The epidemiology of convulsive status epilepticus in children: a critical review

Yield of emergent neuroimaging in children with new-onset seizure and status epilepticus

PURPOSE

To determine the yield of emergent neuroimaging among children with new-onset seizures presenting with status epilepticus.

METHOD

We performed a cross-sectional study of children seen at a single ED between 1995 and 2012 with new-onset seizure presenting with status epilepticus. We defined status epilepticus as a single seizure or multiple seizures without regaining consciousness lasting 30 min or longer. Our primary outcome was urgent or emergent intracranial pathology identified on neuroimaging. We categorized neuroimaging results as emergent if they would have changed acute management as assessed by a blinded neuroradiologist and neurologist. To ensure abnormalities were not missed, we review neuroimaging results for 30 days following the initial episode of SE.

RESULTS

We included 177 children presenting with new-onset seizure with status epilepticus, of whom 170 (96%) had neuroimaging performed. Abnormal findings were identified on neuroimaging in 64/177 (36%, 95% confidence interval 29-43%) children with 15 (8.5%, 95% confidence interval 5.2-14%) children having urgent or emergent pathology. Four (27%) of the 15 children with urgent or emergent findings had a normal non-contrast computed tomography scan and a subsequently abnormal magnetic resonance image. Longer seizure duration and older age were associated with urgent or emergent intracranial pathology.

CONCLUSION

A substantial minority of children with new-onset seizures presenting with status epilepticus have urgent or emergent intracranial pathology identified on neuroimaging. Clinicians should strongly consider emergent neuroimaging in these children. Magnetic resonance imaging is the preferred imaging modality when available and safe.

Predictors of Outcome of Convulsive Status Epilepticus Among an Egyptian Pediatric Tertiary Hospital

Convulsive status epilepticus is a common neurologic emergency in pediatrics. We aimed to study the etiology, clinical features, and prognostic factors among pediatric patients with convulsive status epilepticus. Seventy patients were included in this cohort study from pediatric emergency department of the specialized Children Hospital of Cairo University. The outcome was evaluated using the Glasgow Outcome Score. Acute symptomatic etiology was the most common cause of convulsive status epilepticus. Refractory convulsive status epilepticus was observed more significantly in cases caused by acute symptomatic etiologies. The outcome was mortality in 26 (37.1%) patients, severe disability in 15 (21.4%), moderate disability in 17 (24.3%), and good recovery in 12 (17.1%) patients. The significant predictor of mortality was lower modified Glasgow Coma Scale score on admission, whereas lower modified Glasgow Coma Scale score on admission and refractory convulsive status epilepticus were the significant predictors for disability and mortality.

Continuous electroencephalogram detection of non-convulsive seizures in the pediatric intensive care unit: review of the utility and impact on management and outcomes

Non-convulsive seizures (NCS) are common among critically ill children with acute encephalopathy. Continuous electroencephalogram (CEEG) monitoring is an indispensable tool to detect NCS, which is essential to guiding management and assessing prognosis. Risk factors for NCS are highest in pediatric intensive care unit (PICU) patients with altered mental status (AMS) and a recently witnessed clinical seizure, acute changes on neuroimaging, and/or interictal abnormalities on CEEG. Screening for at least 24 hours in at risk pediatric populations is ideal, but around half of NCS may be detected within the first hour. Rapid treatment of prolonged seizures or status epilepticus is critical, as higher seizure burdens have been associated with poorer outcomes in critically ill children. This review integrates current information on critically ill children with AMS and the use of CEEGs, risk factors for NCS, duration of CEEG monitoring, and how the detection of NCS impacts management and outcomes.

Demographics and outcomes of patients with pediatric febrile convulsive status epilepticus

BACKGROUND

Convulsive status epilepticus with fever is common and may be related to neurological sequela in children. However, there are limited data on the demographics and risk factors of this phenomenon. Thus, we aimed to describe the demographics and risk factors of neurological sequela among children with convulsive status epilepticus with fever.

METHODS

We reviewed convulsive status epilepticus with fever cases in the pediatric intensive care unit at Kobe Children's Hospital between 2002 and 2013. We included patients with intrinsic neurological disease, and excluded those with obvious central nervous system infection. Cases of neurological worsening were categorized as poor outcome using the pediatric cerebral performance category scale. Possible risk factors for poor outcome included age, sex, neurological medical history, seizure duration, body temperature, and level of consciousness.

RESULTS

A total of 253 patients (128 males), aged 1 month to 15 years (mean 45 ± 40 months), were enrolled. Three patients (1.2%) died during hospitalization, and 32 (12.6%) patients had a poor outcome. A univariate analysis identified male sex, absence of epilepsy history, body temperature above 40°C on admission, seizure duration longer than 120 minutes, impaired consciousness at 12 hours after onset, and presence of nonconvulsive seizure as potential predictors of poor outcome. A multivariate analysis, revealed that an absence of epilepsy history (odds ratio = 11.18), body temperature above 40°C on admission (odds ratio = 3.39), or impaired consciousness at 12 hours after onset (odds ratio = 41.85) was associated with poor outcome.

CONCLUSIONS

Our study indicated that absence of epilepsy history, high temperature, and/or prolonged impaired consciousness were associated with brain injury.

Developmental patterns of postictal refractoriness and potentiation akin to cortical stimulation

Postictal refractoriness checked by paired stimulations of the limbic structures was demonstrated to fail in rats<2 weeks old. Cortical epileptic afterdischarges were used in our study to examine if this phenomenon is restricted to old cortical structures or if it is a general one. Rats 12, 15, 18, 25, and 90 days old with implanted electrodes formed the experimental groups. Stimulation was performed by 15-s series of 1-msec pulses with suprathreshold intensity and frequency of 8 Hz. Paired stimulation of the cerebral cortex in 12-day-old rats elicited the second afterdischarge, even if the 30-s interval was used. Refractoriness started to appear in the third postnatal week and developed progressively so that 25-day-old rats did not differ from adult animals, that is, an interval longer than 1 min was necessary for elicitation of the second seizure.

Pediatric status epilepticus: identification and evaluation

PURPOSE OF REVIEW

Status epilepticus is an acute neurologic emergency, the incidence of which is increasing in the United States as the definition evolves and our detection abilities improve. We will present the current definition of status epilepticus, including a recently modified operational definition for use in the clinical setting. We will also provide updates on identifying children in status epilepticus, etiologic considerations, and the rationale for diagnostic testing.

RECENT FINDINGS

Recent data reveal the benefits of MRI vs. computed tomography in new-onset status epilepticus, as well as high rates of identification of electrographic seizures in patients with unexplained acute encephalopathy in pediatric ICU settings. Genetic testing should be considered in young children with recurrent status epilepticus.

SUMMARY

Prompt recognition and diagnostic evaluation of the child in status epilepticus will help identify causes, which may require specific treatment, and help in the management of this life-threatening condition. Laboratory work, neuroimaging, electroencephalogram or continuous video electroencephalogram, lumbar puncture, and genetic testing may be considered in the evaluation of the child in status epilepticus.

Clinical Profile of Status epilepticus (SE) in Children in a Tertiary Care Hospital in Bihar

BACKGROUND

Status epilepticus (SE) is a common, life threatening neurologic disorder that is essentially an acute, prolonged epileptic crisis. SE can represent an exacerbation of a pre-existing seizure disorder, the initial manifestation of a seizure disorder, or an insult other than a seizure disorder.

OBJECTIVES

To study the aetiology, clinical profile, and outcome of SE in pediatric age group. Setting and study design: Prospective study at a tertiary care medical college hospital in Bihar, India.

MATERIALS AND METHODS

Study was carried out for a period of one year (from April 2008 to March 2009). Seventy patients of SE in the age group of six month to 12 years were included in the study. Clinical history, general and systemic examination and relevant investigations along with pretested questionnaire were used to categorise different variables. Independent t-test was used for continuous variables and chi-square test for categorical variables.

RESULTS

Mean age for the study population was found to be 5.94 years (SD=3.152). Preponderance of male (60%) over female (40%) was observed. Aetiology included Idiopathic (27.14%), remote symptomatic (20%), acute symptomatic (47.14%), febrile (2.86%) and progressive encephalopathy (2.86%) groups. Generalised tonic clonic convulsion (GTC) convulsion was observed in 91.4% of SE patients while 8.6% had partial SE. Eighteen patients (25.7%) had prior history of convulsion whereas 52 patients (74.3%) presented with SE as first episode of convulsion. In our study, mortality rate was found to be 31.4% and acute symptomatic causes were responsible for most of the deaths.

CONCLUSION

SE is a severe life threatening emergency with substantial morbidity and mortality. Patients with younger age and male sex are slightly more vulnerable to develop SE. Longer duration of SE and acute symptomatic aetiologies are independent predictors for poor outcome.

The aetiology of convulsive status epilepticus: a study of 258 cases in Western China

PURPOSE

To investigate the characteristics of the aetiologies of convulsive status epilepticus (CSE) in Western China and to identify the relationships of these aetiologies with the prognoses.

METHODS

Consecutive registration and prospective observation of 258 cases of CSE in the Sichuan Epilepsy Center were performed from 1996 to 2010 to study the aetiology of CSE. The relationships of the aetiologies with the demographics, outcomes and complications of CSE were analysed using a logistic regression model.

RESULTS

The mean age was 37.6 ± 20.21 years. The majority of the CSE (62.4%) cases were acute symptomatic cases, and the primary cause was central nervous system (CNS) infection (33.7%). Histories of epilepsy were present in 51.9% of the patients. Pre-existing epilepsy occurred due to discontinuation or reduction of antiepileptic drugs (AEDs) in 31.3% of the CSE patients. Anoxia/poisoning (p<0.05, OR 8.0, 95% CI 1.34-47.77) was an independent predictor of mortality. CNS infections (p<0.001, OR 8.99, 95% CI 3.52-22.92), cerebrovascular diseases (p =0.001, OR 6.75, 95% CI 2.11-21.61) and anoxia/poisoning (p<0.01, OR 7.64, 95% CI 1.93-30.21) were the major risk factors for complications associated with CSE.

CONCLUSIONS

(1) Compared to developed countries, CNS infections seemed to be more likely to be the cause of CSE in developing countries. (2) Noncompliance with AEDs among patients with epilepsy was a prominent and avoidable trigger of CSE.

Role of antineuronal antibodies in children with encephalopathy and febrile status epilepticus

Status epilepticus in childhood is more common, with a different range of causes and a lower risk of death, than convulsive status epilepticus in adults. Acute central nervous system infections appear to be markers for morbidity and mortality. Nevertheless, central nervous infection is usually presumed in these conditions. Many aspects of the pathogenesis of acute encephalitis and acute febrile encephalopathy with status epilepticus have been clarified in the past decade. The pathogenesis is divided into direct pathogens invasion or immune-mediated mechanisms. Over the past few decades, the number of antineuronal antibodies to ion channels, receptors, and other synaptic proteins described in association with central nervous system disorders has increased dramatically, especially their role in pediatric encephalitis and status epilepticus. These antineuronal antibodies are divided according to the location of their respective antigens: (1) intracellular antigens, including glutamic acid decarboxylase and classical onconeural antigens such as Hu (antineuronal nuclear antibody 1, ANNA1), Ma2, Yo (Purkinje cell autoantibody, PCA1), Ri (antineuronal nuclear antibody 2, ANNA2), CV2/CRMP5, and amphiphysin; and (2) cell membrane ion channels or surface antigens including voltage-gated potassium channel receptor, N-methyl-d-aspartate receptor, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor, γ-aminobutyric acid(B) receptor, leucine-rich glioma-inactivated protein 1, and contactin-associated protein-like 2. Identifying the mechanism of the disease may have important therapeutic implications.

Long-term survival and outcome in children admitted to kilifi district hospital with convulsive status epilepticus

Objectives. The incidence of convulsive status epilepticus (CSE) is high in Africa but the long-term outcome is unknown. We examined the neurocognitive outcome and survival of children treated for CSE in a Kenyan hospital 3 to 4 years after discharge. Methods. The frequency and nature of neurological deficits among this group of children were determined and compared to a control group. The children were screened with the Ten Questions Questionnaire for neurodevelopmental impairment if alive and those that screened positive were invited for further assessment to determine the pattern and extent of their impairment. A verbal autopsy was performed to determine the cause of death in those that died. Results. In the 119 cases followed-up, 9 (8%) died after discharge, with the majority having seizures during their fatal illness. The 110 survivors (median age 5 years) had significantly more neurological impairments on the screening compared to 282 controls (34/110 (30.9%) versus 11/282 (3.9%), OR = 11.0, 95% CI 5.3–22.8). Fifteen percent of the cases had active epilepsy. Conclusions. This study demonstrates the considerable burden of CSE in African children. Strategies to manage children with CSE that are acceptable to the community need to be explored to improve the longer-term outcome.

A novel mechanism for simulation of partial seizures in an infant

INTRODUCTION

Seizures are a common pediatric emergency, occurring in 4% to 6% of all children by the age of 16 years. Seizures are also present in many patients with critical illness requiring resuscitation. Whereas some high-fidelity simulators have built-in seizure mechanisms, others do not. We report a novel inexpensive mechanism replicating a partial seizure in the SimBaby mannequin and the use of this mechanism in several high-fidelity in situ simulations.

METHODS

A brake lever set and a brake cable/housing for a mountain bike were attached under the skin of the SimBaby mannequin, through the groin, out of the axilla, and around the left arm. The cable was hidden under sheets and taped to the floor. The cable length allowed the controller to be several feet away from the mannequin while controlling the seizures. In our emergency department in situ simulations, this person is the educator who runs the mannequin or a confederate participating in the scenario.

RESULTS

The instructor controlling the seizure mechanism was able to stand unobtrusively in the corner during the in situ simulations and activate the seizure as indicated. Simulation participants clearly recognized that the infant was seizing and reacted appropriately as per the scenario (status epilepticus, head trauma, and tricyclic antidepressant ingestion).

CONCLUSIONS

We report a novel and inexpensive mechanism to accurately simulate partial seizures, using commonly available inexpensive bicycle components.

Prolonged febrile seizures, clinical characteristics, and acute management

PURPOSE

Prolonged febrile seizures (PFS) lasting ≥15 min have been associated with increased risk for epilepsy in later life. Initial treatment, mostly prehospital, aims to prevent its evolution to febrile status epilepticus (FSE) and reduce adverse outcome. Paucity of information is available on the immediate treatment before reaching a hospital facility.

METHODS

We obtained data, prospectively, on all children who presented from January 2008 to March 2010 with PFS to the emergency rooms of four Israeli medical centers. Information related to seizure semiology, treatment, and medical history was collected into a predefined pro forma form and reviewed centrally.

KEY FINDINGS

Sixty children, median age 18.3 months (interquartile range [IQR] 12-28) were included with a median seizure duration of 35 min (IQR 26-60), 43 (71.7%) lasting ≥30 min. Seizures had focal onset in 34 infants (57%). Fifty-four families (90%) activated the ambulance service; median ambulance arrival time was 8 min (IQR 5-10), 33 (61%) were medically treated by the ambulance paramedic, of whom 15 (45%) responded to treatment. Twelve children with active seizures did not receive medications. Initial treatment with rectal diazepam was more common in those with seizure duration >30 min.

SIGNIFICANCE

Most children with PFS are treated with antiepileptic drugs early by the ambulance service. However, even timely treatment does not prevent status epilepticus in the majority of cases. These data highlight the need for effective early treatment of this common pediatric emergency.

The brain, seizures and epilepsy throughout life: understanding a moving target

The human brain is a tremendously complex and still enigmatic three-dimensional structure, composed of countless interconnected neurons and glia. The temporal evolution of the brain throughout life provides a fourth dimension, one that influences every element of the brain's function in health and disease. This temporal evolution contributes to the probability of seizure generation and to the type and the nature of these seizures. The age-specific properties of the brain also influence the consequences of seizures on neuronal structure and behavior. These, in turn, govern epileptic activity and cognitive and emotional functions, contributing to the diverse consequences of seizures and epilepsy throughout life.

The epidemiology of seizure disorders in infancy and childhood: definitions and classifications

Seizures are one of the most common neurological symptoms that occur in infancy and childhood. They represent many different disorders with many different causes. Neonatal seizures occur in ~1.5% of neonates, febrile seizures in 2-4% of young children, and epilepsy in up to 1% of children and adolescents. Seizures provoked by other acute insults such as head trauma also occur although their precise frequency in children is hard to estimate. Ultimately, seizures are symptoms of various neurological insults and conditions. Although neonatal seizures, febrile seizures, and epilepsy overlap to a degree in that children with neonatal or febrile seizures are at increased risk of epilepsy, these different disorders have somewhat different risk factors and their own epidemiology. Furthermore, to the extent that environmental (e.g., infections, malnutrition) and medical system factors (vaccinations, prenatal care) and population genetics play roles, very different risks and patterns are seen in different areas of the world. Within each of these sets of disorders, designated as neonatal or febrile seizures and epilepsy, there are many highly specific conditions that, especially in the case of epilepsy, may have considerable implications for treatment and prognosis and consequently may require care from a specialist.

Epidemiology of Status Epilepticus Among Children in Qatar in 2008

AbstractBackground:Convulsive status epilepticus (CSE) in childhood is a medical emergency and its epidemiology should be studied separately from adult CSE; this study reviewed pediatric cases reported in Qatar in 2008.Methods:A retrospective study for a defined pediatric age group (30 days <  age <  15 years) with SE was carried out in Qatar for 12 months and included 25 patients.Results::Of the patients, 56% male, 44% female, 56% were younger than 2 years, and 52% had febrile status epilepticus, 76.9% of whom were boys. All who displayed prolonged seizure status (more than 45 min) had abnormal EEG and brain CT readings and required a prolonged stay in PICU; 20% had history of status epilepticus before.Conclusions::The incidence of SE in Qatar is similar to reports around the world, and the age-specific incidence pattern is similar as well. Febrile status epilepticus is the most important cause especially in boys. Symptomatic SE has a significantly longer duration with higher risk for recurrence than idiopathic SE.

Management of patients with status epilepticus treated at a pediatric intensive care unit in Turkey

We investigated the etiology, treatment, and prognosis of patients treated for status epilepticus at a pediatric intensive care unit. Medical records of 89 patients admitted to a pediatric intensive care unit with status epilepticus were reviewed retrospectively. Patients ranged in age from 2 months to 18 years (mean age ± S.D., 4.7 ± 3.8 years). Seizure etiologies comprised remote symptomatic in 47 (52.7%), febrile in 15 (16.9%), acute symptomatic in 12 (13.5%), and unknown in 15 (16.9%). Seizure durations ranged from 30-60 minutes in 58 patients, whereas 31 manifested refractory seizures longer than 60 minutes. Seizure control was achieved within 30 minutes in 55 patients, from 30-60 minutes in 19, and after 60 minutes in 15. Rectal diazepam was administered to 38 (42.7%) patients before admission to the hospital. Length of intensive care unit stay increased with increasing seizure duration (P < 0.05). The total mortality rate was 3.4%. This lower mortality rate may be considered evidence of the effectiveness and reliability of the status epilepticus treatment protocol in our pediatric intensive care unit. Prehospital rectal diazepam administration and the treatment of brain edema in the intensive care unit may be useful in the management of patients with status epilepticus.

Intractable seizures in a 4-month-old girl

A 4-month-old, 7-kg girl with a 3-day history of mild diarrhea was brought into a rural emergency department (ED) by private vehicle. The patient's parents reported that the child was in her usual state of health until the past several days, when she began having multiple loose stools. After an extensive interview, the family said she was born full term without any complications. She had never been hospitalized and was up to date on all of her immunizations. Family also stated emphatically that there was no alteration in her formula concentration and intake before her presentation. Approximately 30 minutes before her arrival, her parents noticed "shaking of the extremities" consistent with seizure activity. Concurrently, they noted she had irregular respirations and was not acting at her baseline.

Effect of mild hypothermia on glutamate receptor expression after status epilepticus

Hypothermia has been shown to have neuroprotective effects in various models of neurological damage. However, its therapeutic effect on pediatric status epilepticus (SE) is still unknown. We conducted a study to investigate whether hypothermia can have an adjuvant effect on pilocarpine-induced status epilepticus in immature rats when combined with diazepam treatment. Pilocarpine-induced status epilepticus was maintained for either 30 min or 60 min, which was followed by injection with diazepam (10mg/kg body weight) and/or treatment with mild hypothermia (core temperature to 33°C). We found that the spike-wave amplitude and frequency after SE during treatment with diazepam and hypothermia was significantly lower than treatment with diazepam alone. Mild hypothermia significantly reduced the number of cells undergoing necrosis and apoptosis. In addition, α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) receptor subunit GluR1 was shown to be up-regulated by SE, while GluR2 was shown to be down-regulated. However, after combination therapy with diazepam and mild hypothermia for 8h, the expression of GluR1 was decreased and GluR2 was increased relative to the levels of diazepam alone treated juveniles. We also found that the expression of mGluR-1a was also decreased relative to diazepam alone. These findings suggest that mild hypothermia might further protect against pilocarpine-induced status epilepticus in immature rats by regulating glutamate receptor expression. This study was conducted using a pediatric model of SE so as to gain a better understanding of the role of hypothermia in the developing brain.

The role of magnetic resonance imaging in the follow-up of children with convulsive status epilepticus

AIM

The aim of this study was to determine the yield of magnetic resonance imaging (MRI) after an episode of childhood convulsive status epilepticus (CSE) and to identify the clinical predictors of an abnormal brain scan.

METHOD

Children were recruited following an episode of CSE from an established clinical network in north London. Eighty children (age range 1mo-16y; 39 males; 41 females) were enrolled and seen for clinical assessment and brain MRI within 13 weeks of suffering from an episode of CSE. Scans were reviewed by two neuroradiologists and classified as normal (normal/normal-variant) or abnormal (minor/major abnormality). Factors predictive of an abnormal scan were investigated using logistic regression.

RESULTS

Eighty children were recruited at a mean of 31.8 days (5-90d) after suffering from CSE. Structural abnormalities were found in 31%. Abnormal neurological examination at assessment (odds ratio [OR] 190.46), CSE that was not a prolonged febrile seizure (OR 77.12), and a continuous rather than an intermittent seizure (OR 29.98) were all predictive of an abnormal scan. No children with previous neuroimaging had new findings that altered their clinical management.

INTERPRETATION

Brain MRI should be considered for all children with a history of CSE who have not previously undergone MRI, especially those with non-prolonged febrile seizure CSE, those with persisting neurological abnormalities 2 to 13 weeks after CSE, and those with continuous CSE.

Status epilepticus in children: causes, clinical features and short-term outcome

BACKGROUND

We aimed to evaluate the cause, clinical profile, and short-term outcome of status epilepticus cases that were admitted to our pediatric emergency unit between 1 January and 31 December 2008.

METHODS

We studied the clinical features of 59 seizures that occurred in 56 patients aged between 3 months and 15 years with the diagnosis of status epilepticus. We observed the clinical course and outcome of 53 cases for 6 to 18 months. The correlation between the cause of the seizure and the patient's age at the time of status epilepticus was evaluated as well as the correlation between the risk of seizure recurrence and family history of seizure, the neurological status of the patient prior to seizure and the presence of epilepsy.

RESULTS

The most common cause of status epilepticus is febrile illness in children younger than 2 years and idiopathic/cryptogenic and remote symptomatic causes in children older than 2 years. The rate of recurrence of seizure was significantly higher in cases with existing neurological abnormalities, prior epilepsy and seizures with remote symptomatic causes. The most common triggering factors of status epilepticus development in cases with epilepsy were noncompliance for anti-epileptic drugs and infectious fever.

CONCLUSIONS

In our study, the risk factors for seizure recurrence were the presence of prior epilepsy, existence of neurological abnormalities and remote symptomatic causes. We argue that improving the compliance of patients and their families to take medicine appropriately and training them in how to cope with febrile illnesses may decrease the recurrence of seizures.

Identification and evaluation of the child in status epilepticus

Status epilepticus (SE) is an acute neurologic emergency that requires prompt recognition and initiation of treatment. Recognition can be difficult because SE comes in many forms and has been defined differently over the past decade. We present the general consensus definition of SE and how to use the definition, including a modified operational definition, to guide management. Furthermore, evaluation of the child who presents in SE is important to determine the etiology and identify underlying causes that may require additional treatment. Evaluation may include measurement of electrolytes, lumbar puncture, drug levels, electroencephalography, and/or neuroimaging. Recent data are presented that update the current practice parameter guidelines and also indicate that neuroimaging is important in cases of new-onset SE and can help significantly in the diagnosis and management.

Lessons from the laboratory: the pathophysiology, and consequences of status epilepticus

Status epilepticus (SE) is the most common neurologic emergency of childhood. Experimental models parallel several clinical features of SE including (1) treatment is complicated by an increasing probability that benzodiazepines will fail with increasing seizure duration and (2) outcome varies with age and etiology. Studies using these models showed that the activity-dependent trafficking of GABA(A) receptors contributes in part to the progressive decline in GABA-mediated inhibition and the failure of the benzodiazepines. Furthermore, laboratory studies have provided evidence that age and inciting stimulus interact to determine the neuronal circuits activated during SE (ie, functional anatomy) and that differences in functional anatomy can partially account for variations in SE outcome. Future laboratory studies are likely to provide an additional understanding of the cellular and molecular mechanisms that underlie SE and its consequences. Such studies are necessary in the development of rational emergent therapy for SE and its long-term outcomes.

Refractory metabolic acidosis as a complication of high-dose midazolam infusion for pediatric status epilepticus

BACKGROUND

The use of midazolam for the treatment of status epilepticus in children has generally been shown to be well tolerated and safe. Furthermore, encouraging efficacy has been observed when pediatric patients with status epilepticus have received continuous intravenous infusions of midazolam.

CASE PRESENTATION

A 9-year-old girl was treated with high-dose, continuous intravenous infusion of midazolam for the management of refractory status epilepticus. The patient developed a severe hyperchloremic, non-anion gap metabolic acidosis and resultant hemodynamic compromise, necessitating significant inotropic support and the initiation of a vasopressor infusion. We speculate that this complication was due to the preparation of parenteral midazolam with hydrochloric acid. The midazolam infusion was stopped, and, in less than 5 hours, the patient's metabolic acidosis resolved. The patient's inotropic and vasopressor infusions could only be weaned after discontinuing the use of high-dose midazolam.

CONCLUSIONS

Although this complication was observed in only 1 pediatric patient with cortical dysplasia, caution and close clinical and laboratory surveillance should be exercised when administering continuous intravenous infusions of midazolam to pediatric patients.

Analysis of convulsive status epilepticus in children of Taiwan

Convulsive status epilepticus is a medical emergency with significantly associated mortality and morbidity. The demographic data and outcomes of convulsive status epilepticus in children were collected for descriptive analysis. We retrospectively reviewed cases of convulsive status epilepticus in the Pediatric Intensive Care Unit of Chang Gung Children's Hospital between 1999 and 2006. We enrolled 141 patients with 198 episodes of convulsive status epilepticus, aged 2 months to 18 years: 24.8% of first episodes developed convulsive status epilepticus, with a duration of over 60 minutes. First episodes of convulsive status epilepticus were most often evidenced in febrile status during acute central nerve system infections (48.2%), and in nonfebrile status during acute noncentral nerve system illness in previously epileptic children (28.4%). Before their first episode, 63.8% of children were neurologically healthy, and 12.2% exhibited a prolonged febrile seizure. The most common etiology of mortality was acute central nervous system infection. The immediate mortality rate was 7.1%. Convulsive status epilepticus in childhood is more common, with a different range of causes and a lower risk of death, than convulsive status epilepticus in adults. Acute central nervous system infections appear to be markers for morbidity and mortality.

Arresting a Seizure by Dropping a Little Acid

Seizure Termination by Acidosis Depends on ASIC1a. Ziemann AE, Schnizler MK, Albert GW, Severson MA, Howard MA 3rd, Welsh MJ, Wemmie JA. Nat Neurosci 2008;11(7):816–822. Most seizures stop spontaneously; however, the molecular mechanisms that terminate seizures remain unknown. Observations that seizures reduced brain pH and that acidosis inhibited seizures indicate that acidosis halts epileptic activity. Because acid-sensing ion channel 1a (ASIC1a) is exquisitely sensitive to extracellular pH and regulates neuron excitability, we hypothesized that acidosis might activate ASIC1a, which would terminate seizures. Disrupting mouse ASIC1a increased the severity of chemoconvulsant-induced seizures, whereas overexpressing ASIC1a had the opposite effect. ASIC1a did not affect seizure threshold or onset, but shortened seizure duration and prevented seizure progression. CO2 inhalation, long known to lower brain pH and inhibit seizures, required ASIC1a to interrupt tonic-clonic seizures. Acidosis activated inhibitory interneurons through ASIC1a, suggesting that ASIC1a might limit seizures by increasing inhibitory tone. Our results identify ASIC1a as an important element in seizure termination when brain pH falls and suggest both a molecular mechanism for how the brain stops seizures and new therapeutic strategies.

The pilocarpine model of temporal lobe epilepsy

Understanding the pathophysiogenesis of temporal lobe epilepsy (TLE) largely rests on the use of models of status epilepticus (SE), as in the case of the pilocarpine model. The main features of TLE are: (i) epileptic foci in the limbic system; (ii) an “initial precipitating injury”; (iii) the so-called “latent period”; and (iv) the presence of hippocampal sclerosis leading to reorganization of neuronal networks. Many of these characteristics can be reproduced in rodents by systemic injection of pilocarpine; in this animal model, SE is followed by a latent period and later by the appearance of spontaneous recurrent seizures (SRSs). These processes are, however, influenced by experimental conditions such as rodent species, strain, gender, age, doses and routes of pilocarpine administration, as well as combinations with other drugs administered before and/or after SE. In the attempt to limit these sources of variability, we evaluated the methodological procedures used by several investigators in the pilocarpine model; in particular, we have focused on the behavioural, electrophysiological and histopathological findings obtained with different protocols. We addressed the various experimental approaches published to date, by comparing mortality rates, onset of SRSs, neuronal damage, and network reorganization. Based on the evidence reviewed here, we propose that the pilocarpine model can be a valuable tool to investigate the mechanisms involved in TLE, and even more so when standardized to reduce mortality at the time of pilocarpine injection, differences in latent period duration, variability in the lesion extent, and SRS frequency.