Stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs): a common EEG phenomenon in the critically ill

PURPOSE: To describe an underrecognized EEG phenomenon in critically ill patients undergoing continuous EEG monitoring (cEEG). We named these EEG patterns stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs). METHODS: We reviewed 150 consecutive patients undergoing cEEG during a 9-month period and compared those with and without SIRPIDs. SIRPIDs were defined as periodic, rhythmic, or ictal-appearing discharges that were consistently induced by alerting stimuli. RESULTS: We identified 33 patients with SIRPIDs (22%). SIRPID patterns included periodic epileptiform discharges in 21 patients (nine lateralized) and rhythmic patterns with evolution that fulfilled criteria for ictal discharges in 18 patients (12 unilateral). Eight patients had prior epilepsy; 24 had acute brain injury. Half the patients (17 of 33) had seizures, clinical or subclinical, during the acute illness in addition to SIRPIDs, and half (16 of 33) did not. No significant difference was found in the incidence of clinical seizures in patients with SIRPIDs (30%) compared with those without (45%). Clinical status epilepticus was more common in patients with focal (43%) or ictal-appearing (33%) SIRPIDs than in those without SIRPIDs (17%). CONCLUSIONS: Rhythmic, periodic, or ictal-appearing EEG patterns are commonly elicited by stimulation in critically ill, encephalopathic patients. Recording video, documenting patient stimulation, or repetitively examining patients during cEEG is necessary to recognize these patterns and to differentiate SIRPIDs from spontaneous seizures. Further research is necessary to determine the pathophysiologic, prognostic, and therapeutic significance of SIRPIDs.     

Prognostic value of myoclonus status in comatose survivors of cardiac arrest

Generalized myoclonus status is common in comatose patients after cardiac resuscitation, but its prognostic value is uncertain. We studied the clinical, radiologic, and pathologic findings in 107 consecutive patients who remained comatose after cardiac resuscitation. Myoclonus status was present in 40 patients (37%). Features more prevalent in patients with myoclonus status were burst suppression on electroencephalograms, cerebral edema or cerebral infarcts on computed tomography scans, and acute ischemic neuronal change in all cortical laminae. All patients with myoclonus status died. Of 67 patients without myoclonus, 20 awakened. We conclude that myoclonus status in postanoxic coma should be considered an agonal phenomenon that indicates devastating neocortical damage. Its presence in comatose patients after cardiac arrest must strongly influence the decision to withdraw life support.     

Termination patterns of stimulus-induced rhythmic,periodic, or ictal patterns and spontaneous electrographic seizures

Objective

To investigate the ability of the evolution and termination patterns to distinguish stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs) from spontaneous electrographic seizures, a challenge to the neurophysiologist and clinician.

Stimulus‐induced rhythmic,periodic ictal discharges during funduscopic examination in a patient with status epilepticus

Stimulus‐induced rhythmic, periodic, or ictal discharges (SIRPIDs), an unusual pattern in electroencephalography, have been described in critically‐ill encephalopathic patients in response to alerting stimuli. The phenomenon may be seen in patients with a broad range of aetiologies, including cerebral infarct, haemorrhage, anoxia, and degenerative diseases. Here, we report a unique case of status epilepticus presenting with SIRPIDs during funduscopic examination‐induced focal to bilateral tonic‐clonic seizures.     

Low frequency nonevolving generalized periodic epileptiform discharges and the borderland of hypoxic nonconvulsive status epilepticus in comatose patients after cardiac arrest

To explore the EEG boundary of nonconvulsive status epilepticus (NCSE) and the concept of “possible NCSE”, we studied 14 consecutive patients with ≤ 2-Hz nonevolving periodic generalized epileptiform discharges (GPDs) in their first EEG after out of hospital cardiac arrest (OHCA). The pattern was associated with myoclonus in 11 patients. EG reactivity to antiseizure drugs (benzodiazepines and propofol), but without clinical improvement, was noted in 8 patients, satisfying the diagnostic criteria of “possible NCSE”. Resolution of GPDs and emergence of physiological rhythms in follow-up EEGs and/or subsequent clinical improvement were noted in 6 of them, strongly suggesting that the initial slow nonevolving GPD pattern reflected NCSE significantly contributing to their coma. Background rhythms from 10 to 90% of the periods between GPDs were noted in 9 patients and appeared to correlate with reactivity of the GPD pattern to antiseizure drugs when 20% or more. Ten patients died, and four were discharged to longer care rehabilitation centers. Although based on few observations, preliminary evidence appears to indicate that in this context, nonevolving GPD frequencies as low as 0.8 Hz can reflect clinically significant NCSE and, therefore, warrant appropriate testing for possible reactivity. There is also some preliminary indication that background rhythms may be another important diagnostic and, perhaps, prognostic indicator, but this needs to be tested in large prospective studies.This article is part of a Special Issue entitled “Status Epilepticus”.     

Functional MRI study of the primary somatosensory cortex in comatose survivors of cardiac arrest

It is difficult to assess cerebral function in comatose patients. Because earlier functional neuroimaging studies demonstrate associations between cerebral metabolism and levels of consciousness, fMRI in comatose survivors of cardiac arrest could provide further insight into cerebral function during coma. Using fMRI, cerebral activation to somatosensory stimulation to the palm of the hand was measured in 19 comatose survivors of cardiac arrest and in 10 healthy control subjects and was compared to somatosensory-evoked potential (SSEP) testing of the median nerve. Changes in the blood oxygenation-level dependent signal (BOLD) in the primary somatosensory cortex (S1) contralateral to the stimulated hand were quantified. Clinical outcome was assessed using the Glasgow Outcome Scale (GOS) and the modified Rankin Scale at 3 months post-cardiac arrest. Five out of 19 patients were alive at 3 months. Patients who survived cardiac arrest showed greater BOLD in S1 contralateral to somatosensory stimulation of the hand compared to patients who eventually did not. Greater BOLD was also seen in S1 of patients who retained their SSEP N20 waveforms. There were also positive correlations between BOLD in S1 with both levels of consciousness and measures of outcome at 3 months. In summary, this study demonstrates that BOLD in the S1 contralateral to somatosensory stimulation of the hand varies with clinical measures of the level of consciousness during coma.     

Stimulus-induced bilateral central periodic discharges, cortical myoclonus and arousal responses in mild reversible coma

Objective: To study the association between stimulus-induced periodic epileptiform discharges (PEDs), arousal EEG responses and limb jerking in a comatose patient with reversible viral encephalitis. Methods: We recorded video EEG in Intensive Care Unit (ICU) for strictly clinical purposes. Back averaging was performed off-line using Neuroscan 4.3. Results: We recorded spontaneous and stimulus-induced bilateral central PEDs (bi-central PEDs) that were followed by phasic vertex potentials, customarily considered as EEG arousal responses. Bi-central PEDs were associated with myoclonus when provoked by strong and protracted stimuli, but remained subclinical when elicited by auditory or mild tactile stimuli. Spontaneous and stimulus-induced bi-central PEDs disappeared after full neurological recovery. Conclusion: These findings link stimulus-induced PEDs to epileptic cortical myoclonus, and further suggest that in certain comatose patients they may represent reflex epileptic activity, even when clinically silent. The term "reflex seizures of the critically ill" may be appropriate in such patients. Our findings may also provide a model of the reciprocal relationship between arousals and epileptiform activity. Significance: Consideration of the possibility that stimulus-induced PEDs are reflexive epileptic phenomena in some comatose ICU patients may rationalise further their acute management, including antiepileptic treatment.     

Brief electroencephalography rhythmic discharges (BERDs) in the neonate with seizures: their significance and prognostic implications

We aimed to explore the significance and prognostic implications of paroxysmal brief electroencephalography (EEG) rhythmic discharges (BERDs) in neonatal seizures. The 52 neonates in this study were divided into 3 groups: (1) BERDs only: 9 neonates, (2) BERDs + conventional EEG seizures: 11 babies, (3) Conventional EEG seizures only: 32 babies. We analyzed the BERDs and compared outcomes in the 3 groups: there was no significant difference in mortality and neurodevelopmental or background EEG impairment. Similar to conventional EEG seizures, BERDs are also associated with an increased mortality, morbidity, and EEG background abnormalities. Fewer babies with BERDS appear to develop postneonatal seizures suggesting their epileptogenic potential is less. In the appropriate clinical context, BERDs should be considered as miniseizures.     

Ethics in the intensive care unit with emphasis on medical futility in comatose survivors of cardiac arrest.

Medical futility refers to situations or cases in which treatment offers no meaningful benefit to the patient. Brain death does not pose a management problem because patients are considered to be dead. Management of other cases requires sequential considerations. First, the prognosis must be established with certainty. Then, if it is determined that there is no possibility of the patient regaining conscious awareness, a level of care should be decided through discussions involving the physician and significant others. Usually there is a consensus that high-level intensive care is not justified to maintain such a low quality of life. When the patient's advance directives or the substitute decision maker's request differs from the physician's recommendations, there are methods of resolving the issues that respect ethical and legal principles.     

Duration of rhythmic EEG patterns in neonates: new evidence for clinical and prognostic significance of brief rhythmic discharges.

OBJECTIVE: This study aimed at identifying the characteristics - especially the duration - of rhythmic discharges in neonatal EEG, and their association with clinical neonatal problems. Specifically, we aimed at testing the diagnostic and prognostic validity of using 10 s as minimal duration for defining electroencephalographic seizures. DESIGN AND METHODS: The polysomnographies of 340 neonates were reviewed, and episodes of rhythmic discharges were identified, analyzed, and quantified. The study sample was divided into 3 groups: one in which the maximal duration of rhythmic discharges was shorter than 10 s (brief rhythmic discharges, BRD), a second one in which there were rhythmic discharges longer than 10 s (long rhythmic discharges, LRD), and finally a group in which no rhythmic discharge was found (No-RD). These 3 groups of subjects were compared for the baseline and outcome clinical data. RESULTS: From the 340 neonates studied, 210 did not present any form of rhythmic discharge, 67 (19. 7%) had only BRD episodes, and 63 (18.5%) had at least one LRD episode. Prevalence of rhythmic discharges was low among healthy full term newborns, and was significantly higher among preterm and high-risk newborns. Electrophysiological characteristics of rhythmic discharges did not differ between healthy neonates and high-risk ones. Accompanying clinical manifestations were present in 26.3% of the LRD group, but also in 15.9% of the BRD group. The presence of BRD was significantly associated with leukomalacia and with hypoglycemia in the cross-sectional analysis of baseline data, and with an increased risk for abnormal neurodevelopmental outcome after a mean follow-up period of 47 months (adjusted relative risk=4.90, P<0.01). CONCLUSIONS: The present data demonstrate an association between BRD and clinical history of hypoxic-ischemic encephalopathy, especially when complicated by leukomalacia, and also with a prognosis of increased risk for abnormal neurodevelopmental outcome. The clinical and prognostic significance of isolated BRD justifies the need to include these brief episodes in future studies of neonatal seizures.     

Occurrence of nonconvulsive seizures,periodic epileptiform discharges,and intermittent rhythmic delta activity in rat focal ischemia

A significant proportion of neurologic patients suffer electroencephalographic (EEG) seizures in the acute phase following traumatic or ischemic brain injury, including many without overt behavioral manifestations. Although such nonconvulsive seizures may exacerbate neuropathological processes, they have received limited attention clinically and experimentally. Here we characterize seizure episodes following focal cerebral ischemia in the rat as a model for brain injury-induced seizures. Cortical EEG activity was recorded continuously from both hemispheres up to 72 h following middle cerebral artery occlusion (MCAo). Seizure discharges appeared in EEG recordings within 1 h of MCAo in 13/16 (81%) animals and consisted predominantly of generalized 1-3 Hz rhythmic spiking. During seizures animals engaged in quiet awake or normal motor behaviors, but exhibited no motor convulsant activity. Animals had a mean of 10.6 seizure episodes within 2 h, with a mean duration of 60 s per episode. On average, seizures ceased at 1 h 59 min post-MCAo in permanently occluded animals and did not occur following reperfusion at 2 h in transiently occluded animals. In addition to seizures, periodic lateralized epileptiform discharges (PLEDs) appeared over penumbral regions in the injured hemisphere while intermittent rhythmic delta activity (IRDA) recurred in the contralateral hemisphere with frontoparietal dominance. PLEDs and IRDA persisted up to 72 h in permanent MCAo animals, and early onset of the former was predictive of prolonged seizure activity. The presentation of these EEG waveforms, each with characteristic features replicating those in clinical neurologic populations, validates rat MCAo for study of acutely induced brain seizures and other neurophysiological aspects of brain injury.     

On the prognostic value of ictal EEG patterns in temporal lobe epilepsy surgery: A cohort study

PurposeTo investigate the prognostic value of ictal scalp EEG patterns in drug-resistant temporal lobe epilepsy associated with hippocampal sclerosis (MTLE-HS) prior to undergoing temporal lobectomy.MethodsScalp EEGs of the first seizure recorded during presurgical long-term video-EEG monitoring of 284 patients were reviewed. Patients were divided according to seizure laterality as either unilateral, when the EEG was restricted to one cerebral hemisphere for the entire seizure, or bilateral, when there was involvement of both hemispheres during the seizure. In patients with unilateral hippocampal sclerosis (HS), seizures were subdivided according to the side of initial ictal activity in relation to the side of the HS, as concordant, non-lateralising or contralateral. Postsurgical seizure outcome, according to Engel's classification, was verified at 1, 2, and 5 years after surgery.ResultsThere was no significant association between ictal EEG characteristics and postsurgical seizure outcome. An Engel I seizure outcome was observed in 87.1% of the patients with unilateral ictal EEGs and in 79.6% of those with bilateral ictal EEGs (p = 0.092).ConclusionAnalysis of the localisation, morphology, and lateralisation of ictal EEG patterns did not provide prognostic information regarding seizure-free status in patients with MTLE-HS undergoing temporal lobectomy.     

The prognostic value of evoked responses from primary somatosensory and auditory cortex in comatose patients.

OBJECTIVE: To evaluate somatosensory and auditory primary cortices using somatosensory evoked potentials (SEPs) and middle latency auditory evoked potentials (MLAEPs) in the prognosis of return to consciousness in comatose patients. METHODS: SEPs and MLAEPs were recorded in 131 severe comatose patients. Latencies and amplitudes were measured. Coma had been caused by transient cardiac arrest (n=49), traumatic brain injury (n=22), stroke (n=45), complications of neurosurgery (n=12) and encephalitis (n=3). One month after the onset of coma patients were classified as awake, still comatose or dead. Three months after (M3), they were classified into one of the 5 categories of the Glasgow outcome scale (GOS). RESULTS: At M3, 41.2% were dead, 47.3% were conscious (GOS 3-5) and 11.5% had not recovered consciousness. None of the patients in whom somatosensory N20 and auditory Pa were absent did return to consciousness and in the post-anoxic group, reduced cortical amplitude too was always associated with bad outcome. Conversely, N20 and Pa were present, respectively, in 33/69 and 34/69 patients who did not recover. CONCLUSIONS: The prognostic value of SEPs and MLAEPs in comatose patients depends on the cause of coma. Measurement of response amplitudes is informative. Abolition of cortical SEPs and/or cortical MLAEPs precludes post-anoxic comatose patients from returning to consciousness (100% specificity). In any case, the presence of short latency cortical somatosensory or auditory components is not a guarantee for return to consciousness. Late components should then be recorded.