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

The destruction of the myelin sheath that coats nerve cells prevents signals from being properly conducted within the nerve. This decreases its ability to communicate with other cells. The most common cause of central pontine myelinolysis is a rapid, drastic change in sodium levels in the body. Most commonly, this 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 the other conditions themselves.

People at risk include those with low sodium levels from any cause, alcoholism, Wernicke-Korsakoff syndrome, general ill health, and malnutrition associated with serious illnesses.

• Weakness in the face, arms, or legs, usually affecting both sides of the body
• Muscle spasms in the face, arms, or legs
• Double vision
• Reduced vision
• Confusion, delirium
• Speech changes, poor enunciation
• Difficulty swallowing
• Reduced alertness, drowsy or sleepy, lethargic, poorly responsive

• Hand tremor
• Hallucinations
• Eyes -- pupils different size
• Uncontrollable eye movements
• Constipation

An examination may indicate involvement of all four arms and legs (spastic quadriplegia) or weakness of the face, arms, and legs (upper motor neuron syndromes). Reflexes may be abnormal. An eye examination may show loss of control of eye muscles, particularly cranial nerve VI paralysis (see cranial mononeuropathy VI).

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 evoked response audiometry (BERA)