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Understanding Encephalitis

Not to be confused with Encephalopathy:

Encephalitis - the brain itself is swollen or inflamed

Encephalopathy - refers to the mental state that can happen because of multiple types of health problems.

However, Encephalitis can cause Encephalopathy

Since our Central Nervous System is made up of both the brain and the spinal cord an important distinction to note:

Encephalitis is the inflammation of the brain and Myelitis is the inflammation of the spinal cord. However, when both the brain and the spinal cord are involved, the condition is called Encephalomyelitis.

Let’s move onto the EEG patterns and some possible causes:

Patterns observed with EEG for patients who have encephalitis are usually known as generalized nonspecific cerebral abnormalities including background slowing, rhythmic slow-wave activity (theta or delta activity), or spike discharges.


Spike discharges

Some examples of Encephalitis:

Subacute sclerosing pan-encephalitis (SSPE)

This neurodegenerative complication of the measles virus infection in childhood is worthy of mention; due to the decline in the measles vaccination, it is becoming more likely to be seen in years to come. The characteristic EEG pattern is high voltage periodic complexes, usually generalized or bilateral.

It’s Morphology can differ between patients. The periodicity varies from a few to many seconds, with a gradual reduction of the interval between complexes, and eventual disappearance of complexes as disease progresses. Background cerebral activity between complexes is initially normal, with increasing slow activity and then attenuation in later stages. The complexes are usually associated with myoclonic jerks. Most SSPE presents in children and adolescents.

Autoimmune Encephalitis (AE)

Traditional encephalitis is caused by a virus or bacteria. But autoimmune encephalitis occurs when the body's immune system unexpectedly creates antibodies to attack the brain.

Autoimmune encephalitis (AE) is characterized by rapidly progressive encephalopathy with subacute memory impairment, confusion, and often seizures caused by inflammation of the central nervous system.

Autoimmune encephalitis is often associated with seizures and is increasingly recognized as a common cause of new-onset refractory status epilepticus (NORSE).

Herpes Simplex Encephalitis (HSE)

The EEG in the acute stage of herpes simplex encephalitis (HSE) can show a variety of abnormalities, including uni- or bilateral periodic sharp waves or attenuation of amplitude, focal or generalized slow waves or epileptiform discharges, or electrical seizures. Most familiar is the description of periodic lateralized epileptiform discharges or (PLEDs). One thing to note is that PLEDS are often absent early on.

Creutzfeldt-Jacob disease (CJD)

This is definitely a board exam favorite!

Creutzfeldt-Jakob disease, also known as CJD, is a rare degenerative disease of the brain that is fatal. It is one of a group of diseases known as the transmissible spongiform encephalopathies.

Creutzfeldt-Jakob (KROITS-felt YAH-kobe) disease, also known as CJD, is a rare brain disorder that leads to dementia. It belongs to a group of human and animal diseases known as prion disorders. Symptoms of Creutzfeldt-Jakob disease can be similar to those of Alzheimer's disease. But Creutzfeldt-Jakob disease usually gets worse much faster and leads to death.

Creutzfeldt-Jakob disease (CJD) received public attention back in the 1990s when some people in the UK became sick with a form of the disease. They developed variant CJ, known as vCJD, after eating meat from diseased cattle. However, most cases of Creutzfeldt-Jakob disease haven't been linked to eating beef.

All types of CJD are serious but they are very rare. About 1 to 2 cases of CJD are diagnosed per million people around the world each year. The disease most often affects older adults.

The risk of getting CJD is low. The disease can't be spread through coughing or sneezing. CJD can develop in three ways:

  • Sporadically. Most people with Creutzfeldt-Jakob disease develop the disease for no apparent reason. This type, called spontaneous CJD or sporadic CJD, accounts for most cases.

  • By inheritance. Fewer than 15% of people with CJD have a family history. They may test positive for genetic changes associated with the disease. This type is referred to as familial CJD.

  • By contamination. A small number of people have developed CJD as a result of medical procedures. These procedures included injections of pituitary human growth hormone from an infected source. They also included cornea and skin transplants from people who had CJD. Medical centers have changed their procedures to eliminate these risks.

Also, a few people have developed Creutzfeldt-Jakob disease after brain surgery with contaminated instruments. This happened because standard cleaning methods don't destroy the prions that cause the disease. Today instruments that may have been contaminated with CJD are destroyed.

Rasmussen syndrome or Rasmussen Encephalitis

Fun fact: The condition is named after Theodore Rasmussen, a neurosurgeon who first described it in 1958.

Rasmussen's encephalitis is a progressive disease characterised by drug-resistant focal epilepsy, progressive hemiplegia, and cognitive decline, with unihemispheric brain atrophy. The disorder is rare and affects mostly children or young adults.

Rasmussen's encephalitis (RE) is a very rare, chronic inflammatory neurological disease that usually affects only one hemisphere (half) of the brain. It most often occurs in children under the age of 10 but can also affect adolescents and adults.

It is characterized by the onset of intractable focal seizures together with progressive hemiparesis in a previously normal child. Progressive cognitive impairment may also develop.

These patients have frequent and often drug resistant focal motor seizures that may evolve to bilateral tonic clonic seizures

This deep dive touched on several types of Encephalitis - but this broad specific brain condition can have many causes and immediate treatment is essential. As technologists our role is critical in ensuring physicians have the tools they need to best take care of these patients. Knowing the key distinctions to recognize and understand these conditions are essential to our contribution to their care.

Roya Tompkins, MS, REEG/EP T, RPSGT


Medscape: Encephalopathic EEG patterns

Journal of Neuro Crital Care


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