What are the clinical features of central pontine demyelination syndrome?

Clinical Features of Central Pontine Demyelination Syndrome

Central pontine myelinolysis (CPM) presents with a spectrum of neurological manifestations ranging from mild symptoms to severe locked-in syndrome, with the severity not necessarily correlating with the size of the pontine lesion on imaging.

Etiology and Risk Factors

• Most commonly associated with rapid correction of hyponatremia (primary mechanism)
• Predisposing conditions include:
  • Chronic alcoholism
  • Malnutrition
  • Liver disease
  • Renal failure
  • Organ transplantation
  • Burns
  • Prolonged diuretic use

Clinical Presentation

Neurological Manifestations

• Early symptoms (may appear within days of rapid sodium correction):

  • Altered mental status/encephalopathy
  • Dysarthria
  • Dysphagia
  • Behavioral changes

• Progressive symptoms:

  • Spastic quadriparesis
  • Pseudobulbar palsy
  • Bulbar dysfunction
  • "Locked-in" syndrome in severe cases (consciousness preserved with quadriplegia and inability to speak)
  • Coma

Neuropsychiatric Manifestations

• May occur as the primary presentation, especially in early stages 1
• Can include:
  • Acute psychosis
  • Personality changes
  • Paranoia
  • Hallucinations
  • Catatonia

Severity Spectrum

• Mild cases: Subtle neurological deficits that may be overlooked
• Moderate cases: Combination of motor and bulbar symptoms
• Severe cases: Complete paralysis with preserved consciousness (locked-in syndrome)
• Fatal cases: Progression to coma and death

Diagnostic Features

MRI Findings

• Characteristic symmetric, trident-shaped lesion in the central pons ("piglet sign") 2
• T2-weighted and FLAIR sequences show hyperintense signal
• Diffusion-weighted imaging shows restricted diffusion in acute phase
• Initial MRI may be normal in early stages, with changes appearing 1-2 weeks later 1

Clinical Course

• Symptoms typically develop 2-6 days after rapid correction of hyponatremia
• Progressive deterioration over days to weeks
• Recovery may occur over months with supportive care 2
• Size of pontine lesion does not necessarily correlate with clinical severity or outcome 3

Associated Conditions

Extrapontine Myelinolysis (EPM)

• Similar demyelinating lesions occurring outside the pons 4
• Common locations:
  • Cerebellar white/gray matter junctions
  • Thalamus
  • Basal ganglia/striatum
  • Cerebral cortex
  • Subcortical white matter

Coexisting Conditions

• Wernicke's encephalopathy (may have overlapping clinical features)
• Hepatic encephalopathy
• Electrolyte disturbances

Pitfalls and Caveats

1. Diagnostic challenges:

   • Initial normal MRI doesn't exclude CPM; repeat imaging in 1-2 weeks if clinical suspicion is high 1
   • Mild forms may be misdiagnosed as other neurological or psychiatric disorders

2. Clinical variability:

   • Severity of symptoms doesn't always correlate with lesion size on imaging 3
   • Neuropsychiatric symptoms may predominate in some cases without obvious focal deficits 1

3. Monitoring considerations:

   • Patients with risk factors require close monitoring during correction of hyponatremia
   • Symptoms may develop days after electrolyte correction, requiring continued vigilance

4. Treatment implications:

   • No specific pharmacotherapy exists for promoting remyelination 2
   • Physical therapy has shown benefit in recovery 2

Understanding the diverse clinical presentations of CPM is crucial for early recognition, particularly in at-risk populations, as prompt diagnosis may improve outcomes through supportive care and rehabilitation.