Osmotic Demyelination Syndrome Despite Appropriate Hyponatremia Correction

Abstract

Acute demyelination of the pons or extrapontine areas results in an osmotic demyelination syndrome (ODS), previously referred to as central pontine myelinolysis (CPM) or extra pontine myelinolysis (EPM). It is caused by osmotic dysregulation in the brain. Multiple risk factors have been known to contribute to these osmotic disturbances. Among them, osmotic stress caused by rapid correction of hyponatremia is the most common cause. Other risk factors include liver failure, alcohol dependence, malnutrition, and malignancy. Symptoms can vary depending on the location of the demyelination. It has a high rate of morbidity and mortality. We present a case of ODS in a malnourished patient who was found to have alcoholic hepatitis and invasive colon cancer. The initial presentation was sepsis secondary to pneumonia. The patient was found to be severely hyponatremic at the time of admission, and the hyponatremia was corrected as per the recommendations. The initial non-contrast head computed tomography (CT) scan was unremarkable. However, the hospital course was complicated by a deteriorating neurological exam with encephalopathy despite not overcorrecting the sodium. A short-term follow-up brain magnetic resonance imaging (MRI) eventually revealed ODS. Initially, the findings of ODS were masked due to symptoms of alcohol withdrawal. However, the patient had a quick recovery with the improvement of all the neurological findings.

Keywords: alcohol withdrawal; hyponatremia; invasive colon cancer; osmotic demyelination syndrome.

Figure 1. Appropriate correction of sodium at a rate of less than 8 mmol/L/24 hours

Figure 2. Contrast-enhanced computed tomography (CT) scan of the pelvis

Axial (A) and sagittal (B) images from contrast-enhanced CT of the pelvis showed a large rectosigmoid mass (arrow) suggestive of a colorectal malignancy

Figure 3. Initial and repeat non-contrast computed tomography (CT) scans of the brain

(A) Axial and (B) sagittal views on a non-contrast CT head scan showing no abnormalities; (C) axial and (D) sagittal views on a non-contrast CT head scan three weeks later showing hypodensity (arrow) in the central pons, suggesting central pontine myelinolysis (CPM)

Figure 4. Axial diffusion-weighted (DWI) magnetic resonance imaging (MRI)

(A) MRI demonstrates diffusion restriction involving the central pons (white arrow), sparing the periphery (yellow arrow), as well as corticospinal tract (curved white arrow). (B) Axial and (C) coronal flair images showing extra pontine involvement with T2 prolongation involving the bilateral pons (arrowhead) in addition to the central pons (white arrow).