Brain magnetic resonance imaging and proton MR spectroscopic findings after metabolic crisis in 3-methylcrotonylglycinuria

Abstract

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopic (MRS) findings in 3-methylcrotonylglycinuria presenting with acute metabolic decompensation in a previously healthy 7-year-old female are described. The patient was hospitalized with fever, irritability, gastrointestinal problems, drowsiness, signs of upper motor neuron deficit, and rapidly progressive respiratory distress requiring assisted ventilation. Laboratory workup showed severe metabolic acidosis, and the diagnosis of 3-methylcrotonylglycinuria was established by the mass spectrometry analysis of urine sample. Although initial CT imaging workup was found to be gross normal, subsequent MRI of the brain in the early chronic stage of the disease showed symmetrical ill-defined signal abnormalities within medulla oblongata, pons, inferior cerebellar peduncles, and periventricular white matter in cerebral hemispheres. Diffusion-weighted images were unremarkable. Single-voxel proton MRS showed elevated levels of lactate, branched-chain amino acids, as well as glutamine and glutamate. To the best of our knowledge, this is the first reported case of late onset 3-methylcrotonylglycinuria with complete MRI and MRS workup in the early chronic phase after metabolic crisis.

Neuroimaging Findings of Organic Acidemias and Aminoacidopathies

“…Neuroimaging findings are nonspecific. During the acute phase, a hyperintense signal at T2-weighted and FLAIR MR imaging-with matching diffusion changes-may be seen bilaterally in the globi pallidi, thalami, cerebral peduncles, medulla oblongata, pons, inferior cerebellar peduncles, and periventricular white matter (25). Confluent and multifocal T2-hyperintense signal changes in the white matter may be the only neuroimaging findings (26).…”

“…At follow-up, a rapid progression of gray and white matter atrophy associated with subdural hematomas is seen. 1 H MR spectroscopy may reveal elevated levels of lactate, branched-chain amino acids, glutamine, and glutamate (25). However, in mildly symptomatic or asymptomatic patients, neuroimaging findings are typically normal.…”