From Electroclinical to Electrometabolic Status Epilepticus?
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EDITORIAL
From Electroclinical to Electrometabolic Status Epilepticus? Gregory Kapinos1 • Jan Claassen2
Ó Springer Science+Business Media New York 2016
Electroencephalographic periodic discharges (PDs) have a complex clinical significance and carry unclear therapeutic implication [1–7], best understood along the ‘‘ictal-interictal continuum’’ (IIC) put forth by Chong and Hirsch [3]. These epileptiform patterns are not a homogenous group, with diverse electroencephalographic characteristics [2, 3, 6, 7], differing syndromal context [2, 6], variable clinical expression [2–6], and most importantly, may have vastly different underlying etiologies and prognoses [1–6]. In order to define at what point PDs behave like nonconvulsive seizures (NCSZs), epilepsy and neurocritical care experts [1–7] proposed that there might be more of a gray zone along this IIC [3], than a clear dichotomy, ictal versus non-ictal [7]. Over the past decade, a debate has been ongoing about the clinical significance of these ambiguous ‘‘semi-ictal’’ patterns, also known as ‘‘boundary syndromes’’ [2, 6]. As experts expressed their opinions on which patterns are harmful enough to warrant treatment [1, 3–5], a second axis has been proposed, where ‘‘injuriousness’’ or ‘‘worth treating’’ is separately represented on the y-axis, while keeping ‘‘ictal signature’’ on the x-axis [3]. One avenue of research has identified a strong correlation between PDs on the IIC and subsequent NCSZs or non-convulsive status epilepticus (NCSE), with reviews articulating this gradation in severity of PDs [2, 3, 6, 7].
& Gregory Kapinos [email protected] 1
Departments of Neurosurgery and Neurology, Hofstra Northwell School of Medicine, 300 Community Drive, Tower, 9th Floor, Manhasset, NY 11030, USA
2
Department of Neurology, College of Physicians & Surgeons, Columbia University, New York, NY, USA
Distinctively, another avenue of research identified which patterns are responsible for an altered brain function (from encephalopathy to coma), nicely compiled in recent synopses [2, 5, 6], but the link between PDs on the IIC and functional outcome remains less certain [1–6]. Another direction of research studied the physiologic repercussions of PDs, ultimately suggesting a link between interictal periodic patterns and secondary brain injury (as inferred by increased vasogenic or cytotoxic edema [8, 9] or increase in lactate-pyruvate ratio [10]), seen as similar sequelae to those resulting from NCSZs [10–12]. Many questions remain, as causality has not been proven [1, 12], but inferences may be made from these physiologic characteristics [4] that have been evoked to guide management [4, 5]. This body of evidence led to the concept of a nosologic umbrella under which a patient, with EEG evidence of IIC that does not meet formal seizure criteria, would be considered to be in ‘‘status epilepticus’’ (SE), if the clinical exam and overall context are compelling for high risk of NCSE [2, 3, 5, 6, 13]. ‘‘Electro-clinical status epilepticus’’ (ECSE) is elegantly proposed as a te
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