Central pontine myelinolysis Health Article

Definition

Central pontine myelinolysis is brain cell dysfunction caused by the destruction of the layer (myelin sheath) covering nerve cells in the brainstem (pons).

Alternative Names

CPM

Causes, incidence, and risk factors

The destruction of the myelin sheath that covers nerve cells prevents signals from being properly transmitted in the nerve. This decreases the nerve's ability to communicate with other cells.

The most common cause of central pontine myelinolysis is a quick change in the body's sodium levels. This most often occurs when someone is being treated for low levels of sodium (hyponatremia) and the levels rise too fast. It also can occasionally occur when high levels of sodium in the body (hypernatremia) are corrected too quickly.

This condition does not occur on its own. It is a complication of treatment for other conditions or from the other conditions themselves.

Risks include:

• Alcoholism
• General ill health
• Low sodium levels from any cause
• Malnutrition from serious illnesses
• Wernicke-Korsakoff syndrome

Symptoms

• Confusion, delirium
• Difficulty swallowing
• Double vision
• Muscle spasms in the face, arms, or legs
• Reduced alertness, drowsiness or sleepiness, lethargy, poor responses
• Reduced vision
• Speech changes, poor enunciation
• Weakness in the face, arms, or legs, usually affecting both sides of the body

Other possible symptoms include:

• Constipation
• Different size pupils in the eyes
• Hallucinations
• Hand tremor
• Uncontrollable eye movements

Signs and tests

An examination may show:

• Abnormal reflexes
• Cranial nerve VI paralysis (see cranial mononeuropathy VI)
• Involvement of all four arms and legs (spastic quadriplegia)
• Loss of eye muscle control
• Weakness of the face, arms, and legs (upper motor neuron syndromes)

A head MRI scan would reveal an abnormality in the brainstem (pons). This is the main diagnostic test.

Other tests may include:

• Blood sodium levels and other blood tests
• Brainstem auditory evoked response (BAER)