Extrapontine Demyelination from Hypernatremia Correction
Yes, correction of hypernatremia can cause extrapontine demyelination, particularly when the correction occurs too rapidly. 1 While osmotic demyelination syndrome (ODS) is more commonly associated with rapid correction of hyponatremia, it can also occur following rapid correction of hypernatremia.
Pathophysiology and Risk Factors
Osmotic demyelination can occur when there are rapid changes in serum sodium levels, causing shifts in brain osmolality that the brain cannot adapt to quickly enough:
- During hypernatremia, the brain increases intracellular osmolytes to prevent cellular dehydration
- When hypernatremia is corrected too rapidly, these adaptive mechanisms cannot reverse quickly enough
- This osmotic stress can lead to demyelination in both pontine and extrapontine regions 2, 1
Risk factors that increase susceptibility to osmotic demyelination include:
- Malnutrition
- Liver disease
- Alcoholism
- Burns
- Hypokalemia 3
Evidence from Clinical Cases
A documented pediatric case reported a 14-year-old leukemic, malnourished boy who developed central pontine and extrapontine myelinolysis after rapid correction of hypernatremia (serum sodium 170 mmol/L). The correction rate exceeded 0.5 mmol/L/hour, resulting in progressive neurological impairment with characteristic clinical features of ODS 1.
Another case report described a patient who developed extrapontine myelinolysis involving the posterior limbs of bilateral internal capsules due to acute hypernatremia, even though the increasing rate of serum sodium did not exceed the recommended safety range 2.
Safe Correction Guidelines
To prevent osmotic demyelination when correcting hypernatremia:
- Correction rate should not exceed 10 mmol/L per 24 hours (even more cautious approach needed in high-risk patients) 3
- For patients with additional risk factors (liver disease, malnutrition, etc.), limit correction to less than 8 mmol/L per 24 hours 4, 3
- More gradual correction is recommended for chronic hypernatremia (>48 hours duration) compared to acute hypernatremia 5
The ESPGHAN/ESPEN/ESPR guidelines specifically recommend a reduction rate of 10-15 mmol/L/24h for hypernatremia correction to avoid cerebral edema, seizures, and neurological injury 5.
Clinical Manifestations of Osmotic Demyelination
Symptoms typically develop 2-7 days after rapid correction and may include:
- Spastic quadriparesis
- Pseudobulbar palsy
- Altered consciousness
- Seizures
- Movement disorders
In milder cases, transient confusion may be the only symptom 6.
Diagnostic Approach
If osmotic demyelination is suspected following hypernatremia correction:
- MRI is the imaging modality of choice, though lesions may not be visible until 7-10 days after symptom onset 6
- Typical findings include symmetric lesions in the pons and/or extrapontine regions (basal ganglia, thalamus, internal capsule, cerebellum)
- CSF analysis may show elevated myelin basic protein with otherwise normal findings 6
Prevention Strategies
- Calculate the total sodium deficit and distribute correction over several days
- Monitor serum sodium levels every 2-4 hours initially during correction
- Adjust fluid therapy if correction is proceeding too rapidly
- Consider using desmopressin (1-2 μg IV/SC every 6-8 hours) to slow correction if it's occurring too quickly 4
Treatment
If osmotic demyelination has occurred, supportive care is the mainstay of treatment. Some case reports suggest potential benefit from:
- Corticosteroids
- Intravenous immunoglobulins
- Supportive care 1
Recovery may begin approximately 2 weeks after the insult and can continue for up to a year, though residual deficits are common 6.
In summary, while osmotic demyelination is more frequently associated with hyponatremia correction, it is a well-documented complication of hypernatremia correction as well. Careful attention to correction rates is essential to prevent this potentially devastating neurological complication.