Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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October 13, 2014
Osmotic Demyelination Syndrome
- Background: Osmotic myelinolysis, or central pontine myelinolysis, is seen when rapid osmolality changes occur, typically after rapid correction of hyponatremia. The exact incidence is unknown, but it occurs more commonly in chronically malnourished alcoholic patients and after rapid correction of hyponatremia.
- It is unclear why the pons is preferentially involved. Extrapontine myelinolysis can be seen in thalami, basal ganglia, midbrain, subcortical white matter, and cerebellum.
- Relevant Clinical Information Typically, patients will present with encephalopathy due to hyponatremia, which improves after intravenous sodium replacement therapy. Neurological decline appears over the next 48–72 hours with symptoms that include spastic quadriparesis, pseudobulbar palsy, seizures, and coma.
- Key Diagnostic Images:
- Increased signal intensity within the central pons on long TR sequences, especially in a trident configuration, typically sparing the coricospinal tracts.
- In the acute setting, restricted diffusion can be seen. There is typically no enhancement after paramagnetic intravenous contrast administration, and 10–50% of cases will have extrapontine involvement
- In the chronic setting, residual T2 signal abnormalities, cavitation, and facilitated diffusion are seen.
- DDx: In the adequate clinical setting, central pontine involvement is pathognomonic of this disease.
- Rx: Prognosis is dismal, and treatment is based on supportive therapy.
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