Central Pontine Myelinolysis

Area of the brain known as the pons. Source: Wikimedia Commons

Central pontine myelinolysis (CPM) is a neurological disorder that most frequently occurs after too rapid medical correction of sodium deficiency (hyponatremia). The rapid rise in sodium concentration is accompanied by the movement of small molecules and water out of brain cells. Through a mechanism that is only partly understood, the shift in water and brain molecules leads to the destruction of myelin, a substance that surrounds and protects nerve fibers. Nerve cells (neurons) can also be damaged. Certain areas of the brain are particularly susceptible to myelinolysis, especially the part of the brainstem called the pons.  The pons relays information between the cerebellum and cerebrum. It regulates breathing and controls consciousness and arousal.

Signs and Symptoms

The initial symptoms of myelinolysis, which begin to appear two to three days after hyponatremia is corrected, include a depressed level of awareness, difficulty speaking (dysarthria or mutism), and difficulty swallowing (dysphagia).  Additional symptoms often arise over the next one to two weeks including impaired thinking, weakness or paralysis in the arms and legs, stiffness, impaired sensation, and difficulty with coordination.  At its most severe, myelinolysis can lead to coma, “locked-in” syndrome (which is the complete paralysis of all of the voluntary muscles in the body except for those that control the eyes), and death.

Although many affected people improve over weeks to months, some have permanent disability. Some also develop new symptoms later including behavioral or intellectual impairment or movement disorders like [[parkinsonism]] or tremor.

Causes

The destruction of the myelin sheath that coats nerve cells prevents signals from being properly conducted within the nerve. This decreases the nerve's 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. CPM also can occasionally occur when high levels of sodium in the body (hypernatremia) are corrected too quickly.

Diagnosis

• A neurological exam will show confusion, horizontal gaze paralysis (the person cannot look left or right), and spastic quadriplegia (the inability to control movements of tha arms and legs).

• An MRI of the brain will show an intense symmetric demyelination in the pons.

Treatment

The ideal treatment for myelinolysis is to prevent the disorder by identifying individuals at risk and following careful guidelines for evaluation and correction of hyponatremia. These guidelines aim to safely restore the serum sodium level, while protecting the brain. For those who have hyponatremia for at least two days, or for whom the duration is not known, the rate of rise in the serum sodium concentration is carefully controlled over a 24-hour period.

For those who develop myelinolysis, treatment is supportive. Some physicians have tried to treat myelinolysis with steroid medication or other experimental therapies, but none has been proven effective. Individuals are likely to require extensive and prolonged physical therapy and rehabilitation.  Those patients who develop parkinsonian symptoms may respond to the same drugs that work for individuals with Parkinson disease.

Prevention

Central pontine myelinolysis can be prevented by gradually, normalizing low or high sodium levels. It is important to understand that certain medications can change sodium levels very quickly.

Chances of Developing

Risk factors

Anyone, including adults and children, who undergoes a rapid rise in serum sodium is at risk for myelinolysis. Some individuals who are particularly vulnerable are chronic alcoholics and liver transplant patients. Myelinolysis has occurred in individuals undergoing renal dialysis, burn victims, people with HIV-AIDS, people over-using water loss pills (diuretics), and women with eating disorders such as anorexia or bulimia. The risk for CPM is greater if the serum (blood) sodium was consistently low for at least 2 days before correction.

Related Problems

Comorbidity

Some affected individuals will also have damage in other areas of the brain, which is called extrapontine myelinolysis (EPM).

Clinical Trials

No ongoing clinical trials were found at this time. Check here

Research

• A case of myelinolysis and quadriplegia associated with hypoglycemia after the administration of the antibiotic levofloxacin is reviewed. ^[1]
• Lithium toxicity in conjuction with hyponatremia is described as the contributing cause in a case of central pontine and extra-pontine myelinolysis in a pregnant woman. ^[2]
• Central pontine myelinolysis may occur in the absence of hyponatremia. A case of a woman with chronic alcoholism without hyponatremia which resulted in CPM is discussed. ^[3]

Expected Outcome

The prognosis for myelinolysis is variable. Some individuals die and others recover completely. Although the disorder was originally considered to have a mortality rate of 50% or more, improved imaging techniques and early diagnosis have led to a better prognosis for many people. Most individuals improve gradually, but still continue to have challenges with speech, walking, emotional ups and downs, and forgetfulness.

References

1. ↑ Vallurupalli S, Huesmann G, Gregory J, Jakoby MG 4th. Levofloxacin-associated hypoglycaemia complicated by pontine myelinolysis and quadriplegia. Diabet Med. 2008 Jul;25(7):856-9. Abstract
2. ↑ Bejot Y, Depierre P, Osseby GV, Troisgros O, Moreau T, Giroud M. Central pontine and extra-pontine myelinolysis: A complication of lithium toxicity in a pregnant woman. Clin Neurol Neurosurg. 2008 Jul 1. [Epub ahead of print] Abstract
3. ↑ Hagiwara K, Okada Y, Shida N, Yamashita Y. Extensive central and extrapontine myelinolysis in a case of chronic alcoholism without hyponatremia: a case report with analysis of serial MR findings. Intern Med. 2008;47(5):431-5. Epub 2008 Mar 3. Abstract | Full Text

External Links

American Academy of Neurology