Pyruvate dehydrogenase activity in the rat cerebral cortex following cerebral ischemia

The effect of cerebral ischemia on the activity of pyruvate dehydrogenase (PDH) enzyme complex (PDHC) was investigated in homogenates of frozen rat cerebral cortex following 15 min of bilateral common carotid occlusion ischemia and following 15 min, 60 min, and 6 h of recirculation after 15 min of ischemia. In frozen cortical tissue from the same animals, the levels of labile phosphate compounds, glucose, glycogen, lactate, and pyruvate was determined. In cortex from control animals, the rate of [1(-14)C]pyruvate decarboxylation was 9.6 +/- 0.5 nmol CO2/(min-mg protein) or 40% of the total PDHC activity. This fraction increased to 89% at the end of 15 min of ischemia. At 15 min of recirculation following 15 min of ischemia, the PDHC activity decreased to 50% of control levels and was depressed for up to 6 h post ischemia. This decrease in activity was not due to a decrease in total PDHC activity. Apart from a reduction in ATP levels, the acute changes in the levels of energy metabolites were essentially normalized at 6 h of recovery. Dichloroacetate (DCA), an inhibitor of PDH kinase, given to rats at 250 mg/kg i.p. four times over 2 h, significantly decreased blood glucose levels from 7.4 +/- 0.6 to 5.1 +/- 0.3 mmol/L and fully activated PDHC. In animals in which the plasma glucose level was maintained at control levels of 8.3 +/- 0.5 mumol/g by intravenous infusion of glucose, the active portion of PDHC increased to 95 +/- 4%. In contrast, the depressed PDHC activity at 15 min following ischemia was not affected by the DCA treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Preischemic hyperglycemia and postischemic alteration of rat brain pyruvate dehydrogenase activity

Transient cerebral ischemia in normoglycemic animals is followed by a decrease in glucose utilization, reflecting a postischemic cerebral metabolic depression and a reduction in the activity of the pyruvate dehydrogenase complex (PDHC). Preischemic hyperglycemia, which aggravates ischemic brain damage and invariably causes seizure, is known to further reduce cerebral metabolic rate. To investigate whether these effects are accompanied by changes in PDHC activity, the postischemic cerebral cortical activity of this enzyme was investigated in rats with preischemic hyperglycemia (plasma glucose 20-25 mM). The results were compared with those obtained in normoglycemic animals (plasma glucose 5-10 mM). The activated portion of PDHC and total PDHC activity were measured in neocortical samples as the rate of decarboxylation of [14C]pyruvate in crude brain mitochondrial homogenates after 5 min, 15 min, 1 h, 6 h, and 18 h of recirculation following 15 min of incomplete cerebral ischemia. In normoglycemic animals the fraction of activated PDHC, which rises abruptly during ischemia, was reduced to 19-25% during recirculation compared with 30% in sham-operated controls. In hyperglycemic rats the fraction of activated PDHC was higher during the first 15 min of recirculation. However, after 1 and 6 h of recirculation, the fraction was reduced to values similar to those measured in normoglycemic animals. Fifteen of 26 rats experienced early (1-4 h post ischemia) seizures in the recovery period. The PDHC activity appeared unchanged prior to these early postischemic seizures. We conclude that the accentuated depression of postischemic metabolic rate observed in hyperglycemic animals is not coupled to a corresponding postischemic depression of PDHC.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of duration of cerebral ischemia on brain pyruvate dehydrogenase activity, energy metabolites, and blood flow during reperfusion in gerbil brain

The objective of this study was to determine whether the duration of an ischemic insult effects the activity of the mitochondrial enzyme pyruvate dehydrogenase (PDH) in relation to the recovery of metabolites and regional cerebral blood flow (rCBF) immediately after ischemia and during reperfusion in gerbil cortex. Cerebral ischemia was induced, using the bilateral carotid artery occlusion method, for 20 or 60 min, followed by reperfusion up to 120 min. Immediately after ischemia PDH activity increased threefold regardless of ischemic duration. In the 60-min ischemic group, PDH remained activated, the recovery of high energy phosphates and the clearance of lactate were poor, and the rCBF was 48% of controls after 20-min reperfusion, decreasing gradually to 26% at 120-min reperfusion. In the 20-min ischemic group, PDH activity normalized quickly, the restoration of energy phosphates was good, there was a quick reduction in lactate within the first 60 min of reperfusion, and the rCBF was 65% of control at 20-min reperfusion, and remained over 48% of control throughout reperfusion. Recovery of metabolism after reperfusion did not parallel the changes in rCBF in either group, most noticeably in the 60-min ischemic group. The slow normalization of PDH activity reflected the poor recovery of metabolites in the 60-min ischemic group, indicating that PDH activity is important in the resynthesis of energy metabolites during reperfusion. In conclusion, prolonging the ischemic insult effected PDH activity during reperfusion, impaired recovery of energy metabolites, and worsened the recovery of rCBF.     

Extracellular pH in the rat brain during hypoglycemic coma and recovery

It has previously been shown that hypoglycemic coma is accompanied by marked energy failure and by loss of cellular ionic homeostasis. The general proposal is that shortage of carbohydrate substrate prevents lactic acid formation and thereby acidosis during hypoglycemic coma. The objective of the present study was to explore whether rapid downhill ion fluxes, known to occur during coma, are accompanied by changes in extra- and/or intracellular pH (pHe and/or pHi), and how these relate to the de- and repolarization of cellular membranes. Cortical pHe was recorded by microelectrodes in insulin-injected rats subjected to 30 min of hypoglycemic coma, with cellular membrane depolarization. Some rats were allowed up to 180 min of recovery after glucose infusion and membrane repolarization. Arterial blood gases and physiological parameters were monitored to maintain normotension, normoxia, normocapnia, and normal plasma pH. Following depolarization during hypoglycemia, a prompt, rapidly reversible alkaline pHe shift of about 0.1 units was observed in 37/43 rats. Immediately thereafter, all rats showed an acid pH shift of about 0.2 units. This shift developed during the first minute, and pHe remained at that level until repolarization was induced. Following repolarization, there was an additional, rapid, further lowering of pHe by about 0.05 units, followed by a more prolonged decrease in pHe that was maximal at 90 min of recovery (delta pHe of approximately -0.4 units). The pHe then slowly normalized but was still decreased (-0.18 pH units) after 180 min when the experiment was terminated. The calculated pHi showed no major alterations during hypoglycemic coma or after membrane repolarization following glucose administration.(ABSTRACT TRUNCATED AT 250 WORDS)     

MK801 decreases glutamate release and oxidative metabolism during hypoglycemic coma in piglets.

Hypoglycemic coma increases extracellular excitatory amino acids, which mediate hypoglycemic neuronal degeneration. Cerebral oxygen consumption increases during hypoglycemic coma in piglets. We tested the hypothesis that the NMDA-receptor antagonist dizocilpine (MK801) attenuates the increase in cerebral oxygen consumption during hypoglycemia. We measured EEG, cerebral blood flow (CBF), cerebral oxygen consumption (CMRO(2)) and cortical microdialysate levels of glutamate, aspartate and glycine in pentobarbital-anesthetized piglets during 60 min of insulin-induced hypoglycemic coma. NMDA-receptor distribution was measured by autoradiography. MK801 (0.75 mg/kg i.v.) was given within 5 min after onset of isoelectric EEG. Saline- and MK801-treated normoglycemic control animals were also studied. Brain temperature was maintained at 38.5+/-0.5 degrees C. MK801 prevented the 5--10-fold increase in glutamate and aspartate occurring in saline-treated hypoglycemic animals, and attenuated the increase in CMRO(2). Increases in CBF of 200--400% during hypoglycemic coma were not affected by MK801. MK801 did not alter CBF, CMRO(2) or microdialysate amino acid levels in normoglycemic control animals. Parietal cortex corresponding to microdialysis sites was highly enriched in NMDA receptors, and the density and distribution overall of NMDA receptor binding sites were comparable to that reported in other species. We conclude that NMDA receptor activation plays a central role in hypoglycemia-induced glutamate release, and contributes to increased cerebral oxygen consumption. Neuroprotective effects of MK801 during hypoglycemia in piglets may involve inhibitory effects on glutamate release and oxidative metabolism.     

Electrolyte shifts between brain and plasma in hypoglycemic coma

Hypoglycemia of sufficient severity to cause cessation of EEG activity (coma) is accompanied by energy failure and by loss of ion homeostasis, the latter encompassing a marked rise in extracellular fluid (ECF) K+ concentration and a fall in ECF Ca2+ concentration. Presumably, ECF Na+ concentration decreases as well. In the present study, the extent that the altered ECF-plasma gradients give rise to net ion fluxes between plasma and tissue is explored. Accordingly, whole tissue contents of Ca2+, Mg2+, K+, and Na+ were measured. The experiments were carried out in anaesthetized and artificially ventilated rats given insulin i.p.; cerebral cortical tissue was sampled at the stage of slow-wave EEG activity, after 10, 30, and 60 min of coma (defined as isoelectric EEG), as well as after 1.5, 6, and 24 h of recovery. In the precomatose animals (with a slow-wave EEG pattern), no changes in electrolyte contents were observed. During coma, tissue Na+ content increased progressively and the K+ content fell (each by 20 mumol g-1 during 60 min). During recovery, these alterations were reversed within the first 6 h. The Mg2+ content remained unchanged. In spite of the appreciable plasma to ECF Ca2+ gradient, no significant calcium accumulation was observed. It is concluded significant calcium accumulation was observed. It is concluded that hypoglycemia leads to irreversible neuronal necrosis in the absence of gross accumulation of calcium in the tissue.     

Epileptiform discharges in presence of continuous background activity in anoxic coma

The EEGs of a group of patients in anoxic coma following cardiorespiratory arrest were retrospectively studied. Twelve of 70 patients had at least one EEG recorded during the acute period which consisted of epileptiform discharges in the presence of continuous diffuse background activity. Nine of the patients died while three made a generally favorable recovery. The analysis confirms the prediction of a recent revision of EEG grades in coma that this particular pattern of activity is of uncertain prognostic significance. This is in contrast to the occurrence of epileptiform discharges during discontinuous "burst suppression" activity which generally indicates a fatal outcome.     

Pyruvate dehydrogenase complex: metabolic link to ischemic brain injury and target of oxidative stress

The mammalian pyruvate dehydrogenase complex (PDHC) is a mitochondrial matrix enzyme complex (greater than 7 million Daltons) that catalyzes the oxidative decarboxylation of pyruvate to form acetyl CoA, nicotinamide adenine dinucleotide (the reduced form, NADH), and CO(2). This reaction constitutes the bridge between anaerobic and aerobic cerebral energy metabolism. PDHC enzyme activity and immunoreactivity are lost in selectively vulnerable neurons after cerebral ischemia and reperfusion. Evidence from experiments carried out in vitro suggests that reperfusion-dependent loss of activity is caused by oxidative protein modifications. Impaired enzyme activity may explain the reduced cerebral glucose and oxygen consumption that occurs after cerebral ischemia. This hypothesis is supported by the hyperoxidation of mitochondrial electron transport chain components and NAD(H) that occurs during reperfusion, indicating that NADH production, rather than utilization, is rate limiting. Additional support comes from the findings that immediate postischemic administration of acetyl-L-carnitine both reduces brain lactate/pyruvate ratios and improves neurologic outcome after cardiac arrest in animals. As acetyl-L-carnitine is converted to acetyl CoA, the product of the PDHC reaction, it follows that impaired production of NADH is due to reduced activity of either PDHC or one or more steps in glycolysis. Impaired cerebral energy metabolism and PDHC activity are associated also with neurodegenerative disorders including Alzheimer's disease and Wernicke-Korsakoff syndrome, suggesting that this enzyme is an important link in the pathophysiology of both acute brain injury and chronic neurodegeneration.     

Pyruvate dehydrogenase phosphate (PDHb) phosphatase activity in fibroblasts from Leigh's disease

The defective activation of pyruvate dehydrogenase complex (PDHC) in Leigh's disease (subacute necrotizing encephalomyelopathy) could be due to deficiency of pyruvate dehydrogenase phosphate (PDHb) phosphatase (EC 3.1.3.43). This enzyme catalyzes the dephosphorylation and activation of phospho-PDHC. In cultured skin fibroblasts, we assayed this enzyme by measuring the rate of activation of the exogenously added, purified phospho-PDHC (bovine kidney). PDHb phosphatase activity did not differ significantly among normal control cells, Leigh's lines, spinocerebellar ataxias, or other neurologic disorders. The results do not support the idea that PDHb phosphatase is deficient in Leigh's disease.     

Insulin and IGF-1 regularize energy metabolites in neural cells expressing full-length mutant huntingtin

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder linked to the expression of mutant huntingtin. Bioenergetic dysfunction has been described to contribute to HD pathogenesis. Thus, treatment paradigms aimed to ameliorate energy deficits appear to be suitable candidates in HD. In previous studies, we observed protective effects of insulin growth factor-1 (IGF-1) in YAC128 and R6/2 mice, two HD mouse models, whereas IGF-1 and/or insulin halted mitochondrial-driven oxidative stress in mutant striatal cells and mitochondrial dysfunction in HD human lymphoblasts. Here, we analyzed the effect of IGF-1 versus insulin on energy metabolic parameters using striatal cells derived from HD knock-in mice and primary cortical cultures from YAC128 mice. STHdh^Q111/Q111 cells exhibited decreased ATP/ADP ratio and increased phosphocreatine levels. Moreover, pyruvate levels were increased in mutant cells, most probably in consequence of a decrease in pyruvate dehydrogenase (PDH) protein expression and increased PDH phosphorylation, reflecting its inactivation. Insulin and IGF-1 treatment significantly decreased phosphocreatine levels, whereas IGF-1 only decreased pyruvate levels in mutant cells. In a different scenario, primary cortical cultures derived from YAC128 mice also displayed energetic abnormalities. We observed a decrease in both ATP/ADP and phosphocreatine levels, which were prevented following exposure to insulin or IGF-1. Furthermore, decreased lactate levels in YAC128 cultures occurred concomitantly with a decline in lactate dehydrogenase activity, which was ameliorated with both insulin and IGF-1. These data demonstrate differential HD-associated metabolic dysfunction in striatal cell lines and primary cortical cultures, both of which being alleviated by insulin and IGF-1.     

Effect of nicardipine, a Ca channel blocker, on pyruvate dehydrogenase activity and energy metabolites during cerebral ischemia and reperfusion in gerbil brain

The purpose of this study was to determine if nicardipine, a calcium ion channel blocker, affects pyruvate dehydrogenase (PDH) activity and improves energy metabolism during cerebral ischemia and reperfusion. Cerebral ischemia was induced, using the bilateral carotid artery occlusion method, for 60 min followed by reperfusion up to 120 min in gerbils. Nicardipine (1 mg/kg) or saline (vehicle-treated) was given to gerbils 30 min prior to the occlusion of the common carotid arteries. PDH activity and metabolites (ATP, PCr, and lactate) were measured in cortex prior to ischemia, immediately following ischemia, and after each reperfusion period. After 60 min ischemia, PDH activity increased in both groups, and was significantly higher in the nicardipine-treated group. After 20 min reperfusion, PDH activity in the nicardipine-treated group recovered to control levels, whereas, the PDH activity in the vehicle-treated group remained elevated, and was higher than the nicardipine-treated animals. At 60 and 120 min reperfusion, the activities in the vehicle-treated group were significantly below control levels, there were no differences, however, between the two groups. ATP and PCr concentrations were markedly depleted immediately after ischemia in both groups. ATP levels at 20 min reperfusion and PCr levels at 60 min reperfusion were significantly higher in the nicardipine-treated group. Lactate concentrations in both groups increased 7–8 fold, similarly, immediately after ischemia. During reperfusion, the lactate remained elevated in both groups, though the levels in the nicardipine-treated group were lower than those in the vehicle-treated group, but not significantly. Nicardipine treatment normalized PDH activity quickly and improved energy metabolism after reperfusion.     

Neuronal subclass-selective loss of pyruvate dehydrogenase immunoreactivity following canine cardiac arrest and resuscitation

Chronic impairment of aerobic energy metabolism accompanies global cerebral ischemia and reperfusion and likely contributes to delayed neuronal cell death. Reperfusion-dependent inhibition of pyruvate dehydrogenase complex (PDHC) enzyme activity has been described and proposed to be at least partially responsible for this metabolic abnormality. This study tested the hypothesis that global cerebral ischemia and reperfusion results in the loss of pyruvate dehydrogenase immunoreactivity and that such loss is associated with selective neuronal vulnerability to transient ischemia. Following 10 min canine cardiac arrest, resuscitation, and 2 or 24 h of restoration of spontaneous circulation, brains were either perfusion fixed for immunohistochemical analyses or biopsy samples were removed for Western immunoblot analyses of PDHC immunoreactivity. A significant decrease in immunoreactivity was observed in frontal cortex homogenates from both 2 and 24 h reperfused animals compared to samples from nonischemic control animals. These results were supported by confocal microscopic immunohistochemical determinations of pyruvate dehydrogenase immunoreactivity in the neuronal cell bodies located within different layers of the frontal cortex. Loss of immunoreactivity was greatest for pyramidal neurons located in layer V compared to neurons in layers IIIc/IV, which correlates with a greater vulnerability of layer V neurons to delayed death caused by transient global cerebral ischemia.     

Controlled cortical impact injury and craniotomy result in divergent alterations of pyruvate metabolizing enzymes in rat brain

Dysregulated glucose metabolism and energy deficit is a characteristic of severe traumatic brain injury (TBI) but its mechanism remains to be fully elucidated. Phosphorylation of pyruvate dehydrogenase (PDH) is the rate-limiting mitochondria enzyme reaction coupling glycolysis to the tricarboxylic acid cycle. Phosphorylation of PDH E1α1 subunit catalyzed by PDH kinase (PDK) inhibits PDH activity, effectively decoupling aerobic glycolysis whereas dephosphorylation of phosphorylated PDHE1α1 by PDH phosphatase (PDP) restores PDH activity. We recently reported altered expression and phosphorylation of pyruvate dehydrogenase (PDH) following TBI. However, little is known about PDK and PDP involvement. We determined PDK (PDK1-4) and PDP isoenzyme (PDP1-2) mRNA and protein expression in rat brain using immunohistochemistry and in situ hybridization techniques. We also quantified PDK and PDP mRNA and protein levels in rat brain following TBI using quantitative real-time PCR and Western blot, respectively. Controlled cortical impact-induced TBI (CCI-TBI) and craniotomy significantly enhanced PDK1-2 isoenzyme mRNA expression level but significantly suppressed PDP1 and PDK4 mRNA expression after the injury (4h to 7days). CCI-TBI and craniotomy also significantly increased PDK1-4 isoenzyme protein expression but suppressed PDP1-2 protein expression in rat brain. In summary, the divergent changes between PDK and PDP expression indicate imbalance between PDK and PDP activities that would favor increased PDHE1α1 phosphorylation and enzyme inhibition contributing to impaired oxidative glucose metabolism in TBI as well as craniotomy.     

Physiologic and prognostic significance of "alpha coma".

A patient with posthypoxic "alpha coma" is described whose EEGs were recorded before coma, within two hours following the onset of coma and after recovery. The differences observed between the alpha activity during coma and that seen before and after suggest that the alpha activity during coma and the physiologic alpha rhythm are different phenomena. This case, as well as others reported, also suggests that "alpha coma" resolving in the first 24 hours following hypoxia may have a better prognosis than "alpha coma" detected after the first day, and stresses the need for EEG monitoring begun in the immediate period following hypoxia in order to assess accurately the prognostic significance of this EEG pattern in the early stages of postanoxic encephalopathy. The aetiology of "alpha coma" also affects outcome. The survival rate appears higher in patients with respiratory arrest than in those with combined cardiopulmonary arrest.     

The effect of a dihydropyridine calcium antagonist (isradipine) on selective neuronal necrosis

The experiments were designed to test the possibility that calcium influx into neurons via voltage sensitive calcium channels (VSCCs) contribute to brain damage in two conditions in which any amelioration of neuronal necrosis may be assumed not to occur through an improvement of blood flow, viz., hypoglycemic coma and brief transient ischemia. Hypoglycemic coma is thought to lead to neuronal necrosis by release of glutamate and cellular influx of calcium during the insult, while damage due to brief transient ischemia may, at least in part, result from increased calcium cycling across cell membranes in the postinsult period. The insults were delivered to anesthetized rats, and the localization and density of neuronal necrosis were evaluated by histopathology following 1 week of recovery. One dihydropyridine calcium antagonist (isradipine), given in doses which have been reported to ameliorate ischemic damage due to stroke, failed to reduce damage incurred by 30 min of hypoglycemic coma, or 15 min of transient forebrain ischemia. Provided that it can be assumed that isradipine in the doses employed reduced calcium influx via VSCCs, the results support the notion that calcium influx through VSCCs plays only a minor pathogenetic role in global/forebrain ischemia or in hypoglycemia, and they suggest that the effect of blockers of VSCCs in stroke, if any, is due to both blockade of VSCCs and increase in blood flow.     

The effect of dichloroacetate on brain lactate levels following incomplete ischemia in the hyperglycemic rat

Dichloroacetate (DCA) is known to prevent the phosphorylation of the pyruvate dehydrogenase complex (PDHC) by blocking the action of PDH kinase. This action allows the active PDHC to exert its effect on the metabolism of glucose, lactate and alanine to acetyl CoA. DCA has been shown to reduce serum lactate levels in humans and animals in such conditions as diabetes, phenformin-induced hepatic failure, exercise, and endotoxin-induced shock. Lactic acidosis in the brain has often been postulated as a cause of neuronal damage following ischemia and hypoxia. Therefore, we examined the effect of intravenously administered DCA (100 mg/kg) in rats that were rendered hyperglycemic by intravenous glucose (2 g/kg), and then made to undergo 15 minutes of incomplete cerebral ischemia by bilateral carotid ligation and systemic hypotension (mean arterial pressure of 50 mm Hg). DCA significantly reduced serum lactate levels pre-ischemia, but had no effect on serum lactate levels after ischemia induction. Brain levels of lactate, ATP and PCr after 15 minutes of incomplete ischemia were unaffected by DCA. We conclude that in this in-vivo model the control of PDHC activity in the brain may be different than that in the periphery, and that DCA was not effective in reducing brain tissue lactate levels.     

Quantitative EEG during early recovery from hypoxic-ischemic injury in immature piglets: burst occurrence and duration.

This study examined the course of EEG recovery in an animal model of hypoxic-ischemic injury. The model used periods of hypoxia, room air and asphyxia to induce cardiac arrest. One-week-old piglets (n = 16) were exposed to a period of hypoxia, room air and complete asphyxia for 7 minutes. After cardiac arrest and resuscitation, two EEG features were evaluated as prognostic indicators of behavioral outcome as assessed by a neuroscore at 24 hours after insult. A prominent EEG feature was the number and duration of bursts evident during recovery. Episodes of bursting were detected through the thresholds on sustained periods of elevated power. After the animal was resuscitated, the EEG was monitored continuously for 4 hours. To assess outcome in the recovering animal, a behavioral testing scale was used to test the animal's neurological capabilities. Trends of EEG burst counts were measured through thresholds on sustained power changes. Bursts are energy transients in the EEG record. High degrees of bursting were characteristic of animals having good neurological condition whereas piglets having low burst counts had poor 24 hr neuroscores. At 100 min the average burst rate of the good neuroscore outcome group was more than 8 per min and was significantly different from the poor outcome group's level of 2.7 (p < or = 0.05). When these counts were weighted by their total duration, differences between groups increased (p < or = 0.02). This study showed that the QEEG measure of burst counts and duration together provided a strong prognostic indication of the 24 hour outcome after asphyxic injury in a neonatal animal model. The critical determinant of the bursting character was the time when bursting occurred. Bursting occurring early in recovery was a good gauge of outcome. We conclude that quantitative EEG analysis and interpretation can be an important tool for the outcome determination during recovery from cerebral injury states.     

Falsely pessimistic prognosis by EEG in post-anoxic coma after cardiac arrest: the borderland of nonconvulsive status epilepticus

Background. Prognostication following anoxic coma relies on clinical assessment and is assisted by neurophysiology. A non-evolving EEG spike burst/isoelectric suppression pattern after the first 24 hours almost invariably indicates poor outcome, while an evolving pattern implies nonconvulsive status epilepticus (NCSE) that may "hide" surviving brain activity and is amenable to treatment. Case study. We present the case of a 53-year-old woman who had a witnessed out-of-hospital ventricular fibrillation cardiac arrest, was resuscitated by paramedics, but remained comatose. An EEG, performed 36 hours post-insult, showed an unremitting, non-evolving, unresponsive 2-6?Hz high-voltage spike burst/isoelectric suppression pattern, which remained unchanged at 96 hours post-insult, following therapeutic hypothermia. During this period, she was completely off sedation and taking triple antiepileptic treatment, without systemic confounding disorders. Although the initial pattern was indicative of poor neurological outcome, she eventually made meaningful functional recovery; the last EEG showed satisfactory background rhythms and stimulus-induced epileptiform discharges without seizures. Conclusion. In post-anoxic coma, non-evolving >2?Hz spike burst/isoelectric suppression pattern may still reflect NCSE and therefore should be considered in the diagnostic EEG criteria for NCSE. Such borderline patterns should not dissuade physicians from intensifying treatment until more confident prognostication can be made.