Encephalopathy

Encephalopathy is a term for any diffuse disease of the brain that alters brain function or structure. Encephalopathy may be caused by advanced and severe disease states, infections, or as a result of taking certain medications. The three main causes of encephalopathy are liver disease, kidney disease, and lack of oxygen to the brain. Symptoms can include subtle personality changes, inability to concentrate, lack of energy, fatigue, progressive loss of consciousness, and abnormal involuntary movements. Symptoms vary with the severity and type of encephalopathy.

Encephalopathy may vary in severity from only subtle changes in mental state to a more advanced state that can lead to deep coma. Cerebral edema or brain swelling is common in severe encephalopathy and causes an increase in pressure inside the skull.

Types

Encephalopathy can be caused by many things. Some of the types of encephalopathy include:

• Hypoxic Encephalopathy occurs when the brain does not receive enough oxygen; this can occur if there is inadequate oxygen in the blood or if there is inadequate blood flow (perfusion) to the brain. As a result, the brain is damaged. Causes of hypoxia include: respiratory failure, smoke inhalation, carbon monoxide poisoning, heart attack (cardiac arrest), birth injuries during the birthing process (severe hemorrhage), severe blood loss, drowning, strangulation, asphyxiation caused by smoke inhalation, choking, compressions of the trachea (windpipe), high altitudes, complications of anesthesia, and paralysis of respiratory muscles.

• Hepatic Encephalopathy. Occurs when liver diseases suchs as hepatititis, cirrhosis, or liver failure cause toxins to accumulate and damage the brain and nervous system. The liver normaly removes these toxins from the body. However, when the liver does not work properly, these substance can build up.^[1]

• Uremic Encephalopathy.Occurs as a result of end-stage renal (kidney) disease and failure results in the build up of toxins that can damage the brain and nervous system.^[2]

• Transmissible Spongiform Encephalopathy. This is a type of encephalopathy that is caused by an infectious agent. Two forms are bovine spongiform encephalopathy (BSE), also known as mad cow disease, and variant Creutzfeldt-Jakob disease (CJD). These conditions are caused by a particle called a prion which is made up of an abnormal protein and is capable of being transmitted to an animal and/or human.^[3]

Signs and Symptoms

The main feature of encephalopathy is an altered mental state. Depending on the type and severity of encephalopathy, common neurological symptoms are progressive loss of memory, loss of the ability to think, personality changes, inability to concentrate, lethargy, and progressive loss of consciousness. Other neurological symptoms may include myoclonus (involuntary twitching of a muscle or group of muscles), nystagmus (rapid, involuntary eye movement), tremor, muscle wasting and weakness, dementia, seizures, and loss of ability to swallow or speak.

Causes

Encephalopathy may be caused by infectious agents such as bacteria or viruses. It can also be caused by metabolic disturbances, brain tumors, increased pressure in the skull, prolonged exposure to toxic elements (including solvents, drugs, radiation, paints, industrial chemicals, and certain metals), chronic progressive trauma, poor nutrition, or lack of oxygen or blood flow to the brain.

Diagnosis

Many tests are used in the diagnosis of encephalopathy. These tests will vary based on what the doctor suspects is the cause of the symptoms. Blood tests (including complete blood count, ammonia, glucose, and lactate levels), blood cultures (to determine if bacteria are present), spinal fluid examination, kidney function tests, imaging studies, electroencephalograms (EEGs), head CT or MRI, and similar diagnostic studies may be used to differentiate the various causes of encephalopathy.

Treatment

Treatment depends on and varies according to the type and severity of the encephalopathy. A doctor will provide specific instructions for proper care and treatment. Anticonvulsants (anti-seizure medicines) may be prescribed to reduce or halt any seizures. Changes to diet and nutritional supplements may help some patients. In severe cases, dialysis or organ replacement surgery may be needed.

Clinical Trials

Several clinical trials are examining the safety and efficacy of treatments for different types of encephalopathy. For hepatic encephalopathy, studies are examining the potential benefits of exercise or drugs to reduce the amount of ammonia in the blood. Another promising idea is the use of erythropoietin, a drug which slows or prevents apoptosis (cell death), to prevent permanant damage in asphyxiated infants.

Prognosis

Treating the underlying cause of the disorder may improve symptoms. If the source can be found in time, there is a good chance of a favorable outcome. However, if prolonged the encephalopathy may cause permanent structural changes and irreversible damage to the brain. Some encephalopathies can be fatal.

References

1. ↑ Butterworth RF. Hepatic encephalopathy. Alcohol Res Health. 2003;27(3):240-6. Abstract
2. ↑ Moe SM, Sprague SM. Uremic encephalopathy. Clin Nephrol. 1994 Oct;42(4):251-6. Abstract
3. ↑ Brown P. Bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease. BMJ. 2001 Apr 7;322(7290):841-4. Citation | Full Text | PDF