Osmotic demyelination syndrome

View Details

Status

Done

Aetiology

Etiologies	N (%) n = 18
Hyponatremia	9 (50.0)
Alcoholism	5 (27.8)
Multiple myeloma	1 (5.6)
Uremia	1 (5.6)
Terlipressin used	1 (5.6)
Hypokalemia	1 (5.6)
After general anesthesia	1 (5.6)
Hypernatremia	1 (5.6)
Diabetes insipidus	1 (5.6)

Risk factors

Serum sodium (Na⁺) < 105 mmol/L

Hypokalaemia

Chronic excessive alcohol consumption

Malnutrition

Advanced liver disease

> 18 mmol/L increase in Na⁺ within 48 hours

Limits (Not Targets) for Sodium Rise

High-risk patients: < 8 mmol/L increase in any 24-hour period
Normal-risk patients: < 10–12 mmol/L increase in any 24-hour period

Pathophysiology

Chronic Hyponatremia Adaptation:

Brain cells adapt to prolonged low sodium by extruding organic and inorganic osmolytes to reduce cell swelling.

Rapid Sodium Correction:

A sudden increase in serum sodium causes extracellular osmolality to rise quickly, but brain cells cannot rapidly reaccumulate osmolytes.

Osmotic Stress and Cell Shrinkage:

The resulting osmotic gradient leads to rapid water efflux from brain cells, causing cellular dehydration and shrinkage.

Selective Oligodendrocyte Apoptosis:

Oligodendrocytes, the cells responsible for myelinating CNS axons, are particularly sensitive to this osmotic stress, undergoing apoptosis.

Demyelination:

This process leads to symmetrical, noninflammatory demyelination in susceptible areas, notably the pons and other oligodendrocyte-rich brain structures.

The brain undergoes volume adaptation in response to gradual-onset hyponatraemia of hypotonic state adaptation Water pin Loss sodium. potassiu and chloride LOSS of orgaNc osnWVtes Adrogue HO, Madias NE, NEJM. 2000; 342; 21: 1581-1589. — The brain undergoes volume adaptation in response to gradual-onset hyponatraemia

Clinical features

Encephalopathy: 61%

Dysarthria/dysphonia: 50%

Extrapyramidal symptoms: 39%

Seizures: 22%

May take up to 2 weeks to manifest

Feature	Central Pontine Myelinolysis (CPM)	Extrapontine Myelinolysis (EPM)
Site	Pons (brainstem)	Basal ganglia, thalamus, cerebral cortex
Core symptoms	Spastic quadriparesis, pseudobulbar palsy	Altered mental status, movement disorders
Additional features	Dysarthria, dysphagia, coma, "locked-in"	Parkinsonism, dystonia, akinetic mutism

Radiology

Central pontine myelinosis

(a) T2 and (b) T2 FLAIR images demonstrating symmetric hyperintensities in the central pons; (c) axial diffusion weighted image; (d) ADC map demonstrating restricted diffusion changes in the central pons; (e) sagittal T1 image demonstrating hypointensities in the pons.

notion image

Osmotic demyelination syndrome White areas in the middle of the pons Massive demyelination of descending axons May take up to 2 weeks to manifest

Extra pontine myelinosis

(a, b) axial diffusion-weighted images demonstrating restricted diffusion in the cerebral cortex and the basal ganglia; (c) T1 and (d) ADC map showing hypointensities in the basal ganglia; (e) T2 image demonstrating symmetric hyperintensities in the basal ganglia

Management

Desmopressin s/c to prevent further water losses eg 2-4µg every 8 hours (as necessary)

If there the serum Sodium coming up too fast can be replace by giving water rather than giving desmopressin

Replace water orally or as 5% dextrose (IV 3ml/kg/h)

Recheck serum Na⁺ hourly and continue therapy infusion until serum Na⁺ is reduce to goal

Re-lowering serum Na+ E 20 18 16 14 12 10 8 6 4 2 AAJte Water Low to Moderate RiSk OOS Desmopressin s/c to prevent further water losses eg 2-4 gg every 8 hours (as necessary) Replace water orally or as 5% dextrose (IV 3 mL/kg/h) GOAL High Risk ot OOS Recheck serum Na+ hourly and continue therapy infusion until serum Na+ is reduced to goal — Re-lowering serum Na⁺

Made with Bullet