What are the signs of central pontine myelinolysis (CPM)?

Signs and Symptoms of Central Pontine Myelinolysis (CPM)

Central pontine myelinolysis presents with a range of neurological manifestations including spastic quadriparesis, dysarthria, pseudobulbar palsy, and encephalopathy, with severe cases progressing to locked-in syndrome or coma. 1

Clinical Presentation

Motor Symptoms

• Spastic quadriparesis (tetraparesis) due to damage to descending motor tracts is a hallmark feature 1
• Pseudobulbar paralysis affecting speech and swallowing functions 1
• "Locked-in" syndrome in severe cases, characterized by complete paralysis except for vertical eye movements 1, 2
• Gait abnormalities and frequent falls may be early manifestations 2

Bulbar and Speech Symptoms

• Dysarthria (difficulty articulating speech) due to involvement of corticobulbar tracts 1
• Dysphagia (difficulty swallowing) as part of pseudobulbar palsy 1
• Mutism in advanced cases 3

Cognitive and Psychiatric Manifestations

• Encephalopathy of varying severity 1
• Acute psychosis, which can sometimes be the predominant or earliest manifestation 2
• Personality changes, paranoia, hallucinations, or catatonia may occur, especially when extrapontine areas are involved 2
• Altered consciousness ranging from confusion to coma 1, 3

Less Common Presentations

• Cerebellar syndrome with ataxia and coordination difficulties 1
• Generalized weakness that may precede more specific neurological deficits 2

Risk Factors and Associated Conditions

• Most commonly associated with rapid correction of hyponatremia (correction exceeding 12 mEq/24h) 1
• Frequently seen in patients with:
  • Chronic alcoholism 4
  • Malnutrition 4
  • Liver disease 4
  • Prolonged vomiting leading to electrolyte disturbances 3
• Rarely, can occur with hyperglycemia even with normal sodium levels due to osmotic shifts 5

Diagnostic Features

Imaging Findings

• Magnetic resonance imaging (MRI) is the imaging procedure of choice 1
• Characteristic MRI findings include:
  • Area of prolonged T1 and T2 relaxation in the central pons 1
  • Symmetric lesions in the central portion of the base of the pons 1
  • Lesions may have a characteristic "trident" or "bat-wing" shape 6
• Initial MRI may be unremarkable, with changes becoming apparent on repeat imaging 1-2 weeks later 2

Pathological Features

• Demyelination affecting the central portion of the base of the pons 1
• No inflammatory changes are present 1
• Blood vessels appear normal on pathological examination 1
• In some cases, similar demyelinating lesions may be found in extrapontine locations (extrapontine myelinolysis) 2, 3

Clinical Course and Prognosis

• Clinical deterioration often follows correction of electrolyte abnormalities 3
• Recovery is variable, ranging from no improvement to substantial recovery 1
• Prevention is critical by limiting correction of serum sodium to no more than 12 mEq/24h in hyponatremic patients 1

Important Considerations

• CPM can occur even when sodium correction rates are within recommended limits 1
• Neuropsychiatric symptoms may predominate in early stages, before classic motor symptoms develop 2
• Extrapontine involvement can occur and may contribute to the clinical presentation 2, 3
• CPM should be considered in patients with acute neurological deterioration following correction of electrolyte abnormalities, particularly hyponatremia 1, 3