What are the symptoms of Central Pontine Myelinolysis (CPM)?

Symptoms of Central Pontine Myelinolysis (CPM)

Central pontine myelinolysis presents with a characteristic constellation of neurological symptoms including quadriparesis, dysarthria, dysphagia, and locked-in syndrome in severe cases, typically developing after rapid correction of hyponatremia or in patients with chronic alcoholism. 1, 2

Clinical Presentation

Core Neurological Symptoms

• Motor abnormalities:

  • Quadriparesis/quadriplegia (progressive weakness in all limbs)
  • Spastic paralysis
  • Locked-in syndrome (complete paralysis with preserved consciousness and eye movements)
  • Dystonia and rigidity
  • Parkinsonian features

• Bulbar dysfunction:

  • Dysarthria (slurred speech)
  • Dysphagia (difficulty swallowing)
  • Impaired gag reflex

• Oculomotor disturbances:

  • Horizontal gaze palsy
  • Impaired eye movements
  • Preserved vertical eye movements and blinking (particularly in locked-in syndrome)

• Other neurological manifestations:

  • Altered mental status (confusion, delirium)
  • Behavioral changes
  • Seizures (less common)
  • Ataxia
  • Tremors

Clinical Course

The typical progression of symptoms follows a biphasic pattern 2, 3:

1. Initial phase:

   • Encephalopathy or altered mental status
   • May have transient improvement after correction of underlying condition

2. Delayed phase (typically 2-7 days after initial insult):

   • Rapid deterioration with progressive motor deficits
   • Development of bulbar symptoms
   • Potential progression to locked-in syndrome in severe cases

Diagnostic Imaging Findings

MRI is the gold standard for diagnosis 1:

• Characteristic "trident-shaped" hyperintense signal in the central pons on T2-weighted images
• Relative sparing of the periphery of the pons and corticospinal tracts
• Hypointense signal on T1-weighted images
• Lesions typically symmetrical and non-enhancing

Risk Factors and Associated Conditions

CPM most commonly occurs in the context of:

• Rapid correction of hyponatremia (>10-12 mEq/L in 24 hours) 4, 2
• Chronic alcoholism 3, 5
• Malnutrition
• Liver disease or liver transplantation
• Diabetes mellitus with hyperglycemia 6
• Severe burns
• Prolonged diuretic use

Clinical Pitfalls and Special Considerations

• CPM can develop even with normal serum sodium levels, particularly in alcoholic patients 6, 5
• Symptoms may be delayed, appearing several days after the osmotic insult
• Extrapontine myelinolysis may occur concurrently, affecting the basal ganglia, thalamus, and cerebellum
• The severity of clinical manifestations does not always correlate with imaging findings 3
• Recovery can occur but may take months to years of intensive rehabilitation 2

Prevention

Prevention is crucial as treatment options are limited:

• Slow correction of hyponatremia (<8 mEq/L in 24 hours, <12 mEq/L in 48 hours) 4
• Close monitoring of serum sodium levels during correction
• Particular caution in high-risk patients (alcoholics, malnourished)

Early recognition of symptoms and prompt MRI imaging are essential for diagnosis and management of this serious neurological condition.