Central pontine myelinolysis
Central pontine myelinolysis is osmotic demyelination of the central pons, almost always from overly rapid correction of chronic hyponatremia. It presents days after correction with delirium, dysarthria, dysphagia, and spastic quadriparesis, and is diagnosed by history plus MRI. Prevention (limiting correction rate) is the only reliable therapy.
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What this article covers
- Overview
Definition: central pontine myelinolysis is a form of osmotic demyelination syndrome in which rapid osmotic shifts, almost always from overcorrection of chronic hyponatremia, strip myelin from the…
- Epidemiology
Uncommon but underrecognized: true incidence is unclear because mild cases are missed, but it occurs almost exclusively in patients with severe, chronic hyponatremia (serum sodium under 120 mmol/L) that is corrected too quickly.
- Risk factors
Chronic, severe hyponatremia: duration over 48 hours and serum sodium under 120 mmol/L before correction is the dominant risk factor.
- Pathophysiology
Astrocyte injury is the initiating event: chronic hyponatremia causes astrocytes to extrude organic osmolytes (myo-inositol, taurine, glutamate) to protect cell volume; this adaptation takes days.
- Clinical features
Biphasic presentation is the diagnostic pattern: encephalopathy from hyponatremia initially improves with correction, then new deficits appear after an asymptomatic interval of 2 to 6 days.
- Differential diagnosis
Basilar artery occlusion: also causes quadriparesis, dysarthria, and locked-in presentation, but has abrupt onset without the biphasic sodium-correction history and shows acute infarct restricted…
- Diagnosis
Diagnosis is established first by the clinical pattern, then confirmed by imaging: a documented episode of rapid correction of chronic hyponatremia followed by a delayed corticospinal/corticobulbar…
- Management
First, there is no reversal drug once demyelination is fixed: stop any further rise in serum sodium immediately once the diagnosis is suspected, and address any ongoing osmotic derangement before it advances.
- Complications
Permanent motor disability: residual spastic quadriparesis or hemiparesis is common after severe injury.
- Prognosis
Outcome is more favorable than once believed: with modern supportive care, roughly two-thirds of patients achieve a good or fair functional recovery over weeks to months.
- Prevention
Limit the rate of hyponatremia correction: raise serum sodium by no more than 8 mmol/L in any 24-hour period, and no more than 18 mmol/L in 48 hours, regardless of the correction method used.
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