Centropontine myelinolysis

Centropontine myelinolysis is a particular form of osmotic demyelination syndrome (ODS), the individualization of which is debated. It is considered rare and has a poor prognosis, but its actual incidence is unknown.

Etiologies

All causes of abrupt variation in osmotic gradient, the most frequent being too rapid correction of hyponatremia. Less frequently encountered: hypokalemia, hyperglycemia, ketoacidosis, etc.

Contributing factors: alcoholism (main FF), malnutrition, vomiting, dialysis, polydipsia, liver failure, associated hypokalemia, etc.

Etiopathogenic factors

The presumed etiopathogenesis is that of a sudden change in the osmotic gradient, leading to an abrupt outflow of water from the cells. This not only destroys the myelin sheaths, but also the oligodendrocytes and axons. The pontine region is most often affected (in 80% of cases), but other cerebral areas may be involved (in 30% of cases in association with pontine lesions, in 20% of cases in isolation).

In the vast majority of cases, this osmotic variation is the result of too-rapid correction of hyponatremia by saline infusions. The risk is all the greater the deeper the hyponatremia (< 115 mEq/l) and the more chronic it is.

Clinical

Clinical: after clinical improvement due to correction of hyponatremia, quadriparesis, pseudo-bulbar syndrome (swallowing and speech disorders), ocular motor disorders and even locked-in-state may rapidly occur. The classic course is towards coma and death, with an abysmal functional prognosis in the event of survival.

However, it is assumed that many pauci-symptomatic or even asymptomatic cases are ignored.

Additional tests

• Cerebral MRI - generally necessary and sufficient for diagnosis
  • T1 and T2/FLAIR: initially normal, then appearance of hypointense lesions in T1 and hyperintense lesions in T2. T2* normal. Gadolinium may be taken.
  • Diffusion: DWI restriction (hyperintense) = most sensitive
  • Main differential diagnosis: ischemic stroke. Clinical data and non-observance of arterial territories can make the difference.
• Cerebral CT-scanner
  • Non-contrast: generally normal in the acute phase. May show hypodensities of the centro-pontine region in the status phase.
  • With contrast medium: may show typically symmetrical contrast.

CT-scanner - T1 sequence + contrast medium - symmetrical contrast in the centropontine region

MRI - DWI sequence - centro-pontine diffusion restriction (hyperintensity)

Therapeutic management - Treatments

Treatment consists in correcting the cause of the syndrome as quickly as possible.

• Most frequent case: too rapid correction of hyponatremia - If, despite all precautions, the correction limit of 0.5 mEq/ l/ hour is exceeded (maximum 12 mEq/ l/ day on day 1) → give infusions of NaCl 0.45% or glucose solution + minirin, then scrupulously respect the recommended correction limits.

Once the syndrome has set in, there is no treatment other than supportive therapy.

Author

Dr Shanan Khairi, MD

Bibliography

Bradley WG et al., Neurology in clinical practice, 5th ed., Butterworth-Heinemann, e-dition, 2007

Cambier J et al., Neurologie, 13e édition, Masson, 2012

Osborn AG et al, Brain, Elsevier, 2018

Stern RD, Osmotic demyelination syndrome (ODS) and overly rapid correction of hyponatremia, UpToDate, 2023