{
  "abstract": "A female patient in early childhood with a history of morbid obesity and global developmental delay presented with acute encephalopathy requiring emergent intubation for airway protection. The neurologic examination was limited by sedative/paralytic therapy. General chemistry panel testing revealed the following: sodium 206 mEq/L, potassium 2.6 mmol/L, chloride 163 mEq/L, bicarbonate 29 mEq/L, blood urea nitrogen 42 mmol/L, creatinine 2.6 µmole/L and glucose 111 mg/dL. Urinalysis showed a specific gravity of 1005 and a urine osmolality of 265 mOsm/kg. Brain CT revealed no acute abnormalities (not shown). Together, these findings were consistent with extreme hypernatremia secondary to diabetes insipidus with acute kidney injury. Serum sodium was corrected over the course of 5 days ( figure 1), with a target correction rate of ≤12 mEq/L per 24 hours. The patient received intravenous hypotonic saline and desmopressin to control free water loss, and her sodium levels were monitored every 4–6 hours. Fluid balance was tracked closely, and sodium correction remained within safe limits throughout hospitalisation, resulting in resolved encephalopathy without focal neurologic findings. MRI demonstrated an absent posterior pituitary bright spot and no diffusion-weighted abnormalities to suggest acute ischaemia. However, fluid attenuation inversion recovery MRI sequences demonstrated hyperintensities in the bilateral amygdala/hippocampi, insular cortex and cerebellar hemispheres along with contrast enhancement of the perisylvian regions (figure 2). These findings were consistent with osmotic demyelinating syndrome (ODS) that was not present on prior MRI performed for workup of developmental delay (not shown). Alternative aetiologies for the imaging abnormalities were considered, including hypoxic-ischaemic injury, sedative-related neurotoxicity, atypical posterior reversible encephalopathy syndrome, autoimmune encephalitis and toxic/metabolic encephalopathy. However, the lesion distribution, lack of additional metabolic derangements and clinical course were most consistent with extrapontine myelinolysis (EPM). She was started on desmopressin, and serum sodium remained normal for more than 1 year post presentation. The aetiology of developmental delay and diabetes insipidus remains unknown as workup including chromosomal microarray, Prader-Willi methylation testing and genetic obesity panel testing was normal.",
  "authors": [
    {
      "affiliations": [
        "Children’s Hospital of Orange County, Orange, California, USA"
      ],
      "name": "Zain Jandial"
    },
    {
      "affiliations": [
        "Pediatrics, University of California Irvine, Irvine, California, USA",
        "Pediatrics, Children’s Hospital Orange County, Orange, California, USA"
      ],
      "name": "John Ross Crawford"
    }
  ],
  "title": "Unusual MRI findings in a child with extreme hypernatremia",
  "uid": "ca3e5bbf-5ad1-58aa-bc8b-4ca694a96e22"
}