Enzymdefekte des Harnstoffzyklus in der Differentialdiagnose der akuten Enzephalopathie im Erwachsenenalter Diagnostik und aktuelle Therapiekonzepte

Six enzyme defects of the urea cycle have been described. Ornithine transcarbamylase deficiency is the most frequent of these diseases. The cumulative frequency is 1:8000. Most patients become symptomatic in childhood, but onset of symptoms may occur later in childhood or even adulthood. The patients present with recurrent episodes of an unspecific acute encephalopathy, seizures and clouding of consciousness to a variable degree. Focal neurological signs such as hemiparesis, aphasia or ataxia may also occur. These episodes may be triggered by infection, protein overload or drugs. Diagnostic are increased blood ammonia levels. Characteristic patterns of plasma amino acids and the determination of orotic acid in the urine mostly discriminate the individual disorders. Further diagnostic steps include the allopurinol challenge test, liver or skin biopsy for measurement of enzyme activity and molecular genetic studies. Treatment requires restriction of protein intake, supplementation of arginine and activation of alternative pathways of nitrogen excretion with benzoate or phenylbutyrate. Untreated, the acute episode may be lethal. Long-term treatment improves the clinical outcome considerably. Urea cycle defects should be included in the differential diagnosis of any encephalopathy or coma of unclear origin, and blood ammonia should be determined early in the evaluation of such patients.     

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

Ornithine transcarbamylase deficiency is an X linked disorderand the most common inherited cause of hyperammonaemia. Fluctuating concentrations of ammonia, glutamine, and otherexcitotoxic amino acids result in a chronic or episodically recurringencephalopathy. A heterozygous female patient first presented withprotein intolerance, attacks of vomiting, and signs of mentalretardation in early childhood. At the age of 16 complex partialseizures occurred which were treated with sodium valproate. Seven daysafter initiation of valproate therapy, she developed severehyperammonaemic encephalopathy with deep somnolence. The maximumconcentration of ammonia was 480 µmol/l. After withdrawal ofvalproate, three cycles of plasma dialysis, and initiation of aspecific therapy for the inborn metabolic disease, ammoniaconcentrations fell to normal values. The patient remitted, returningto her premorbid state. Valproate can cause high concentrations ofammonia in serum in patients with normal urea cycle enzymes and mayworsen a pre-existing hyperammonaemia caused by an enzymatic defect ofthe urea cycle. Sufficient diagnostic tests for the detection ofmetabolic disorders must be performed before prescribing valproate forpatients with a history of encephalopathy.

     

Ultrastructural findings in citrullinaemia in Holstein-Friesian calves

Summary Ultrastructural findings in the brains and livers of four calves affected with citrullinaemia due to a hereditary deficiency of the urea cycle enzyme arginosuccinate synthetase are described. The calves were affected in the 1st week of life with severe neurological disease characterised by depression, head pressing, stupor, convulsions and coma, accompanied by marked elevation of plasma citrulline and increasing plasma ammonia levels. Lesions included mild to moderate diffuse astroglial oedema in the cerebrocortical grey matter, and mild to severe hepatocellular hydropic change. The onset of the severe neurological signs was correlated with increasing levels of plasma ammonia, and the cerebral lesions were considered consistent with a bovine hyperammonaemic encephalopathy.Supported in part by an Australian Wool Corporation postgraduate scholarship (PAWH)     

Carbamyl phosphate synthetase-l deficiency discovered after valproic acid-induced coma

Valproic acid induced coma is presented in an adult patient without a history of metabolic disease. Liver biopsy revealed a reduction in activity of carbamyl phosphate synthetase-I, an enzyme obligated for transformation of ammonia to urea in the urea cycle. After recovery CT scan follow-up showed marked cerebral atrophy which did not exist prior to the state of coma. Risk factors are discussed.     

Ammonia: Key factor in the pathogenesis of hepatic encephalopathy

There is substantial clinical and experimental evidence to suggest that ammonia toxicity is a major factor in the pathogenesis of hepatic encephalopathy associated with subacute and chronic liver disease. Ammonia levels in patients with severe liver disease are frequently found to be elevated both in blood and cerebrospinal fluid (csf). Hepatic encephalopathy results in neuropathological damage of a similar nature (Alzheimer type II astrocytosis) to that found in patients with congenital hyperammonemia resulting from inherited defects of urea cycle enzymes. Following portocaval anastomosis in the rat, blood ammonia concentration is increased 2-fold, and brain ammonia is found to be increased 2–3-fold. Administration of ammonia salts or resins to rats with a portocaval anastomosis results in coma and in Alzheimer type II astrocytosis. Since the CNS is devoid of effective urea cycle activity, ammonia removal by brain relies on glutamine formation. Cerebrospinal fluid and brain glutamine are found to be significantly elevated in cirrhotic patients with encephalopathy and in rats following portocaval anastomosis. In both cases, glutamine is found to be elevated in a region-dependent manner. Several mechanisms have been proposed to explain the neurotoxic action of ammonia. Such mechanisms include: (i) Modification of blood-brain barrier transport; (ii) alterations of cerebral energy metabolism; (iii) direct actions on the neuronal membrane; and (iv) decreased synthesis of releasable glutamate, resulting in impaired glutamatergic neurotransmission.     

A case of late-onset carbamoyl phosphate synthetase I deficiency, presenting periodic psychotic episodes coinciding with menstrual periods]

Carbamoyl phosphate synthetase I deficiency (CPSID) is a rare metabolic disorder affecting the first enzymatic step of urea cycle. We report clinical manifestations of a female case of late-onset CPSID in Japan. An 18-year-old girl was admitted to emergency room due to acute comatose state. Her parents had no apparent consanguineous history. She had suffered from intermittent psychotic episodes (excitation, aggressive behavior and insomnia) with nausea and vomiting from the age of 13, mostly coinciding with menstrual period. She had minor learning disability without major neurological deficits and convulsions. Her mental status was estimated as normal in her intermenstrual period. She had been diagnosed as having hysteria and premenstrual syndrome. Her neurological findings on admission showed deep coma and hypotonic tetraparesis. Plasma ammonia level was markedly elevated (684 micrograms/dl) without significant liver dysfunction. Blood urea nitrogen decreased to 6 mg/dl. Continuous venovenous filtration with subsequential administration of sodium benzoate and l-arginine was started to eliminate blood ammonia. Although the plasma ammonia level decreased to 300 mu/dl in next 10 hours, severe cerebral edema was observed in head computed tomography subsequently, followed by marked cerebral atrophy. Finally, her consciousness status became almost alert a month after the onset, but her mental status was severely retarded. CPSI activity of her biopsied liver markedly decreased and she was diagnosed as having CPS ID. CPSI cDNA analysis of her biopsied liver demonstrated a V1149G mutation. Genomic DNA analysis showed that she was heterozygous in V1149G mutation. The mutation allele was derived from her father. The causative factor for absence or very low level of maternal CPSI mRNA will require further analysis.     

Ornithine transcarbamylase deficiency presenting as encephalopathy during adulthood following bariatric surgery

BACKGROUND: Neurological complications following bariatric surgery are rare. Whereas nutritional deficiencies are the most common cause of neurological symptoms, the unmasking of previously subclinical metabolic disorders can also lead to significant morbidity. OBJECTIVE: To characterize the clinical presentation, serum biochemical fluctuations, and functional enzymatic analysis of a case of functional ornithine transcarbamylase deficiency unmasked by a dietary change following bariatric surgery. DESIGN: Case report. SETTING: Tertiary referral center, hospital (inpatient) setting. PATIENT: A 29-year-old woman who presented with intermittent encephalopathy associated with recurrent hyperammonemia. INTERVENTIONS: Clinical, biochemical, and mutational studies. RESULTS: The pattern of intermittent hyperammonemia and encephalopathy following oral and parenteral nutrition suggested a urea cycle abnormality. Functional enzymatic assay results showed markedly reduced ornithine transcarbamylase activity in the absence of known coding mutations. CONCLUSION: Previously asymptomatic ornithine transcarbamylase deficiency should be suspected in adult patients who develop recurrent hyperammonemia and encephalopathy following bariatric surgery.     

The effect of electrical stimulation of the hypothalamus and other brain areas on urea cycle enzymatic activities in the liver in rabbits--experimental studies on brain and liver interrelationship--.

Changes in urea cycle enzymatic activities in the liver induced by intracerebral electrical stimulation in rabbits with chronically implanted electrodes in the hypothalamus, the thalamus, and the limbic area were studied in comparison with these activities in non-stimulated controls. In stimulating the ventromedial nucleus of the hypothalamus, the two-hour sessions were followed by significantly reduced activity in arginase and the arginine synthetase system in the liver, but the six-hour stimulation sessions were followed by normal range activity in these enzymes. In stimulating the lateral hypothalamic area, the two-hour sessions were followed by only slightly reduced activity in the arginine synthetase system in the liver. Stimulation of the center median nucleus of the thalamus, the medial area of the amygdala and the dorsal hippocampus produced no significant changes in urea cycle enzymatic activities in the liver. The possibility that ammonia metabolism in the liver may be modified through some functional linkage between the brain and the liver was suggested.     

Febrile infection responsive epilepsy syndrome („FIRES“)

Encephalitis is generally presumed, even when severe seizures follow banal febrile infection and pathogen detection in cerebrospinal fluid fails. This retrospective, multicenter study analyzed the data from 23 children aged 3–15 years (median 6 years) with prolonged or recurrent seizures occurring 2–14 days (median 5 days) after fever onset (20 children with airway or non-specific infections). Cerebrospinal fluid studies revealed 2–42 cells/µl (median 5 cells/µl), but no pathogens. Electroencephalograms showed diffuse slowing or multifocal discharges. Magnetic resonance imaging demonstrated slightly increased signal intensities with hippocampal or temporal predilection in 10 children. During the course, 48% of the children who survived developed pronounced brain atrophy. Brain biopsies, performed in 7 children, showed gliosis but no inflammation. Anesthetic barbiturates were used in 15 children, immunotherapy in 10. Two children died, 8 remained in a minimally responsive vegetative state, 9 developed therapy-refractory epilepsy and 2 developed memory or behavioral disturbances, while only 2 children recovered completely and without significant neuropsychological deficits. The lack of evidence for encephalitis suggests an immune-mediated pathomechanism of this predominantly severe encephalopathy with refractory seizures in children. Therefore, the term “febrile infection responsive epilepsy syndrome (FIRES)” is proposed.     

Magnetic resonance spectroscopy in adult-onset citrullinemia: elevated glutamine levels in comatose patients

BACKGROUND: Adult-onset type II citrullinemia is an inborn error of urea cycle metabolism that can lead to hyperammonemic encephalopathy and coma. However, type II citrullinemia is rare outside Japan, and diagnosis and treatment can be delayed. Magnetic resonance spectroscopy may be a useful adjunct to magnetic resonance imaging, and has been applied to noninvasively study chemical metabolism in the human brain. PATIENTS: We describe 2 patients with type II citrullinemia who presented with episodic postprandial somnolence and coma. Diffusion-weighted magnetic resonance imaging showed bilaterally symmetrical signal abnormalities of the insular cortex and cingulate gyrus. On magnetic resonance spectroscopy, glutamine and glutamate levels were elevated, and choline and myo-inositol levels were decreased. The diagnosis of citrullinemia was confirmed based on elevated plasma ammonia and citrulline levels. CONCLUSION: Characteristic features found at the time of magnetic resonance imaging and magnetic resonance spectroscopy may be helpful for early diagnosis of type II citrullinemia in adult patients who present with hyperammonemic encephalopathy and coma.     

Adverse effects of branched chain amino acid transfusion on type-II citrullinemia--report of an adult case

A 24-year-old man was admitted to our hospital, because two days before the admission he had abruptly lost consciousness following generalized convulsive seizures. He had a past history of transient amnesia and a favor for peanuts. His grandparents had a record of consanguinity. On admission, he was comatose and flaccid with his four extremities. Laboratory examination revealed the followings; mild degree of abnormal liver function, slight elevation of blood ammonia, irregular theta basic rhythm on EEG, marked brain edema on CT and a normal liver ultrasonography. From the second hospital day, in addition to antiepileptic drugs and adrenocorticosteroids, branched chain amino acid was administered to reactivate damaged brain functions. Thereafter, the concentration of blood ammonia increased to more than 3,000 micrograms/dl, and as a result he fell into status epilepticus. On the fourth hospital day, the levels of citrulline in the plasma and urine taken on the first hospital day were found to have increased by 20 and 100 times, respectively. Although the transfusion of branched chain amino acid was stopped, he died while in coma on the 12th hospital day. Enzymatic analyses of necropsied liver specimens revealed that the quantitative activity of argininosuccinate synthetase had decreased to less than 10% in his urea cycle. In this patient, it was noted that, after transfusion of branched chain amino acid, his brain activities turned worse and blood ammonia was markedly elevated. There is a possibility that intravenous administration of branched chain amino acid may interrupt the urea cycle balance in an adult patient of citrullinemia with dysfunction of the brain, kidney and muscle, especially with brain edema.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical features of carbamyl phosphate synthetase-I deficiency in an adult

Carbamyl phosphate synthetase-I (CPS-I) catalyzes the first reaction required for the conversion of ammonia to urea through the urea cycle. Severe CPS-I deficiency causes marked hyperammonemia with encephalopathy in infancy and usually results in death within the first few months of life. We describe a 33-year-old woman whose CPS-I activity is less than 5% of normal. She has had mild, intermittent symptoms throughout life but has never experienced severe encephalopathy. Although mildly retarded, she has no major neurological deficits. Therapy with a low-protein diet, lactulose, and sodium benzoate has prevented recurrence of hyperammonemia and symptoms. Cranial computed tomographic scans demonstrate prominent lucency of cerebral white matter, and cerebral evoked potential recordings indicate slowed central conduction. These findings suggest that the metabolic disturbances in this patient may have adversely affected central myelin formation or maintenance. This woman represents, to our knowledge, the oldest reported patient with CPS-I deficiency, and the case illustrates the need to consider urea cycle disorders in the differential diagnosis of intermittent neurological symptoms regardless of the patient's age.     

A female case of ornithine transcarbamylase deficiency with marked computed tomographic abnormalities of the brain

The patient, 2 years and 9 months of age, was referred to our hospital with complaints of frequent vomiting, left hemiconvulsion and deep coma. The serum ammonia level was 251 micrograms/dl. Urine had a high orotate level (3,900 mumol/g creatinine). There was 7% residual of ornithine transcarbamylase (OTC) activity in the liver. Activities of other enzymes of the urea cycle were within normal limits. CT scanning on admission showed diffuse low density of both frontal lobes and of the right temporo-parietal lobe, narrowing of the right lateral ventricle and a shift of the mid-line to the left. The diffuse low density area was not enhanced after contrast medium injection. Follow-up CT scanning showed progressive bilateral ventricular dilatation and cerebral and cerebellar atrophy.     

An autopsied case of type II citrullinemia--transient effectiveness with either citrate or benzoate to the consciousness disturbance

A 44-year-old man suffered from repeated impairment of consciousness associated with flapping tremor, myoclonus and generalized convulsions, and died in coma 6 months after admission. He had had a psychosomatically underdeveloped childhood, with a propensity for legumes without a family history of the same or a record of consanguinity. On admission, he had disturbed consciousness and emaciation without other physical abnormalities. The EEG revealed diffuse slow waves with occasional appearance of triphasic waves. A high level of serum citrulline (534.7 nmol/ml) was recognized and the assay of urea cycle enzymes in the liver demonstrated decreased argininosuccinate synthetase (ASS) activity (0.062 U/g liver, 7.4% of that in normal liver), although no kinetic abnormality was found. Accordingly he was diagnosed as having type II citrullinemia. In addition, this case could be classified as cluster type of localization of the ASS in the liver by immunohistochemical study. There were characteristic findings concerning his clinical picture and laboratory data, such as a significant correlation between the grade of disturbed consciousness and arterial blood gas pH (r = 0.61, p less than 0.01). However, the blood ammonia level did not always correlate with the severity of disturbed consciousness. Oral treatment with sodium citrate and sodium benzoate was very effective, though transiently, for disturbed consciousness in this case. Pathological findings of the autopsied liver were fatty change and fibrosis. Neuropathologically, characteristic findings were brain edema with cerebellar tonsilar herniation, laminar necrosis with spongy formation in cerebral cortex, and Alzheimer type II glia. The relationship between citrullinemia and other hepatic encephalopathy was also discussed.     

Encephalopathy due to carnitine deficiency in an adult patient with gluten enteropathy

A 48-year-old male patient had two episodes of fever, headache, confusion and seizures following an upper respiratory tract infection. Electroencephalography (EEG) revealed diffuse slowing of background activity. Plasma free carnitine and serum lipid levels were low; fecal fat content and serum antigliadin antibodies were elevated. Duodenal biopsy was compatible with gluten enteropathy. Symptoms improved after the patient was started on a gluten-free diet and carnitine replacement therapy. No recurrence was observed within a four-year follow-up. Carnitine deficiency in adulthood is unusual, and encephalopathy due to carnitine deficiency as a result of celiac disease has not been described previously.     

Non-convulsive status epilepticus of frontal origin as the first manifestation of Hashimoto's encephalopathy

Hashimoto's encephalopathy is an often misdiagnosed, life threatening, condition which improves promptly with steroid therapy. Since clinical manifestations are heterogeneous and non-specific, the diagnosis is often difficult. Several case reports of Hashimoto's encephalopathy presenting with partial or generalised seizures are described, but only a few have focused on status epilepticus as the first clinical manifestation. We report two patients presenting with repetitive and prolonged seizures characterised by progressive reduction in contact and reactivity associated with frontal/diffuse polyspike-and-wave activities. This condition, which can be interpreted as a form of non-convulsive status epilepticus (NCSE) of frontal origin, was refractory to antiepileptic drugs but responded promptly to high doses of intravenous steroid treatment. In cases of unexplained encephalopathy with EEG documentation of NCSE, the early recognition and treatment of Hashimoto's encephalopathy may lead to a favourable prognosis. [Published with video sequences].     

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.     

Burn encephalopathy in children

Among 287 children with burns treated over a recent two-year period, 13 (5%) showed evidence of encephalopathy. The major clinical symptoms were an altered sensorium and seizures. The majority of symptoms began later than 48 hours after the burn and were accompanied by multiple metabolic aberrations including hypocalcemia. Three children had a relapsing course, and 1 had temporarily enlarged cerebral ventricles. Eleven children improved to normal. In the majority of instances, burn encephalopathy probably reflects central nervous system dysfunction resulting from complex metabolic, hematological, and hemodynamic abnormalities rather than from a single metabolic abnormality.     

Partial Recovery from Cortical Blindness Following Monoxide Intoxication

Patients with carbon monoxide (CO) intoxication may show neurological signs such as headache, seizures, extrapyramidal findings, and coma. However, cortical blindness is rare in these cases. This study describes a woman exhibiting confusion and axial rigidity after CO intoxication. Ten days after intoxication, her pupils were isonormocoric and reactive to light. A fundoscopic examination was normal, but visual acuity was light-perception in both eyes. There were diffuse EEG slow waves. Magnetic resonance imaging (MRI) demonstrated bilateral hyperintensity in the basal ganglia. The P100 latencies of visual evoked potentials (VEP) were increased and dispersed. One year later, the patient's visual acuity was almost normal and VEPs showed mild dispersion in P100 latencies. The authors found this case of interest because cortical blindness due to CO intoxication is only rarely seen with a relatively good outcome.     

The encephalopathy of sepsis

Twelve fatal cases of encephalopathy associated with sepsis were examined in a ten-year retrospective study. The sources of infection and organisms isolated were variable. Six of the patients had focal neurologic signs; five had seizures. The level of consciousness varied from drowsiness to deep coma, and electroencephalograms revealed diffuse or multifocal abnormalities. Computed tomographic head scans and cerebrospinal fluid examinations were usually unremarkable. Eight patients had disseminated microabscesses in the brain at autopsy. Four patients had proliferation of astrocytes and microglia in the cerebral cortex, a feature associated with metabolic encephalopathies. Additional findings included cerebral infarcts, brain purpura, multiple small white matter hemorrhages, and central pontine myelinolysis. Although sepsis may cause encephalopathy by producing disturbances in cerebral synaptic transmission and cerebral energy production through a toxic mechanism, bacterial invasion of the brain with the formation of disseminated microabscesses is also an important cause.