What are the manifestations of Osmotic Demyelination Syndrome (ODS)?

Manifestations of Osmotic Demyelination Syndrome (ODS)

Osmotic demyelination syndrome (ODS) typically presents with a biphasic clinical course, characterized by initial neurological improvement after correction of hyponatremia, followed by neurological deterioration 2-7 days later with symptoms including dysarthria, dysphagia, oculomotor dysfunction, and quadriparesis. 1

Clinical Presentation

Neurological Manifestations

• Initial phase: Seizures or encephalopathy following rapid sodium correction
• Transient improvement: Brief period of apparent recovery
• Secondary deterioration (2-7 days after sodium correction):
  • Dysarthria
  • Dysphagia
  • Oculomotor dysfunction (eye movement abnormalities)
  • Quadriparesis (weakness in all four limbs)
  • Altered consciousness ranging from confusion to coma
  • Behavioral changes
  • Seizures
  • Locked-in syndrome in severe cases 1, 2

Movement Disorders

• Tremor
• Cogwheel rigidity (Parkinson-like)
• Dystonia
• Ataxia
• Spasticity 3, 2

Cranial Nerve Involvement

• Bilateral facial palsy
• Ophthalmoplegia (paralysis of eye muscles)
• Bulbar symptoms affecting speech and swallowing 3

Radiological Findings

MRI Features

• Central Pontine Myelinolysis (CPM):

  • Hyperintense lesions in the median portion of the pons on T2/FLAIR sequences
  • Typically symmetrical "bat-wing" or trident-shaped lesions
  • Sparing of the periphery of the pons and corticospinal tracts 4, 5

• Extrapontine Myelinolysis (EPM):

  • Lesions in areas outside the pons including:
    • Basal ganglia
    • Thalamus
    • Cerebellum
    • Cerebral white matter
    • Hippocampus 2, 6

Risk Factors and Associations

Primary Risk Factors

• Rapid correction of hyponatremia (>8 mEq/L in 24 hours)
• Severe hyponatremia (<120 mEq/L) 1

Additional Risk Factors

• Advanced liver disease
• Alcoholism
• Malnutrition
• Severe metabolic derangements:
  • Hypophosphatemia
  • Hypokalemia
  • Hypoglycemia
• Low cholesterol
• Prior encephalopathy
• Liver transplantation
• Female gender
• Elderly patients 1, 2, 6

Disease Course and Complications

Progression

• Symptoms typically develop 2-7 days after rapid correction of sodium
• Can range from mild neurological deficits to severe, life-threatening complications
• Fatal cases have been reported, with mortality rates historically high (33-55%) 4, 2

Complications

• Respiratory failure requiring ventilatory support
• Permanent neurological deficits
• Status epilepticus
• Irreversible coma
• Death 4

Diagnostic Approach

Laboratory Findings

• Evidence of recent sodium correction
• History of severe hyponatremia (<120 mEq/L)
• Other electrolyte disturbances (hypokalemia, hypophosphatemia)
• In some cases, elevated liver enzymes or evidence of malnutrition 1, 6

Neuroimaging

• MRI is the diagnostic modality of choice
• CT scan may be normal in early stages
• Radiological findings may lag behind clinical symptoms by 2-4 weeks
• Follow-up MRI may show evolution of lesions 2, 5

Prognosis

The prognosis of ODS has improved with earlier recognition and MRI-based diagnosis, but remains serious:

• 33-55% of patients either die or remain permanently dependent on nursing care
• Some patients may show gradual improvement over months
• Recovery can be complete in mild cases, especially with early recognition and supportive care 2

Prevention

Prevention is the cornerstone of management:

• Limit sodium correction to 4-6 mEq/L per 24-hour period in high-risk patients
• Do not exceed 8 mEq/L in 24 hours in patients with liver disease
• If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1

ODS remains a serious neurological complication with significant morbidity and mortality. Early recognition of the characteristic biphasic clinical course and prompt neuroimaging are essential for diagnosis and management.