Types of Encephalopathy | Knowledge Brush-Up

I have always enjoyed pulling together the clinical puzzle pieces for my assigned patients. Recently, I needed a “brush up” on my knowledge to understand the different types and causes of encephalopathy. I’m all about sharing information, so here is a summary of what I learned.

Traumatic Encephalopathy

Chronic traumatic encephalopathy (CTE) is a brain disease usually caused by repeated head traumas. A diagnosis can only be made after an autopsy to study sections of the brain is done. Therefore, CTE is rare and not well understood at this time. Here are a few key points:

• Majority of CTE cases occur in athletes that play contact sports, such as football, hockey, and boxing. It may also occur in military personnel that have been exposed to explosive blasts.

• CTE is the result of multiple head traumas over a period of time. However, symptoms usually appear until years, sometimes decades, after the head injury. A 2017 study looked at 111 brains of former deceased NFL players and found 110 of the 111 showed clear signs of CTE post-mortem. It is not known just how many people are living with CTE.

Toxic Encephalopathy

Underlying conditions, such as infection or exposure to toxic substances can cause toxins to build up in the blood and eventually damage the brain. There are three types of toxic encephalopathy: hepatic, uremic and infectious.

Hepatic Encephalopathy

This type of encephalopathy occurs when the liver is unable to remove toxins, such as ammonia, from our blood. Toxins can build up to the point of entering into the brain, causing confusion, mood changes and other symptoms. Here are a few of the conditions that can contribute to hepatic encephalopathy:

• Dehydration
• Alcoholic binges
• Overdose of certain drugs

Uremic Encephalopathy

This type of encephalopathy occurs when our kidneys are unable to remove toxins and waste products, like uremia, from our blood. In kidney failure and acute kidney injury, toxins build in the blood and affect the brain. This build up usually occurs when the estimated glomerular filtration rate (eGFR) falls and remains below 15mL/min.

Infectious Encephalopathy

This type of encephalopathy occurs when infection causes inflammation of the brain tissue or the tissues that line the brain or spinal cord. The source of infection may be a bacteria, virus or fungus. Jakob-Creutzfeldt disease is a rare form of infectious encephalopathy caused by prions, which are a type of protein. Infections in other parts of the body, such as urinary tract infections or sepsis can also lead to infectious encephalopathy.

About Metabolic Encephalopathy

This is the diagnosis that sparked my quest for information. Metabolic encephalopathy is an umbrella term for all of the above types of toxic encephalopathy. I most often care for patients with a metabolic encephalopathy diagnosis linked to:

• Sepsis
• Urinary tract infections
• Pneumonia
• Bacteremia
• Malignant hypertension
• Dehydration and acute kidney injury
• Drug overdose
• Diabetic ketoacidosis

Wernicke's Encephalopathy

This condition, also known as Wernicke’s disease, is caused by vitamin B deficiency from alcoholism, poor nutritional intake, or poor food absorption.

Hashimoto Encephalopathy

This rare type of encephalopathy occurs in people with Hashimoto’s disease. Hashimoto’s disease is a rare autoimmune condition that causes your immune system to attack your thyroid. How the condition is linked to infectious encephalitis is not well understood.

Glycine Encephalopathy

Glycine encephalopathy occurs when high levels of glycine, an amino acid, builds in the brain. The condition is genetic and usually appears soon after birth.

Hypoxic-ischemic Encephalopathy

This type occurs when your brain does not get enough oxygen, which results in brain damage. Hypoxia may be because of carbon monoxide poisoning, cardiac arrest or near-drowning.

Let’s Hear from You

What types of encephalopathy do you encounter in your own practice?

References

Cruetzfeldt-Jakob Fact Sheet (CDC)

Study aims to track mild traumatic brain injuries over decades

National Institute of Health’s Encephalopathy Information Page

What Is Encephalopathy?