Serum and CSF glutamine levels in valproate-related 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.

Influence of the glutamate-glutamine cycle on valproic acid-associated hepatotoxicity in pediatric patients with epilepsy

INTRODUCTION

Although valproic acid is generally well tolerated, hepatotoxicity is a common side effect in patients receiving long-term treatment. However, the mechanisms underlying valproic acid-associated hepatotoxicity remain elusive.

METHODS

To investigate the mechanisms and explore the potential risk factors for valproic acid-associated hepatotoxicity, 165 age-matched pediatric patients were recruited for laboratory tests and glutamate-glutamine cycle analysis.

RESULTS

The concentration of glutamate in patients with hepatotoxicity was significantly greater than that in control patients, while the concentration of glutamine in patients with hepatotoxicity was significantly lower than that in control patients (P <0.05). In addition, the frequencies of the heterozygous with one mutant allele and homozygous with two mutant alleles genotypes in glutamate-ammonia ligase rs10911021 were significantly higher in the hepatotoxicity group than those in the control group (47.1 percent versus 32.5 percent, P = 0.010; 17.6 percent versus 5.2 percent, P = 0.001, respectively). Moreover, heterozygous carriers with one mutant allele and homozygous carriers with two mutant alleles genotypes of glutamate-ammonia ligase rs10911021 exhibited significant differences in the concentrations of glutamine and glutamate concentrations (P ˂ 0.001 and P = 0.001, respectively) and liver function indicators (activities of aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyl transferase, P <0.001, respectively). Furthermore, logistic regression analysis indicated that glutamate-ammonia ligase rs10911021 (P = 0.002, odds ratio: 3.027, 95 percent confidence interval, 1.521 - 6.023) and glutamate (P = 0.001, odds ratio: 2.235, 95 percent confidence interval, 1.369 - 3.146) were associated with a greater risk for hepatotoxicity, while glutamine concentrations were negatively associated with hepatotoxicity (P = 0.001, odds ratio: 0.711, 95 percent confidence interval, 0.629 - 0.804).

DISCUSSION

Understanding pharmacogenomic risks for valproic acid induced hepatotoxicity might help direct patient specific care. Limitations of our study include the exclusive use of children from one location and concomitant medication use in many patients.

CONCLUSION

Perturbation of the glutamate-glutamine cycle is associated with valproic acid-associated hepatotoxicity. Moreover, glutamate-ammonia ligase rs10911021, glutamate and glutamine concentrations are potential risk factors for valproic acid-associated hepatotoxicity.

Nonhepatic hyperammonemic encephalopathy following bariatric surgery: A systematic review

BACKGROUND

Nonhepatic Hyperammonemic encephalopathy (NHAE) following Bariatric Surgery (BS), mainly Roux-en-Y Gastric Bypass (RYGB) and Biliopancreatic Diversion (BPD) is a potentially devastating condition if not diagnosed and managed promptly.

METHODS

A literature review was performed using PRISMA guidelines. Eighteen studies and 3 conference abstracts with a total of 33 patients were included in this review.

RESULTS

Majority (28 patients, 84.8 %) had RYGB. Seven patients (21.2 %) had associated metabolic disorders. 60 % of patients presented with neurological symptoms or signs such as confusion, cognitive and/or psychomotor changes, and decreased reflexes. Two patients presented with status epilepticus. In 30 of the 33 patients an elevated serum ammonia levels was reported (90.9 %). The overall mortality was 39.3 %.

CONCLUSION

NHAE is a rare condition following bariatric surgery (in particular bypass procedures), carrying a high mortality rate. The signs and symptoms are predominantly neurological and may be mistaken for Wernicke's encephalopathy or other more common neurological conditions. Serum ammonia levels should be checked in those who present with these symptoms and signs. Prompt treatment might be life saving in patients with NHAE.

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.

HYPERAMMONAEMIA AND COGNITIVE IMPAIRMENT IN EPILEPSY PATIENTS TREATED WITH VALPROIC ACID - PRELIMINARY STUDY

OBJECTIVE

The aim: To determine whether VPA pharmacotherapy, mainly in the group of patients using subtherapeutic doses of VPA, could contribute to the occurrence of cognitive impairment.

PATIENTS AND METHODS

Materials and methods: The study involved 14 patients: six women and eight men, aged 24 - 77 years (mean SD ± - 52.36±13.71) diagnosed with epilepsy in accordance with the ILAE criteria (International League Against Epilepsy), in whom the main clinical complaint, in addition to poor control of epileptic seizures, were impaired concentration, attention and memory impairment.

RESULTS

Results: Mild cognitive impairment - MCI was diagnosed in 4 patients (28.57%) (3 with elevated ammonia levels, 1 without), in 1 patient (7.14%) there was a mild level of dementia. In only one MCI case, elevated serum concentrations of valproic acid were also recorded. It is very important to highlight that cognitive impairment has never been diagnosed before (prior to VPA therapy) in this group. Of these 5 patients, in four cases, after discontinuation of the drug, an improvement in the clinical condition was achieved. In a patient with mild level dementia, the termination of therapy did not give a similar effect. This proves the possibility of other mechanisms responsible for generating these sometimes irreversible disorders.

CONCLUSION

Conclusions: Regardless of the dose and concentration of ammonia in blood serum of patients diagnosed with epilepsy, VPA therapy may cause various, significant dysfunctions that significantly impair quality of life.

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.

Valproate-Induced Hyperammonemic Encephalopathy Following Accidental Ingestion in a Toddler

Clinical manifestations of valproic acid (VPA) toxicity can range from just mild confusion and drowsiness to serious encephalopathy, leading to depressed sensorium and even coma and death. The exact cause(s) of how VPA influences the integrity of brain function remains unknown. Nevertheless, several mechanisms have been postulated including a surge in the blood ammonia concentration. Valproic acid-induced hyperammonemic encephalopathy is a rare yet serious sequalae and that can lead to grave outcomes. We report a case of hyperammonemic encephalopathy with preserved liver function following a moderate VPA intoxication in a toddler, who was successfully managed conservatively. Additionally, we briefly discuss mechanistic basis of VPA toxicity and highlight some of the available potential therapies.

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.

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.

Refining Delirium: A Transtheoretical Model of Delirium Disorder with Preliminary Neurophysiologic Subtypes

The development of delirium indicates neurophysiologic disruption and predicts unfavorable outcomes. This relationship between delirium and its outcomes has inspired a generation of studies aimed at identifying, predicting, and preventing both delirium and its associated sequelae. Despite this, evidence on delirium prevention and management remains limited. No medication is approved for the prevention or treatment of delirium or for its associated psychiatric symptoms. This unmet need for effective delirium treatment calls for a refined approach. First, we explain why a one-size-fits-all approach based on a unitary biological model of delirium has contributed to variance in delirium studies and prevents further advance in the field. Next, in parallel with the shift from dementia to "major neurocognitive disorder," we propose a transtheoretical model of "delirium disorder" composed of interactive elements-precipitant, neurophysiology, delirium phenotype, and associated psychiatric symptoms. We explore how these relate both to the biopsychosocial factors that promote healthy cognition ("procognitive factors") and to consequent neuropathologic sequelae. Finally, we outline a preliminary delirium typology of specific neurophysiologic disturbances. Our model of delirium disorder offers several avenues for novel insights and clinical advance: it univocally differentiates delirium disorder from the phenotype of delirium, highlights delirium neurophysiology as a treatment target, separates the core features of delirium from associated psychiatric symptoms, suggests how procognitive factors influence the core elements of delirium disorder, and makes intuitive predictions about how delirium disorder leads to neuropathologic sequelae and cognitive impairment. Ultimately, this model opens several avenues for modern neuroscience to unravel this disease of antiquity.

Antiepileptic Drugs and Liver Disease

Acute, symptomatic seizures or epilepsy may complicate the course of hepatic disease. Choosing the most appropriate antiepileptic drug in this setting represents a difficult challenge, as most medications are metabolized by the liver. This article focuses on the acute and chronic treatment of seizures in patients with advanced liver disease and reviews the hepatotoxic potential of specific antiepileptic drugs. Newer antiepileptic drugs without, or with minimal, hepatic metabolism, such as levetiracetam, lacosamide, topiramate, gabapentin, and pregabalin should be used as first-line therapy. Medications undergoing extensive hepatic metabolism, such as valproic acid, phenytoin, and felbamate should be used as drugs of last resort. In special circumstances, as in patients affected by acute intermittent porphyria, exposure to most antiepileptic drugs could precipitate attacks. In this clinical scenario, bromides, levetiracetam, gabapentin, and vigabatrin constitute safe choices. For the treatment of status epilepticus, levetiracetam and lacosamide, available in intravenous preparations, are good second-line therapies after benzodiazepines fail to control seizures. Hepatotoxicity is also a rare and unexpected side effect of some antiepileptic drugs. Drugs such as valproic acid, phenytoin, and felbamate, have a well-recognized association with liver toxicity. Other antiepileptic drugs, including phenobarbital, benzodiazepines, ethosuximide, and the newer generations of antiepileptic drugs, have only rarely been linked to hepatotoxicity. Thus physicians should be mindful of the pharmacokinetic profile and the hepatotoxic potential of the different antiepileptic drugs available to treat patients affected by liver disease.

5-FU-induced leukoencephalopathy with reversible lesion of splenium of corpus callosum in a patient with colorectal cancer

5-Fluorouracil (5-FU), a commonly used antimetabolite and antineoplastic agent, has been approved for treatment of various cancers. Neurotoxicities are considered extremely rare side effects of 5-FU. We present a case of 5-FU-induced encephalopathy with diffusion-restricted reversible lesion of the splenium of the corpus callosum in a patient with colorectal cancer. The patient presented with confusion, dysarthria and agitation after 5-FU infusion. The prognosis of this toxic effects of 5-FU is usually good if recognised and treated in time. Emergency physicians, general practitioners and oncologists should be aware of this rare side effects of 5-FU chemotherapy and its diagnosis and treatment.

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.

Medicinal-Induced Behavior Disorders

Commonly used medications can have neuropsychiatric and behavioral effects that may be idiosyncratic or metabolic in nature, or a function of interactions with other drugs, toxicity, or withdrawal. This article explores an approach to the patient with central nervous system toxicity, depending on presentation of sedation versus agitation and accompanying physical signs and symptoms. The effects of antihypertensives, opioids, antibiotics, antiepileptic agents, steroids, Parkinson's disease medications, antipsychotics, medications for human immunodeficiency virus infection, cancer chemotherapeutics, and immunotherapies are discussed. A look at the prevalence of adverse reactions to medications and the errors underlying such occurrences is included.

Fatal Nonhepatic Hyperammonemia in ICU Setting: A Rare but Serious Complication following Bariatric Surgery

Bariatric surgery is well established in reducing weight and improving the obesity-associated morbidity and mortality. Hyperammonemic encephalopathy following bariatric surgery is rare but highly fatal if not diagnosed in time and managed aggressively. Both macro- and micronutrients deficiencies play a role. A 42-year-old Hispanic female with a history of Roux-en-Y Gastric Bypass Procedure was brought to ED for progressive altered mental status. Physical exam was remarkable for drowsiness with Glasgow Coma Scale 11, ascites, and bilateral pedal edema. Labs showed elevated ammonia, low hemoglobin, low serum prealbumin, albumin, HDL, and positive toxicology. She remained obtunded despite the treatment with Narcan and flumazenil and the serum ammonia level fluctuated despite standard treatment with lactulose and rifaximin. Laboratory investigations helped to elucidate the etiology of the hyperammonemia most likely secondary to unmasking the functional deficiency of the urea cycle enzymes. Hyperammonemia in the context of normal liver function tests becomes diagnostically challenging for physicians. Severe hyperammonemia is highly fatal. Early diagnosis and aggressive treatment can alter the prognosis favorably.

Pronounced reversible hyperammonemic encephalopathy associated with combined valproate-topiramate therapy in a 7-year-old girl

Valproate is one of the most frequently used anticonvulsive drugs in children and adults. Valproate is a generally well tolerated medication. However, encephalopathy with or without hyperammonemia is one of its rare adverse events. We present a 7-year-old girl who suffered from epilepsy with generalized tonic-clonic seizures and absence epilepsy. She was initially treated with topiramate. Methylprednisolone pulse therapy and long-term therapy with valproate were initiated due to an increase of seizure frequency. At day 5 of therapy, a further increase of seizure frequency was observed followed by lethargy and somnolence. Liver enzymes remained within normal range, but ammonia serum levels increased to a maximum of 544 mmol/l. Discontinuing valproate and starting potassium-benzoate and sodium-phenylbutyrate improved the clinical condition and ammonia serum levels. Haemodialysis was not required. Cranial magnetic resonance imaging ruled out brain edema. The patient was further on successfully treated with a combination of both, topiramate and levetiracetam. Seizures did not recur and development was normal until now (3 years later). To the best of our knowledge, we observed the highest ammonia serum levels ever reported in valproate-induced hyperammonemia with a complete remission of the subsequent encephalopathy. Topiramate might increase the risk of valproate-induced encephalopathy by carbonic anhydrase inhibition.

Ornithine transcarbamylase deficiency presenting with acute reversible cortical blindness

Acute focal neurologic deficits are a rare but known presentation of ornithine transcarbamylase deficiency, particularly in females. We describe here a 6-year-old girl with newly diagnosed ornithine transcarbamylase deficiency who presents with an episode of acute cortical blindness lasting for 72 hours in the absence of hyperammonemia. Her symptoms were associated with a subcortical low-intensity lesion with overlying cortical hyperintensity on fluid-attenuated inversion recovery magnetic resonance imaging (MRI) of the occipital lobes. Acute reversible vision loss with these MRI findings is an unusual finding in patients with ornithine transcarbamylase deficiency. Our findings suggest a role for oxidative stress and aberrant glutamine metabolism in the acute clinical features of ornithine transcarbamylase deficiency even in the absence of hyperammonemia.

Drug-induced cerebellar ataxia: a systematic review

BACKGROUND AND OBJECTIVES

Cerebellar ataxia can be induced by a large number of drugs. We here conducted a systemic review of the drugs that can lead to cerebellar ataxia as an adverse drug reaction (ADR).

METHODS

We performed a systematic literature search in Pubmed (1966 to January 2014) and EMBASE (1988 to January 2014) to identify all of the drugs that can have ataxia as an ADR and to assess the frequency of drug-induced ataxia for individual drugs. Furthermore, we collected reports of drug-induced ataxia over the past 20 years in the Netherlands by querying a national register of ADRs.

RESULTS

Drug-induced ataxia was reported in association with 93 individual drugs (57 from the literature, 36 from the Dutch registry). The most common groups were antiepileptic drugs, benzodiazepines, and antineoplastics. For some, the number needed to harm was below 10. Ataxia was commonly reversible, but persistent symptoms were described with lithium and certain antineoplastics.

CONCLUSIONS

It is important to be aware of the possibility that ataxia might be drug-induced, and for some drugs the relative frequency of this particular ADR is high. In most patients, symptoms occur within days or weeks after the introduction of a new drug or an increase in dose. In general, ataxia tends to disappear after discontinuation of the drug, but chronic ataxia has been described for some drugs.

Sodium valproate-related hyperammonaemic encephalopathy

A 59-year-old man with a background of poststroke epilepsy, lung cancer, chronic obstructive pulmonary disease and hypertension, presented to the medical assessment unit with acute confusion and altered consciousness. Medications included sodium valproate, aspirin and antihypertensives. On examination he was confused, with his Glasgow Coma Scale fluctuating between 10 and 14. Routine blood tests, thyroid function tests, serum sodium valproate level, urine dip, CT of the brain and cerebrospinal fluid analysis were all normal. EEG revealed changes consistent with an encephalopathic process. Serum ammonia was elevated (75 µg/dL), consistent with a diagnosis of valproate-related hyperammonaemic encephalopathy. Sodium valproate was changed to a different antiepileptic drug and his confusion gradually resolved. Valproate-related hyperammonaemic encephalopathy is a treatable condition which should be considered as a diagnosis in anyone taking sodium valproate with new onset confusion, even in the presence of therapeutic sodium valproate levels and normal liver function tests.

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.

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.

Encephalopathy in acute liver failure resulting from acetaminophen intoxication: new observations with potential therapy

OBJECTIVE

Hyperammonemia is a major contributing factor to the encephalopathy associated with liver disease. It is now generally accepted that hyperammonemia leads to toxic levels of glutamine in astrocytes. However, the mechanism by which excessive glutamine is toxic to astrocytes is controversial. Nevertheless, there is strong evidence that glutamine-induced osmotic swelling, especially in acute liver failure, is a contributing factor: the osmotic gliopathy theory. The object of the current communication is to present evidence for the osmotic gliopathy theory in a hyperammonemic patient who overdosed on acetaminophen.

DESIGN

Case report.

SETTING

Johns Hopkins Hospital.

PATIENT

A 22-yr-old woman who, 36 hrs before admission, ingested 15 g acetaminophen was admitted to the Johns Hopkins Hospital. She was treated with N-acetylcysteine. Physical examination was unremarkable; her mental status was within normal limits and remained so until approximately 72 hrs after ingestion when she became confused, irritable, and agitated.

INTERVENTIONS

She was intubated, ventilated, and placed on lactulose. Shortly thereafter, she was noncommunicative, unresponsive to painful stimuli, and exhibited decerebrate posturing. A clinical diagnosis of cerebral edema and increased intracranial pressure was made. She improved very slowly until 180 hrs after ingestion when she moved all extremities. She woke up shortly thereafter.

MEASUREMENTS AND MAIN RESULTS

Despite the fact that hyperammonemia is a major contributing factor to the encephalopathy observed in acute liver failure, the patient's plasma ammonia peaked when she exhibited no obvious neurologic deficit. Thereafter, her plasma ammonia decreased precipitously in parallel with a worsening neurologic status. She was deeply encephalopathic during a period when her liver function and plasma ammonia had normalized. Plasma glutamine levels in this patient were high but began to normalize several hours after plasma ammonia had returned to normal. The patient only started to recover as her plasma glutamine began to return to normal.

CONCLUSIONS

We suggest that the biochemical data are consistent with the osmotic gliopathy theory--high plasma ammonia leads to high plasma glutamine--an indicator of excess glutamine in astrocytes (the site of brain glutamine synthesis). This excess glutamine leads to osmotic stress in these cells. The lag in recovery of brain function presumably reflects time taken for the astrocyte glutamine concentration to return to normal. We hypothesize that an inhibitor of brain glutamine synthesis may be an effective treatment modality for acute liver failure.

Astrocyte glutamine synthetase: importance in hyperammonemic syndromes and potential target for therapy

Many theories have been advanced to explain the encephalopathy associated with chronic liver disease and with the less common acute form. A major factor contributing to hepatic encephalopathy is hyperammonemia resulting from portacaval shunting and/or liver damage. However, an increasing number of causes of hyperammonemic encephalopathy have been discovered that present with the same clinical and laboratory features found in acute liver failure, but without liver failure. Here, we critically review the physiology, pathology, and biochemistry of ammonia (i.e., NH3 plus NH4+) and show how these elements interact to constitute a syndrome that clinicians refer to as hyperammonemic encephalopathy (i.e., acute liver failure, fulminant hepatic failure, chronic liver disease). Included will be a brief history of the status of ammonia and the centrality of the astrocyte in brain nitrogen metabolism. Ammonia is normally detoxified in the liver and extrahepatic tissues by conversion to urea and glutamine, respectively. In the brain, glutamine synthesis is largely confined to astrocytes, and it is generally accepted that in hyperammonemia excess glutamine compromises astrocyte morphology and function. Mechanisms postulated to account for this toxicity will be examined with emphasis on the osmotic effects of excess glutamine (the osmotic gliopathy theory). Because hyperammonemia causes osmotic stress and encephalopathy in patients with normal or abnormal liver function alike, the term "hyperammonemic encephalopathy" can be broadly applied to encephalopathy resulting from liver disease and from various other diseases that produce hyperammonemia. Finally, the possibility that a brain glutamine synthetase inhibitor may be of therapeutic benefit, especially in the acute form of liver disease, is discussed.

Valproic Acid-induced hyperammonemia in the elderly: a review of the literature

Valproic acid and its derivatives are commonly used to treat many psychiatric conditions in the elderly. Hyperammonemia is a less common but important side effect of these drugs. The elderly patient appears highly vulnerable to this side effect of this group of medications. In this paper, we systematically review the published literature for hyperammonemia induced by valproic acid and its derivatives. We describe the three reported cases and review possible treatment strategies for this condition.

Valproate-induced hyperammonemic encephalopathy treated by hemodialysis

Valproate-induced hyperammonemic encephalopathy is an unusual but serious complication that may occur in people with normal liver-associated enzyme levels, despite normal therapeutic doses and serum levels of valproate. Here, we describe an adolescent girl who had absence seizure and complained about progressive dizziness and general malaise several days after restarting valproate. Then, she presented vomiting and decreased consciousness three weeks after valproate use. Notably, her serum ammonia level was five times the upper limit of normal (184 micrommol/L), with normal liver-associated enzyme and supra-therapeutic valproate level. EEG showed continuous generalized slowing. The tandem mass analysis revealed carnitine deficiency. Consciousness improved after emergent hemodialysis. Ammonia level and EEG also returned to normal. Possible mechanisms, risk factors and the treatments of valproate-induced hyperammonemic encephalopathy are described. Physicians should consider this possibility when consciousness disturbance occurs in patients treated with valproate.

CNS adverse events associated with antiepileptic drugs

A variety of newer antiepileptic drugs (AEDs) are now available for treating patients with epilepsy in addition to the 'conventional' drugs that have been available throughout a large part of the last century. Since these drugs act to suppress the pathological neuronal hyperexcitability that constitutes the final substrate in many seizure disorders, it is not surprising that they are prone to causing adverse reactions that affect the CNS.Information on adverse effects of the older AEDs has been mainly observational. Equally, whilst the newer drugs have been more systematically studied, their long-term adverse effects are not clearly known. This is illustrated by the relatively late emergence of the knowledge of visual field constriction in the case of vigabatrin, which only became known after several hundred thousand patient-years of use. However, older drugs continue to be studied and there has been more recent comment on the possible effect of valproate (valproic acid) on cognition following exposure to this drug in utero.With most AEDs, there are mainly dose-related adverse effects that could be considered generic, such as sedation, drowsiness, incoordination, nausea and fatigue. Careful dose titration with small initial doses can reduce the likelihood of these adverse effects occurring. Adverse effects such as paraesthesiae are more commonly reported with drugs such as topiramate and zonisamide that have carbonic anhydrase activity. Weight loss and anorexia can also be peculiar to these drugs. Neuropsychiatric adverse effects are reported with a variety of AEDs and may not be dose related. Some drugs, such as carbamazepine when used to treat primary generalized epilepsy, can exacerbate certain seizure types. Rare adverse effects such as hyperammonaemia with valproate are drug specific. There are relatively very few head-to-head comparisons of AEDs and limited information is available in this regard.In this review, we discuss the available literature and provide a comprehensive summary of adverse drug reactions of AEDs affecting the CNS.

Valproate-induced hyperammonemic encephalopathy

Valproate-induced hyperammonemic encephalopathy is an unusual but serious complication that can occur in people with normal liver-associated enzyme levels, and despite normal therapeutic doses and serum levels of valproate. Here, we describe an adolescent girl suffering from absence seizures, who complained of progressive dizziness and general malaise several days after restarting valproate. She developed vomiting and decreased consciousness after 3 weeks of valproate use. She had a serum ammonia level five times higher than the upper normal limit, normal liver-associated enzymes, and a supra-therapeutic valproate level. Electroencephalography (EEG) showed continuous generalized slowing. Tandem mass spectrometry analysis revealed carnitine deficiency. Her consciousness improved after emergent hemodialysis. Her ammonia level and EEG also became normal. Possible mechanisms, risk factors and treatments of valproate-induced hyperammonemic encephalopathy are described. Physicians should consider this possibility when consciousness disturbance occurs in patients treated with valproate.

Amino acid cerebrospinal fluid/plasma ratios in children: influence of age, gender, and antiepileptic medication

OBJECTIVE

The purpose of this work was to investigate the influence of age, gender, and antiepileptic therapy on amino acid cerebrospinal fluid/plasma ratios in children.

PATIENTS AND METHODS

Concentrations of 17 amino acids measured by ion-exchange chromatography with ninhydrin detection in plasma and cerebrospinal fluid from 68 patients with neurologic diseases were used to calculate their cerebrospinal fluid/plasma ratios (70 measurements; 28 female patients [29 punctures] and 40 male patients [41 punctures]). Age dependence and the effects of gender and antiepileptic medication on amino acid cerebrospinal fluid/plasma ratios were investigated by linear multiple regression analysis, and nonstandardized predicted mean values for 2 age groups were calculated (cutoff: 3 years old).

RESULTS

The cerebrospinal fluid/plasma ratios ranged between 0.02 for glycine and 0.93 for glutamine. Age had a significant influence on cerebrospinal fluid/plasma ratios for valine, isoleucine, leucine, and tyrosine, with higher ratios in younger children. Gender had a significant influence only on the glutamine cerebrospinal fluid/plasma ratio (female patients had lower ratios). Cerebrospinal fluid/plasma ratios of glutamine and tyrosine were significantly elevated by valproate therapy and those of serine, asparagine, glutamine, valine, methionine, and phenylalanine by phenobarbital therapy. No significant influence of age, gender, and antiepileptic drugs was detectable on cerebrospinal fluid/plasma ratios of threonine, proline, glycine, alanine, histidine, ornithine, lysine, and arginine.

CONCLUSIONS

Cerebrospinal fluid/plasma ratios, especially for essential neutral amino acids and for serine, asparagine, and glutamine were influenced to different degrees by age, gender, and antiepileptic therapy.

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.

Non-convulsive status epilepticus secondary to valproic acid-induced hyperammonemic encephalopathy

BACKGROUND

Valproic acid (VPA) may induce hyperammonemic encephalopathy. On the other hand, seizure-inducing effects of antiepileptic drugs (AEDs) may be a paradoxical reaction or a result of AED-induced encephalopathy (commonly induced by VPA).

METHODS

We present the case of a 19-year-old male who developed acute mental status changes consistent with encephalopathy evolving into repetitive seizures with oral automatisms induced by relatively small doses of VPA.

RESULTS

Although serum hepatic enzymes, such as AST and ALT, were normal, serum ammonia concentration was high, i.e. 70 micromol/l (normal range 9-33 micromol/l). Administration of VPA was discontinued immediately after admission. The patient's condition improved during the second week of hospitalization and ammonium levels returned to normal.

CONCLUSION

In conclusion, although uncommon, a possible induction of non-convulsive status epilepticus by valproate-induced hyperammonemic encephalopathy should be taken into account and properly managed by discontinuation of the drug.

Different clinical manifestations of hyperammonemic encephalopathy

Valproate is an effective anticonvulsant. Although it is usually well tolerated, it has been associated with many neurological, hematopoietic, hepatic, and digestive system side effects. Among these side effects, hyperammonemia without clinical or laboratory evidence of hepatotoxicity is rare and is an important clinical consideration. The aim of this article was to evaluate the reasons for the unexpected symptoms observed in seven patients with epilepsy patients during valproate treatment. We evaluated seven adult patients with localization-related epilepsy who presented with different acute or subacute neurological symptoms related to valproate-induced hyperammonemic encephalopathy. Four of the seven patients had acute onset of confusion, decline in cognitive abilities, and ataxia. Two had subacute clinical symptoms, and the other patient had symptoms similar to those of acute toxicity. These unusual clinical symptoms and similar cases had not been reported in the literature before. Serum ammonia levels were elevated in all seven patients. After discontinuation of valproate, complete clinical improvement was observed within 5-10 days. On the basis of our work, we suggest that the ammonia levels of a patient who has new neurological symptoms and has been taking valproate must be checked. Clinicians should be aware that these clinical symptoms may be related to valproate-induced hyperammonemic encephalopathy. The symptoms have been observed to resolve dramatically after withdrawal of the drug.

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.

Aggravation of epilepsy by antiepileptic drugs

Antiepileptic drugs may paradoxically worsen seizure frequency or induce new seizure types in some patients with epilepsy. The mechanisms of seizure aggravation by antiepileptic drugs are mostly unknown and may be related to specific pharmacodynamic properties of these drugs. This article provides a review of the various clinical circumstances of seizure exacerbation and aggravation of epilepsy by antiepileptic drugs as well as a discussion of possible mechanisms underlying the occasional paradoxical effect of these drugs. Antiepileptic drug-induced seizure aggravation can occur virtually with all antiepileptic medications. Drugs that aggravate seizures are more likely to have only one or two mechanisms of action, either enhanced gamma-aminobutyric acid-mediated transmission or blockade of voltage-gated sodium channels. Antiepileptic drug-induced seizure exacerbation should be considered and the accuracy of diagnosis of the seizure type should be questioned whenever there is seizure worsening or the appearance of new seizure types after the introduction of any antiepileptic medication.

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.

Cerebral ammonia uptake and accumulation during prolonged exercise in humans

We evaluated whether peripheral ammonia production during prolonged exercise enhances the uptake and subsequent accumulation of ammonia within the brain. Two studies determined the cerebral uptake of ammonia (arterial and jugular venous blood sampling combined with Kety-Schmidt-determined cerebral blood flow; n = 5) and the ammonia concentration in the cerebrospinal fluid (CSF; n = 8) at rest and immediately following prolonged exercise either with or without glucose supplementation. There was a net balance of ammonia across the brain at rest and at 30 min of exercise, whereas 3 h of exercise elicited an uptake of 3.7 +/- 1.3 micromol min(-1) (mean +/-s.e.m.) in the placebo trial and 2.5 +/- 1.0 micromol min(-1) in the glucose trial (P < 0.05 compared to rest, not different across trials). At rest, CSF ammonia was below the detection limit of 2 microm in all subjects, but it increased to 5.3 +/- 1.1 microm following exercise with glucose, and further to 16.1 +/- 3.3 microm after the placebo trial (P < 0.05). Correlations were established between both the cerebral uptake (r2 = 0.87; P < 0.05) and the CSF concentration (r2 = 0.72; P < 0.05) and the arterial ammonia level and, in addition, a weaker correlation (r2 = 0.37; P < 0.05) was established between perceived exertion and CSF ammonia at the end of exercise. The results let us suggest that during prolonged exercise the cerebral uptake and accumulation of ammonia may provoke fatigue, e.g. by affecting neurotransmitter metabolism.

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.

Encephalopathy and myoclonus triggered by valproic acid

In recent years, the use of valproic acid (VPA) as a mood-stabilizing agent has continuously increased. Although VPA usually is well tolerated, its use in combination with other psychotropic compounds might bear an elevated risk of adverse reactions. Here, we present the case of a 42-year-old male suffering from treatment-resistant psychotic depression, who was prescribed VPA additionally to lithium, clomipramine, flupentixol and risperidone. By doing so, he developed myoclonus, tremor and encephalopathy with sedation and marked EEG background slowing. Most notably, these side effects occurred in the presence of normal VPA and ammonia serum concentrations. On VPA discontinuation, all symptoms vanished and EEG normalized. We thus suggest that direct VPA-induced encephalopathy in the absence of ammonemia does exist, in this case probably facilitated by psychotropic polypharmacy.

Identification of abnormal neuronal metabolism outside the seizure focus in temporal lobe epilepsy

PURPOSE

The aim of this study was to identify metabolically abnormal extrahippocampal brain regions in patients with temporal lobe epilepsy with (TLE-MTS) and without (TLE-no) magnetic resonance imaging (MRI) evidence for mesial-temporal sclerosis (MTS) and to assess their value for focus lateralization by using multislice 1H magnetic resonance spectroscopic imaging (MRSI).

METHODS

MRSI in combination with tissue segmentation was performed on 14 TLE-MTS and seven TLE-no and 12 age-matched controls. In controls, N-acetylaspartate/(creatine + choline) [NAA/(Cr+Cho)] of all voxels of a given lobe was expressed as a function of white matter content to determine the 95% prediction interval for any additional voxel of a given tissue composition. Voxels with NAA/(Cr+Cho) below the lower limit of the 95% prediction interval were defined as "pathological" in patients and controls. Z-scores were used to identify regions with a higher percentage of pathological voxels than those in controls.

RESULTS

Reduced NAA/(Cr+Cho) was found in ipsilateral temporal and parietal lobes and bilaterally in insula and frontal lobes. Temporal abnormalities identified the epileptogenic focus in 70% in TLE-MTS and 83% of TLE-no. Extratemporal abnormalities identified the epileptogenic focus in 78% of TLE-MTS but in only 17% of TLE-no.

CONCLUSIONS

TLE is associated with extrahippocampal reductions of NAA/(Cr+Cho) in several lobes consistent with those brain areas involved in seizure spread. Temporal and extratemporal NAA/(Cr+Cho) reductions might be helpful for focus lateralization.

Ultrastructure of astrocytes in the cortex of the hippocampal gyrus and in the neocortex of the temporal lobe in experimental valproate encephalopathy and after valproate withdrawal

The aim of the study was to analyse the astrocyte ultrastructure within the hippocampal gyre cortex and neocortex of the temporal lobe in valproate encephalopathy induced by chronic administration of an anti-epileptic drug - sodium valproate (VPA) to rats for 1, 3, 6, 9 and 12 months, once daily intragastrically, in a dose of 200 mg/kg b.w. and after its withdrawal for 1 and 3 months. Prolonged application of VPA caused damage to protoplasmic astrocytes of the cortex regions examined, mainly in the pyramidal layer, which intensified in the later stages of the experiment, especially after 9 and 12 months. Ultrastructural alterations in astroglia during this experiment did not differ significantly between the hippocampal cortex and neocortex. The most pronounced astroglial abnormalities, concerning about 2/3 of protoplasmic astrocytes after 9 and 12 months, were characterized by considerable swelling of cells, with the presence of empty vacuolar structures in the cytoplasm, a substantial decrease in the number of gliofilaments or even their complete loss, which indicated fibrillopoietic failure of the cell, and the appearance of astrocytes showing phagocytic activity. The astrocytic changes coexisted with distinct damage to neurones and structural elements of the blood-brain barrier. One month after termination of chronic exposure to the drug, the abnormalities did not subside, whereas after 3 months features of distinct normalization could be observed in a considerable number, more than a half, of astrocytes. In valproate encephalopathy, apart from any direct effect of VPA and/or its metabolites on astrocytes, the main cause of the protoplasmic astroglial damage in the cortex of the CNS structures examined could be associated with changes in microcirculation in the cortex (vasogenic factor), leading to its ischaemia.