Central pontine myelinolysis

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at September 20, 2016
StartDiseasesCentral pontine myelinolysis

Central pontine myelinolysis (CPM) is a neurological disorder that affects the brainstem. Central pontine myelinolysis, also known as osmotic demylination syndrome or central pontine demyelination, occurs most often in response to treatment for hyponatrenia. CPM can cause serious complications, such as locked-in syndrome, permanent disability, and coma. While there is no cure for CPM, symptoms of the disease can be managed.


Definition & Facts

CPM is a neurological disorder in which the myelin sheath which covers the nerve cells in the brain are severely damaged. Specifically, the nerve cells in the pons, located in the brainstem, are destroyed. The pons serves as a message center for several areas in the brain. Without the pons, the brain is not able to function because messages cannot be transmitted.

Additionally, many important nerves, such as the trigeminal nerve, abducens nerve, vestibulocochlear nerve, and facial nerves originate in the pons. The pons also plays an important role in controlling sleep cycles.

CPM was first described in a paper by Adams and colleagues in 1958. “Pontine” refers to the brainstem while, “myelinolysis” refers to the destruction of the myelin that protects the nerves. CPM is typically caused by another medical condition.

Symptoms & Complaints

CPM affects both movement and cognition. Poor or delayed responses and reflexes, tremors, poor balance, difficulty swallowing, and poor enunciation or slowed speech are all symptoms of CPM.

Muscle weakness in the face, arms, and legs may also occur, and both sides of the body are usually affected. Those with central pontine myelinolysis may also experience confusion or delirium, hallucinations, and decreased alertness, sleepiness, drowsiness, or lethargy.

CPM may lead to serious complications, such as permanent disability where an individual needs help with daily activities, such as bathing, eating, and toileting.

Locked-in syndrome may also result from CPM. Locked-in syndrome is a rare neurological disorder where a person's voluntary muscles are completely paralyzed except for the muscles controlling eye movement. Those with locked-in syndrome are awake and conscious, but they lack the ability to speak or move.

Though some people with CPM can improve with appropriate treatment, the nerve damage caused by the disorder is long-term, and the symptoms one experiences as a result are usually chronic. Many people with CPM will have chronic problems with mobility, response time, and balance. Others may be permanently disabled.


The most common cause of CPM is a sudden rise in the body's sodium level. This most often occurs when someone is treated for hyponatremia (low sodium levels in the blood). Sodium is an electrolyte and helps maintain the amount of water in and around the cells in the body. Symptoms of hyponatremia include headache, nausea, vomiting, confusion, seizures, fatigue, irritability and restlessness, coma, and muscle spasms, muscle cramps, or weakness. Occasionally CPM can also be caused when hypernatremia (high sodium levels in the blood) is treated too quickly.

Liver disease, chronic alcoholism, and malnutrition increase one's risk of developing central pontine myelinolysis because these conditions can change the sodium levels in the blood. Patients may also develop CPM after a liver transplant. Individuals with Wilson's disease or neoplasia as well as burn victims are also at increased risk.

Diagnosis & Tests

A doctor will be able to recognize abnormal reflexes and responses, confusion, slowed speech or poor enunciation, and muscle weakness with a physical examination, but she cannot diagnose CPM based on a physical exam alone. A blood test can be used to measure sodium levels in the blood.

A magnetic resonance imaging (MRI) scan is the most useful diagnostic tool for central pontine myelinolysis. An MRI scan utilizes field gradients, magnetic fields, and radio waves to create images of the brain. An MRI scan will be able to clearly show where and how much damage has been done to the myelin sheaths covering the nerves in the brainstem. However, it may take weeks before nerve damage shows up on an MRI scan.

A physician may also order a brainstem auditory evoked response (BAER) test. BAER is utilized in the diagnosis of nervous system disorders. During the BAER, the patient sits in a reclining chair or lies on a table. Electrodes are placed on the patient's scalp and earlobes. The patient then listens to a series of clicks or tones through a pair of headphones, and the brain's response is measured. Abnormal test results help support a diagnosis of central pontine myelinolysis.

Treatment & Therapy

Central pontine myelinolysis is a medical emergency. Someone experiencing symptoms of the condition should go to the hospital immediately, though most individuals who develop CPM are already in the hospital for another medical condition. Fluids and medication to stabilize sodium levels in the blood is the first line of treatment for CPM.

Once sodium levels are stabilized, treatment focuses on the management of symptoms. Dopaminergic medications, such as levodopa and others utilized in the treatment of Parkinson's disease can be used to help control tremors and improve one's ability to speak and swallow.

Physical therapy may also be helpful for those who have CPM. Muscle strengthening, coordination, balance, range of motion, and ambulation (walking) exercises can help a patient improve and maintain balance, range of motion, and muscle strength.

Though some people still die as a result of central pontine myelinolysis, most survive. One's prognosis largely depends on how many nerves in the pons are damaged. Early diagnosis and treatment lead to the best outcomes.

Prevention & Prophylaxis

Gradual and controlled treatment of low sodium levels in the blood help prevent the development of CPM. Knowing the symptoms of low sodium levels in the blood and getting treatment for them right away can also help someone prevent this neurological condition.

Alcoholics should seek help for their condition which may take the form of psychotherapy, group therapy, and other options in order to reduce their risk of developing central pontine myelinolysis among other health conditions

Central pontine myelinolysis is a serious neurological disorder affecting the pons. The condition can lead to major complications and permanent disability for those who develop it. Early diagnosis and treatment tend to lead to the best treatment outcomes.