurrent excitation among pyramidal cells. Synaptic scaling succeeded in recovering the network target firing rate for all degrees of deafferentation (fraction of deafferented cells), but there was a critical degree of deafferentation for pathological network reorganization. For deafferentation degrees below this value, homeostatic upregulation of recurrent excitation had minimal effect on the macroscopic network dynamics. For deafferentation above this threshold, however, a slow periodic oscillation appeared, patterns of activity were less sparse, and bursting occurred in individual neurons. Also, comparison of spike-triggered afferent and recurrent excitatory conductances revealed that information transmission was strongly impaired. These results suggest that homeostatic plasticity can lead to secondary functional impairment in case of cortical disorders associated with cell loss.

Neuroimaging and Neurophysiology of Periodic Lateralized Epileptiform Discharges: Observations and Hypotheses

PURPOSE

We assessed neuroimaging lesion type and distribution in patients with periodic lateralized epileptiform discharges (PLEDs), with a view to identifying electrographic differences between PLEDs associated with differing lesion locations. Our observations led us to consider a conceptual synthesis between PLEDs and periodic complexes (PCs).

METHODS

Retrospective review of acute neuroimaging results (CT/MRI) on patients identified to have EEG PLEDs, for the period 1999-2003 (n=106). Blinded classification of original EEG recordings.

RESULTS

Neuroimaging abnormalities were classified as acute or chronic cortical, or acute or chronic subcortical. Seven out of 106 scans were classified nonlesional. Overall approximately 70% of scans had cortical abnormalities, whether acute or chronic; approximately 23% had subcortical abnormalities. "Cortical" PLEDs were significantly longer in duration (p<0.05) and more variable in morphology (p<0.01) than "subcortical" PLEDs.

CONCLUSIONS

Structural brain disease commonly, but not invariably, underlies PLEDs; lesion type is spatiotemporally variable. Cortical and subcortical PLEDs have distinct EEG signatures. There is evidence that these may relate to mechanisms for other pathological large-scale oscillatory brain synchronies (e.g., PCs).

Clinical characteristics and prognostic factors of postencephalitic epilepsy in children

The goal of this study was to clarify the clinical characteristics and prognostic factors of childhood postencephalitic epilepsy. Forty-four patients (20 boys and 24 girls; age range 21 months to 17 years, mean age 8.1 +/- 4.6 years) with postencephalitic epilepsy were selected from the 798 epileptic children treated and followed up at our hospital between 1993 and 2003. The clinical data included clinical features, electroencephalograms (EEGs), and neuroimages, all reviewed and analyzed retrospectively. Based on their post-treatment seizure outcomes, the children were divided into favorable (n = 20) and poor outcome groups (n = 24). Between the two groups, the age at encephalitis, cerebrospinal fluid findings, and seizure type were comparable. Factors indicating a poor prognosis for these patients during the acute phase of encephalitis were (1) status epilepticus occurring as the first seizure (P < .005), (2) slow background activity (P < .001) and multifocal spike discharges on EEGs (P < .01), and (3) herpes simplex viral encephalitis (P < .01). Our findings indicated that patients with status epilepticus and multifocal spikes on EEG during acute encephalitis have an increased risk of developing intractable epilepsy. To improve the outcome of postencephalitic epilepsy, intervention must occur earlier in the encephalitis stage.

SPECT in periodic lateralized epileptiform discharges (PLEDs): A case report on PLEDs

Periodic lateralized epileptiform discharges (PLEDs), which are known as unusual electroencephalogram (EEG) patterns, are described in a patient who had stroke and seizures. This patient underwent Tc-99m HMPAO (hexamethyl propylene amine oxime) brain single photon emission computed tomography (SPECT) imaging both during PLEDs on EEG and after the cessation of PLEDs. The initial SPECT study revealed increased CBF in the left frontal and parietal cortex extending through the left temporal region and in the left basal ganglium. After the PLEDs disappeared, the second SPECT study showed decreased perfusion on the left frontal and parietal region in the brain. Brain SPECT findings supported the contention that PLEDs may be an ictal phenomenon. Here we also present a review on PLEDs and contributions of brain SPECT as a functional imaging modality to investigate the underlying mechanism of this interesting EEG pattern.