Maple syrup urine disease: magnetic resonance imaging findings in three patients.

Maple syrup urine disease (MSUD) is an autosomal recessive inherited metabolic disorder, caused by branched-chain alpha-ketoacid dehydrogenase (BCKD) deficiency, leading to toxic accumulation of branched-chain amino acids (BCAAs) including leucine, isoleucine and valine and their corresponding a-ketoacids. The diagnosis of MSUD is based on elevated BCAAs and allo-isoleucine in plasma, and branched-chain hydroxyacids and ketoacids in urine. The identification of alloisoleucine >5 µmol/L is considered pathognomonic. Moreover, brain magnetic resonance imaging (MRI) showing atypical signal intensity and oedema is characteristic of MSUD. Recognition of the classical neuro-radiological findings of MSUD is particularly useful in local settings as many healthcare facilities lack the resources to measure Plasma Amino Acids (PAA). We report three cases of MSUD, in whom the disorder was strongly suspected at presentation, based on classical brain MRI findings, which was urgently confirmed by PAA analysis.

Paroxysmal spasticity of lower extremities as the initial symptom in two siblings with maple syrup urine disease.

Maple syrup urine disease (MSUD) is a rare autosomal recessive metabolic disorder caused by mutations in genes that encode subunits of the branched­chain α­ketoacid dehydrogenase (BCKD) complex. Impairment of the BCKD complex results in an abnormal accumulation of branched­chain amino acids and their corresponding branched­chain keto acids in the blood and cerebrospinal fluid, which are neurovirulent and may become life­threatening. An 11­day­old boy was admitted to the hospital with paroxysmal spasticity of lower extremities. Of note, his 10­year­old sister presented similar symptoms during the neonatal period, and her condition was diagnosed as MSUD when she was 1.5 years old. Genetic screening was performed, and the boy and his sister exhibited two novel compound heterozygous mutations in the branched chain keto acid dehydrogenase E1 subunit ß (BCKDHB) gene: A substitution from guanine to adenine in the coding region at position 1,076 (c.1,076G>A) in exon 10 and a deletion of a thymine at position 705 (c.705delT) in exon 6. The missense mutation c.1076G>A results in an amino acid substitution from arginine to lysine at position 359 (p.Arg359Lys), whereas the mutation c.705delT results in the replacement of a cysteine at position 235 with a stop codon (p.Cys235Ter). Neither of the BCKDHB alleles in the compound heterozygote patients is able to generate normal E1ß subunits, resulting in a possible impairment of the activity of the BCKD complex. In the present study, it was hypothesized that the two novel heterozygous mutations in the BCKDHB gene found in the Chinese family may be responsible for the phenotype of the two siblings with MSUD.

A case of classical maple syrup urine disease that was successfully managed by living donor liver transplantation.

Classical MSUD is often fatal without appropriate medical interventions because of metabolic crisis. There are numerous reports suggesting the therapeutic potential of deceased donor liver transplantation for MSUD. However, the usefulness of LDLT for MSUD is unknown. We report a case of classical MSUD, which was successfully managed by LDLT from the patient's father at 1 year of age. Abnormal brain findings, which were cured with effective treatment, gradually disappeared after LDLT. The patient then developed normally. Findings from this case suggest the importance of LDLT for maintaining low leucine levels and subsequent normal neurological development. Although LDLT involves a modest surgical insult, LDLT with a related donor achieves acceptable leucine levels for life.

[MR spectroscopy in metabolic disorders of the brain]. / MR-Spektroskopie bei Stoffwechselerkrankungen des Gehirns.

CLINICAL ISSUE: Metabolic disorders of the brain often present a particular challenge for the neuroradiologist, since the disorders are rare, changes on conventional MR are often non-specific and there are numerous differential diagnoses for the white substance lesions. STANDARD RADIOLOGICAL METHODS: As a complementary method to conventional brain MRI, MR spectroscopy may help to reduce the scope of the differential diagnosis. Entities with specific MR spectroscopy patterns are Canavan disease, maple syrup urine disease, nonketotic hyperglycinemia and creatine deficiency.

Two homozygous mutations in the exon 5 of BCKDHB gene that may cause the classic form of maple syrup urine disease.

Maple syrup urine disease (MSUD) is a rare autosomal recessive genetic disorder caused by defects in the catabolism of the branched-chain amino acids (BCAAs). Classic form of MSUD (CMSUD) is caused by mutations in BCKDHA, BCKDHB, DBT genes mostly. In this study, we analyzed the clinical and genetic characteristics of two patients with CMSUD. Two homozygous mutations, c.517G > T (p.Asp173Tyr) and c.503G > A (p.Arg168His), both in the exon 5 of BCKDHB were detected respectively. The novel mutation p.Asp173Tyr of patient A, inherited from his parents, is predicted to affect conformation of protein by computer analysis. The reported mutation p.Arg168His observed in patient B seemed to occur in a maternal uniparental disomy inheritance manner. Review of related literature revealed that most missense mutations in exon 5 of BCKDHB in homozygous genotype often result in CMSUD because of its incorrect conformation, and exon 5 of BCKDHB might be a susceptible region. Thus the novel homozygous mutation p.Asp173Tyr and the founder homozygous mutation p.Arg168His may be responsible for the clinical presentation of the two CMSUD patients, facilitating the future genetic counselling and prenatal diagnosis.

Continuous venovenous hemofiltration rapidly lowers toxic metabolites in a patient with MSUD and imminent cerebral herniation.

Maple syrup urine disease (MSUD) is an inborn error of amino acid metabolism. During catabolic stress encephalopathy and brain swelling that can culminate in brain herniation may occur. Beyond the neonatal period, these metabolic decompensations normally can be treated with a conservative dietary emergency regimen. Nevertheless in exceptionally severe cases also older patients may require extracorporeal interventions. We present the case of a 12-year-old patient with cerebral edema and imminent cerebral herniation. Continuous venovenous hemofiltration (CVVH) caused a prompt decrease of the toxic metabolite levels as well as an improvement of the patient's condition.

Neonatal neurological disorders involving the brainstem: neurosonographic approaches through the squamous suture and the foramen magnum.

Brainstem damage which often indicates a critical condition is usually underestimated by trans-anterior-fontanel neurosonography (NS) owing to the far-field limitations. Instead, NS alternately scanning through the squamous suture of the temporal bones and the foramen magnum could provide a better visualization of the brainstem structures. The NS characteristics of brainstem lesions caused by various neonatal neurological disorders, such as hypoxic-ischemic encephalopathy (HIE), metabolic encephalopathy, birth trauma and bacterial meningoencephalitis, can be depicted at the acute stage. An echogenic change in the midbrain was found in patients with HIE or metabolic encephalopathy. In addition to the echogenic change, bilateral transtentorial temporal lobe herniation distorting the contour of the midbrain was observed in a patient with group B streptococcus meningoencephalitis, whereas echogenic changes at the level of the pons and/or the medulla oblongata, mainly localized in the dorsal part, could be observed in newborns with severe HIE, maple syrup urine disease or birth trauma. In this pictorial assay, we demonstrate the feasibility of NS imaging in evaluating the entire brainstem structure of critically ill neonates in the near field and illustrate the characteristic features of brainstem involvement in various neonatal neurological disorders along with computed tomography or magnetic resonance imaging correlation.

Computed tomography findings in maple syrup urine disease.

Maple syrup urine disease (MSUD) is an inherited metabolic disorder characterised by a severe, usually lethal, neonatal course unless dietary intake of branched chain amino acids is restricted. We describe a patient with MSUD who had computed tomography (CT) changes of diffuse white matter hypodensity, particularly in the deep white cerebellar matter, brain stem, cerebral peduncles, thalamus and posterior limb of the internal capsule. With dietary treatment, there was neurological improvement with simultaneous disappearance of the oedema. These CT changes are typical of MSUD, hence are relevant findings in the neuroradiologic differential diagnosis of a possible metabolic disorder.

Cranial ultrasonography in maple syrup urine disease.

We performed serial cranial ultrasonography in four newborns affected by maple syrup urine disease. Symmetric increase of echogenicity of periventricular white matter, basal ganglia (mainly pallidi), and thalami was detected in the acute stage. The degree of ultrasonography abnormalities paralleled the clinical course of the disease.

Computed tomography in maple syrup urine disease.

Maple Syrup Urine Disease (MSUD) is an inherited metabolic disorder characterized by a severe, usually lethal, neonatal course in the early stages with pseudotumor cerebri and pathologically documented increased cerebral water content. CT and MRI studies in MSUD are few and the data are overlapping. This study reports CT features before and after dietary treatment in three patients; two with classical MSUD and one with an intermediate variant of MSUD. At diagnosis, CT consistently showed evidence of abnormally high lucidity involving not only white matter, but also areas of grey matter, particularly the pallidum. Furthermore, these CT changes are present both in the acute phase of classical MSUD and in an intermediate variant of the disease. The observed abnormalities evolve favorably under dietary treatment, simultaneously with clinical and neurological improvement. It is concluded that the observed CT changes indicate a diagnosis of MSUD and are relevant findings in the neuroradiologic differential diagnosis in acutely ill newborns, in which a metabolic disease may be not immediately suspected.

Maple syrup urine disease: findings on CT and MR scans of the brain in 10 infants.

Ten infants with classical maple syrup urine disease (MSUD) and two with variant MSUD had a total of 26 CT scans and 13 MR examinations of the brain during different stages of their disease. We found that inter- and intrapatient analyses of CT and MR findings at times ranging from 3 days to 7 months were typical enough to suggest the MSUD diagnosis. Imaging studies showed the natural course of the disease and, in a few cases, illustrated the effects of therapy. CT scans typically are negative during the first few days of life, then a marked, generalized, diffuse edema appears. In addition, a localized, more severe edema (the MSUD edema) is seen, which involves the deep cerebellar white matter, the dorsal part of the brainstem, the cerebral peduncles, and the dorsal limb of the internal capsule. Both the generalized and the MSUD edema subside during the second month of life, then may disappear totally or leave a well-defined, low-density zone around the lateral ventricles and small, low-attenuation lesions within the brainstem, respectively. With the disappearance of the edema, some loss of brain substance becomes obvious.

CT and MRI in maple syrup urine disease.

We describe a patient with a variant form of maple syrup urine disease who had unusual CT and MRI features that raised the suspicion of a metabolic disease. There were low density and abnormal signal in the white matter and pallida. Sponginess in these areas is the likely explanation for these findings.

[Cranial computed tomography in maple syrup urine disease]. / Die kraniale Computertomographie bei der Ahornsiruperkrankung.

Cranial computed tomography in the initial stage of the intermediate phenotype of maple syrup urine disease (MSUD) demonstrates diffuse, symmetric hypodensities in white and grey matter, which show a complete return to normal after early introduction of an adequate protein-restrictive diet. If diagnosis of this disease is missed or delayed, progressive global (end-stage) atrophy will take place over several years. A decrease in density values correlates well with the total cerebral lipid and water content (closely related to myelinisation), whereas progression and grade of atrophy show a relationship with the severity of pathological white and grey matter changes that are not demonstrable with computed tomography but can be proven histologically. Analysis of both morphological parameters corresponds well with clinical-neurological outcome and therapeutic success.