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Brain
Diagnosis
Pathology-Based Diagnoses
Inherited Metabolic/Degenerative Disorders
Organic and Aminoacidopathies
Miscellaneous Organic/Aminoacidopathies
Miscellaneous Organic/Aminoacidopathies
Surjith Vattoth, MD, FRCR
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KEY FACTS

  • Terminology

    • Imaging

      • Clinical Issues

        TERMINOLOGY

        • Abbreviations

          • Organic acidopathies: β-ketothiolase deficiency (βKD); biotinidase deficiency (BD); Canavan disease (CD), D-2-hydroxyglutaric aciduria (D2HGA); glutaric aciduria type 1 (GA1); glutaric aciduria type 2 (GA2) or multiple acyl coenzyme A dehydrogenase deficiency (MADD); holocarboxylase synthetase deficiency (HSD); 3-hydroxybutyric aciduria (3HBA); 3-hydroxy-3-methylglutaryl coenzyme A lyase deficiency (3HMGD); isovaleric acidemia (IA); L-2-hydroxyglutaric aciduria (L2HGA); 3-methylcrotonyl coenzyme A carboxylase deficiency (MCCD); 3-methylglutaconic aciduria (MGA); deafness, encephalopathy, Leigh-like syndrome (MEGDEL syndrome); methylmalonic acidemia (MMA); multiple carboxylase deficiency (MCD); 5-oxoprolinuria (5Ox) or pyroglutamic aciduria; propionic acidemia (PA)
          • Aminoacidopathies: Cobalamin metabolism disorder (Cbl); cystathionine β-synthase deficiency (CBSD); hyperhomocysteinemia (HHcy); maple syrup urine disease (MSUD); methionine adenosyltransferase deficiency (MAT I/IIID), 5,10-methylene-tetrahydrofolate reductase deficiency (MTHFRD); molybdenum cofactor deficiency (MOCD); nonketotic hyperglycinemia (NKH); phenylketonuria (PKU); tyrosinemia type 1 (TYRSN1); sulfite oxidase deficiency (SOD)

        • Definitions

          • Inborn errors of metabolism due to defects in intermediary metabolic pathways of carbohydrates, amino acids, & fatty acid oxidation; lead to abnormal organic acid & amino acid accumulation in multiple organs, including brain
          • Acidemia: Accumulation of acids in blood; aciduria: Urinary excretion of these acids
          • Urea cycle disorders often discussed along with aminoacidemias
            • Ornithine transcarbamylase deficiency, citrullinemia, carbamoyl phosphate synthetase 1 deficiency, argininosuccinate aciduria, argininemia, & N-acetyl glutamate synthase deficiency

        IMAGING

        • General Features

          • Aminoacidopathies

            • Organic Acidopathies

              DIFFERENTIAL DIAGNOSIS

                PATHOLOGY

                • General Features

                  CLINICAL ISSUES

                  • Presentation

                    • Demographics

                      • Natural History & Prognosis

                        • Treatment

                          Selected References

                          1. Topaloglu R et al: Do not miss rare and treatable cause of early-onset hemolytic uremic syndrome: cobalamin C deficiency. Nephron. 142(3):258-63, 2019
                          2. Wajner M et al: Screening for organic acidurias and aminoacidopathies in high-risk Brazilian patients: eleven-year experience of a reference center. Genet Mol Biol. 42(1 suppl 1):178-85, 2019
                          3. Reddy N et al: Neuroimaging findings of organic acidemias and aminoacidopathies. Radiographics. 38(3):912-31, 2018
                          4. Huemer M et al: Guidelines for diagnosis and management of the cobalamin-related remethylation disorders cblC, cblD, cblE, cblF, cblG, cblJ and MTHFR deficiency. J Inherit Metab Dis. 40(1):21-48, 2017
                          5. Kölker S et al: The phenotypic spectrum of organic acidurias and urea cycle disorders. Part 1: the initial presentation. J Inherit Metab Dis. ePub, 2015
                          6. Kölker S et al: The phenotypic spectrum of organic acidurias and urea cycle disorders. Part 2: the evolving clinical phenotype. J Inherit Metab Dis. ePub, 2015
                          7. Wortmann SB et al: Eyes on MEGDEL: distinctive basal ganglia involvement in dystonia deafness syndrome. Neuropediatrics. 46(2):98-103, 2015
                          8. Krishna SH et al: Congenital genetic inborn errors of metabolism presenting as an adult or persisting into adulthood: neuroimaging in the more common or recognizable disorders. Semin Ultrasound CT MR. 35(2):160-91, 2014
                          9. Makrides V et al: Transport of amino acids in the kidney. Compr Physiol. 4(1):367-403, 2014
                          10. Yoon HJ et al: Devastating metabolic brain disorders of newborns and young infants. Radiographics. 34(5):1257-72, 2014
                          11. Thomas B et al: MRI of childhood epilepsy due to inborn errors of metabolism. AJR Am J Roentgenol. 194(5):W367-74, 2010
                          12. Barbagallo M et al: Two siblings with a homozygous MTHFR C677T (G80A-RFC1) mutation and stroke. Childs Nerv Syst. 25(3):361-5, 2009
                          13. Del Balzo F et al: MTHFR homozygous mutation and additional risk factors for cerebral infarction in a large Italian family. Pediatr Neurol. 40(1):63-7, 2009
                          14. Gorgone G et al: Hyperhomocysteinemia in patients with epilepsy: does it play a role in the pathogenesis of brain atrophy? A preliminary report. Epilepsia. 50 Suppl 1:33-6, 2009
                          15. Bishop L et al: Severe methylenetetrahydrofolate reductase (MTHFR) deficiency: a case report of nonclassical homocystinuria. J Child Neurol. 23(7):823-8, 2008
                          16. Ding XQ et al: MRI abnormalities in normal-appearing brain tissue of treated adult PKU patients. J Magn Reson Imaging. 27(5):998-1004, 2008
                          17. Indolfi G et al: Cryptogenic stroke in a boy with atrial septal defect and hyperhomocysteinemia. J Child Neurol. 23(9):1070-1, 2008
                          18. Shyambabu C et al: Serum vitamin B12 deficiency and hyperhomocystinemia: a reversible cause of acute chorea, cerebellar ataxia in an adult with cerebral ischemia. J Neurol Sci. 273(1-2):152-4, 2008
                          19. Thauvin-Robinet C et al: The adolescent and adult form of cobalamin C disease: clinical and molecular spectrum. J Neurol Neurosurg Psychiatry. 79(6):725-8, 2008
                          20. van Spronsen FJ et al: The truth of treating patients with phenylketonuria after childhood: the need for a new guideline. J Inherit Metab Dis. 31(6):673-9, 2008
                          21. Vatanavicharn N et al: Reversible leukoencephalopathy with acute neurological deterioration and permanent residua in classical homocystinuria: A case report. J Inherit Metab Dis. Epub ahead of print, 2008
                          22. Anderson PJ et al: Are neuropsychological impairments in children with early-treated phenylketonuria (PKU) related to white matter abnormalities or elevated phenylalanine levels? Dev Neuropsychol. 32(2):645-68, 2007
                          23. Giovannini M et al: Phenylketonuria: dietary and therapeutic challenges. J Inherit Metab Dis. 30(2):145-52, 2007
                          24. Leuzzi V et al: The pathogenesis of the white matter abnormalities in phenylketonuria. A multimodal 3.0 tesla MRI and magnetic resonance spectroscopy (1H MRS) study. J Inherit Metab Dis. 30(2):209-16, 2007
                          25. Matthews RG et al: Defects in homocysteine metabolism: diversity among hyperhomocyst(e)inemias. Clin Chem Lab Med. 45(12):1700-3, 2007
                          26. Obeid R et al: The role of hyperhomocysteinemia and B-vitamin deficiency in neurological and psychiatric diseases. Clin Chem Lab Med. 45(12):1590-606, 2007
                          27. Vermathen P et al: Characterization of white matter alterations in phenylketonuria by magnetic resonance relaxometry and diffusion tensor imaging. Magn Reson Med. 58(6):1145-56, 2007
                          28. Castro R et al: Homocysteine metabolism, hyperhomocysteinaemia and vascular disease: an overview. J Inherit Metab Dis. 29(1):3-20, 2006
                          29. Cattaneo M: Hyperhomocysteinemia and venous thromboembolism. Semin Thromb Hemost. 32(7):716-23, 2006
                          30. Franco LP et al: Proton MR spectroscopy in hyperhomocysteinemia with elevated blood methionine levels. J Magn Reson Imaging. 23(3):404-7, 2006
                          31. Pérez-Dueñas B et al: Global and regional volume changes in the brains of patients with phenylketonuria. Neurology. 66(7):1074-8, 2006
                          32. Sinclair AJ et al: Recurrent dystonia in homocystinuria: a metabolic pathogenesis. Mov Disord. 21(10):1780-2, 2006
                          33. Wong A et al: Hyperhomocysteinemia is associated with volumetric white matter change in patients with small vessel disease. J Neurol. 253(4):441-7, 2006
                          34. Boxer AL et al: Executive dysfunction in hyperhomocystinemia responds to homocysteine-lowering treatment. Neurology. 64(8):1431-4, 2005
                          35. Braverman NE et al: Characteristic MR imaging changes in severe hypermethioninemic states. AJNR Am J Neuroradiol. 26(10):2705-6, 2005
                          36. Duncan IC et al: Spontaneous isolated posterior communicating artery dissection in a young adult with hyperhomocysteinemia. AJNR Am J Neuroradiol. 26(8):2030-2, 2005
                          37. Fowler B: Homocysteine: overview of biochemistry, molecular biology, and role in disease processes. Semin Vasc Med. 5(2):77-86, 2005
                          38. Herrmann M et al: Homocysteine--a newly recognised risk factor for osteoporosis. Clin Chem Lab Med. 43(10):1111-7, 2005
                          39. Kono K et al: Diffusion-weighted MR imaging in patients with phenylketonuria: relationship between serum phenylalanine levels and ADC values in cerebral white matter. Radiology. 236(2):630-6, 2005
                          40. Linnebank M et al: Methionine adenosyltransferase (MAT) I/III deficiency with concurrent hyperhomocysteinaemia: two novel cases. J Inherit Metab Dis. 28(6):1167-8, 2005
                          41. Longo D et al: MRI and 1H-MRS findings in early-onset cobalamin C/D defect. Neuropediatrics. 36(6):366-72, 2005
                          42. Pfaendner NH et al: MR imaging-based volumetry in patients with early-treated phenylketonuria. AJNR Am J Neuroradiol. 26(7):1681-5, 2005
                          43. Ricci D et al: Assessment of visual function in children with methylmalonic aciduria and homocystinuria. Neuropediatrics. 36(3):181-5, 2005
                          44. Tallur KK et al: Folate-induced reversal of leukoencephalopathy and intellectual decline in methylene-tetrahydrofolate reductase deficiency: variable response in siblings. Dev Med Child Neurol. 47(1):53-6, 2005
                          45. Anderson PJ et al: Neuropsychological functioning in children with early-treated phenylketonuria: impact of white matter abnormalities. Dev Med Child Neurol. 46(4):230-8, 2004
                          46. Ekinci B et al: Two siblings with homocystinuria presenting with dystonia and parkinsonism. Mov Disord. 19(8):962-4, 2004
                          47. Sijens PE et al: 1H MR chemical shift imaging detection of phenylalanine in patients suffering from phenylketonuria (PKU). Eur Radiol. 14(10):1895-900, 2004
                          48. Tada H et al: Reversible white matter lesion in methionine adenosyltransferase I/III deficiency. AJNR Am J Neuroradiol. 25(10):1843-5, 2004
                          49. Gizewska M et al: Different presentations of late-detected phenylketonuria in two brothers with the same R408W/R111X genotype in the PAH gene. J Intellect Disabil Res. 47(Pt 2):146-52, 2003
                          50. Harvey Mudd S et al: Infantile hypermethioninemia and hyperhomocysteinemia due to high methionine intake: a diagnostic trap. Mol Genet Metab. 79(1):6-16, 2003
                          51. Kahler SG et al: Metabolic disorders and mental retardation. Am J Med Genet C Semin Med Genet. 117C(1):31-41, 2003
                          52. Kirkham FJ: Is there a genetic basis for pediatric stroke? Curr Opin Pediatr. 15(6):547-58, 2003
                          53. Kohara K et al: MTHFR gene polymorphism as a risk factor for silent brain infarcts and white matter lesions in the Japanese general population: The NILS-LSA Study. Stroke. 34(5):1130-5, 2003
                          54. Moats RA et al: Brain phenylalanine concentrations in phenylketonuria: research and treatment of adults. Pediatrics. 112(6 Pt 2):1575-9, 2003
                          55. Sener RN: Diffusion MRI findings in phenylketonuria. Eur Radiol. 13 Suppl 6:L226-9, 2003
                          56. Sener RN: Phenylketonuria: diffusion magnetic resonance imaging and proton magnetic resonance spectroscopy. J Comput Assist Tomogr. 27(4):541-3, 2003
                          57. Biancheri R et al: Early-onset cobalamin C/D deficiency: epilepsy and electroencephalographic features. Epilepsia. 43(6):616-22, 2002
                          58. Koch R et al: Phenylketonuria in adulthood: a collaborative study. J Inherit Metab Dis. 25(5):333-46, 2002
                          59. Stabler SP et al: Elevated plasma total homocysteine in severe methionine adenosyltransferase I/III deficiency. Metabolism. 51(8):981-8, 2002
                          60. Akar N et al: Common mutations at the homocysteine metabolism pathway and pediatric stroke. Thromb Res. 102(2):115-20, 2001
                          61. Biancheri R et al: Cobalamin (Cbl) C/D deficiency: clinical, neurophysiological and neuroradiologic findings in 14 cases. Neuropediatrics. 32(1):14-22, 2001
                          62. Dezortová M et al: MR in phenylketonuria-related brain lesions. Acta Radiol. 42(5):459-66, 2001
                          63. Phillips MD et al: Diffusion-weighted imaging of white matter abnormalities in patients with phenylketonuria. AJNR Am J Neuroradiol. 22(8):1583-6, 2001
                          64. Powers JM et al: Neurological and neuropathologic heterogeneity in two brothers with cobalamin C deficiency. Ann Neurol. 49(3):396-400, 2001
                          65. Rossi A et al: Early-onset combined methylmalonic aciduria and homocystinuria: neuroradiologic findings. AJNR Am J Neuroradiol. 22(3):554-63, 2001
                          66. Weglage J et al: Normal clinical outcome in untreated subjects with mild hyperphenylalaninemia. Pediatr Res. 49(4):532-6, 2001
                          67. Baethmann M et al: Hydrocephalus internus in two patients with 5,10-methylenetetrahydrofolate reductase deficiency. Neuropediatrics. 31(6):314-7, 2000
                          68. Brenton DP et al: Adult care in phenylketonuria and hyperphenylalaninaemia: the relevance of neurological abnormalities. Eur J Pediatr. 159 Suppl 2:S114-20, 2000
                          69. Dyer CA: Comments on the neuropathology of phenylketonuria. Eur J Pediatr. 159 Suppl 2:S107-8, 2000
                          70. Huttenlocher PR: The neuropathology of phenylketonuria: human and animal studies. Eur J Pediatr. 159 Suppl 2:S102-6, 2000
                          71. Koch R et al: Blood-brain phenylalanine relationships in persons with phenylketonuria. Pediatrics. 106(5):1093-6, 2000
                          72. Leuzzi V et al: Clinical significance of brain phenylalanine concentration assessed by in vivo proton magnetic resonance spectroscopy in phenylketonuria. J Inherit Metab Dis. 23(6):563-70, 2000
                          Related Anatomy
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                          Related Differential Diagnoses
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                          References
                          Tables

                          Tables

                          KEY FACTS

                          • Terminology

                            • Imaging

                              • Clinical Issues

                                TERMINOLOGY

                                • Abbreviations

                                  • Organic acidopathies: β-ketothiolase deficiency (βKD); biotinidase deficiency (BD); Canavan disease (CD), D-2-hydroxyglutaric aciduria (D2HGA); glutaric aciduria type 1 (GA1); glutaric aciduria type 2 (GA2) or multiple acyl coenzyme A dehydrogenase deficiency (MADD); holocarboxylase synthetase deficiency (HSD); 3-hydroxybutyric aciduria (3HBA); 3-hydroxy-3-methylglutaryl coenzyme A lyase deficiency (3HMGD); isovaleric acidemia (IA); L-2-hydroxyglutaric aciduria (L2HGA); 3-methylcrotonyl coenzyme A carboxylase deficiency (MCCD); 3-methylglutaconic aciduria (MGA); deafness, encephalopathy, Leigh-like syndrome (MEGDEL syndrome); methylmalonic acidemia (MMA); multiple carboxylase deficiency (MCD); 5-oxoprolinuria (5Ox) or pyroglutamic aciduria; propionic acidemia (PA)
                                  • Aminoacidopathies: Cobalamin metabolism disorder (Cbl); cystathionine β-synthase deficiency (CBSD); hyperhomocysteinemia (HHcy); maple syrup urine disease (MSUD); methionine adenosyltransferase deficiency (MAT I/IIID), 5,10-methylene-tetrahydrofolate reductase deficiency (MTHFRD); molybdenum cofactor deficiency (MOCD); nonketotic hyperglycinemia (NKH); phenylketonuria (PKU); tyrosinemia type 1 (TYRSN1); sulfite oxidase deficiency (SOD)

                                • Definitions

                                  • Inborn errors of metabolism due to defects in intermediary metabolic pathways of carbohydrates, amino acids, & fatty acid oxidation; lead to abnormal organic acid & amino acid accumulation in multiple organs, including brain
                                  • Acidemia: Accumulation of acids in blood; aciduria: Urinary excretion of these acids
                                  • Urea cycle disorders often discussed along with aminoacidemias
                                    • Ornithine transcarbamylase deficiency, citrullinemia, carbamoyl phosphate synthetase 1 deficiency, argininosuccinate aciduria, argininemia, & N-acetyl glutamate synthase deficiency

                                IMAGING

                                • General Features

                                  • Aminoacidopathies

                                    • Organic Acidopathies

                                      DIFFERENTIAL DIAGNOSIS

                                        PATHOLOGY

                                        • General Features

                                          CLINICAL ISSUES

                                          • Presentation

                                            • Demographics

                                              • Natural History & Prognosis

                                                • Treatment

                                                  Selected References

                                                  1. Topaloglu R et al: Do not miss rare and treatable cause of early-onset hemolytic uremic syndrome: cobalamin C deficiency. Nephron. 142(3):258-63, 2019
                                                  2. Wajner M et al: Screening for organic acidurias and aminoacidopathies in high-risk Brazilian patients: eleven-year experience of a reference center. Genet Mol Biol. 42(1 suppl 1):178-85, 2019
                                                  3. Reddy N et al: Neuroimaging findings of organic acidemias and aminoacidopathies. Radiographics. 38(3):912-31, 2018
                                                  4. Huemer M et al: Guidelines for diagnosis and management of the cobalamin-related remethylation disorders cblC, cblD, cblE, cblF, cblG, cblJ and MTHFR deficiency. J Inherit Metab Dis. 40(1):21-48, 2017
                                                  5. Kölker S et al: The phenotypic spectrum of organic acidurias and urea cycle disorders. Part 1: the initial presentation. J Inherit Metab Dis. ePub, 2015
                                                  6. Kölker S et al: The phenotypic spectrum of organic acidurias and urea cycle disorders. Part 2: the evolving clinical phenotype. J Inherit Metab Dis. ePub, 2015
                                                  7. Wortmann SB et al: Eyes on MEGDEL: distinctive basal ganglia involvement in dystonia deafness syndrome. Neuropediatrics. 46(2):98-103, 2015
                                                  8. Krishna SH et al: Congenital genetic inborn errors of metabolism presenting as an adult or persisting into adulthood: neuroimaging in the more common or recognizable disorders. Semin Ultrasound CT MR. 35(2):160-91, 2014
                                                  9. Makrides V et al: Transport of amino acids in the kidney. Compr Physiol. 4(1):367-403, 2014
                                                  10. Yoon HJ et al: Devastating metabolic brain disorders of newborns and young infants. Radiographics. 34(5):1257-72, 2014
                                                  11. Thomas B et al: MRI of childhood epilepsy due to inborn errors of metabolism. AJR Am J Roentgenol. 194(5):W367-74, 2010
                                                  12. Barbagallo M et al: Two siblings with a homozygous MTHFR C677T (G80A-RFC1) mutation and stroke. Childs Nerv Syst. 25(3):361-5, 2009
                                                  13. Del Balzo F et al: MTHFR homozygous mutation and additional risk factors for cerebral infarction in a large Italian family. Pediatr Neurol. 40(1):63-7, 2009
                                                  14. Gorgone G et al: Hyperhomocysteinemia in patients with epilepsy: does it play a role in the pathogenesis of brain atrophy? A preliminary report. Epilepsia. 50 Suppl 1:33-6, 2009
                                                  15. Bishop L et al: Severe methylenetetrahydrofolate reductase (MTHFR) deficiency: a case report of nonclassical homocystinuria. J Child Neurol. 23(7):823-8, 2008
                                                  16. Ding XQ et al: MRI abnormalities in normal-appearing brain tissue of treated adult PKU patients. J Magn Reson Imaging. 27(5):998-1004, 2008
                                                  17. Indolfi G et al: Cryptogenic stroke in a boy with atrial septal defect and hyperhomocysteinemia. J Child Neurol. 23(9):1070-1, 2008
                                                  18. Shyambabu C et al: Serum vitamin B12 deficiency and hyperhomocystinemia: a reversible cause of acute chorea, cerebellar ataxia in an adult with cerebral ischemia. J Neurol Sci. 273(1-2):152-4, 2008
                                                  19. Thauvin-Robinet C et al: The adolescent and adult form of cobalamin C disease: clinical and molecular spectrum. J Neurol Neurosurg Psychiatry. 79(6):725-8, 2008
                                                  20. van Spronsen FJ et al: The truth of treating patients with phenylketonuria after childhood: the need for a new guideline. J Inherit Metab Dis. 31(6):673-9, 2008
                                                  21. Vatanavicharn N et al: Reversible leukoencephalopathy with acute neurological deterioration and permanent residua in classical homocystinuria: A case report. J Inherit Metab Dis. Epub ahead of print, 2008
                                                  22. Anderson PJ et al: Are neuropsychological impairments in children with early-treated phenylketonuria (PKU) related to white matter abnormalities or elevated phenylalanine levels? Dev Neuropsychol. 32(2):645-68, 2007
                                                  23. Giovannini M et al: Phenylketonuria: dietary and therapeutic challenges. J Inherit Metab Dis. 30(2):145-52, 2007
                                                  24. Leuzzi V et al: The pathogenesis of the white matter abnormalities in phenylketonuria. A multimodal 3.0 tesla MRI and magnetic resonance spectroscopy (1H MRS) study. J Inherit Metab Dis. 30(2):209-16, 2007
                                                  25. Matthews RG et al: Defects in homocysteine metabolism: diversity among hyperhomocyst(e)inemias. Clin Chem Lab Med. 45(12):1700-3, 2007
                                                  26. Obeid R et al: The role of hyperhomocysteinemia and B-vitamin deficiency in neurological and psychiatric diseases. Clin Chem Lab Med. 45(12):1590-606, 2007
                                                  27. Vermathen P et al: Characterization of white matter alterations in phenylketonuria by magnetic resonance relaxometry and diffusion tensor imaging. Magn Reson Med. 58(6):1145-56, 2007
                                                  28. Castro R et al: Homocysteine metabolism, hyperhomocysteinaemia and vascular disease: an overview. J Inherit Metab Dis. 29(1):3-20, 2006
                                                  29. Cattaneo M: Hyperhomocysteinemia and venous thromboembolism. Semin Thromb Hemost. 32(7):716-23, 2006
                                                  30. Franco LP et al: Proton MR spectroscopy in hyperhomocysteinemia with elevated blood methionine levels. J Magn Reson Imaging. 23(3):404-7, 2006
                                                  31. Pérez-Dueñas B et al: Global and regional volume changes in the brains of patients with phenylketonuria. Neurology. 66(7):1074-8, 2006
                                                  32. Sinclair AJ et al: Recurrent dystonia in homocystinuria: a metabolic pathogenesis. Mov Disord. 21(10):1780-2, 2006
                                                  33. Wong A et al: Hyperhomocysteinemia is associated with volumetric white matter change in patients with small vessel disease. J Neurol. 253(4):441-7, 2006
                                                  34. Boxer AL et al: Executive dysfunction in hyperhomocystinemia responds to homocysteine-lowering treatment. Neurology. 64(8):1431-4, 2005
                                                  35. Braverman NE et al: Characteristic MR imaging changes in severe hypermethioninemic states. AJNR Am J Neuroradiol. 26(10):2705-6, 2005
                                                  36. Duncan IC et al: Spontaneous isolated posterior communicating artery dissection in a young adult with hyperhomocysteinemia. AJNR Am J Neuroradiol. 26(8):2030-2, 2005
                                                  37. Fowler B: Homocysteine: overview of biochemistry, molecular biology, and role in disease processes. Semin Vasc Med. 5(2):77-86, 2005
                                                  38. Herrmann M et al: Homocysteine--a newly recognised risk factor for osteoporosis. Clin Chem Lab Med. 43(10):1111-7, 2005
                                                  39. Kono K et al: Diffusion-weighted MR imaging in patients with phenylketonuria: relationship between serum phenylalanine levels and ADC values in cerebral white matter. Radiology. 236(2):630-6, 2005
                                                  40. Linnebank M et al: Methionine adenosyltransferase (MAT) I/III deficiency with concurrent hyperhomocysteinaemia: two novel cases. J Inherit Metab Dis. 28(6):1167-8, 2005
                                                  41. Longo D et al: MRI and 1H-MRS findings in early-onset cobalamin C/D defect. Neuropediatrics. 36(6):366-72, 2005
                                                  42. Pfaendner NH et al: MR imaging-based volumetry in patients with early-treated phenylketonuria. AJNR Am J Neuroradiol. 26(7):1681-5, 2005
                                                  43. Ricci D et al: Assessment of visual function in children with methylmalonic aciduria and homocystinuria. Neuropediatrics. 36(3):181-5, 2005
                                                  44. Tallur KK et al: Folate-induced reversal of leukoencephalopathy and intellectual decline in methylene-tetrahydrofolate reductase deficiency: variable response in siblings. Dev Med Child Neurol. 47(1):53-6, 2005
                                                  45. Anderson PJ et al: Neuropsychological functioning in children with early-treated phenylketonuria: impact of white matter abnormalities. Dev Med Child Neurol. 46(4):230-8, 2004
                                                  46. Ekinci B et al: Two siblings with homocystinuria presenting with dystonia and parkinsonism. Mov Disord. 19(8):962-4, 2004
                                                  47. Sijens PE et al: 1H MR chemical shift imaging detection of phenylalanine in patients suffering from phenylketonuria (PKU). Eur Radiol. 14(10):1895-900, 2004
                                                  48. Tada H et al: Reversible white matter lesion in methionine adenosyltransferase I/III deficiency. AJNR Am J Neuroradiol. 25(10):1843-5, 2004
                                                  49. Gizewska M et al: Different presentations of late-detected phenylketonuria in two brothers with the same R408W/R111X genotype in the PAH gene. J Intellect Disabil Res. 47(Pt 2):146-52, 2003
                                                  50. Harvey Mudd S et al: Infantile hypermethioninemia and hyperhomocysteinemia due to high methionine intake: a diagnostic trap. Mol Genet Metab. 79(1):6-16, 2003
                                                  51. Kahler SG et al: Metabolic disorders and mental retardation. Am J Med Genet C Semin Med Genet. 117C(1):31-41, 2003
                                                  52. Kirkham FJ: Is there a genetic basis for pediatric stroke? Curr Opin Pediatr. 15(6):547-58, 2003
                                                  53. Kohara K et al: MTHFR gene polymorphism as a risk factor for silent brain infarcts and white matter lesions in the Japanese general population: The NILS-LSA Study. Stroke. 34(5):1130-5, 2003
                                                  54. Moats RA et al: Brain phenylalanine concentrations in phenylketonuria: research and treatment of adults. Pediatrics. 112(6 Pt 2):1575-9, 2003
                                                  55. Sener RN: Diffusion MRI findings in phenylketonuria. Eur Radiol. 13 Suppl 6:L226-9, 2003
                                                  56. Sener RN: Phenylketonuria: diffusion magnetic resonance imaging and proton magnetic resonance spectroscopy. J Comput Assist Tomogr. 27(4):541-3, 2003
                                                  57. Biancheri R et al: Early-onset cobalamin C/D deficiency: epilepsy and electroencephalographic features. Epilepsia. 43(6):616-22, 2002
                                                  58. Koch R et al: Phenylketonuria in adulthood: a collaborative study. J Inherit Metab Dis. 25(5):333-46, 2002
                                                  59. Stabler SP et al: Elevated plasma total homocysteine in severe methionine adenosyltransferase I/III deficiency. Metabolism. 51(8):981-8, 2002
                                                  60. Akar N et al: Common mutations at the homocysteine metabolism pathway and pediatric stroke. Thromb Res. 102(2):115-20, 2001
                                                  61. Biancheri R et al: Cobalamin (Cbl) C/D deficiency: clinical, neurophysiological and neuroradiologic findings in 14 cases. Neuropediatrics. 32(1):14-22, 2001
                                                  62. Dezortová M et al: MR in phenylketonuria-related brain lesions. Acta Radiol. 42(5):459-66, 2001
                                                  63. Phillips MD et al: Diffusion-weighted imaging of white matter abnormalities in patients with phenylketonuria. AJNR Am J Neuroradiol. 22(8):1583-6, 2001
                                                  64. Powers JM et al: Neurological and neuropathologic heterogeneity in two brothers with cobalamin C deficiency. Ann Neurol. 49(3):396-400, 2001
                                                  65. Rossi A et al: Early-onset combined methylmalonic aciduria and homocystinuria: neuroradiologic findings. AJNR Am J Neuroradiol. 22(3):554-63, 2001
                                                  66. Weglage J et al: Normal clinical outcome in untreated subjects with mild hyperphenylalaninemia. Pediatr Res. 49(4):532-6, 2001
                                                  67. Baethmann M et al: Hydrocephalus internus in two patients with 5,10-methylenetetrahydrofolate reductase deficiency. Neuropediatrics. 31(6):314-7, 2000
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