Valproate-induced hyperammonemic encephalopathy

Valproate encephalopathy: Case series and literature review

Valproate encephalopathy is one of the unusual and severe but treatable side effect. This research focuses on four female patients who had valproate medication for epilepsy and developed an increased frequency of seizures, exacerbated disruption of consciousness, gastrointestinal problems, cognitive dysfunction, ataxia, and psychobehavioral abnormalities. The patient's symptoms improved over time once sodium valproate was stopped. As a result, when using sodium valproate, one should be aware of the risk of sodium valproate encephalopathy and cease using the medication right once if any of the above symptoms of unknown etiology manifest clinically. We also go over the potential pathogenesis that lead to valproate encephalopathy and the heightened risk of encephalopathy from taking antiepileptic medications together. It was stressed how crucial it is to identify, diagnose, and treat sodium valproate encephalopathy as soon as possible.

Hyperammonemic encephalopathy induced by valproic acid

Valproate (VPA) is broad-spectrum antiepileptic drug. Several adverse reactions including hepatotoxicity, fetal risk and pancreatitis are well known and labelled as boxed warnings in the USA. One adverse reaction that is less well known but clinically significant for its severe morbidity is hyperammonemic encephalopathy. We present a case of woman with hyperammonemic encephalopathy following the initiation of VPA therapy; she had a favourable outcome with discontinuation of the drug and prompt treatment with lactulose and L-carnitine.

Unusual case of sodium valproate-induced hyperammonaemia encephalopathy

There is limited information about sodium valproate-induced hyperammonaemia encephalopathy (VPAIHE). The aim of this case report is to provide medical practitioners with a greater awareness of the possible development of hyperammonaemia due to sodium valproate use and its associated complications.This paper describes a middle-aged man with a history of bipolar affective disorder who was admitted with a manic relapse secondary to medication non-compliance. His admission was complicated by an intensive care unit admission to manage medical compromise in the context of sodium VPAIHE.

Risk factors of hyperammonemia in epilepsy patients with valproic acid therapy

BACKGROUND

Hyperammonemia can occur after acute overdose or chronic use of valproic acid (VPA). Although VPA-related hyperammonemic encephalopathy (VHE) is a rare complication of VPA therapy, early recognition of VHE and identifying its risk factors are important because VHE can lead to loss of consciousness and increased seizure frequency.

PURPOSE

The purpose of our study is to evaluate the risk factors of hyperammonemia in epilepsy patients during treatment with VPA therapy.

METHODS

We reviewed the medical records of 1084 adult patients with epilepsy and enrolled 116 patients with VPA therapy who had results of blood levels of ammonia over a 3-year period. Hyperammonemia was defined as a blood ammonia level exceeding 80 µg/dL. Correlations of blood levels of ammonia with dosages and blood levels of VPA were evaluated. We further performed univariate and multivariate linear regression analyses to identify risk factors for hyperammonemia in epilepsy patients treated with VPA therapy.

RESULTS

Blood levels of ammonia were well correlated with dosages of VPA (p = 0.036), but not with blood levels of VPA (p = 0.463). Hyperammonemia was more common in patients with higher VPA dosage and higher total drug loads of concurrent antiseizure medications (ASMs). Hyperammonemia was also associated with the use of topiramate and phenobarbital. In multivariate analysis, we identified total drug load of ASMs (p = 0.003) and use of topiramate (p = 0.007) as independent predictors of hyperammonemia. Four patients (4/116, 3.4 %) had clinical symptoms of VHE. Three of them had hyperammonemia while the other patient had normal blood level of ammonia with a high blood level of VPA.

CONCLUSION

Our study shows that higher total drug loads of concurrent ASMs and use of topiramate were independent risk factors of hyperammonemia in epilepsy patients with VPA therapy. Although the incidence of VHE was not high in our study, clinicians should be aware of this potential adverse effect of VPA therapy, especially in patients with polytherapy of ASMs including topiramate.

Valproate-related hyperammonemic encephalopathy with generalized suppression EEG: a case report

BACKGROUND

Valproic acid (VPA) is a prevalent antiseizure medication (ASM) used to treat epilepsy. Valproate-related hyperammonemic encephalopathy (VHE) is a type of encephalopathy that can occur during neurocritical situations. In VHE, the electroencephalogram (EEG) displays diffuse slow waves or periodic waves, and there is no generalized suppression pattern.

CASE PRESENTATION

We present a case of a 29-year-old female with a history of epilepsy who was admitted for convulsive status epilepticus (CSE), which was controlled by intravenous VPA, as well as oral VPA and phenytoin. The patient did not experience further convulsions but instead developed impaired consciousness. Continuous EEG monitoring revealed a generalized suppression pattern, and the patient was unresponsive. The patient's blood ammonia level was significantly elevated at 386.8 μmol/L, indicating VHE. Additionally, the patient's serum VPA level was 58.37 μg/ml (normal range: 50-100 μg/ml). After stopping VPA and phenytoin and transitioning to oxcarbazepine for anti-seizure and symptomatic treatment, the patient's EEG gradually returned to normal, and her consciousness was fully restored.

DISCUSSION

VHE can cause the EEG to display a generalized suppression pattern. It is crucial to recognize this specific situation and not to infer a poor prognosis based on this EEG pattern.

Valproate-Induced Hyperammonemic Encephalopathy Causing New-Onset Seizures

Valproate-induced hyperammonemic encephalopathy (VHE) is a rare and severe side effect that can occur with valproic acid (VPA) therapy, despite therapeutic doses and normal serum levels of valproate. The typical signs of this condition include a sudden onset of impaired consciousness, focal neurologic symptoms, and an increase in seizure frequency. The exact cause of VHE is unknown, but it is believed to be related to the accumulation of toxic VPA metabolites and increased levels of ammonia that can cause swelling of the astrocytes and cerebral edema. We present a case of a 19-year-old male patient with a history of bipolar disorder on valproic acid 250 mg daily, admitted to the hospital after a new-onset seizure. He was found to have elevated levels of ammonia in his blood, despite having therapeutic levels of valproate and no liver dysfunction. His symptoms improved with discontinuation of the medication and his ammonia levels decreased. We discuss possible mechanisms and risk factors leading to encephalopathy while on valproate therapy. VHE should be considered a possibility when patients treated with valproate show signs of impaired consciousness.

Acute Valproate-Induced Encephalopathy in Status Epilepticus: A Registry-Based Assessment

BACKGROUND

Valproate-induced encephalopathy (VIE) affects between 0.1% and 2.5% of patients under long-term epilepsy treatment. Its frequency and characteristics in adults with status epilepticus (SE) is, however, unknown.

OBJECTIVE

The aim of this study was to characterize the frequency and the clinico-biological characteristics of VIE in adult SE patients.

METHODS

We reviewed all patients included in our institutional SE registry who were treated for an SE episode between November 2021 and February 2023 and identified 39 patients who received valproate for their SE treatment. Acute VIE was defined by worsening of consciousness having led to the discontinuation of valproate, and improvement of consciousness within 96 hours after discontinuation of valproate during acute hospital treatment.

RESULTS

Patients had a mean valproate intravenous loading dose of 34.5 mg/kg and a mean maintenance dose of 15.3 mg/kg/d (1078 mg/d). Four out of 29 patients with measured ammonium had hyperammonemia. We identified four (10%) patients fulfilling acute VIE criteria. Median time from administration of valproate to the occurrence of VIE, and to resolution of VIE after cessation of valproate treatment, was 2 days for each. Three of the four VIE patients had no associated hyperammonemia. Patients who developed VIE more frequently had a history of liver disease (p = 0.023), and tended to be younger, but other clinical variables did not differ significantly from patients without VIE, including valproate loading or maintenance doses, SE cause, duration or severity, other concomitant antiseizure medications (none received topiramate, phenobarbital, or primidone).

CONCLUSION

Pending larger studies, VIE in SE seems relatively frequent and difficult to foresee; clinical alertness to symptoms is mandatory, even without hyperammonemia, and valproate withdrawal should be considered in suspected cases.

Treatment of pediatric convulsive status epilepticus

Status epilepticus is one of the most common life-threatening neurological emergencies in childhood with the highest incidence in the first 5 years of life and high mortality and morbidity rates. Although it is known that a delayed treatment and a prolonged seizure can cause permanent brain damage, there is evidence that current treatments may be delayed and the medication doses administered are insufficient. Here, we summarize current knowledge on treatment of convulsive status epilepticus in childhood and propose a treatment algorithm. We performed a structured literature search via PubMed and ClinicalTrails.org and identified 35 prospective and retrospective studies on children <18 years comparing two and more treatment options for status epilepticus. The studies were divided into the commonly used treatment phases. As a first-line treatment, benzodiazepines buccal/rectal/intramuscular/intravenous are recommended. For status epilepticus treated with benzodiazepine refractory, no superiority of fosphenytoin, levetirazetam, or phenobarbital was identified. There is limited data on third-line treatments for refractory status epilepticus lasting >30 min. Our proposed treatment algorithm, especially for children with SE, is for in and out-of-hospital onset aids to promote the establishment and distribution of guidelines to address the treatment delay aggressively and to reduce putative permanent neuronal damage. Further studies are needed to evaluate if these algorithms decrease long-term damage and how to treat refractory status epilepticus lasting >30 min.

Genetic and environmental risk factors of acute infection-triggered encephalopathy

Acute encephalopathy is a constellation of syndromes in which immune response, metabolism and neuronal excitation are affected in a variable fashion. Most of the syndromes are complex disorders, caused or aggravated by multiple, genetic and environmental risk factors. Environmental factors include pathogenic microorganisms of the antecedent infection such as influenza virus, human herpesvirus-6 and enterohemorrhagic Escherichia coli, and drugs such as non-steroidal anti-inflammatory drugs, valproate and theophylline. Genetic factors include mutations such as rare variants of the SCN1A and RANBP2 genes, and polymorphisms such as thermolabile CPT2 variants and HLA genotypes. By altering immune response, metabolism or neuronal excitation, these factors complicate the pathologic process. On the other hand, some of them could provide promising targets to prevent or treat acute encephalopathy.

Einfluss von Medikamenten auf das EEG: Eine Übersicht

Eine Vielzahl von Präparaten mit Einfluss auf das zentrale Nervensystem, insbesondere Medikamente, die zur Standard-Therapie auf neurologischen Intensiv- und Überwachungsstationen gehören, haben einen Einfluss auf den elektroenzephalograhischen (EEG) Befund. Diese Effekte reichen von geringen Einflüssen auf Grundrhythmus und EEG-Amplituden bis zur Auslösung von epileptiformer Aktivität und Anfallsmustern. Kenntnisse über die zu erwartenden Veränderungen sind daher relevant, um neben krankheitsassoziierten Auffälligkeiten im Rahmen der Differentialdiagnostik auch medikamentöse Ursachen bedenken zu können und etwaige therapeutische Konsequenzen einzuleiten. In dem vorliegenden Übersichtartikel werden neben Einflüssen von Analgosedierung und antikonvulsiven Medikamenten auch Effekte von Neuroleptika, Antidepressiva, Immunsuppressiva sowie Antibiotika auf das EEG diskutiert.

Extrahepatic portosystemic shunts as an unusual but treatable cause of hyperammonemic encephalopathy in a noncirrhotic patient - a case report

We report a case of hyperammonemic encephalopathy due to extrahepatic portosystemic shunts in a noncirrhotic patient. A 79-year-old woman suffered from episodic confusion, disorientation, dysphasia and fluctuating level of consciousness. Electroencephalography (EEG) showed encephalopathic changes and serum levels of ammonia were elevated. Further investigation revealed mesenterorenal and mesenterocaval shunts, which had possibly evolved after pancreatic surgery 5 years ago. After shunt obliteration, the symptoms completely resolved, ammonia levels dropped to the normal range and EEG findings normalized. Clinicians should be aware of this rare but treatable cause of encephalopathy in noncirrhotic patients.

Case Report: Triphasic Waves in a 9-Year-Old Girl With Anti-NMDAR Encephalitis

BACKGROUND

Triphasic waves (TWs) are mainly described in association with metabolic encephalopathy, especially hepatic encephalopathy. Now, as different conditions including non-metabolic and structural abnormalities have been reported to be associated with TWs, the presence of TWs becomes a non-specific finding for metabolic encephalopathy.

CASE PRESENTATION

We report the first case of anti-NMDAR encephalitis in a 9-year-old girl presenting with TWs on EEG. The TWs background EEG lasted for about 12 h on the 40th day of the disease course. No epileptic wave was found during a series of EEG examinations. The child was discharged from the hospital and no neurological sequelae remained after a six-month follow-up.

CONCLUSIONS

TWs are not specific to metabolic encephalopathy, but can also occur in children with autoimmune encephalitis. This case achieved a good prognosis after the early initiation of immunotherapy.

Case Report: A Case of Valproic Acid-Induced Hyperammonemic Encephalopathy Associated With the Initiation of Lithium: A Re-duplicable Finding

INTRODUCTION

Hyperammonemic encephalopathy (HAE) is a serious adverse effect of valproate semisodium, which is facilitated by the potential for drug interaction. However, despite frequent co-prescription of valproate semisodium and lithium, the role of this combination in the occurrence of HAE has not been defined in the literature. This case report concerns the occurrence of HAE concomitant with the initiation of lithium in a 29-year-old patient who had been placed on valproate semisodium for a schizoaffective disorder.

CASE REPORT

Due to a relapse while on a combined antipsychotic and mood-stabilizing therapy (paliperidone palmitate and valproate semisodium), a cross-taper from valproate semisodium to lithium was proposed. The initiation of lithium was accompanied by an acute confusional syndrome, an elevated serum valproate level and hyperammonemia suggestive of drug-induced HAE. The discontinuation of lithium and reduction of valproate semisodium led to neurological improvement, until a recrudescence of psychiatric symptoms justified a rechallenge of the combination within the framework of a new cross-taper. As soon as Lithium was re-initiated, an increase in the serum valproate level and hyperammonemia were again noted.

DISCUSSION

The mechanisms of valproate-related HAE involve various metabolic pathways. In this case, exploration of the iatrogenic hypothesis focused on the imputability of concomitant cannabis use and co-prescriptions of benzodiazepines, antipsychotics, and in all likelihood, mood stabilizers.

CONCLUSION

Therefore, this case study suggests that Lithium plays a role in serum valproate level elevation, and supports the hypothesis of an association between an elevated serum valproate level, hyperammonemia and reversible encephalopathy. A more in-depth pharmacokinetic exploration would provide a better understanding of the mechanisms of these interactions and support for the benefit-risk balance associated with this frequent co-prescription.

Triphasic Waves: Historical Overview of an Unresolved Mystery

SUMMARY

Triphasic waves are a fascinating and mysterious EEG feature. We now have to accept that, at times, epileptiform discharges may have a blunted "triphasic morphology," and that there may be great difficulty in distinguishing between these often similar forms. The aim of this review was to describe the evolution in our understanding of triphasic waves that has occurred regarding the pathophysiology of triphasic waves, their most frequent causes, and the diagnostic difficulties involved in interpretation and differentiation from nonconvulsive status epilepticus.

Non-hyperammonaemia valproate-induced encephalopathy: A case report

WHAT IS KNOWN AND OBJECTIVE

Valproate sodium is an effective antiepileptic drug (AED). Serious adverse effects of valproate sodium are uncommon. This case report illustrates the existence of non-hyperammonaemia valproate-induced encephalopathy.

CASE DESCRIPTION

A 47-year-old woman with epilepsy who developed valproate-induced encephalopathy without hyperammonaemia after valproate sodium treatment, and the symptoms completely subsided after withdrawal of valproate sodium.

WHAT IS NEW AND CONCLUSION

Early diagnosis and identification of the mechanisms of non-hyperammonaemia valproate-induced encephalopathy are important. Immediate discontinuation of valproate sodium results in rapid resolution of symptoms in these patients.

Post-stroke epileptogenesis is associated with altered intrinsic properties of hippocampal pyramidal neurons leading to increased theta resonance

Brain insults like stroke, trauma or infections often lead to blood-brain barrier-dysfunction (BBBd) frequently resulting into epileptogenesis. Affected patients suffer from seizures and cognitive comorbidities that are potentially linked to altered network oscillations. It has been shown that a hippocampal BBBd in rats leads to in vivo seizures and increased power at theta (3-8 Hz), an important type of network oscillations. However, the underlying cellular mechanisms remain poorly understood. At membrane potentials close to the threshold for action potentials (APs) a subpopulation of CA1 pyramidal cells (PCs) displays intrinsic resonant properties due to an interplay of the muscarine-sensitive K⁺-current (I_M) and the persistent Na⁺-current (I_NaP). Such resonant neurons are more excitable and generate more APs when stimulated at theta frequencies, being strong candidates for contributing to hippocampal theta oscillations during epileptogenesis. We tested this hypothesis by characterizing changes in intrinsic properties of hippocampal PCs one week after post-stroke epileptogenesis, a model associated with BBBd, using slice electrophysiology and computer modeling. We find a higher proportion of resonant neurons in BBBd compared to sham animals (47 vs. 29%), accompanied by an increase in their excitability. In contrast, BBBd non-resonant neurons showed a reduced excitability, presented with lower impedance and more positive AP threshold. We identify an increase in I_M combined with either a reduction in I_NaP or an increase in I_Leak as possible mechanisms underlying the observed changes. Our results support the hypothesis that a higher proportion of more excitable resonant neurons in the hippocampus contributes to increased theta oscillations and an increased likelihood of seizures in a model of post-stroke epileptogenesis.

Approach to Pediatric Intractable Migraine

PURPOSE OF REVIEW

Intractable migraine in children and adolescents is a significant cause of disability and decreased quality of life (QoL) in this population. Challenges include lack of unifying definition for intractable migraine, and limited data on best-practice management in this age group, with most current treatment pathways extrapolated from adult studies or expert consensus.

RECENT FINDINGS

A comprehensive approach in the evaluation and management of intractable migraine in this age group encompasses excluding secondary causes of headache; making an accurate diagnosis; identifying and appropriately managing modifiable risk factors; and initiating appropriate pharmacologic therapy to reduce disability, improve health-related quality of life, reduce risk of progression, and develop adaptive pain coping strategies. Several strategies for management of pediatric intractable migraine including use of acute medications, bridge therapy in outpatient setting, emerging therapies for preventive therapy, and a stepwise combination therapy for management of pediatric intractable migraine in emergency and inpatient setting are presented based on available clinical data, safety/tolerability, availability, cost-effectiveness, and expert consensus. This descriptive review of the available literature focuses on approach to therapy for acute intractable migraine in a pediatric population including outpatient, emergency department (ED), and inpatient management.

Managing valproic acid toxicity-related hyperammonaemia: an unpredicted course

A 20-year-old woman presented following an intentional overdose of valproic acid. Use of valproic acid, either acute or chronic, can result in hyperammonaemia. Mild hyperammonaemia with chronic use is mostly asymptomatic but can also present with concern for encephalopathy. Acute valproic acid toxicity results in significant hyperammonaemia, which can contribute to encephalopathy. Levocarnitine is the treatment of choice in valproic acid toxicity-related hyperammonaemia. For severe cases of encephalopathy, intermittent haemodialysis can also be considered. To our knowledge, this is the first case report to clearly show symptom relapse and hyperammonaemia after discontinuing levocarnitine. We recommend levocarnitine therapy for at least 72 hours, followed by an additional 24 hours of monitoring for symptom relapse and hyperammonaemia after levocarnitine discontinuation.

Valproate but not levetiracetam slows the EEG alpha peak frequency - A pharmaco-EEG study

OBJECTIVE

Studies of the effect of valproate (VPA) on the background EEG have shown varying results. Therefore, we compared the effect of VPA and levetiracetam (LEV) on the EEG alpha peak frequency (APF).

METHODS

We retrospectively examined the APF in resting-state EEG of patients undergoing inpatient video-EEG monitoring (VEM) during withdrawal of VPA or LEV. We assessed APF trends by computing linear fits across individual patients' APF as a function of consecutive days, and correlated the APF and daily antiseizure medication (ASM) doses on a single-patient and group level.

RESULTS

The APF in the VPA-group significantly increased over days with falling VPA doses (p = 0.005, n = 13), but did not change significantly in the LEV-group (p = 0.47, n = 18). APF correlated negatively with daily ASM doses in the VPA-group (average of r = -0.74 ± 0.12 across patients, p = 0.0039), but not in the LEV-group (average of r = -0.17 ± 0.18 across patients, p = 0.4072).

CONCLUSIONS

Our results suggest that VPA treatment slows the APF. This APF reduction correlates with the daily dose of VPA and is not present in LEV treatment.

SIGNIFICANCE

Our study identifies a VPA-related slowing of the APF even in patients without electroencephalographic or overt clinical signs of encephalopathy.

Potential Therapeutic Role of Carnitine and Acetylcarnitine in Neurological Disorders

BACKGROUND

Current therapy of neurological disorders has several limitations. Although a high number of drugs are clinically available, several subjects do not achieve full symptomatic remission. In recent years, there has been an increasing interest in the therapeutic potential of L-carnitine (LCAR) and acetyl-L-carnitine (ALCAR) because of the multiplicity of actions they exert in energy metabolism, as antioxidants, neuromodulators and neuroprotectors. They also show excellent safety and tolerability profile.

OBJECTIVE

To assess the role of LCAR and ALCAR in neurological disorders.

METHODS

A meticulous review of the literature was conducted in order to establish the linkage between LCAR and ALCAR and neurological diseases.

RESULTS

LCAR and ALCAR mechanisms and effects were studied for Alzheimer's disease, depression, neuropathic pain, bipolar disorder, Parkinson's disease and epilepsy in the elderly. Both substances exert their actions mainly on primary metabolism, enhancing energy production, through β-oxidation, and the ammonia elimination via urea cycle promotion. These systemic actions impact positively on the Central Nervous System state, as Ammonia and energy depletion seem to underlie most of the neurotoxic events, such as inflammation, oxidative stress, membrane degeneration, and neurotransmitters disbalances, present in neurological disorders, mainly in the elderly. The impact on bipolar disorder is controversial. LCAR absorption seems to be impaired in the elderly due to the decrease of active transportation; therefore, ALCAR seems to be the more effective option to administer.

CONCLUSION

ALCAR emerges as a simple, economical and safe adjuvant option in order to impair the progression of most neurological disorders.

Chronic Valproic Acid Administration Increases Plasma, Liver, and Brain Ammonia Concentration and Suppresses Glutamine Synthetase Activity

Asymptomatic valproic acid (VPA)-induced hyperammonemia in the absence of liver impairment is fairly common. However, the underlying mechanisms through which VPA causes elevation in plasma ammonia (NH₄) remains under investigation. Male Sprague Dawley rats (n = 72) were randomly allocated to receive VPA 400 mg/kg, 200 mg/kg, or vehicle IP daily for either 8, 14, or 28 consecutive days. The behavioral effects of VPA were assessed. Plasma, liver, and prefrontal cortex (PFC), striatum (Str), and cerebellum (Cere) were collected 1 h post last injection and assayed for NH₄ concentration and glutamine synthetase (GS) enzyme activity. Chronic VPA treatment caused attenuation of measured behavioral reflexes (p < 0.0001) and increase in plasma NH₄ concentration (p < 0.0001). The liver and brain also showed significant increase in tissue NH₄ concentrations (p < 0.0001 each) associated with significant reduction in GS activity (p < 0.0001 and p = 0.0003, respectively). Higher tissue NH₄ concentrations correlated with reduced GS activity in the liver (r = −0.447, p = 0.0007) but not in the brain (r = −0.058, p = 0.4). Within the brain, even though NH₄ concentrations increased in the PFC (p = 0.001), Str (p < 0.0001), and Cere (p = 0.01), GS activity was reduced only in the PFC (p < 0.001) and not in Str (p = 0.2) or Cere (p = 0.1). These results suggest that VPA-induced elevation in plasma NH₄ concentration could be related, at least in part, to the suppression of GS activity in liver and brain tissues. However, even though GS is the primary mechanism in brain NH₄ clearance, the suppression of brain GS does not seem to be the main factor in explaining the elevation in brain NH₄ concentration. Further research is urgently needed to investigate brain NH₄ dynamics under chronic VPA treatment and whether VPA clinical efficacy in treating seizure disorders and bipolar mania is impacted by its effect on GS activity or other NH₄ metabolizing enzymes.

Influence of valproate-induced hyperammonemia on treatment decision in an adult status epilepticus cohort

INTRODUCTION

Status epilepticus (SE) is a neurological emergency in which immediate intervention is required to prevent permanent brain damage and death. Intravenous (IV) valproic acid (VPA) is often used for the treatment of SE. However, IV VPA frequently increases the blood ammonia level. In this study, we explore the impact of IV VPA-induced hyperammonemia (HA) on treatment management of SE and discuss the challenges related to this particular condition.

METHODS

We used data from medical records of 31 adult patients (≥18 years) treated with IV VPA for SE at Oslo University Hospital between January 2006 and October 2019. Clinical and blood sample data and information about the influence of HA on treatment were collected. Correlations between ammonia levels and other continuous or categorical variables were tested using the Pearson's correlation coefficient. The Kruskal-Wallis H-test was used to analyze associations between different variables and treatment decisions.

RESULTS

Thirty of 31 patients had increased ammonia level during IV VPA treatment. In 16/30 patients, VPA was discontinued, and in 6/30 patients, the dose was reduced. We found a difference in the median peak ammonia level among the groups where VPA was discontinued (99 μmol/l), reduced (71 μmol/l), and continued (55.5 μmol/l) (P = 0.008). Also clinical status, measured by West Haven Criteria, varied among the groups where VPA was discontinued (3.5), reduced (2.5), and continued (2.0) (P = 0.01). Treatment decisions at peak ammonia were not associated with the level of liver enzymes and bilirubin.

CONCLUSION

Hyperammonemia had a substantial impact on further management. To date, no recommendations exist on how to manage VPA-induced HA in SE. We call for systematic prospective studies and evidence-based guidelines.

Use of carglumic acid in valproate-induced hyperammonemia: 25 pediatric cases

Hyperammonemic encephalopathy is a rare but potentially dangerous complication of the antiepileptic drug (AED) sodium valproate (VPA). We report a retrospective study of 25 pediatric patients, (15 females [60%]; age: 7.6 ± 4.9 years), with different underlying disorders, who suffered from hyperammonemia due to VPA and who were treated with carglumic acid (CA). The duration of treatment with VPA was 15 ± 1 month, with a dose of 40 ± 16.6 mg/kg/d. VPA blood levels were 75.5 ± 60 mg/L with seven patients being overdosed (>100 mg/L). Twenty-three patients received concomitant treatment with other AEDs. The initial dose of CA was 100 mg/kg. Subsequently, CA doses of 25 mg/kg were given to 22 patients every 6 hours (average treatment length 2.17 ± 1.1 days) until ammonemia was normalized. In nine patients, CA was used in combination with other drugs to treat hyperammonemia. In all cases, blood ammonia levels were brought under control and symptoms of hyperammonemia resolved. Two hours after CA administration, the average reduction in ammonium levels was 53 ± 29 and 88.6 ± 47.5 μmol/L at 24 hours, resulting in a statistically significant decrease when compared to pretreatment levels. There were no statistically significant differences between sexes, in the presence or not of cognitive impairment or previous carnitine treatment. There were no statistically significant differences when comparing treatment with CA plus ammonia scavengers vs CA alone. In 17 patients (68%) VPA was discontinued and 62% of the patients who maintained treatment had recurrent episodes of hyperammonemia.

Valproate-induced hyperammonemic encephalopathy: a case report

Background

Hyperammonemic encephalopathy is a rare and serious adverse reaction to valproate. Although there is documentation of this reaction in previous reports, very little is still known about the exact mechanism of action. In addition, there are no established guidelines of the next steps needed when a patient does develop this reaction. Therefore, this case report highlights what is known as well as the areas of research still needed.

Case presentation

Our patient was a 57-year-old Caucasian woman with a medical history of bipolar I disorder, opioid use disorder, benzodiazepine use disorder, and Crohn’s disease who was admitted to our behavioral health unit for suicidal ideation. She had been experiencing multiple panic attacks for 2.5 weeks along with poor sleep, increased energy, excessive spending, and feelings of helplessness. The patient was diagnosed with bipolar I disorder, manic episode without psychotic features, and benzodiazepine use disorder. She was started on valproic acid, citalopram, propranolol, and quetiapine. By day 6 of her hospitalization, the patient had altered mental status, varying levels of consciousness, confusion, and ataxic gait. Her ammonia levels were found to be elevated. All of her medications were discontinued, and lactulose was initiated. She returned to her baseline mentation within 48 hours and was discharged with lithium and quetiapine. The treatment team concluded that this patient had valproate-induced hyperammonemic encephalopathy, a rare but reversible reaction to valproate.

Conclusion

Fortunately, rapid identification of this rare condition led to a favorable outcome in our patient. This case report illustrates the course of treatment in a patient who experienced this reaction and reviews current knowledge as well as areas of needed research in regard to valproate-induced hyperammonemic encephalopathy.

Noncirrhotic hyperammonemia: A factor behind dementia to alter mental status

Healthcare givers were recommended to check serum ammonia level for elderly patients with acute-on-chronic alteration of mental status. Early initiation of antihyperammonemia therapy may benefit improvement of alteration of mental status. Baseline mental status becomes necessary for diagnose the acute alteration of mental status and monitor the therapeutic process.

Dealing with the storm: An overview of seizure precipitants and spontaneous seizure worsening in drug-resistant epilepsy

In drug-resistant epilepsy, periods of seizure stability may alternate with abrupt worsening, with frequent seizures limiting the individual's independence and physical, social, and psychological well-being. Here, we review the literature focusing on different clinical scenarios related to seizure aggravation in people with drug-resistant epilepsy. The role of antiseizure medication (ASM) changes is examined, especially focusing on paradoxical seizure aggravation after increased treatment. The external provocative factors that unbalance the brittle equilibrium of seizure control are reviewed, distinguishing between unspecific triggering factors, specific precipitants, and 'reflex' mechanisms. The chance of intervening surgical or medical conditions, including somatic comorbidities and epilepsy surgery failure, causing increased seizures is discussed. Spontaneous exacerbation is also explored, emphasizing recent findings on subject-specific circadian and ultradian rhythms. Awareness of external precipitants and understanding the subject-specific spontaneous epilepsy course may allow individuals to modify their lifestyles. It also allows clinicians to counsel appropriately and to institute suitable medical treatment to avoid sudden loss of seizure control.

CPS1 T1405N polymorphism, HDL cholesterol, homocysteine and renal function are risk factors of VPA induced hyperammonemia among epilepsy patients

PURPOSE

Valproic acid (VPA) is frequently used in the treatment of epilepsy. The adverse effects of VPA include hyperammonemia (HA) which is characterized by abnormally elevated blood ammonia level. Carbamoyl-Phosphate Synthase 1 (CPS1) is an enzyme catalyzing the initial step of removing ammonia from blood. Studies have demonstrated that the CPS1 polymorphism rs1047891-A allele carriers were susceptible to VPA-induced HA. However, the evidences remained controversial. In this study, we sought to validate the association between rs1047891 and VPA-induced HA by combining the association results from previous studies together.

METHODS

We first conducted a systematic meta-analysis to determine whether rs1047891 was statistically significant. Then, we further evaluated the pleiotropic effects of rs1047891 using published genome-wide association studies (GWAS) and UKBB results. A conditional analysis was conducted to investigate whether the association between rs1047891 and VPA-induced HA was mediated by cardiovascular or renal disease risk factors or vice versa.

RESULTS

The allelic, dominant and recessive ORs of rs1047891-A were all significant in our fixed-effect meta-analysis. In GWAS catalog and UKBB data, rs1047891 was associated with basal metabolic rate, adiposity and hematology traits, cardiovascular and renal disease risk factors. We further proved that plasma HDL cholesterol and homocysteine level, in addition to eGFR by serum creatinine, were associated with VPA-induced HA risk independently from rs1047891 polymorphism.

CONCLUSION

In conclusion, the SNP rs1047891 was associated with VPA-induce HA among epilepsy patients. Meanwhile, plasma HDL cholesterol and homocysteine level had independent effects from it.

Intravenous use of valproic acid in status epilepticus is associated with high risk of hyperammonemia

PURPOSE

The aim of the study was to examine the frequency of hyperammonemia secondary to valproic acid treatment in status epilepticus and to describe the characteristics of the patients.

METHODS

All patients with established status epilepticus during 2014 to 2016 at Ryhov County Hospital were identified in a retrospective case series. Clinical and laboratory findings were collected from electronic medical files and the Metavision database at the intensive care unit (ICU). Hyperammonemia was defined as a concentration of at least 50 μmol/L.

RESULTS

11 of 40 patients developed hyperammonemia. These patients had a significantly longer stay at the ICU (12.6 vs 2.5 days) and at the hospital (22 vs 11 days). All patients with hyperammonemia were treated at the ICU and all received antibiotics. 12 patients were treated with intravenous valproic acid outside the ICU. Hyperammonemia was not related to Body Mass Index, time to initiation of therapy or laboratory abnormalities except anemia (Hemoglobin 104 vs 122 g/l). There was no difference in mortality between groups.

CONCLUSION

The risk of hyperammonemia is almost 40% in patients receiving intravenous valproic acid in the ICU setting. The underlying mechanisms are probably either individual susceptibility or high metabolic demands. A high vigilance should be recommended. These data require further research via prospective designs in which multiple variables are controlled to explore the effects of individual factors on treatment outcome.

Risk Factors for Valproic Acid-induced Hyperammonaemia in Chinese Paediatric Patients with Epilepsy

This study was aimed at identifying genetic and non-genetic risk factors for valproic acid (VPA)-induced hyperammonaemia in Chinese paediatric patients with epilepsy. A total of 210 epileptic patients, treated with VPA as monotherapy, were enrolled and classified into hyperammonaemia and control groups according to their blood ammonia level (cut-off value 50 μmol/L). Serum concentrations of VPA and its major metabolites were simultaneously determined by ultrahigh-performance liquid chromatography-tandem mass spectrometry. Six single nucleotide polymorphisms in the candidate genes, CYP2C9, CYP2A6, CYP2B6 and CPS1, were analysed by a matrix-assisted laser desorption ionization-time of flight mass spectrometry method or nested PCR. Significant differences in age, aspartate transaminase level and the incidence of liver injury were observed between patients of hyperammonaemia and control groups. Genotype distributions of CYP2C9*3, CYP2A6*4 and CPS1 4217C>A allelic variants were also significantly different between the two groups. According to multiple regression analysis, a significant negative correlation was detected between age and the blood ammonia level, while liver injury, the concentration-dose ratio (CDR) of VPA and 2-propyl-4-pentenoic acid (4-ene VPA), and the presence of CYP2A6*4 or CPS1 4217C>A showed positive correlations with the blood ammonia level. In addition, the risk factors for hyperammonaemia identified by logistic regression analysis were as follows: a younger age (odds ratio [OR] = 0.85; 95% confidence interval [CI] = 0.76-0.96; p = 0.007), occurrence of liver injury (OR = 4.60; 95% CI = 1.27-16.74; p = 0.021), higher CDR of 4-ene VPA (OR = 1.08; 95% CI = 1.03-1.14; p = 0.001), and carrying mutant alleles of CYP2C9*3 (OR = 3.42; 95% CI = 1.15-10.19; p = 0.028), CYP2A6*4 (OR = 3.23; 95% CI = 1.40-7.48; p = 0.006) and CPS1 4217C>A (OR = 3.25; 95% CI = 1.52-6.94; p = 0.002). Our findings indicated that multiple genetic and non-genetic risk factors that were identified can be used to predict the development of VPA-induced hyperammonaemia in Chinese paediatric patients with epilepsy.

A model of blood-ammonia homeostasis based on a quantitative analysis of nitrogen metabolism in the multiple organs involved in the production, catabolism, and excretion of ammonia in humans

Increased blood ammonia (NH₃) is an important causative factor in hepatic encephalopathy, and clinical treatment of hepatic encephalopathy is focused on lowering NH₃. Ammonia is a central element in intraorgan nitrogen (N) transport, and modeling the factors that determine blood-NH₃ concentration is complicated by the need to account for a variety of reactions carried out in multiple organs. This review presents a detailed quantitative analysis of the major factors determining blood-NH₃ homeostasis – the N metabolism of urea, NH₃, and amino acids by the liver, gastrointestinal system, muscle, kidney, and brain – with the ultimate goal of creating a model that allows for prediction of blood-NH₃ concentration. Although enormous amounts of NH₃ are produced during normal liver amino-acid metabolism, this NH₃ is completely captured by the urea cycle and does not contribute to blood NH₃. While some systemic NH₃ derives from renal and muscle metabolism, the primary site of blood-NH₃ production is the gastrointestinal tract, as evidenced by portal vein-NH₃ concentrations that are about three times that of systemic blood. Three mechanisms, in order of quantitative importance, release NH₃ in the gut: 1) hydrolysis of urea by bacterial urease, 2) bacterial protein deamination, and 3) intestinal mucosal glutamine metabolism. Although the colon is conventionally assumed to be the major site of gut-NH₃ production, evidence is reviewed that indicates that the stomach (via Helicobacter pylori metabolism) and small intestine and may be of greater importance. In healthy subjects, most of this gut NH₃ is removed by the liver before reaching the systemic circulation. Using a quantitative model, loss of this “first-pass metabolism” due to portal collateral circulation can account for the hyperammonemia observed in chronic liver disease, and there is usually no need to implicate hepatocyte malfunction. In contrast, in acute hepatic necrosis, hyperammonemia results from damaged hepatocytes. Although muscle-NH₃ uptake is normally negligible, it can become important in severe hyperammonemia. The NH₃-lowering actions of intestinal antibiotics (rifaximin) and lactulose are discussed in detail, with particular emphasis on the seeming lack of importance of the frequently emphasized acidifying action of lactulose in the colon.

Valproic acid-induced hyperammonemia: Incidence, clinical significance, and treatment management

Introduction:

Valproic acid (VPA)–induced hyperammonemia poses several clinical challenges in psychiatric medicine. The reported incidence of this adverse effect varies widely across the literature. Furthermore, practitioners treat hyperammonemia in asymptomatic patients although studies suggest this practice is unnecessary. The purpose of this study is to evaluate if patients with VPA-induced hyperammonemia are appropriately identified for treatment based on their symptom presentation as well as determine the most efficacious treatment approach for VPA-induced hyperammonemia.

Methods:

This study was completed at a community teaching hospital, and patients were retrospectively identified from June 1, 2011, to June 30, 2016, and included if they were admitted to a psychiatric unit, received at least 1 dose of VPA, and had at least 1 ammonia level drawn during admission. Hyperammonemia was defined as greater than 47 μmol/L, and symptomatic hyperammonemia was defined based on specific symptom presentation. The treatment modality was successful if the ammonia level was within normal range at discharge.

Results:

Of the 357 patients screened, 347 patients met all inclusion criteria for analysis. The reported incidence of hyperammonemia was found to be 36% with 43.2% of those patients presenting with symptoms. Lactulose initiation was the most common treatment modality chosen (48.7%). Discontinuation of VPA was the most effective treatment (56.3% success rate).

Discussion:

The results demonstrate that many patients with elevated ammonia levels are asymptomatic and therefore, based on findings within the literature, may not require treatment. Although lactulose was found to be the most common treatment initiated, the most effective was discontinuation of VPA.

Burst Suppression Pattern on Electroencephalogram Secondary to Valproic Acid-Induced Hyperammonemic Encephalopathy

BACKGROUND

Valproic acid may induce hyperammonemic encephalopathy. Various electroencephalogram (EEG) abnormalities have been documented in association with this condition, but not burst suppression, an abnormal EEG pattern that is associated with severe encephalopathy.

METHODS

Serial EEGs, clinical observations, and laboratory findings were analyzed.

PATIENT DESCRIPTION

This 13-year-old girl with autism and intractable epilepsy experienced increased seizures; her valproic acid dose was increased and other antiepileptic drugs were administered. She became lethargic, and her EEG showed a burst suppression pattern. Her ammonia concentration was increased to 101 μmol/L and her valproic acid level was increased to 269.9 mg/L. Valproic acid was discontinued and carnitine was administered. Subsequently she became more alert, her ammonia concentration decreased, and her EEG changed from a burst suppression pattern to a continuous pattern. Within three days, she was back to her baseline level of functioning.

CONCLUSIONS

Valproic acid-induced hyperammonemic encephalopathy can produce a burst suppression EEG patternin the patient's.

Association between the blood concentrations of ammonia and carnitine/amino acid of schizophrenic patients treated with valproic acid

Background

Administration of valproic acid (VPA) is complicated with approximately 0.9% of patients developing hyperammonemia, but the pathogenesis of this adverse effect remains to be clarified. The aim of the present study was to search for mechanisms associated with VPA-induced hyperammonemia in the light of changes in serum amino acids concentrations associated with the urea cycle of schizophrenic patients.

Method

Blood samples (10 mL) were obtained from 37 schizophrenic patients receiving VPA for the prevention of violent behaviors in the morning after overnight fast. Blood concentrations of ammonia, VPA, free carnitine, acyl-carnitine, and 40 amino acids including glutamate and citrulline were measured for each patient. Univariate and multivariate regression analyses were performed to identify amino acids or concomitantly administered drugs that were associated with variability in the blood concentrations of ammonia.

Result

The blood ammonia level was positively correlated with the serum glutamate concentration (r = 0.44, p < 0.01) but negatively correlated with glutamine (r = −0.41, p = 0.01), citrulline (r = −0.42, p = 0.01), and glycine concentrations (r = −0.54, p < 0.01). It was also revealed that the concomitant administration of the mood stabilizers (p = 0.04) risperidone (p = 0.03) and blonanserin (p < 0.01) was positively associated with the elevation of the blood ammonia level.

Conclusion

We hypothisized that VPA would elevate the blood ammonia level of schizophrenic patients. The observed changes in serum amino acids are compatible with urea cycle dysfunction, possibly due to reduced carbamoyl-phosphate synthase 1 (CPS1) activity. We conclude that VPA should be prudently prescribed to schizophrenic patients, particularly those receiving mood stabilizers or certain antipsychotics.

Hyperammonemic coma after craniotomy: Hepatic encephalopathy from upper gastrointestinal hemorrhage or valproate side effect?: Case report and literature review

RATIONALE

Postoperative coma is not uncommon in patients after craniotomy. It generally presents as mental state changes and is usually caused by intracranial hematoma, brain edema, or swelling. Hyperammonemia can also result in postoperative coma; however, it is rarely recognized as a potential cause in coma patients. Hyperammonemic coma is determined through a complicated differential diagnosis, and although it can also be induced as a side effect of valproate (VPA), this cause is frequently unrecognized or confused with upper gastrointestinal hemorrhage (UGH)-induced hepatic encephalopathy. We herein present a case of valproate-induced hyperammonemic encephalopathy (VHE) to illustrate the rarity of such cases and emphasize the importance of correct diagnosis and proper treatment.

PATIENT CONCERNS AND DIAGNOSES

A 61-year-old woman with meningioma was admitted into our hospital. Radical resection of the tumor was performed, and the patient recovered well as expected. After administration of valproate for 7 days, the patient was suddenly found in a deep coma, and her mental state deteriorated rapidly. The diagnoses of hepatic encephalopathy was confirmed. However, whether it origins from upper gastrointestinal hemorrhage or valproate side effect is uncertain.

INTERVENTIONS AND OUTCOMES

The patient's condition fluctuated without improvement during the subsequent 3 days under the treatment of reducing ammonia. With the discontinuation of valproate treatment, the patient regained complete consciousness within 48 hours, and her blood ammonia decreased to the normal range within 4 days.

LESSONS SUBSECTIONS

VHE is a rare but serious complication in patients after craniotomy and is diagnosed by mental state changes and elevated blood ammonia. Thus, the regular perioperative administration of VPA, which is frequently neglected as a cause of VHE, should be emphasized. In addition, excluding UGH prior to providing a diagnosis and immediately discontinuing VPA administration are recommended.

Valproate induced hyperammonemic encephalopathy treated by haemodialysis

Valproate (VPA)-induced hyperammonemic encephalopathy is an unusual, but serious, adverse effect of divalproex sodium (DVPX) treatment and if untreated can lead to raised intracranial pressure, seizures, coma, and eventually death. It can, however, be reversed if an early diagnosis is made. It is therefore extremely important to recognize it and discontinue DVPX treatment. Our patient developed sudden deterioration of sensorium, drowsiness, lethargy, and later severe comatose state after few days of starting DVPX with high levels of serum ammonia despite therapeutic levels of VPA and normal liver function test. He responded to hemodialysis, cerebral decongestants, and other intensive supportive measures.

Valproic acid as an antiepileptic drug: Is there a clinical relevance for the epilepsy surgeon?

Valproic acid (VPA) has been associated with coagulation factors deficiency, platelet dysfunction and hemorrhagic complications. We investigated 169 patients with drug resistant epilepsy (DRE), who underwent surgery, to look for clinical implications of VPA associated bleeding problems. All patients had normal preoperative coagulation profile. VPA was a part of polytherapy in 54% of patients (Group A), however 46% patients were not on VPA (Group B). The groups were comparable with mean age of 17.3±10.3years. Mean duration of surgery in group A and B were 255±70 and 250±60min respectively (p=0.26). Average blood loss in group A was 399±254 and 389±228ml in group B. (p=0.62). The percentage of total blood volume lost was 12.7% (Group A) and 17.7% (Group B) respectively (p=0.7). There were no bleeding complications in either group. Hyperammonemic encephalopathy occurred in 4 patients postoperateively requiring withdrawal or dose reduction of VPA. No mortality was recorded. We conclude that VPA does not increase clinically relevant perioperative haemorrhagic complications in patients having normal coagulation screen and platelet counts. However, hyperammonemic encephalopathy is observed in 4% of patients in perioperative period, favorably responding to discontinuation of VPA.

Hyperammonaemia and associated factors in unprovoked convulsive seizures: A cross-sectional study

PURPOSE

Hyperammonaemia is frequently observed in patients who have experienced convulsive seizures. Although excessive muscle contraction is presumed to be responsible for the elevated levels of ammonia, the underlying mechanism is poorly understood. The present study aimed to identify the independent factors associated with ammonia elevation using large-scale multivariate analysis.

METHODS

We conducted a cross-sectional study involving 379 adult patients who had been transported to our emergency department and treated for unprovoked convulsive seizures between August 2010 and September 2015. Elevation of venous plasma ammonia levels was set as the primary endpoint, and patients' clinical and laboratory data were obtained. Those with severe liver dysfunction, known hepatic encephalopathy, or convulsions due to cardiovascular or psychogenic causes, and those taking valproate were excluded.

RESULTS

Using a cut-off value of 50μg/dL, 183 patients (48.3%) were found to have elevated levels of plasma ammonia. Four factors were identified as independent variables associated with hyperammonaemia following seizures: elevated venous lactate, lowered venous pH, sex (male), and longer duration of convulsion.

CONCLUSIONS

The results of the present study revealed independent factors associated with hyperammonaemia following unprovoked convulsive seizures in a larger scale and with more plausible statistical analysis. The authors further suggest that the excessive skeletal muscle contraction and/or respiratory failure during/after convulsive seizure may be the primary mechanism of hyperammonaemia.

Randomized placebo-controlled trial of sodium valproate in progressive supranuclear palsy

OBJECTIVES

Results from preclinical studies suggest that inhibition of glycogen synthase kinase (GSK-3) is a therapeutic option for tauopathies. The aim of the present study was therefore to determine the effects of sodium valproate (VPA), a GSK-3 inhibitor, on disease progression in progressive supranuclear palsy (PSP).

PATIENTS AND METHODS

We performed a double-blind, randomized, placebo-controlled trial, in 28 PSP patients who received VPA (1500mg/day) or matching placebo for 24 months. The primary endpoint was the change from baseline in Progressive Supranuclear Palsy Rating Scale (PSPRS) at 12 and 24 months. Secondary endpoints evaluated the effects of VPA on cognitive and behavioral status (MMSE, Mattis Dementia Rating Scale, Wisconsin Card Sorting, Gröber and Buschke and Oral Denomination 80 tests), tolerability of treatment, and patient compliance.

RESULTS

There were no baseline differences between active treatment and placebo groups in age and clinical rating scores. PSPRS score at 12 months was significantly higher in the VPA than in the placebo group (60.8±20 versus 46.9±18.6 respectively, p=0.01), but was similar between the two groups at 24 months. No significant differences were observed between VPA and placebo groups for the secondary endpoints.

CONCLUSION

Our results suggest that VPA is not effective as a disease-modifying agent in PSP.

Reversible weakness and encephalopathy while on long-term valproate treatment due to carnitine deficiency

We describe a case of a 35-year-old woman who presented with bilateral leg weakness and encephalopathy while on long-term valproate therapy. She was diagnosed with valproate-induced encephalopathy due to carnitine deficiency. Clinical improvement occurred with oral carnitine supplementation. Our case report highlights the importance of considering carnitine deficiency in patients presenting with unexplained neurological signs while on long-term valproate treatment.

Valproic Acid-Induced Hyperammonemic Encephalopathy as a Cause of Neurologic Deterioration after Unruptured Aneurysm Surgery

Neurological deficits after brain surgery are not uncommon, and correct and prompt differential diagnosis is essential to initiate appropriate treatment. We describe a patient suffering from loss of consciousness due to hyperammonemia, following valproic acid treatment after surgery for an unruptured cerebral aneurysm. A 57-year-old female patient underwent successful aneurysmal neck clipping to correct an unruptured aneurysm. Her postoperative course was good, and she received anti-epileptic therapy (valproic acid) and a soft diet. Within a few days the patient experienced mental deterioration. Her serum valproic acid reached toxic levels (149.40 mg/L), and serum ammonia was fifteen times the upper normal limit (553 mmol/L; normal range, 9-33 mmol/L). After discontinuation of valproic acid and with conservative treatment, the patient recovered without any complications. Valproate-induced hyperammonemic encephalopathy is an unusual but serious neurosurgical complication, and should not be disregarded as a possible cause of neurological deficits after neurovascular surgery. Early diagnosis is crucial, as discontinuation of valproic acid therapy can prevent serious complications, including death.

[Incidence and causes of early end in awake surgery for language mapping not directly related to eloquence]

The incidence and causes that may lead to an early end (unfinished cortical/subcortical mapping) of awake surgery for language mapping are little known. A study was conducted on 41 patients with brain glioma located in the language area that had awake surgery under conscious sedation. Surgery was ended early in 6 patients. The causes were: tonic-clonic seizure (1), lack of cooperation due to fatigue/sleep (4), whether or not word articulation was involved, a decreased level of consciousness for ammonia encephalopathy that required endotracheal intubation (1). There are causes that could be expected and in some cases avoided. Tumour size, preoperative aphasia, valproate treatment, and type of anaesthesia used are variables to consider to avoid failure in awake surgery for language mapping. With these results, the following measures are proposed: l) If the tumour is large, perform surgery in two times to avoid fatigue, 2) if patient has a preoperative aphasia, do not use sedation during surgery to ensure that sleepiness does not cause worse word articulation, 3) if the patient is on valproate treatment, it is necessary to rule out the pre-operative symptoms that are not due to ammonia encephalopathy.