Hyperammonaemic encephalopathy after initiation of valproate therapy in unrecognised ornithine transcarbamylase deficiency

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.

Valproic Acid-Associated Hyperammonemia: A Systematic Review

BACKGROUND

Hyperammonemia is an adverse effect that poses clinical uncertainty around valproic acid (VPA) use. The prevalence of symptomatic and asymptomatic hyperammonemia and its relationship to VPA concentration is not well established. There is also no clear guidance regarding its management. This results in variability in the monitoring and treatment of VPA-induced hyperammonemia. To inform clinical practice, this systematic review aims to summarize evidence available around VPA-associated hyperammonemia and its prevalence, clinical outcomes, and management.

METHODS

An electronic search was performed through Ovid MEDLINE, Ovid Embase, Web of Science, and PsycINFO using search terms that identified hyperammonemia in patients receiving VPA. Two reviewers independently performed primary title and abstract screening with a third reviewer resolving conflicting screening results. This process was repeated during the full-text review process.

RESULTS

A total of 240 articles were included. Prevalence of asymptomatic hyperammonemia (5%-73%) was higher than symptomatic hyperammonemia (0.7%-22.2%) and occurred within the therapeutic range of VPA serum concentration. Various risk factors were identified, including concomitant medications, liver injury, and defects in carnitine metabolism. With VPA discontinued, most symptomatic patients returned to baseline mental status with normalized ammonia level. There was insufficient data to support routine monitoring of ammonia level for VPA-associated hyperammonemia.

CONCLUSIONS

Valproic acid-associated hyperammonemia is a common adverse effect that may occur within therapeutic range of VPA. Further studies are required to determine the benefit of routine ammonia level monitoring and to guide the management of VPA-associated hyperammonemia.

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.

Valproic acid-induced encephalopathy: A review of clinical features, risk factors, diagnosis, and treatment

Valproic acid (VPA), or sodium valproate, is a commonly used medication for seizure disorders, migraines, and mental illness. Although VPA is relatively safe, it still has several adverse effects; among these, VPA-induced encephalopathy is the most serious. Valproic acid-induced encephalopathy mainly manifests as acute or subacute encephalopathy and has been associated with hyperammonemia, L-carnitine deficiency, and urea cycle enzyme dysfunction. Delayed identification of VPA-induced encephalopathy could be potentially fatal. Here, we perform an extensive review of relevant literature pertaining to VPA-induced encephalopathy, including its epidemiology, clinical features, possible pathophysiology, risk factors, diagnosis, and treatment.

Status epilepticus secondary to hyperammonaemia: a late presentation of an undiagnosed urea cycle defect

In this report, we describe the diagnosis, investigation and management of a patient presenting with refractory status epilepticus secondary to a previously unrecognised urea cycle defect, ornithine transcarbamylase deficiency, causing a hyperammonaemic encephalopathy. While metabolic disorders will be readily considered in a paediatric population presenting with difficult seizures, it is unusual for such cases to present in adulthood, and maintaining a broad differential in patients with status epilepticus is important. Early recognition and initiation of treatment are vital. Furthermore, the patient had been diagnosed with schizophrenia over a decade previously and more recently started on sodium valproate, a medication known to contribute to hyperammonaemia. This case also emphasises the importance of exclusion of underlying organic disease prior to diagnosis of psychiatric conditions.

Levocarnitine for the Treatment of Valproic Acid-Induced Hyperammonemic Encephalopathy in Children: The Experience of a Large, Tertiary Care Pediatric Hospital and a Poison Center

BACKGROUND

Although rare, symptomatic hyperammonemia is sometimes associated with valproic acid (VPA), especially in children. L-carnitine (levocarnitine), sometimes classified as an essential amino acid, is vital to mitochondrial utilization of fatty acids and can be helpful in treating this condition. The data supporting this, however, are limited.

STUDY QUESTION

The aim of the study was to illustrate the role of L-carnitine in the treatment of patients with VPA-induced hyperammonemic encephalopathy (VPE) at 2 different institutions.

METHODS

Medical records of affected patients were reviewed; data collected included exposure history, clinical manifestations, physical examination, and laboratory values.

RESULTS

There were 13 cases of VPE; 12 were associated with therapeutic dosing and 1 with an overdose. The maximum ammonia concentration was 557 μmol/L, and blood concentrations of VPA ranged from 68 to 600 μg/mL (therapeutic range 50-100 μg/mL). In all cases, liver function tests were normal or only mildly increased. In this study, 12 patients received a daily dose of L-carnitine 100 mg/kg, and 1 received 200 mg/kg (intravenous infusion over 30 minutes) divided every 8 hours until clinical improvement. All patients made a full recovery. None developed adverse effects or reactions, and no cases of toxicity were reported.

CONCLUSION

Our series suggests that intravenous L-carnitine, at a dose of 100 mg·kg·d in 3 divided doses each over 30 minutes until clinical improvement occurs, is a safe and effective treatment in the management of VPE in children.

[Vomiting associated with weight stagnation and convulsions: urea cycle disorder should be suspected]

Dans certaines maladies métaboliques héréditaires, les vomissements peuvent apparaître comme un symptôme étant au premier plan, en particulier les anomalies du cycle de l'urée, qui sont habituellement diagnostiqués en période néonatale ou dans l'enfance. Nous en rapportons un cas de révélation tardive par un état de mal convulsif. Nous rapportons le cas d'une patiente âgée de 13 ans, qui a été hospitalisé pour prise en charge d'un état de mal convulsif et un retard staturo-pondéral. L'interrogatoire a révélé la notion de vomissements chroniques avec des troubles du comportement, ralentissement idéomoteur et céphalées. L'examen a trouvé une ataxie. La ponction lombaire et le scanner cérébral sont normaux. Une ammoniémie nettement augmentée est mise en évidence 75 micromoles/l (11-50). La chromatographie des acides aminés dans le sang a montré une augmentation de la glutamine et de l'alanine, La chromatographie des acides aminés dans les urines a montré une augmentation des acides aminés basiques évoquant un déficit du cycle de l'urée par déficit de l'enzyme Argininosuccinate lyase. La patiente a été traité en urgence par une alimentation exclusivement glucidolipidique, et par benzoate de sodium permettant une amélioration de l'état clinique, et une reprise de poids. Les crises convulsives ont été maîtrisées par le phénobarbital. L'enquête familiale a trouvé une sœur âgée de 20 ans suivie depuis l'âge de 3 ans pour crises convulsives traité par le phénobarbital dont le bilan métabolique réalisé dans notre service a objectivé la même anomalie du cycle de l'urée que sa sœur. A tout âge, devant une encéphalopathie avec épilepsie, vomissement, stagnation pondérale et hyperammoniémie, il faut penser à un déficit du cycle de l'urée. Le diagnostic est très souvent posé lors d'un accès neuro-digestif aigue associant vomissements, troubles de conscience et/ou crises convulsives.

Valproate-induced hyperammonemia - uncovering an underlying inherited metabolic disorder: a case report

Background

Sodium valproate is a commonly used anticonvulsant. It is widely recognized that valproate can cause hyperammonemia, particularly in people with underlying liver disease. Patients with urea cycle disorders are genetically predisposed to this adverse event and can develop severe hyperammonemia if given valproate.

This can occur even if liver functions tests and plasma concentration of valproate are normal, highlighting the importance of checking ammonia levels in any patient presenting with encephalopathy. Specific treatment for hyperammonemia must be implemented promptly.

Case presentation

A 22-year-old white British man with a history of epilepsy post head trauma presented with subacute encephalopathy 4 weeks after the introduction of sodium valproate. His ammonia levels were not checked until 48 hours into his presentation and were found to be elevated. He initially responded to treatment of his hyperammonemia and the raised levels were attributed to sodium valproate. However, as his ammonia levels continued to rise, further investigation led to a diagnosis of ornithine transcarbamylase deficiency.

Conclusions

Ornithine transcarbamylase deficiency is the most common of the urea cycle disorders. This case highlights both the importance of checking ammonia levels early and considering the diagnosis of this X-linked disorder in patients with raised ammonia, as these have implications both for the patient’s acute and further management, and for family screening.

Valproate semisodium-induced encephalopathy: diet and polypharmacy interactions

Despite extensive use of valproate in neurology and psychiatry, valproate-induced encephalopathy is a rarely reported complication. Although initially reported in the paediatric population, case reports are growing in the adult population.

Clinicians need to be aware of this potentially life-threatening complication. We report a case in a 37-year-old woman with bipolar I disorder with previously uncomplicated valproate use, who developed encephalopathy when valproate was restarted a few years later. The patient has provided consent for publication.

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.

Valproate Induced Hyperammonemic Delirium

Sodium valproate induced hyperammonaemic delirium with normal liver function tests is a relatively uncommon adverse effect. It may be mistaken for psychosis or worsening of mania leading to wrong diagnosis and improper management. Plasma ammonia levels should be monitored in all patients developing altered mental status after receiving valproate therapy. This is a case series of hyperammonaemic delirium due to valproate reported to the Department of Pharmacology from Department of Psychiatry over a period of one year.

[Valproate-induced hyperammonemic encephalopathy in a neonate: treatment with carglumic acid]

Valproate-induced hyperammonemic encephalopathy (VHE) is an unusual and serious complication of valproate (VA) treatment. When an early diagnosis is made, it can be reversed with VA withdrawal and early treatment for hyperammonemia. We describe the case of a 20 days old male, who developed a serious VHE after receiving VA for refractory neonatal seizures. The VHE was resolved with VA withdrawal in association with carglumic acid and other measures for hyperammonemia treatment.

Defects in amino acid catabolism and the urea cycle

Symptoms in patients with defects in amino acid catabolism and the urea cycle usually develop because of intoxication of accumulating metabolites. The cumulative prevalence of these disorders is considerable (at least>1:2000 newborns). Timely and correct intervention during the initial presentation and during later episodes is most important. Evaluation of metabolic parameters should be performed on an emergency basis in every patient with symptoms of unexplained metabolic crisis, intoxication, and/or unexplained encephalopathy. A substantial number of patients develop acute encephalopathy or chronic and fluctuating progressive neurological disease. The so-called cerebral organic acid disorders present with (progressive) neurological symptoms: ataxia, myoclonus, extrapyramidal symptoms, and "metabolic stroke." Important diagnostic clues, such as white matter abnormalities, cortical or cerebellar atrophy, and injury of the basal ganglia can be derived from cranial magnetic resonance imaging (MRI). Long-term neurological disease is common, particularly in untreated patients, and the manifestations are varied, the most frequent being (1) mental defect, (2) epilepsy, and (3) movement disorders. Successful treatment strategies are becoming increasingly available. They mostly require an experienced interdisciplinary team including a neuropediatrician and/or later on a neurologist.

Recurrent somnolence in a 17-month-old infant: late-onset ornithine transcarbamylase (OTC) deficiency due to the novel hemizygous mutation c.535C > T (p.Leu179Phe)

Herein, we describe a case of a now 28-month-old boy who presented at the age of 17 months with four episodes of recurrent vomiting and somnolence during a period of four months with increasing severity. A comprehensive clinical and metabolic evaluation revealed normal blood pH and blood glucose, normal cerebral computed tomography and electroencephalogram but an elevated plasma ammonia concentration, which raised the suspicion of a urea cycle disorder. The combination of elevated urinary orotic acid and plasma glutamine with normal citrulline suggested the diagnosis of ornithine transcarbamylase (OTC) deficiency, which was confirmed by molecular genetic testing revealing the novel hemizygous mutation c.535C > T (p.Leu179Phe) of the OTC gene. After restitution of anabolism by administration of parenteral glucose, substitution of citrulline and detoxification of ammonia with sodium benzoate, the patient recovered rapidly and is in a stable metabolic and neurological state since then. This case underlines that the diagnosis of a urea cycle defect should be considered in the differential diagnosis of recurrent idiopathic vomiting in combination with unexplained neurological symptoms also beyond the neonatal period due to the possibility of mild or atypical late-onset presentation (e.g. OTC deficiency in hemizygous males).

Valproate-induced hyperammonaemia superimposed upon severe neuropsychiatric lupus: a case report and review of the literature

This paper presents a case of systemic lupus erythematosus (SLE) with neuropsychiatric features, where the outcome was influenced by the development of hyperammonaemia, probably induced by sodium valproate. A case of severe SLE occurring in a 20-year-old Maori girl is described. Her disease had been characterised by neuropsychiatric features for several years, culminating in persistent seizure activity at the time of her final presentation. Her management with anticonvulsants was complicated by the development of intractable hyperammonaemia which contributed to irreversible clinical deterioration. We have reviewed the English literature for reports of valproate-related hyperammonaemia which has often been described in the setting of seizure and mood disorders. This is the first case where it has been reported, superimposed upon severe neuropsychiatric SLE (NP-SLE). The mechanism by which valproate induces hyperammonaemia remains incompletely understood but is likely to relate to the urea cycle. Under normal metabolic conditions, acyl-CoA is transported into the mitochondria via a carnitine transport system. It is then converted to acetyl-CoA via β-oxidation and eventually to N-acetyl glutamate. This pathway can be interrupted by the introduction of sodium valproate, leading to a reduction of free coenzyme A, acetyl-CoA and carnitine, and resulting in the decreased availability of cofactors necessary for the function of the urea cycle. As this is the primary means of ammonia metabolism, serious elevation in serum ammonia levels may occur in patients on this anticonvulsant medication. In this patient with active NP-SLE, the combined autoimmune and metabolic brain insult contributed to a fatal outcome.

Miscellaneous central nervous system intoxicants

The topic of central nervous system intoxicants encompasses a multitude of agents. This article focuses on three classes of therapeutic drugs, with specific examples in which overdoses require admission to the intensive care unit. Included are some of the newer antidepressants, the atypical neuroleptic agents, and selected anticonvulsant drugs. The importance of understanding pertinent physiology and applicable supportive care is emphasized.

Valproate-induced hyperammonemic encephalopathy: an update on risk factors, clinical correlates and management

INTRODUCTION

Valproate (VPA)-induced hyperammonemic encephalopathy (VHE) is a serious drug-related adverse effect characterized by lethargy, vomiting, cognitive slowing, focal neurological deficits and decreased levels of consciousness ranging from drowsiness to coma.

METHODS

We present a case series (n=5) and also review previous cases of VHE (n=30) in psychiatric patients to provide an update on risk factors, clinical correlates and management of VHE.

RESULTS

To our knowledge, there are 30 (16 female, 14 male) previously reported VHE cases in psychiatric patients. Risk factors for VHE include VPA-drug interactions, mental retardation, carnitine deficiency and presence of urea cycle disorders. Length of VPA treatment, VPA dosage, serum VPA levels and serum ammonia levels do not appear to correlate with onset or severity of VHE.VPA discontinuation is the primary treatment of VHE, although, l-carnitine, lactulose and neomycin have been used adjunctively in some patients.

CONCLUSION

Clinicians should consider VHE in patients taking VPA who present with lethargy, gastrointestinal symptoms, confusion and decreased levels of drowsiness. VPA discontinuation is currently the mainstay of treatment for VHE, although more research is warranted to delineate the underlying risk factors for VHE and consolidate treatment modalities for this potentially life-threatening drug adverse effect.

Ornithine transcarbamylase deficiency diagnosed in pregnancy

Urea cycle enzymes deficiencies are rare metabolic disorders. Ornithine transcarbamylase (OTC) deficiency is the most common type. The syndrome results from a deficiency of the mitochondrial enzyme OTC which catalyses the conversion of ornithine and carbamoyl phosphate to citrulline. It shows X-linked inheritance and typically remains asymptomatic until late infancy or early childhood. The severity of the symptoms depends on the age of the patient and the duration of hyperammonemia. Female heterozygotes are more difficult to diagnose. They suffer from hyperammonemic periods which can be triggered by trauma, infections, surgery, childbirth, parenteral nutrition, and by the initiation of sodium valproate therapy. The prognosis of OTC deficiency is better for those with an onset after infancy, but morbidity from brain damage does not appear to be linked to the number of episodes of hyperammonemia that have occurred. However, early diagnosis and prompt initiation of ammonia-lowering treatment are essential for survival of these patients. This case presents a patient who was diagnosed with OTC deficiency following mental confusion during pregnancy.

New insights on the mechanisms of valproate-induced hyperammonemia: inhibition of hepatic N-acetylglutamate synthase activity by valproyl-CoA

BACKGROUND & AIMS

Hyperammonemia is a frequent side-effect of valproic acid (VPA) therapy, which points to an imbalance between ammoniagenesis and ammonia disposal via the urea cycle. The impairment of this liver-specific metabolic pathway induced either by primary genetic defects or by secondary causes, namely associated with drugs administration, may result in accumulation of ammonia. To elucidate the mechanisms which underlie VPA-induced hyperammonemia, the aim of this study was to evaluate the effect of both VPA and its reactive intermediate, valproyl-CoA (VP-CoA), on the synthesis of N-acetylglutamate (NAG), a prime metabolite activator of the urea cycle.

METHODS

The amount of NAG in livers of rats treated with VPA was quantified by HPLC-MS/MS. The NAG synthase (NAGS) activity was evaluated in vitro in rat liver mitochondria, and the effect of both VPA and VP-CoA was characterized.

RESULTS

The present results clearly show that VP-CoA is a stronger inhibitor of NAGS activity in vitro than the parent drug VPA. The hepatic levels of NAG were significantly reduced in VPA-treated rats as compared with control tissues.

CONCLUSIONS

These data strongly suggest that the hyperammonemia observed in patients under VPA treatment may result from a direct inhibition of the NAGS activity by VP-CoA. The subsequent reduced availability of NAG will impair the flux through the urea cycle and compromise the major role of this pathway in ammonia detoxification.

Transient hyperammonemia due to L-asparaginase therapy in children with acute lymphoblastic leukemia or non-Hodgkin lymphoma

The standard treatment protocol for acute lymphoblastic leukemia (ALL) and non-Hodgkin lymphoma (NHL) in childhood includes intravenous therapy with asparaginase (Asp), which may cause hyperammonemia. In this study, all patients receiving asparaginase therapy at the Hospital for Children and Adolescents of the University of Leipzig between January 2002 and December 2007 were reviewed for the occurrence of hyperammonemia. Fifty-four patients were identified (22 girls, 32 boys; mean age 5.8 years). Blood ammonia concentrations were determined in 4 patients due to suspicious clinical signs. All showed hyperammonemia with NH(3) concentrations between 260 and 700 μmol/L. They received specific acute detoxification therapy consisting in protein restriction, administration of benzoic acid, glucose/insulin. All 4 recovered completely. All patients receiving therapeutic regimes that include asparaginase (Asp) should be monitored for the development of transient hyperammonemia.

Valproate-induced hyperammonemic encephalopathy enhanced by topiramate and phenobarbitone: a case report and an update

Although sodium valproate (VPA)-induced hepatic encephalopathy is a well-recognized entity, VPA can occasionally produce encephalopathy secondary to hyperammonemia in the presence of normal hepatic function, namely valproate-induced non-hepatic hyperammonemic encephalopathy (VNHE). Known risk factors include therapy with multiple antiepileptic drugs, especially when topiramate is one of the drugs; presence of underlying inborn errors of metabolism; febrile states; and insufficient nutritional intake. We describe a 5-year-old male child who developed VNHE while on polypharmacy with topiramate and phenobarbitone; the child also had poor nutritional intake. The encephalopathy reversed with withdrawal of VPA and treatment with L-carnitine. We emphasize the need for early recognition, investigation, and treatment of this potentially life-threatening condition. We also recommend that VPA, topiramate, and phenobarbitone should not be given in combination.

Female heterozygotes for the hypomorphic R40H mutation can have ornithine transcarbamylase deficiency and present in early adolescence: a case report and review of the literature

Introduction

Ornithine transcarbamylase deficiency is the most common hereditary urea cycle defect. It is inherited in an X-linked manner and classically presents in neonates with encephalopathy and hyperammonemia in males. Females and males with hypomorphic mutations present later, sometimes in adulthood, with episodes that are frequently fatal.

Case presentation

A 13-year-old Caucasian girl presented with progressive encephalopathy, hyperammonemic coma and lactic acidosis. She had a history of intermittent regular episodes of nausea and vomiting from seven years of age, previously diagnosed as abdominal migraines. At presentation she was hyperammonemic (ammonia 477 μmol/L) with no other biochemical indicators of hepatic dysfunction or damage and had grossly elevated urinary orotate (orotate/creatinine ratio 1.866 μmol/mmol creatinine, reference range <500 μmol/mmol creatinine) highly suggestive of ornithine transcarbamylase deficiency. She was treated with intravenous sodium benzoate and arginine and made a rapid full recovery. She was discharged on a protein-restricted diet. She has not required ongoing treatment with arginine, and baseline ammonia and serum amino acid concentrations are within normal ranges. She has had one further episode of hyperammonemia associated with intercurrent infection after one year of follow up. An R40H (c.119G>A) mutation was identified in the ornithine transcarbamylase gene (OTC) in our patient confirming the first symptomatic female shown heterozygous for the R40H mutation. A review of the literature and correspondence with authors of patients with the R40H mutation identified one other symptomatic female patient who died of hyperammonemic coma in her late teens.

Conclusions

This report expands the clinical spectrum of presentation of ornithine transcarbamylase deficiency to female heterozygotes for the hypomorphic R40H OTC mutation. Although this mutation is usually associated with a mild phenotype, females with this mutation can present with acute decompensation, which can be fatal. Ornithine transcarbamylase deficiency should be considered in the differential diagnosis of unexplained acute confusion, even without a suggestive family history.

Adult nonhepatic hyperammonemia: a case report and differential diagnosis

This article presents a case report of nonhepatic hyperammonemia, i.e., elevated serum ammonia secondary to a nonhepatic etiology. It then discusses the importance of broadening one's differential diagnosis to include such nonhepatic causes of elevated ammonia levels, and provides a short review of rarer causes of hyperammonemia in the adult population. Treating the underlying condition is the best way to prevent recurrence of hyperammonemia. However, symptomatic treatment should not be delayed while investigating the underlying source.

Epilepsy in inherited metabolic disorders

INTRODUCTION

The study of neurometabolic diseases is still in a prolonged preliminary stage. The catalogue of these diseases continues to grow; some known clinical syndromes have been subdivided into a number of variants once the genes that cause them have been identified, and at the same time new metabolic disorders have been discovered that aggravate or contribute to forms of epilepsy not previously classified as cerebral metabolic disorders.

RESULTS

This review presents the basic principles underlying the recognition and treatment of epilepsy caused by neurometabolic diseases. These disorders are divided (purely for the sake of convenience) into epilepsy presenting in newborn infants, children, and adolescents and adults, recognizing that there is a significant degree of overlap between these chronological stages. Current analytical methods and therapeutic approaches are summarized both from a general point of view and within the context of each clinical syndrome, acknowledging that each patient presents specific peculiarities and that, in general, antiepileptic drugs provide few benefits compared with more specific types of therapy (eg, special diets or vitamins) when indicated. We also include therapeutic recommendations and a general approach to fulminant epilepsies of neurometabolic origin, emphasizing the importance of identifying all of the proband's relatives who may be potential carriers of a genetic disorder during the diagnostic and genetic counselling process. Particular emphasis is placed on disorders for which there is curative treatment and on the importance of follow-up by expert professionals.

CONCLUSION

It is expected that in a few years' time it will be possible to know the metabolomic profile of these diseases (possibly by non-invasive methods), thus facilitating accurate diagnosis and making it possible to establish the response to treatment and to identify all individuals who are carriers or remain minimally symptomatic in terms of their risk of manifesting or transmitting epilepsy.

Lysine 88 acetylation negatively regulates ornithine carbamoyltransferase activity in response to nutrient signals

Ornithine carbamoyltransferase (OTC) is a key enzyme in the urea cycle to detoxify ammonium produced from amino acid catabolism. OTC deficiency is an X-linked genetic disorder ranging from fatal in newborns to hyperammonemia and anorexia in adults. Through affinity purification of acetylated peptides and mass spectrometry, we identified that OTC is acetylated on lysine residues, including Lys88, which is also mutated in OTC-deficient patients. OTC acetylation was confirmed to occur under physiological conditions. Biochemical characterizations revealed that OTC Lys88 acetylation decreases the affinity for carbamoyl phosphate, one of the two OTC substrates, and the maximum velocity, whereas the K(m) for ornithine, the other OTC substrate, is not affected. Furthermore, Lys88 acetylation is regulated by both extracellular glucose and amino acid availability, indicating that OTC activity may be regulated by cellular metabolic status. Our results provide an example of the novel mechanism of regulating metabolic enzyme activity through protein acetylation.

Valproic acid metabolism and its effects on mitochondrial fatty acid oxidation: a review

Valproic acid (VPA; 2-n-propylpentanoic acid) is widely used as a major drug in the treatment of epilepsy and in the control of several types of seizures. Being a simple fatty acid, VPA is a substrate for the fatty acid beta-oxidation (FAO) pathway, which takes place primarily in mitochondria. The toxicity of valproate has long been considered to be due primarily to its interference with mitochondrial beta-oxidation. The metabolism of the drug, its effects on enzymes of FAO and their cofactors such as CoA and/or carnitine will be reviewed. The cumulative consequences of VPA therapy in inborn errors of metabolism (IEMs) and the importance of recognizing an underlying IEM in cases of VPA-induced steatosis and acute liver toxicity are two different concepts that will be emphasized.

[Urea cycle disorders in adult patients]

INTRODUCTION

Urea cycle disorders (UCD) usually present after 24 h to 48 h of life with failure to thrive, lethargy and coma leading to death, but milder forms may occur from infancy to adulthood.

STATE OF THE ART

Survival of children with UCD has significantly improved and the need for transitional care to adulthood has emerged. Adult onset UCD present with chronic or acute neurological, psychiatric and digestive symptoms associated with protein avoidance. Ornithine transcarbamylase (OTC) deficiency, which is inherited as an X-linked disorder, is the most well-described UCD in adults. Acute decompensations associate the triad of encephalopathy, respiratory alkalosis and hyperammonemia. Acute encephalopathy is characterized by brain edema, which is life-threatening without treatment. Specific urea cycle enzyme deficiency can be suspected in the presence of abnormal plasma amino acids concentrations and urinary excretion of orotic acid. A measurement enzyme activity in appropriate tissue, or DNA analysis if available, is required for diagnosis. Treatment requires restriction of dietary protein intake and the use of alternative pathways of waste nitrogen excretion with sodium benzoate and sodium phenylbutyrate. Patients with acute forms may need hemodialysis or hemodiafiltration. Therapeutic goals for OTC deficiency are to maintain plasma ammonia<80 micromol/L, plasma glutamine<1,000 micromol/L, argininemia 80-150 micromol/L and branched chain amino acids within the normal range, in order to prevent episodes of potentially lethal acute hyperammonemia.

CONCLUSION

Potentially fatal acute hyperammonemia may occur in male or female patients at any age. Ammonia should be measured promptly in case of acute neurological and psychiatric symptoms or coma.

Hyperammonemia in the ICU

Patients experiencing acute elevations of ammonia present to the ICU with encephalopathy, which may progress quickly to cerebral herniation. Patient survival requires immediate treatment of intracerebral hypertension and the reduction of ammonia levels. When hyperammonemia is not thought to be the result of liver failure, treatment for an occult disorder of metabolism must begin prior to the confirmation of an etiology. This article reviews ammonia metabolism, the effects of ammonia on the brain, the causes of hyperammonemia, and the diagnosis of inborn errors of metabolism in adult patients.

Neurological implications of urea cycle disorders

The urea cycle disorders constitute a group of rare congenital disorders caused by a deficiency of the enzymes or transport proteins required to remove ammonia from the body. Via a series of biochemical steps, nitrogen, the waste product of protein metabolism, is removed from the blood and converted into urea. A consequence of these disorders is hyperammonaemia, resulting in central nervous system dysfunction with mental status changes, brain oedema, seizures, coma, and potentially death. Both acute and chronic hyperammonaemia result in alterations of neurotransmitter systems. In acute hyperammonaemia, activation of the NMDA receptor leads to excitotoxic cell death, changes in energy metabolism and alterations in protein expression of the astrocyte that affect volume regulation and contribute to oedema. Neuropathological evaluation demonstrates alterations in the astrocyte morphology. Imaging studies, in particular (1)H MRS, can reveal markers of impaired metabolism such as elevations of glutamine and reduction of myoinositol. In contrast, chronic hyperammonaemia leads to adaptive responses in the NMDA receptor and impairments in the glutamate-nitric oxide-cGMP pathway, leading to alterations in cognition and learning. Therapy of acute hyperammonaemia has relied on ammonia-lowering agents but in recent years there has been considerable interest in neuroprotective strategies. Recent studies have suggested restoration of learning abilities by pharmacological manipulation of brain cGMP with phosphodiesterase inhibitors. Thus, both strategies are intriguing areas for potential investigation in human urea cycle disorders.

Valproate-induced hyperammonaemic encephalopathy: review of 14 cases in the psychiatric setting

OBJECTIVES

To review signs and symptoms of valproate-induced hyperammonaemic encephalopathy without hepatotoxicity in the psychiatric setting, explore its mechanisms, and give recommendations for prevention and treatment.

METHODS

Medline search with keywords valproate, ammonia, hyperammonaemia, encephalopathy, and then cross-references to articles obtained through this search. Only cases with indication of valproate for psychiatric condition were included.

RESULTS

Fourteen cases published in the psychiatric setting are reviewed. Valproate-induced hyperammonaemic encephalopathy is a rare adverse event, occurring almost equally in men and women, with a large age range, and reported in two patients with mental retardation. Symptoms appeared either a few days after initiation of valproate therapy, or after several months or years. The main symptoms were fluctuations in consciousness and disorientation. Clinical severity was not related to blood ammonia levels. All patients recovered after valproate-induced hyperammonaemic encephalopathy diagnosis and treatment, usually involving discontinuation of valproate.

CONCLUSIONS

Valproate-induced hyperammonaemic encephalopathy is rare and usually reversible in patients without urea cycle disorders when valproate is discontinued. Therapy with carnitine is recommended. Special caution should be used in patients with mental retardation. Psychiatrists should suspect valproate-induced hyperammonaemic encephalopathy when consciousness deteriorates.

Therapy insight: inborn errors of metabolism in adult neurology--a clinical approach focused on treatable diseases

Inborn errors of metabolism (IEMs) are genetic disorders characterized by dysfunction of an enzyme or other protein involved in cellular metabolism. In most cases, IEMs involve the nervous system. The first clinical symptoms of IEMs usually present in infancy, but in an unknown proportion of cases they can appear in adolescence or adulthood. In this Review, we focus on treatable IEMs, presenting acutely or chronically, that can be diagnosed in an adult neurology department. To make our presentation readily usable by clinicians, the Review is subdivided into eight sections according to the main clinical presentations: emergencies (acute encephalopathies and strokes), movement disorders, peripheral neuropathies, spastic paraparesis, cerebellar ataxia, psychiatric disorders, epilepsy and leukoencephalopathies. Our aim is to present simple guidelines to enable neurologists to avoid overlooking a treatable metabolic disease.

Idiosyncratic adverse reactions to antiepileptic drugs

Idiosyncratic drug reactions may be defined as adverse effects that cannot be explained by the known mechanisms of action of the offending agent, do not occur at any dose in most patients, and develop mostly unpredictably in susceptible individuals only. These reactions are generally thought to account for up to 10% of all adverse drug reactions, but their frequency may be higher depending on the definition adopted. Idiosyncratic reactions are a major source of concern because they encompass most life-threatening effects of antiepileptic drugs (AEDs), as well as many other reactions requiring discontinuation of treatment. Based on the underlying mechanisms, idiosyncratic reactions can be differentiated into (1) immune-mediated hypersensitivity reactions, which may range from benign skin rashes to serious conditions such as drug-related rash with eosinophilia and systemic symptoms; (2) reactions involving unusual nonimmune-mediated individual susceptibility, often related to abnormal production or defective detoxification of reactive cytotoxic metabolites (as in valproate-induced liver toxicity); and (3) off-target pharmacology, whereby a drug interacts directly with a system other than that for which it is intended, an example being some types of AED-induced dyskinesias. Although no AED is free from the potential of inducing idiosyncratic reactions, the magnitude of risk and the most common manifestations vary from one drug to another, a consideration that impacts on treatment choices. Serious consequences of idiosyncratic reactions can be minimized by knowledge of risk factors, avoidance of specific AEDs in subpopulations at risk, cautious dose titration, and careful monitoring of clinical response.

Valproate-induced hyperammonemic encephalopathy

Valproate-induced hyperammonemic encephalopathy (VHE) is an unusual complication characterized by a decreasing level of consciousness, focal neurological deficits, cognitive slowing, vomiting, drowsiness, and lethargy. We have thoroughly reviewed the predisposing factors and their screening, the biochemical and physiopathological mechanisms involved, the different treatments described, and those that are being investigated. Etiopathogenesis is not completely understood, although hyperammonemia has been postulated as the main cause of the clinical syndrome. The increase in serum ammonium level is due to several mechanisms, the most important one appearing to be the inhibition of carbamoylphosphate synthetase-I, the enzyme that begins the urea cycle. Polytherapy with several drugs, such as phenobarbital and topiramate, seems to contribute to hyperammonemia. Hyperammonemia leads to an increase in the glutamine level in the brain, which produces astrocyte swelling and cerebral edema. There are several studies that suggest that treatment with supplements of carnitine can lead to an early favorable clinical response due to the probable carnitine deficiency induced by a valproate (VPA) treatment. Development of the progressive confusional syndrome, associated with an increase in seizure frequency after VPA treatment onset, obliges us to rule out VHE by screening for blood ammonium levels and the existence of urea cycle enzyme deficiency, such as ornithine carbamoyltransferase deficiency. Electroencephalography (EEG) is characterized by signs of severe encephalopathy with continuous generalized slowing, a predominance of theta and delta activity, occasional bursts of frontal intermittent rhythmic delta activity, and triphasic waves. These EEG findings, as well as clinical manifestations and hyperammonemia, tend to normalize after VPA withdrawal.

Nutritional management of urea cycle disorders

Nutritional management of patients who have urea cycle disorders is one of the most challenging tasks in clinical nutrition. The degree to which protein intake should be restricted in urea cycle disorders requires complex calculations which depend on many variables such as specific enzyme defect, age-related growth rate, current health status, level of physical activity, amount of free amino acids administered, energy intake, residual urea cycle function, family lifestyle, use of nitrogen-scavenging medications, and the patient's eating behaviors. This paper presents two case histories and a series of recommendations outlining the nutrition management of urea cycle disorders. It also identifies difficulties that arise in the course of treatment, and suggests practical solutions for overcoming them.

Urea Cycle Disorders: Clinical Presentation Outside the Newborn Period

Although most commonly associated with infancy, the majority of individuals with urea cycle disorders (UCDs) present outside the neonatal period, frequently in childhood. Signs and symptoms are often vague, but recurrent; fulminant presentations associated with acute illness are also common. A disorder of urea cycle metabolism should be considered in children who have recurrent symptoms, especially neurologic abnormalities associated with periods of decompensation. Routine laboratory tests, including measurement of plasma ammonia concentrations, can indicate a potential UCD; however, specific metabolic testing and ultimately enzymatic or molecular confirmation are necessary to establish a diagnosis. Treatment with dietary protein restriction and medications may be challenging in children.

Hiperamonemia secundária ao uso terapêutico de ácido valpróico: relato de caso

O ácido valpróico tem sido amplamente utilizado no tratamento da epilepsia, sendo usualmente bem tolerado, não obstante alguns efeitos colaterais que lhe são atribuídos. Um efeito ainda pouco conhecido é a hiperamonemia, independente da hepatotoxicidade da droga. A hiperamonemia se estabelece no início ou no decurso do tratamento, sendo caracterizada por vômitos, alteração progressiva da consciência, sinais neurológicos focais e aumento na freqüência das crises epilépticas. Descrevemos o caso de menino de seis anos de idade que desenvolveu hiperamonemia pelo uso terapêutico de ácido valpróico. Os exames descartaram aminoacidopatias, acidemias orgânicas e distúrbios do ciclo da uréia, sendo a hipótese de efeito secundário reiterada pela normalização da concentração sangüínea de amônia, após a retirada do medicamento. Os mecanismos da hiperamonemia são discutidos, concluindo-se que o monitoramento da amônia é importante nos pacientes que utilizam o ácido valpróico.

Endocrine and metabolic changes in epileptic patients receiving valproic acid

It has been well known for many years that valproic acid (VPA) therapy can induce obesity and important endocrine dysfunctions; among these dysfunctions, the most common are hyperandrogenism, menstrual disorders, polycystic ovary syndrome, hyperinsulinism, and changes in LH, FSH, and sexual and thyroid hormones. Moreover, abnormalities in pubertal development and impaired skeletal growth have been reported. The aim of this review is to analyze the main effects of VPA on endocrinological functions in patients with epilepsy in order to understand in depth the pathophysiological mechanisms and, consequently, to improve the care of these patients.

Topiramate-valproate-induced hyperammonemic encephalopathy syndrome: case report

A 15-year-old boy with inverted duplication of chromosome 15 was admitted for acute onset of irritability, increasing sleepiness, and worsening of seizures. He had been on valproate and other anti-convulsants. However, he was found to have hyperammonemia within 2 weeks after the addition of low-dose topiramate to valproate. He recovered within 7 days after discontinuation of valproate. Topiramate was tailed off. The reintroduction of valproate monotherapy caused hyperammonemia again without clinical features of encephalopathy. He also developed anticonvulsant hypersensitivity syndrome following the use of phenytoin. We propose the term topiramate-valproate-induced hyperammonemic encephalopathy syndrome to include the following features: excessive sleepiness or somnolence, aggravation of seizures, hyperammonemia, and absence of triphasic waves on electroencephalography in any individual on simultaneous topiramate-valproate therapy. The ammonia level ranged from 1.5 to 2 times normal. The serum valproate level might be within the therapeutic range. The possible mechanism is topiramate-induced aggravation of all the known complications of valproate monotherapy. This condition is reversible with cessation of either valproate or topiramate.

Valproic acid-associated hyperammonemic encephalopathy: a case report from the psychiatric setting

Valproic acid-associated hyperammonemic encephalopathy (VHE) has been described in the neurology and emergency medicine literature, but the case reports identified therein are rarely derived from the psychiatric use of this medication. Valproic acid is widely used as a mood stabilizer in bipolar affective disorder and schizoaffective disorder. Patients with normal blood levels, liver function and metabolic tests may present with markedly elevated ammonia and a variety of neurological symptoms. We report the case of a patient on long-term valproic acid therapy, with stable dosing, who presented with an elevated ammonia level, new-onset tremor, confusion, and loss of consciousness. This case illustrates the need to check ammonia levels in psychiatric patients who are taking valproic acid and who present with new neurological symptoms.

Valproic acid-induced hyperammonemia: a case report

The authors present a case of a patient treated with valproic acid for seizure disorder who presented with acute mental status changes consistent with encephalopathy. Notably, her serum ammonia level was 3 times the upper limit of normal, despite an only mildly elevated aspartate aminotransferase and normal bilirubin. Her serum valproic acid level was in the therapeutic range. Her symptoms resolved with discontinuation of valproic acid and supportive care. The authors review the possible mechanisms of valproic acid-associated hyperammonemia with encephalopathy and propose clinical practice modifications to minimize the incidence of this adverse reaction to this generally well-tolerated and clinically important psychotropic medication.

Valproic Acid—Induced Hyperammonemia and Thrombocytopenia in an Elderly Woman

OBJECTIVE

To describe a case of oral valproic acid—induced hyperammonemia and thrombocytopenia in an elderly patient.

CASE SUMMARY

A 76-year-old white woman presented to the emergency department with generalized weakness, confusion, nausea, and vomiting. She was taking sodium divalproex 750 mg 3 times daily, with valproic acid concentration 144 mg/L. She was admitted to the medical ward. The dose of sodium divalproex was decreased and discontinued. During her hospital stay, the woman's ammonia level rose to 211 μg/dL despite a normal valproic acid concentration. She was confused, somnolent, and had decreased mobility. Her platelet count decreased from 133 to 86 × 103/mm 3 . Gabapentin was prescribed for seizure control. The patient's mental status, ammonia level, and platelet count returned to baseline following discontinuation of valproic acid.

DISCUSSION

It has been reported that valproic acid can interfere with the enzyme carbamoylphosphate synthetase, which is responsible for incorporating ammonia into the urea cycle. It has also been reported that valproic acid can increase the transport of glutamine across the mitochondrial membrane in the kidney, thereby increasing the production of ammonia. The etiology of valproic acid—induced thrombocytopenia has not been elucidated. Using the Naranjo probability scale, a probable relationship between hyperammonemia and valproic acid and a possible relationship between thrombocytopenia and valproic acid were determined.

CONCLUSIONS

Valproic acid can be associated with hyperammonemia and thrombocytopenia. Clinicians should be aware of changes in patients' cognitive and functional capacity, especially elderly patients on sodium divalproex.

Intermittent hyperammonemic encephalopathy in a child with ornithine transcarbamylase deficiency

Ornithine transcarbamylase (OTC) deficiency is an X-linked disorder and the most common inherited cause of hyperammonemia. Clinical manifestations are more severe in hemizygous males who often present in neonatal period. Heterozygous females may be asymptomatic until juvenile or adulthood. Fluctuating concentration of ammonia, glutamine and other excitotoxic amino acids result in a chronic or episodically recurring encephalopathy. The authors report a heterozygous female with OTC deficiency who presented with recurrent encephalopathy.

Hyperammonemic encephalopathy induced by a combination of valproate and pivmecillinam

We describe the clinical and neurophysiological findings in a case of hyperammonemic encephalopathy. A 72-year-old woman taking valproate (VPA), as monotherapy for her partial epilepsy developed urinary tract infection. She was treated with pivmecillinam 600 mg daily. The following days she deteriorated and became stuporous. At admission her serum ammonia level was increased (113 mmol/l) but the liver function appeared normal. EEG showed bilateral triphasic waves and continuous high-amplitude delta-theta wave. The patient recovered rapidly after discontinuation of VPA and i.v. treatment with cefuroxime for her urinary tract infection. VPA-induced hyperammonemic encephalopathy in adults is a rare phenomenon, especially when VPA is used as monotherapy. It has been suggested that the VPA-induced hyperammonemic encephalopathy is due to reduced serum carnitine concentration. Pivmecillinam, a widely used antibiotic for treatment of urinary tract infections, is also known to decrease the serum carnitine concentration. Our case shows that caution is required when treatment with VPA is combined with pivmecillinam due to the risk of developing hyperammonemic encephalopathy.

Ammonia induced encephalopathy from valproic acid in a bipolar patient: case report

Valproic acid is widely used as a mood stabilizer. We report a case of an adult with bipolar disorder taking therapeutic doses of valproic acid, who presented to the emergency department with coma related to hyperammonemia as a complication of valproic acid treatment. Valproic acid was discontinued which resulted in rapid clinical recovery. Valproic acid induced coma was likely related to a urea cycle enzymopathy. Clinicians should consider hyperammonemia in all patients who present with coma and other mental status changes while on valproic acid. In such patients, ammonia level should be obtained in addition to liver function tests.

Urea Cycle Disorders

Urea cycle disorders comprise a group of inborn errors of metabolism that represent unique gene-nutrient interactions whose significant morbidity arises from acute and chronic neurotoxicity associated with often massive hyperammonemia. Current paradigms of treatment are focused on controlling the flux of nitrogen transfer through the hepatic urea cycle by a combination of dietary and pharmacologic approaches. Evolving paradigms include the development of cell and gene therapies. Current research is focused on understanding the pathophysiology of ammonia-mediated toxicity and prevention of neural injury.

Reversible altered consciousness with brain atrophy caused by valproic acid

A 5-year-old female developed alteration of consciousness during 3 days of long-term treatment with valproic acid for localization-related epilepsy. Computed tomography revealed cerebral atrophy, and electroencephalography presented slow background activity. Consciousness cleared only 12 hours after valproic acid was discontinued, and normal electroencephalography results were evident 1 week later. Cerebral atrophy was nonexistent 2 months later. This rapidly developing but reversible alteration of consciousness in parallel with brain atrophy is recognized as a rare idiosyncratic adverse effect of valproic acid.