Neurology -- Correspondence for Claassen et al., 69 (13) 1356-1365

Correspondence published:

Electrographic seizures and periodic discharges after intracerebral hemorrhage: Nitin K Sethi, Josh Torgovnick, Edward Arsura, Prahlad K. Sethi (New Delhi, India) (14 February 2008)

Electrographic seizures and periodic discharges after intracerebral hemorrhage: Gregory L. Krauss (14 February 2008)

Reply from the authors: Jan Claassen, Jan Claassen, Nathalie Jetté, Michael Schmidt, Hyunmi Choi, Jeffrey Jirsch, Jennifer A. Frontera, E. Sander Connolly, Ronald G. Emerson, Stephan A. Mayer, and Lawrence J. Hirsch (14 February 2008)

Electrographic seizures and periodic discharges after intracerebral hemorrhage 14 February 2008

Nitin K Sethi,
NYP-Weill Cornell Medical Center
525 East, 68th Street New York, NY 10021,
Josh Torgovnick, Edward Arsura, Prahlad K. Sethi (New Delhi, India)
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Re: Electrographic seizures and periodic discharges after intracerebral hemorrhage

sethinitinmd{at}hotmail.com Nitin K Sethi, et al.

We read the Claassen et al. article with interest. [1] While we commend the authors for looking into the frequency and significance of electrographic seizures in patients with intracerebral hemorrhage (ICH), we disagree with their conclusions. We do not feel that it is necessary to perform continuous EEG monitoring (cEEG) on every patient who presents with ICH. This issue is also raised by Dr. Fountain in the accompanying editorial. [2]
Our main concern with the study by Claassen et al. is that it was a retrospective review of cEEG data of 102 patients who presented with ICH and underwent monitoring. EEG monitoring was initiated at the clinicians’ discretion usually for altered mental status. No details about the neurological examination were provided.
It has been our experience that a comprehensive neurological examination repeated at regular intervals usually suffices to identify the majority of patients who have electrographic seizures. Furthermore, we have found that treating these patients aggressively with anti-epileptic drugs—sometimes to the extent that all inter-ictal epileptiform discharges are eliminated—does not result in the patient regaining consciousness.
Whether the electrographic seizures are a signature of the damaged brain and their presence indicates some viable albeit malfunctioning neural tissue is still unclear.
References
1. Claassen J, Jette N, Chum F, et al. Electrographic seizures and periodic discharges after intracerebral hemorrhage. Neurology 2007; 69:1356-1365.
2. Fountain NB. Is it time for routine EEG monitoring after intracerebral hemorrhage. Neurology 2007; 69:1312-1313.
Disclosure: The authors report no conflicts of interest.

Electrographic seizures and periodic discharges after intracerebral hemorrhage 14 February 2008

Gregory L. Krauss,
Johns Hopkins University
Meyer 2-147, 600 N. Wolfe St., Baltimore, MD 21287
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Re: Electrographic seizures and periodic discharges after intracerebral hemorrhage

gkrauss{at}jhmi.edu Gregory L. Krauss

Claasen et al describe EEG abnormalities in patients with intracerebral hemorrhages. [1,3] This and several recent studies have a number of limitations:
1) Since only 13% of patients--those with “unexplained or fluctuating mental status or suspected seizures”-- received EEGs, the prevalence of seizures and electrographic ictal patterns for patients with intracerebral hemorrhages is much lower than 31%. The abstract notes only "seizures occurred in 1/3 of patients with intracerebral hemorrhage";
2) 18% of patients had electrographic seizures. However, boundaries between epileptogenic activity and other EEG coma patterns, including NCSE and periodic epileptiform discharges, are often overlapping and unclear. The authors should provide specific working definitions to distinguish these patterns; and
3) The authors skip between concepts of electrographic seizures, seizures, and clinically significant physiological events.
Their conclusion that “research is needed to determine if treating or preventing seizures” might improve outcome in patients with ICH itself blurs the definition of seizures and employs circular logic. The ILAE defined seizures as transient occurrences of signs and symptoms due to abnormal excessive or synchronous neuronal activity in the brain. [4]
In this context, epileptiform EEG abnormalities in a patient with decreased mentation (a possible sign of a seizure) might be best defined as ictal, rather than an interictal finding, based on patients’ responses to AED treatment.
References
3. Chong DJ, Hirsch LJ. Which EEG patterns warrant treatment in the critically ill? J Clin Neurophys. 2005;22:79-91.
4. Fisher RS, van Emde Boas W, Blume W et al. Epileptic seizures and epilepsy:definitions proposed by the international league against epilepsy and the international Bureau for epilepsy. Epilepsia. 2005;46:470-472.
Disclosure: The author reports no conflicts of interest.

Reply from the authors 14 February 2008

Jan Claassen,
Neurological Institute, Columbia University
710 West 168th Street, Unit 91, New York, NY 10032,
Jan Claassen, Nathalie Jetté, Michael Schmidt, Hyunmi Choi, Jeffrey Jirsch, Jennifer A. Frontera, E. Sander Connolly, Ronald G. Emerson, Stephan A. Mayer, and Lawrence J. Hirsch
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Re: Reply from the authors

jc1439{at}columbia.edu Jan Claassen, et al.

We thank Dr. Sethi et al. and Krauss for their interest in our study. [1] We agree with them and Dr. Fountain [2] that not all patients with intracerebral hemorrhage (ICH) require continuous monitoring (cEEG).
As we reported, cEEG was performed in only about 13% of all patients with ICH during this time period; this was also discussed in the limitations section and why we began the Discussion section stressing that this was a “highly selected cohort.” Our sample was comprised primarily of ICH patients that underwent cEEG for markedly impaired, worsening, or fluctuating mental status. Seventy-six percent were stuporous or comatose.
We strongly disagree with Dr. Sethi’s suggestion that serial clinical exams can detect most seizures in these patients, and we appreciate the opportunity to reiterate the most important point of our paper: The majority of seizures in critically ill patients can not be recognized clinically.
In our current study, only one of 18 patients with seizures on cEEG showed a definite clinical correlate, despite that most also had continuous digital video recordings. This confirms earlier studies from our center and others. [5,6] We agree that the significance and treatment implications of the cEEG findings remain unclear. However, both animal and human data suggest that nonconvulsive seizures are harmful, particularly in the acutely injured brain. [7]
We agree with Dr. Krauss that the border between seizures and periodic discharges is often difficult to draw in the setting of acute brain injury. This is the rationale behind the attempt by the American Clinical Neurophysiology Society to redefine these patterns for critically ill patients, an endeavor in which we are highly involved. [8] We used the same definitions of seizures and periodic patterns that we defined in previous publications. [6,9]
The International League Against Epilepsy (ILAE) definition of seizures was not designed for use in encephalopathic patients. [4] Many of the known clinical manifestations of seizures will not be detectable in encephalopathic ICU patients. The term “electrographic seizure pattern” should probably be used rather than “electrographic seizure” to be more precise, though by convention the word “pattern” is typically omitted.
To define ictal vs interictal patterns based on a response to AEDs would be of limited value in the critically ill, as decreased mentation is often partially or completely due to the underlying brain injury and not the ictal pattern itself. Therefore, patients are not likely to respond quickly to AED treatment, even if ictal activity is successfully treated. If they do improve clinically, the “ictal” nature of the pattern can be proven. If they do not improve, no conclusions can be drawn. [7]
Dr. Sethi et al stress that few patients with ICH and seizures will regain consciousness even if treated aggressively. That is not our experience—60% of our patients with ICH and seizures (15/25; Table 4) regained consciousness. [1] Time to diagnosis and duration of nonconvulsive seizure activity have both been shown to be independent predictors of outcome. [10]
It is conceivable that our more rapid and habitual use of cEEG in these patients contributed to this difference in outcome. It is still unclear whether prevention or aggressive early treatment of these patterns will make a difference. It is our hope that individualized, physiologically-based therapy based on multimodality brain monitoring including cEEG will allow us to limit secondary brain injury in these critically ill patients and continue to improve outcomes.
References
5. Vespa PM, O'Phelan K, Shah M, et al. Acute seizures after intracerebral hemorrhage: a factor in progressive midline shift and outcome. Neurology 2003;60:1441-1446.
6. Claassen J, Mayer SA, Kowalski RG, Emerson RG, Hirsch LJ. Detection of electrographic seizures with continuous EEG monitoring in critically ill patients. Neurology 2004;62:1743-1748.
7. Jirsch J, Hirsch LJ. Nonconvulsive seizures: developing a rational approach to the diagnosis and management in the critically ill population. Clin Neurophysiol. 2007;118:1660-1670.
8. Hirsch LJ, Brenner RP, Drislane FW, et al. The ACNS subcommittee on research terminology for continuous EEG monitoring: proposed standardized terminology for rhythmic and periodic EEG patterns encountered in critically ill patients. J Clin Neurophysiol. 2005;22:128-35.
9. Hirsch LJ, Claassen J, Mayer SA, Emerson RG. Stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs): a common EEG phenomenon in the critically ill. Epilepsia. 2004;45:109-123.
10. Young GB, Jordan KG, Doig GS. An assessment of nonconvulsive seizures in the intensive care unit using continuous EEG monitoring: an investigation of variables associated with mortality. Neurology 1996;47:83-89.
Disclosure: The author reports no conflicts of interest.