Bilateral lucency of the globus pallidus complicating methylmalonic acidemia

Follow-up study of neuropsychological scores of infant patients with cobalamin C defects and influencing factors of cerebral magnetic resonance imaging characteristics

Purpose

The purpose of this study was to investigate whether baseline cerebral magnetic resonance imaging (MRI) characteristics could predict therapeutic responsiveness in patients with cobalamin C (cblC) defects.

Materials and methods

The cerebral MRI results of 40 patients with cblC defects were evaluated by a neuroradiologist. Neuropsychological scores and imaging data were collected. Neuropsychological tests were performed before and after standardized treatment.

Results

Thirty-eight patients initially underwent neuropsychological testing [developmental quotient (DQ)]. CblC defects with cerebellar atrophy, corpus callosum thinning and ventricular dilation had significantly lower DQs than those without (P < 0.05). Through a multivariate linear stepwise regression equation after univariate analysis, ventricular dilation was the most valuable predictor of lower DQs. Thirty-six patients (94.7%) underwent follow-up neuropsychological testing. The pre- and post-treatment DQ values were not significantly different (Z = -1.611, P = 0.107). The post-treatment DQ classification (normal, moderately low, or extremely low) showed nearly no change compared to the pretreatment DQ classification (k = 0.790, P < 0.001).

Conclusion

Ventricular dilation, cerebral atrophy and corpus callosum thinning are the main MRI abnormalities of cblC defects, and these manifestations are significantly correlated with delayed development in children. MRI findings can be considered an important tool for determining the severity of cblC defects.

Mitochondrial disease, mitophagy, and cellular distress in methylmalonic acidemia

Mitochondria—the intracellular powerhouse in which nutrients are converted into energy in the form of ATP or heat—are highly dynamic, double-membraned organelles that harness a plethora of cellular functions that sustain energy metabolism and homeostasis. Exciting new discoveries now indicate that the maintenance of this ever changing and functionally pleiotropic organelle is particularly relevant in terminally differentiated cells that are highly dependent on aerobic metabolism. Given the central role in maintaining metabolic and physiological homeostasis, dysregulation of the mitochondrial network might therefore confer a potentially devastating vulnerability to high-energy requiring cell types, contributing to a broad variety of hereditary and acquired diseases. In this Review, we highlight the biological functions of mitochondria-localized enzymes from the perspective of understanding—and potentially reversing—the pathophysiology of inherited disorders affecting the homeostasis of the mitochondrial network and cellular metabolism. Using methylmalonic acidemia as a paradigm of complex mitochondrial dysfunction, we discuss how mitochondrial directed-signaling circuitries govern the homeostasis and physiology of specialized cell types and how these may be disturbed in disease. This Review also provides a critical analysis of affected tissues, potential molecular mechanisms, and novel cellular and animal models of methylmalonic acidemia which are being used to develop new therapeutic options for this disease. These insights might ultimately lead to new therapeutics, not only for methylmalonic acidemia, but also for other currently intractable mitochondrial diseases, potentially transforming our ability to regulate homeostasis and health.

Brain MRI features of methylmalonic acidemia in children: the relationship between neuropsychological scores and MRI findings

Methylmalonic acidemia (MMA) is a severe, heterogeneous disorder of methylmalonate and cobalamin (cbl; vitamin B12) metabolism with a poor prognosis that can cause brain damage. Identifying the magnetic resonance imaging (MRI) findings of MMA might help to make accurate diagnoses earlier in the disease course and exploring the relationship between neuropsychological scores and MRI findings, when therapy is more effective and to improve therapeutic efficacy. Cerebral MRI studies from 37 children with MMA were evaluated by a neuroradiologist. Clinical and imaging data were collected from each patient. All tests were performed during routine investigations and in accordance with the ethical principles of the Declaration of Helsinki. Informed consent was obtained from the guardians of all patients for inclusion in the study. The most common and significant findings were periventricular white matter changes (78.4%), ventricular dilation (29.7%) and cerebral atrophy (40.5%). According to the developmental quotient, the 37 patients were divided into the normal intelligence subgroup (NI, developmental quotient ≥ 85) and the low intelligence subgroup (LI, developmental quotient < 85). The incidence of corpus callosal thinning, cortical atrophy, subcortical white matter changes, and ventricular dilation (grades 0-3) was significantly higher in the LI subgroup than in the NI subgroup (P < 0.05). The incidence of no-mild and moderate-severe ventricular dilation was significantly higher in the LI subgroup than in the NI subgroup (P < 0.05). Ventricular dilatation, cerebral atrophy, white matter changes, and corpus callosal thinning are the main MRI abnormalities in MMA patients, and these manifestations are significantly correlated with delayed development in children.

The correlation between the evolution of bilateral basal ganglia hemorrhage using MR imaging and neurological damage recovery in an infant with methylmalonic aciduria

PURPOSE

We report on one patient with methylmalonic acidemia (MMA) who presented with symmetrical hemorrhage of the caudate nucleus accompanied by severe ventricular dilatation, follow-up magnetic resonance imaging (MRI) findings from one year later, and the clinical manifestations, neuropsychological scores, genetic test results, urine and blood laboratory results and evolution of the disorder.

MATERIALS AND METHODS

This study describes the recent and remote neuropathologic findings, reviews the literature, and discusses the possible pathogenetic mechanisms of these central nervous system lesions.

RESULTS

Patients with MMA may have signs of basal ganglia hemorrhage during acute onset, and the hemorrhage may disappear after treatment. During the treatment, both laboratory examination indexes and neuropsychological scores improved. There was a correlation between the evolution of bilateral basal ganglia hemorrhage using MRI(magnetic resonance imaging) and neurological damage recovery in this infant with MMA.

CONCLUSION

There was a correlation between the evolution of the bilateral basal ganglia hemorrhage using MR imaging and neurological damage recovery in an infant with MMA. We recommend performing conventional MR and diffusion-weighted imaging (DWI) examinations in patients with MMA who present with neurological symptoms.

The proteome of methylmalonic acidemia (MMA): the elucidation of altered pathways in patient livers

Methylmalonic acidemia (MMA) is a heterogeneous and severe autosomal recessive inborn error of metabolism most commonly caused by the deficient activity of the vitamin B12 dependent enzyme, methylmalonyl-CoA mutase (MUT). The main treatment for MMA patients is the dietary restriction of propiogenic amino acids and carnitine supplementation. Despite treatment, the prognosis for vitamin B12 non-responsive patients remains poor and is associated with neonatal lethality, persistent morbidity and decreased life expectancy. While multi-organ pathology is a feature of MMA, the liver is severely impacted by mitochondrial dysfunction which likely underlies the metabolic instability experienced by the patients. Liver and/or combined liver/kidney transplantation is therefore sometimes performed in severely affected patients. Using liver specimens from donors and MMA patients undergoing elective liver transplantation collected under a dedicated natural history protocol (clinicaltrials.gov: NCT00078078), we employed proteomics to characterize the liver pathology and impaired hepatic metabolism observed in the patients. Pathway analysis revealed perturbations of enzymes involved in energy metabolism, gluconeogenesis and Krebs cycle anaplerosis. Our findings identify new pathophysiologic and therapeutic targets that could be valuable for designing alternative therapies to alleviate clinical manifestations seen in this disorder.

The Dystonias

Dystonia is a difficult problem for both the clinician and the scientist. It is sufficiently common to be seen by almost all physicians, yet uncommon enough to prevent any physician from gaining broad experience in its diagnosis and treatment. Each case represents a difficult challenge even to the specialist. The basic scientist is faced with investigating a disorder that is without relevant animal models and which is so rare that obtaining suitable tissue for study is a major obstacle. Dystonia may be idiopathic, or associated with lesions from many sources, including a variety of rare diseases. If idiopathic, it may be genetically transmitted or sporadic. If genetically transmitted, it may be generalized or focal, with symptoms varying in different members of the same family. It may be refractory to treatment, or it may respond to any one of a number of individual drugs that have very different mechanisms of action. For idiopathic dystonias, no clear method of genetic transmission has been established and no consistent pathology identified.

MRI characteristics of globus pallidus infarcts in isolated methylmalonic acidemia

BACKGROUND

Bilateral infarcts confined to the globus pallidus are unusual and occur in conjunction with only a few disorders, including isolated methylmalonic acidemia, a heterogeneous inborn error of metabolism. On the basis of neuroradiographic features of metabolic strokes observed in a large cohort of patients with methylmalonic acidemia, we have devised a staging system for methylmalonic acidemia-related globus pallidus infarcts.

MATERIALS AND METHODS

Forty patients with isolated methylmalonic acidemia and neurologic symptoms underwent clinical brain MR imaging studies, which included 3D-T1WI. Infarcted globus pallidus segments were neuroanatomically characterized, and infarct volumes were measured.

RESULTS

Globus pallidus infarcts were present in 19 patients; all were bilateral, and most were left-dominant. A neuroanatomic scoring system based on the infarct patterns was devised; this revealed a 5-stage hierarchical susceptibility to metabolic infarct, with the posterior portion of the globus pallidus externa being the most vulnerable. Globus pallidus infarct prevalence by methylmalonic acidemia class was the following: cblA (5/7, 71%), cblB (3/7, 43%), mut(o) (10/22, 45%), and mut- (1/4, 25%). Tiny lacunar infarcts in the pars reticulata of the substantia nigra, previously unrecognized in methylmalonic acidemia, were found in 17 patients, 13 of whom also had a globus pallidus infarct.

CONCLUSIONS

The staged pattern of globus pallidus infarcts in isolated methylmalonic acidemia suggests a nonuniform, regionally specific cellular susceptibility to metabolic injury, even for patients having milder biochemical phenotypes. In support of this hypothesis, the delineation of lacunar infarcts in the pars reticulata of the substantia nigra, a tissue functionally and histologically identical to the globus pallidus interna, supports the concept of cell-specific pathology.

Methylmalonic acidemia mimicking diabetic ketoacidosis in an infant

Methylmalonic acidemia (MMA) is an inherited organic acidemia usually present with recurrent episodes of acute illness. A typical episode is ushered in with ketonuria and vomiting, followed by acidosis, dehydration, and lethargy, leading, in the absence of aggressive treatment, to coma and death. We report an infant with MMA presented with diabetes symptoms. A 13-month-old girl complained of polydipsia, diuresis, and loss of weight. She had clinical signs of diabetic ketoacidosis such as dehydration, deep sighing respiration, smell of ketones, lethargy, and vomiting. Laboratory analysis showed hyperglycemia with acidosis and ketonuria. She was treated with parenteral fluid, electrolyte, and insulin infusion. Two days after her discharge, after having a meal rich in protein, she was brought unconscious with hepatomegaly, severe acidosis, ketonuria, and mild hyperammonemia. The absence of hyperglycemia and the presence of neurologic findings suggested organic acidemia. MMA was diagnosed because of methylmalonic aciduria and elevated C3 carnitine esters. Cranial magnetic resonance imaging (MRI) showed increased uptake of radiocontrast material in the basal ganglia bilaterally. A homozygous mutation in exon 4 of the MMAA gene was found in mutation analysis and confirmed the diagnosis of cblA-deficient MMA. Neurologic regression was improved with treatment of low-protein diet, vitamin B12, and l-carnitine. In patients born to consanguineous parents who admit during infancy with severe acidosis refractory to treatment, organic acidemias should be kept in mind, even they have high blood glucose. The definitive diagnosis is important because it may allow a specific treatment and a favorable evolution to prevent the sequelae.

Neurocognitive phenotype of isolated methylmalonic acidemia

OBJECTIVE

Methylmalonic acidemia (MMA) is a metabolic disorder with a poorly defined long-term neurocognitive phenotype. We studied the neuropsychological outcomes of patients and examined clinical covariates that influenced cognition.

METHODS

A diverse cohort with mut, cblA, or cblB subtypes of isolated MMA (N = 43), ages 2 to 32 years, were evaluated at a single center over a 6-year period. The influence of clinical, laboratory, and metabolic parameters on neuropsychological testing results was determined.

RESULTS

Early-onset mut patients (n = 21) manifested the most severe neurocognitive impairments, with a mean ± SD full-scale IQ (FSIQ) of 71.1 ± 14.75. Late-onset mut patients (n = 6) had a mean FSIQ of 88.5 ± 27.62. cblA (n = 7), cblB (n = 6), and mut patients diagnosed prenatally or by newborn screening (n = 3) obtained mean FSIQs in the average range (100.7 ± 10.95, 96.6 ± 10.92, and 106.7 ± 6.66, respectively). Hyperammonemia at diagnosis and the presence of a seizure disorder were associated with a lower FSIQ (P = .001 and P = .041, respectively), but other clinical variables, including basal ganglia injury and mutation status, did not. FSIQ remained stable over longitudinal testing (n = 10). Decreased scores on processing speed, compared with all other intellectual domains, emerged as a specific neurocognitive manifestation.

CONCLUSIONS

The neurocognitive outcomes seen in isolated MMA are highly variable. An earlier age of disease onset, the presence of hyperammonemia at diagnosis, and a history of seizures were associated with more severe impairment. In all patient subtypes, selective deficits in processing speed were present.

An insight into the biochemistry of inborn errors of metabolism for a clinical neurologist

Neurological dysfunction is an important manifestation of inherited metabolic disorders. Although these are more common in childhood, adult onset forms with a different clinical presentation are often encountered. Recent advances in the diagnosis and treatment of these conditions have substantially improved the outcome in many of these conditions. This makes it essential that the practicing physician be familiar with the clinical presentation and diagnosis of these disorders. For the evaluation of a patient with a possible inborn error of metabolism, simple screening tests may aid in the diagnosis and provide direction for more comprehensive laboratory analysis. In this review, we present a practical approach to diagnosis of neurometabolic disorders. Establishing a specific diagnosis in these disorders will enable the clinician in offering a definitive long-term treatment, prognosis and genetic counselling.

Striatal neuroprotection with methylene blue

Recent literature indicates that low-dose Methylene Blue (MB), an autoxidizable dye with powerful antioxidant and metabolic enhancing properties, might prevent neurotoxin-induced neural damage and associated functional deficits. This study evaluated whether local MB may counteract the anatomical and functional effects of the intrastriatal infusion of the neurotoxin rotenone (Rot) in the rat. To this end, stereological analyses of striatal lesion volumes were performed and changes in oxidative energy metabolism in the striatum and related motor regions were mapped using cytochrome oxidase histochemistry. The influence of MB on striatal levels of oxidative stress induced by Rot was determined, and behavioral tests were used to investigate the effect of unilateral MB coadministration on motor asymmetry. Rot induced large anatomical lesions resembling "metabolic strokes," whose size was greatly reduced in MB-treated rats. Moreover, MB prevented the decrease in cytochrome oxidase activity and the perilesional increase in oxidative stress associated with Rot infusion in the striatum. MB also prevented the indirect effects of the Rot-induced lesion on cytochrome oxidase activity in related motor regions, such as the striatal regions rostral and caudal to the lesion, the substantia nigra compacta and reticulata, and the pedunculopontine nucleus. At a network level, MB maintained a global strengthening of functional connectivity in basal ganglia-thalamocortical motor circuits, as opposed to the functional decoupling observed in Rot-alone subjects. Finally, MB partially prevented the behavioral sensorimotor asymmetries elicited by Rot. These results are consistent with protective effects of MB against neurotoxic damage in the brain parenchyma. This study provides the first demonstration of the anatomical, metabolic and behavioral neuroprotective effects of MB in the striatum in vivo, and supports the notion that MB could be a valuable intervention against neural damage associated with oxidative stress and energy hypometabolism.

Mitochondrial dysfunction in mut methylmalonic acidemia

Methylmalonic acidemia is an autosomal recessive inborn error of metabolism caused by defective activity of methylmalonyl-CoA mutase (MUT) that exhibits multiorgan system pathology. To examine whether mitochondrial dysfunction is a feature of this organic acidemia, a background-modified Mut-knockout mouse model was constructed and used to examine mitochondrial ultrastructure and respiratory chain function in the tissues that manifest pathology in humans. In parallel, the liver from a patient with mut methylmalonic acidemia was studied in a similar fashion. Megamitochondria formed early in life in the hepatocytes of the Mut(-/-) animals and progressively enlarged. Liver extracts prepared from the mutants at multiple time points displayed respiratory chain dysfunction, with diminished cytochrome c oxidase activity and reduced intracellular glutathione compared to control littermates. Over time, the exocrine pancreas and proximal tubules of the kidney also exhibited megamitochondria, and older mutant mice eventually developed tubulointerstitial renal disease. The patient liver displayed similar morphological and enzymatic findings as observed in the murine tissues. These murine and human studies establish that megamitochondria formation with respiratory chain dysfunction occur in a tissue-specific fashion in methylmalonic acidemia and suggest treatment approaches based on improving mitochondrial function and ameliorating the effects of oxidative stress.

Methylmalonic acidemia: brain imaging findings in 52 children and a review of the literature

BACKGROUND

Methylmalonic acidemia (MMA) is an autosomal-recessive inborn error of metabolism.

OBJECTIVE

To recognize the CT and MR brain sectional imaging findings in children with MMA.

MATERIALS AND METHODS

Brain imaging studies (47 MR and 5 CT studies) from 52 children were reviewed and reported by a neuroradiologist. The clinical data were collected for each patient.

RESULTS

The most common findings were ventricular dilation (17 studies), cortical atrophy (15), periventricular white matter abnormality (12), thinning of the corpus callosum (8), subcortical white matter abnormality (6), cerebellar atrophy (4), basal ganglionic calcification (3), and myelination delay (3). The brain images in 14 patients were normal.

CONCLUSION

Radiological findings of MMA are nonspecific. A constellation of common clinical and radiological findings should raise the suspicion of MMA.

Looking beyond the basal ganglia: the spectrum of MRI changes in methylmalonic acidaemia

We report imaging abnormalities from 5 brain MR examinations in 4 children with methylmalonic acidaemia between the ages of 20 days and 31 months. In addition to bilateral basal ganglia lesions (pallidum) observed in 3 of 4 children, we found signs of delayed brain maturation (myelination delay, immature gyral pattern, incomplete opercularization) in all children and signs of a white matter disorder in the 3 older children. Unexpectedly, brainstem and cerebellar changes were present in all children. Reviewing the brain imaging changes reported for methylmalonic acidaemia, we discuss the findings and patterns observed in our patients. We postulate that delayed myelination and signs of a white matter disorder as well as brainstem and cerebellar involvement are common findings and may be due to a chronic neurotoxic effect on the developing and ageing brain.

Adenoviral-mediated correction of methylmalonyl-CoA mutase deficiency in murine fibroblasts and human hepatocytes

BACKGROUND

Methylmalonic acidemia (MMA), a common organic aciduria, is caused by deficiency of the mitochondrial localized, 5'deoxyadenosylcobalamin dependent enzyme, methylmalonyl-CoA mutase (MUT). Liver transplantation in the absence of gross hepatic dysfunction provides supportive therapy and metabolic stability in severely affected patients, which invites the concept of using cell and gene delivery as future treatments for this condition.

METHODS

To assess the effectiveness of gene delivery to restore the defective metabolism in this disorder, adenoviral correction experiments were performed using murine Mut embryonic fibroblasts and primary human methylmalonyl-CoA mutase deficient hepatocytes derived from a patient who harbored two early truncating mutations, E224X and R228X, in the MUT gene. Enzymatic and expression studies were used to assess the extent of functional correction.

RESULTS

Primary hepatocytes, isolated from the native liver after removal subsequent to a combined liver-kidney transplantation procedure, or Mut murine fibroblasts were infected with a second generation recombinant adenoviral vector that expressed the murine methylmalonyl-CoA mutase as well as eGFP from distinct promoters. After transduction, [1-14C] propionate macromolecular incorporation studies and Western analysis demonstrated complete correction of the enzymatic defect in both cell types. Viral reconstitution of enzymatic expression in the human methylmalonyl-CoA mutase deficient hepatocytes exceeded that seen in fibroblasts or control hepatocytes.

CONCLUSION

These experiments provide proof of principle for viral correction in methylmalonic acidemia and suggest that hepatocyte-directed gene delivery will be an effective therapeutic treatment strategy in both murine models and in human patients. Primary hepatocytes from a liver that was unsuitable for transplantation provided an important resource for these studies.

Liver transplantation is not curative for methylmalonic acidopathy caused by methylmalonyl-CoA mutase deficiency

Methylmalonic acidopathy resulting from severe methylmalonyl-CoA mutase deficiency causes acute, potentially lethal ketoacidotic episodes, renal failure, and acute and chronic neurologic disease. As dietary and alkali therapy is suboptimal, liver transplantation during infancy has been touted as a potential cure. However, reports in liver transplant recipients about new onset neurologic disease, in the absence of ketoacidosis, and progressive renal insufficiency have cast doubt about its effectiveness. We report the long-term (9 years) outcome for the first patient with severe methylmalonic acidopathy transplanted in the USA and provide new biochemical data that indicate why transplanted patients are still susceptible to "metabolic strokes". In our 10-year-old male patient, there is clear evidence that the de novo synthesis of propionyl-CoA within the CNS leads to brain methylmalonate (MMA) accumulation that is largely unaffected by transplantation. Liver replacement is not a cure for methylmalonic acidopathy.

A homozygous nonsense mutation in the methylmalonyl-CoA epimerase gene (MCEE) results in mild methylmalonic aciduria

Methylmalonic aciduria (MMA-uria) is an autosomal recessive inborn error of amino acid metabolism, involving valine, threonine, isoleucine, and methionine. This organic aciduria may present in the neonatal period with life-threatening metabolic acidosis, hyperammonemia, feeding difficulties, pancytopenia, and coma. Most affected patients have mutations in the methylmalonyl-coenzyme A (methylmalonyl-CoA) mutase gene. Mildly affected patients may present in childhood with failure to thrive and recurrent attacks of metabolic acidosis. Both a higher residual activity of methylmalonyl-CoA mutase as well as the vitamin B12-responsive defects (cblA and cblB) may form the basis of the mild disorder. A few patients with moderate MMA-uria are known in whom no defect could be identified. Here we present a 16-year-old female patient with persisting moderate MMA-uria (approximately 50 mmol/mol creatinine). She was born to consanguineous Caucasian parents. Her fibroblast mutase activity was normal and no effect of vitamin B12 supplementation could be established. Reduced incorporation of 14C-propionate into macromolecules suggested a defect in the propionate-to-succinate pathway. We found a homozygous nonsense mutation (c.139C>T) in the methylmalonyl-CoA epimerase gene (MCEE), resulting in an early terminating signal (p.R47X). Both parents were heterozygous for this mutation; they were found to excrete normal amounts of methylmalonic acid (MMA). This is the first report of methylmalonyl-CoA epimerase deficiency, thereby unequivocally demonstrating the biochemical role of this enzyme in human metabolism.

Diagnostic approach in patients with symmetric imaging lesions of the deep gray nuclei

BACKGROUND

Selective insult to brain deep gray matter nuclei is uncommon, may be congenital or acquired, acute or chronic, and varied in etiology. Determining the etiology relies on history, clinical presentation, laboratory investigations, and lesion pattern on Neuroimaging.

REVIEW SUMMARY

We review the differential diagnosis and clinical, laboratory and neuroimaging pattern of conditions that manifest with lesions of deep gray matter nuclei in the context of representative case studies.

CONCLUSION

While presentations may vary in individual patients, the essentials of history, clinical examination, laboratory evaluation,and neuroimaging lesion pattern can be efficiently directed to differentiate the various etiologies of deep gray matter nuclei lesions. In this review we focus on the etiologic classification and diagnostic approach to acute and chronic conditions that manifest on neuroimaging with bilateral symmetric lesions of deep gray matter nuclei.

Acute extrapyramidal syndrome in mild ornithine transcarbamylase deficiency: metabolic stroke involving the caudate and putamen without metabolic decompensation

A 6-year-old male with partial ornithine transcarbamylase (OTC) deficiency had acute and rapidly progressive symmetrical swelling of the head of the caudate nuclei and putamina. Clinical presentation was ataxia and dysarthria progressing to seizures and coma; these symptoms gradually resolved with supportive management. Although he had been recently treated for mild hyperammonemia, there was no evidence of acute metabolic decompensation prior to presentation, and plasma ammonia and amino acids were consistent with good metabolic control. This case is novel in that the neurological insult affected the neostriatum of the basal ganglia and the episode occurred in the absence of an apparent metabolic abnormality, unique observations in a patient with OTC deficiency.

CONCLUSION

This case suggests that the pathophysiology of metabolic stroke is complicated. It also argues for an evaluation for metabolic stroke in patients with known inborn errors of metabolism who present with unusual neurological symptoms in the absence of biochemical abnormalities. Similarly, this case suggests that patients presenting with unexplained neurological insults might benefit from an evaluation for an inborn error of metabolism.

Progressive neurological deterioration and MRI changes in cblC methylmalonic acidaemia treated with hydroxocobalamin

Cobalamin C (cblC) defects result in decreased activity of both methylmalonyl-CoA mutase and N5-methyltetrahydrofolate:homocysteine methyltransferase (methionine synthase), with subsequent methylmalonic acid-uria and homocystinuria. Patients typically show failure to thrive, developmental delay and megaloblastic anaemia. Vitamin B12 therapy has been beneficial in some cases. We report a now 4-year-old Hispanic girl with cblC disease documented by complementation analysis, with progressive neurological deterioration and worsening head MRI changes while on intramuscular hydroxocobalamin begun at age 3 weeks. Oral carnitine and folic acid were added at age 1 year. Blood levels of methylmalonic acid were reduced to treatment ranges. In the absence of acute metabolic crises, she developed microcephaly, progressive hypotonia and decreased interactiveness. Funduscopic examination was normal at age 13 months. At age 19 months, she developed nystagmus, and darkly pigmented fundi and sclerotic retinal vessels were observed on examination. Her neonatal head MRI was normal. By age 1 year, the MRI showed diffuse white-matter loss with secondary third and lateral ventricle enlargement, a thin corpus callosum, and normal basal ganglia. At age 15 months, progression of the white-matter loss, as well as hyperintense globi pallidi, were present. Interval progression of both grey- and white-matter loss was seen at age 27 months. We therefore caution that progressive neurological deterioration and head MRI abnormalities may still occur in cblC disease, despite early initiation of hydroxocobalamin therapy and improvement in toxic metabolite concentrations in physiological fluids.

Methylmalonic acidaemia with bilateral globus pallidus involvement: a neuropathological study

A 16-month-old boy was hospitalized because of a 1-day history of severe ketoacidosis with lethargy, hypotonia, vomiting, and important dyspnoea. Organic acid assay by gas chromatography-mass spectrometry confirmed the diagnosis of methylmalonic acidaemia (MMA). On the sixteenth day, he developed an acute extrapyramidal disorder. The CT scan of the brain disclosed bilaterally symmetric lucency of basal ganglia. He died at 17 months of age. Post-mortem neuropathological examination, showed severe necrosis with spongiosis, cystic cavitation and numerous lipid-laden macrophages of the globi pallidi, and mild spongiosis of subthalamic nuclei, mammillary bodies, portion of internal capsule adjacent to globus pallidus, superior cerebellar peduncles and tegmentum of brainstem. Pallidal infarction, a focal ischaemic lesion, demonstrates that ischaemia/energy depletion may be important in the etiology of the neuropathology of MMA.

Neurological outcome of methylmalonic acidaemia

OBJECTIVE

To assess the long term outcome of patients with methylmalonic acidaemia in a cross sectional study.

PATIENTS

All 35 patients with methylmalonic acidaemia seen at Great Ormond Street Hospital for Children in London, UK between 1970 and 1996 were studied. They were divided into cobalamin responsive (n = 6) and non-responsive (n = 29), and early and late onset groups.

RESULTS

There was a significant difference between cobalamin responsive and non-responsive groups in severity, survival, and incidence of neurological sequelae. Cobalamin responsive patients had mild disease, irrespective of age at presentation, their neurological complications were less severe, and they are all alive. The cobalamin non-responsive group comprised 19 early and nine late onset patients. The early onset patients had more severe disease at presentation and 14 have died; all late onset patients are alive. There was no significant difference in abnormal neurological signs, although early onset patients had a significantly reduced full scale intelligence quotient and poor cognitive outcome. In both groups, abnormal neurological signs continue to increase with age.

CONCLUSIONS

Cobalamin responsive patients have a better long term outcome. The outcome in the non-responsive patients, particularly the early onset group, remains poor and alternative treatments should therefore be considered early in this group.

Neurological dysfunction in methylmalonic acidaemia is probably related to the inhibitory effect of methylmalonate on brain energy production

Methylmalonic acidaemia is an inherited metabolic disorder caused by a severe deficiency of the activity of the enzyme L-methylmalonyl-CoA mutase or its cofactor 5'-deoxyadenosylcobalamin, resulting in tissue accumulation of large quantities of methylmalonic acid. Among the various clinical features, neurological symptoms are frequently observed. Patients may present cerebral atrophy and basal ganglia abnormalities are common. In the present report, we update the current knowledge on the influence of methylmalonic acid on brain metabolism in the hope of better understanding the neurological dysfunction characteristic of methylmalonic acidaemia. We present evidence showing that the metabolite inhibits brain energy production by various mechanisms and propose that a fall in cellular ATP generation leading to excitotoxicity is crucial for the occurrence of the neurological damage observed in these patients.

Effective immunoglobulin therapy for brief tonic seizures in methylmalonic acidemia

We report on a patient with methylmalonic acidemia (MMA). He experienced a metabolic acidosis attack at 3 weeks of age. He immediately received peritoneal dialysis and exchange transfusion, and recovered from the attack. His MMA phenotype was mut0. Dietary therapy (strict protein restriction) was found to be effective in preventing further attacks, and he had mild hypotonia and impaired psychomotor development. At 9 months of age, he developed brief tonic seizures, which showed polyspike bursts under EEG. His psychomotor development continued to deteriorate. However, intravenous administration of immunoglobulin (200 mg/kg/day for 5 consecutive days) had a dramatic effect; his seizures disappeared and his psychomotor development improved.

Acute basal ganglia infarction in propionic acidemia

An 8-year-old girl with propionic acidemia had acute and rapidly fatal symmetric necrosis of the caudate, globus pallidus, and putamen. Clinical presentation was with acute aphasia, generalized hypotonia, and muscle weakness. There was no evidence of metabolic decompensation, and analysis of the organic acids of the urine indicated good metabolic control. Organic acids in the cerebrospinal fluid were unremarkable. These observations indicate that the pathophysiology of "metabolic stroke" is more complicated than previously thought.

Bilateral striatal lesions in childhood

From 1983 to 1991, 13 patients were identified with a clinical radiologic association characterized by acute or persistent neurologic dysfunction and bilateral lesions in the basal ganglia region demonstrated by ultrasound, computed tomography, or magnetic resonance imaging. Initial clinical manifestations of this group of patients were characterized by extrapyramidal signs (i.e., dystonia 9, hypotonia 2, athetosis 1, rigidity 1), altered state of consciousness in 5, and seizures in 3. The outcomes of most of these patients were poor: 10 had motor sequelae, 9 cognitive impairment, and 4 died. The outcomes of 2 patients, however, were much better than what was expected from the initial presentation. Based on current and previous reports, the diagnostic approach and classification of patients with neurologic dysfunction and bilateral striatal lesions are presented.

Varying neurological phenotypes among muto and mut- patients with methylmalonylCoA mutase deficiency

MethylmalonylCoA mutase (MCM) is a mitochondrial homodimer responsible for the isomerization of methylmalonylCoA to succinylCoA. Apomutase defects are traditionally divided into muto and mut- classes on the basis of residual mutase activity. Clinical findings were reviewed in 20 patients with methylmalonic aciduria secondary to MCM deficiency. All 11 muto patients had an early neonatal presentation; 6 of these patients died in infancy and 3 of 5 survivors had a poor neurological outcome as evidenced by severe delay or spastic quadriparesis with dystonia. The 2 other survivors include a 27-month-old child with a mild delay in verbal and fine motor skills and an adolescent with low normal intelligence. Of the 9 mut- patients, 7 became symptomatic in late infancy or childhood and 2 were picked up on screening. Two of the 9 patients have never had an episode of metabolic decompensation yet both are neurologically compromised; one severely retarded and autistic, the other mildly delayed. Four mut- patients have had episodic acidosis and are neurologically moderately affected, while 3 have had episodic acidosis and are neurologically intact. These results confirm phenotypic pleomorphism without a consistent pattern of neurological injury and suggest some broad correlation between mutase class and phenotype. Survival with good outcome is possible among muto patients as is significant morbidity among mut- patients. Acidosis and metabolic imbalance are not necessary preconditions for significant morbidity.

CT and MRI of the brain in inherited neurometabolic disorders

The incidence of many autosomal recessive neurometabolic disorders is very high in Saudi Arabia, probably as a result of the frequency of consanguineous marriages. Because our hospital is the main referral center for the entire Kingdom, we examine a large number of patients who have a wide spectrum of neurometabolic disorders. We add our experience and review the world literature. Though a specific diagnosis is radiologically possible in a few disorders, the diagnosis must always be verified biochemically. When the patient is referred from a pediatric neurologist with the diagnosis of neurometabolic disorder, the aim of the neuroradiologist is to determine the amount of brain damage present and to follow the response to given therapy. When the patient is referred with a nonspecific diagnosis, such as delayed development, the aim is to suggest the possibility of a neurometabolic disorder and to initiate further evaluation including possible therapy and genetic counseling.

Symmetrical necrosis of the basal ganglia in methylmalonic acidaemia

In a patient with methylmalonic acidaemia (MMAA), persistent neurological symptoms were observed in addition to the acute episodes of metabolic dysequilibrium. CT scan and magnetic resonance imaging revealed bilateral symmetrical necrosis of the globus pallidus. Different episodes of metabolic decompensation, one with severe acidosis, had occurred. Persistent neurological symptoms in patients with MMAA who are appropriately treated suggest irreversible brain damage which appears to occur preferentially at the level of the basal ganglia.

Acute extrapyramidal syndrome in methylmalonic acidemia: "metabolic stroke" involving the globus pallidus

We report four patients with methylmalonic acidemia who developed acute extrapyramidal disease after metabolic decompensation. The neurologic findings resulted from bilateral destruction of the globus pallidus with variable involvement of the internal capsules. This complication was unrelated to a specific gene defect responsible for methylmalonic acidemia or to cyanocobalamin administration. These lesions constitute a "metabolic stroke," probably because of the accumulation of toxic organic acid metabolites, because they cannot be accounted for by hypoxemia or vascular insufficiency.

Mendelian etiologies of stroke

There are many genetic disorders associated with an increased risk for stroke that may easily be overlooked in the evaluation of both adult and pediatric acute stroke victims. The recognition of a genetic disorder as the cause of a stroke has important implications not only for the immediate care of the stroke victim, but often also for others in the patient's family who may be at risk for the same disease and for whom preventive measures sometimes can be taken. We present here a comprehensive review of genetic disorders associated with stroke in the nongeriatric age groups for which a causative role in the evolution of stroke has been recognized or is likely. For each disorder, the major clinical and biochemical characteristics as well as the probable pathogenetic mechanisms of stroke are discussed, together with the appropriate testing required to screen for and confirm the diagnosis. The great variety of genetic disorders and mechanisms causing stroke underscores the increasing importance of understanding genetic disease for appropriate diagnosis and treatment of a common clinical problem affecting both children and adults.