2-[fluorine-18] fluoro-2-deoxy-D-glucose PET scan of the brain in maple syrup urine disease

Neurocognitive profile in a case of maple syrup urine disease

Maple Syrup Urine Disease (MSUD) is a metabolic disease with associated enzyme deficiency and an inability to break down amino acids. Neurotoxic levels can occur resulting in neurological sequelae. Information regarding cognitive functions has suggested greater verbal than visuospatial abilities. Specific neuropsychological functions have not been studied. The objective of this study is to examine the neuropsychological profile in a case of MSUD. We present a case study of a 7-year-old female who has a history of late diagnosis (7 days of age) and poor metabolic control. Consistent with existing literature, a profile of stronger verbal reasoning and memory skills compared with visual-perceptual and nonverbal memory was revealed. Additional weaknesses were demonstrated with attention, emerging executive functions, and fine motor control. The results suggest that while previously described nonverbal reasoning and visuospatial impairments are present, there is likely a more complex pattern of neuropsychological impairments in children with MSUD, especially those with poor metabolic control.

Leucine toxicity in a neuronal cell model with inhibited branched chain amino acid catabolism

Individuals with the inborn error of metabolism, maple syrup urine disease (MSUD), are identified by newborn screening programs and treated with protein-modified diets that allow near normal growth and development. However, regardless of cause, a protein insult leads to metabolic decompensation, resulting in brain cell damage. The mechanism responsible for the damage is not well characterized due, in part, to the lack of an appropriate experimental model system with impaired branched chain alpha-ketoacid dehydrogenase (BCKD) activity. Here, we describe the construction of a rat pheochromocytoma cell (PC12) model harboring a doxycycline-controlled BCKD-kinase transgene. When BCKD-kinase is over-expressed in these cells, the endogenous BCKD activity is decreased, blocking branched chain amino acid (BCAA) catabolism. In cells over-expressing BCKD-kinase, addition of 25 mM leucine to the medium results in cell death. This experimental cell model accurately mimics the neuronal dysfunction in maple syrup urine disease and should facilitate further understanding of the pathophysiology of this disease and neuronal cell branched chain amino acid metabolism in general.

Clinical, fluorine-18 labeled 2-fluoro-2-deoxyglucose positron emission tomography (FDG PET), MRI of the brain and biochemical observations in a patient with 4-hydroxybutyric aciduria; a progressive neurometabolic disease

We report a five-year-old boy with 4-hydroxybutyric aciduria. The child presented with global developmental delay, severe hypotonia and myoclonic seizures. The urine 4-hydroxybutyric acid was 1038 times that of normal, and other organic acids related to its further metabolism were also increased. Electroencephalography showed findings indicative of cerebral dysfunction. However, other neurophysiological studies were normal. Clinical improvement was observed after the administration of vigabatrin and dextromethorphan. Magnetic resonance imaging of the brain revealed cerebellar vermin atrophy and subtle white matter changes in the cerebral hemispheres. Fluorine-18 labeled 2-fluoro-2-deoxyglucose positron emission tomographic (FDG PET) scan of the brain showed a marked decrease in the cerebellar metabolism, probably related to atrophy of cerebellar vermis and secondary cerebellar deafferentation. FDG PET scan is found to be of value in the understanding and assessment of brain functional alterations. It may be useful in monitoring and optimizing treatment strategies of this rare disease.