Case ReportCranial MRI in Acute Hyperammonemic Encephalopathy
Introduction
Hyperammonemia in children may be detected in a variety of conditions, including urea cycle disorders, hepatic encephalopathy, Reye's syndrome, and other metabolic or toxic encephalopathies. Prolonged hyperammonemic encephalopathy could lead to substantial parenchymal brain injury, and surviving patients develop impairment of intellectual function [1], [2]. Few reports are available on magnetic resonance imaging in acute hyperammonemic encephalopathy, and different patterns of imaging findings have been described [3]. Moreover, it is often believed that magnetic resonance imaging might reveal only normal findings, or at best reveal diffuse atrophy. The diagnostic role of magnetic resonance imaging in acute hyperammonemic encephalopathy merits further consideration. Described here are the magnetic resonance imaging observations in three cases of hyperammonemic encephalopathy, each with a different cause.
Section snippets
Patient 1
A 1-year-old boy presented with recurrent seizures, loss of acquired milestones, irritability, and frequent inconsolable crying spells of 20 days duration. There was a history of recurrent vomiting from early infancy. He had had left-side focal motor seizures with secondary generalization from the age of 3 months and was taking 30 mg daily of phenobarbital for control of seizures. He was born by cesarean section to healthy consanguineous parents. Birth and perinatal history were unremarkable.
Discussion
Extensive cortical signal changes were observed in three patients with hyperammonemia due to different underlying etiology. Takanashi et al. [3] have classified magnetic resonance imaging findings in hyperammonemic encephalopathy into four important groups: (a) diffuse cerebral edema followed by diffuse cerebral atrophy, (b) extensive infarct-like abnormality often presenting as acute hemiplegia, (c) ischemic lesions in cerebral vascular territory, and (d) reversible symmetric cortical
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2017, Handbook of Clinical NeurologyCitation Excerpt :Brain imaging may reveal marked cerebral edema, similar to Reye syndrome (Metzeler et al., 2009). There may also be signal change in the insular and cingulate cortices, with sparing of the occipital cortex (in contrast to posterior and white-matter-predominant PRES pattern on MRI) (Bindu et al., 2009). Urea cycle defects including ornithine transcarbamylase deficiency should be excluded by measurement of urinary amino acids and orotic acid, as these can present in a similar manner.
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2013, Clinical RadiologyCitation Excerpt :Subsequent changes in intracellular osmolarity lead to astrocyte swelling and cell death, resulting in cerebral oedema.32 At MRI, the findings are largely similar in children and adults, despite different aetiologies.32,34,35 Bilateral symmetric involvement of the insular cortex and cingulate gyrus is fairly consistent (Fig 6a).32,36