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Abnormalities of the brain in nonketotic hyperglycinemia: MR manifestations
G A Press1, B A Barshop, R H Haas
1Department of Radiology, University of California, School of Medicine, San Diego 92103.
Insights
Magnetic resonance (MR) imaging reveals progressive brain atrophy and delayed myelination in infants with nonketotic hyperglycinemia. These MR findings correlate with known pathology but not with glycine levels.
Area of Science:
- Neurology
- Pediatric Radiology
- Medical Imaging
Background:
- Nonketotic hyperglycinemia (NKH) is a rare metabolic disorder.
- Neuropathological findings in NKH include brain atrophy and dysmyelination.
- Magnetic resonance (MR) imaging can visualize these structural brain changes.
Purpose of the Study:
- To characterize the MR imaging findings in infants with nonketotic hyperglycinemia.
- To assess the age-related progression of brain abnormalities in NKH.
- To correlate MR findings with clinical and biochemical data.
Main Methods:
- Retrospective review of MR imaging studies in seven patients with NKH (age 4 days to 38 months).
- Assessment of parenchymal volume loss, corpus callosum abnormalities, and myelination status on T2-weighted images.
- Correlation of MR findings with cerebrospinal fluid (CSF) and plasma glycine concentrations.
Main Results:
- Progressive atrophy and delayed myelination were observed, with volume loss evident from 4 days of age.
- Abnormalities included supratentorial and infratentorial volume loss and a thin corpus callosum.
- Delayed or absent supratentorial white matter myelination was noted in older infants, while brainstem and cerebellar myelination appeared normal.
- No correlation was found between MR findings and glycine levels.
Conclusions:
- MR imaging demonstrates characteristic age-related brain abnormalities in nonketotic hyperglycinemia.
- The observed MR findings correlate with established neuropathology in NKH.
- MR imaging is a valuable tool for evaluating the central nervous system manifestations of NKH.
Abstract:
MR imaging in seven patients (4 days to 38 months old) with nonketotic hyperglycinemia showed age-related findings of progressive atrophy and delayed myelination. Parenchymal volume loss was found as early as 4 days after birth and increased in severity with increasing age to 27 months. Both supratentorial and infratentorial volume loss were present in the most severely affected patients. The corpus callosum was abnormally thin in all patients. The state of myelination of the CNS was assessed on T2-weighted images. Decreased or absent myelination within supratentorial white-matter tracts was detected in all four patients 10 months of age or older. Myelination of the brainstem and cerebellum progressed normally. No correlation was found between the degree of volume loss or abnormality of myelination demonstrated by MR and the concentration of glycine in the CSF or plasma. Abnormalities shown by MR correlate well with known pathologic findings in patients with nonketotic hyperglycinemia.