Rasmussen Encephalitis

Rasmussen’s encephalitis, Rasmussen syndrome, RE

Rasmussen encephalitis is a very rare brain condition that causes ongoing inflammation affecting one side of the brain, leading to frequent seizures that are difficult to control with medicine, progressive weakness on one side of the body, and mental decline.

Table of contents

• What is Rasmussen Encephalitis?
• Who is Affected
• Symptoms and Their Progression
• Possible Causes
• Diagnosis
• Stages of the Disease
• Treatment Options
• Outlook and Prognosis

What is Rasmussen Encephalitis?

Rasmussen encephalitis is a very rare condition that involves long-term worsening inflammation (swelling and irritation) of one half of the brain, called a hemisphere^[1]. This inflammation leads to frequent seizures and progressive, permanent brain damage^[1]. As the inflammation continues, it causes loss of function of the affected brain hemisphere, resulting in worsening weakness on one side of the body and mental decline^[1].

The condition is named after Theodore Rasmussen, a physician who first described it in 1958^[1]. Rasmussen encephalitis usually affects healthy individuals before symptoms begin^[2]. In most cases, only one hemisphere is affected, and the disease starts in one specific area and spreads across that hemisphere^[2].

Who is Affected

Rasmussen encephalitis is very rare. Researchers estimate that it affects about 2 out of every 10 million people^[1]. Some sources suggest there are an estimated 200 to 500 cases worldwide^[5], with no more than two new cases per year identified in large epilepsy centers^[2].

The condition most commonly affects children between the ages of 2 and 10^[1]. Most cases are seen in children around six to seven years old^[2]. However, Rasmussen encephalitis can also affect adolescents and adults. Around 10% of all cases occur in adolescents and adults^[2].

Symptoms and Their Progression

The first sign of Rasmussen encephalitis is typically a seizure^[1]. Mild weakness in the arm or leg is another common early symptom^[1]. Seizures may have different forms and characteristics, including simple partial seizures, complex partial seizures, generalized tonic-clonic seizures, or status epilepticus^[2].

The most notable seizure type in Rasmussen encephalitis is epilepsia partialis continua, which involves continuous twitching of the face, arm, or leg on one side of the body^[2]. About 50% of patients with Rasmussen encephalitis have this type of seizure^[2]. The seizures usually become frequent, happening every few seconds or minutes^[1]. They are also intractable, which means that medicine cannot completely control them^[1].

Within a few months to a couple of years of the first seizure, additional symptoms typically develop^[1]:

• Mental decline, including issues with thinking, memory, and intellect
• Progressive loss of motor (movement) skills on one side of the body, called hemiparesis (weakness), which often leads to hemiplegia (paralysis on one side of the body)
• Progressive loss of speech and language abilities, called aphasia, if the condition affects the side of the brain that controls language functions (usually the left hemisphere)
• Partial loss of sight in half of the visual field, called hemianopsia

The specific symptoms depend on which hemisphere is affected^[2]. Because of how the nervous system is wired, involvement of one hemisphere causes problems on the opposite side of the body. For example, if the left side of the brain is affected, weakness will appear on the right side of the body^[2].

Over time, patients may develop additional problems such as sensory deficits, dysarthria (difficulty speaking), dysphagia (swallowing difficulties), and psychiatric problems^[2]. Language and thinking disturbances are almost always seen in patients with left-side involvement^[2].

For most people, Rasmussen encephalitis is most severe during the first eight to 12 months after it starts^[1]. After this period, the progression of the condition seems to slow or stop, but the neurological damage is permanent^[1].

Possible Causes

Scientists do not know the exact cause of Rasmussen encephalitis, but there is increasing evidence of an underlying immune disorder^[2]. Researchers have two main theories^[1][5]:

Autoimmune disease theory: An autoimmune disease happens when the immune system attacks healthy tissue for unknown reasons. Researchers think Rasmussen encephalitis may be an autoimmune condition that affects one side of the brain^[1]. Studies suggest that the condition is probably driven by a T-cell response, which are immune cells that normally help fight infections^[3]. In Rasmussen encephalitis, these cells may mistakenly attack brain tissue^[5].

Infection theory: Rasmussen encephalitis may be the result of an unknown virus entering the brain^[1]. Some researchers have suggested that the immune response might be triggered by an infection such as influenza, measles, or cytomegalovirus^[5]. However, researchers have not identified a specific virus despite careful studies of affected brains^[1].

Diagnosis

Healthcare providers diagnose Rasmussen encephalitis based on symptoms and certain test results^[1]. If Rasmussen encephalitis is suspected, a detailed evaluation by a neurologist is necessary^[5]. The neurologist will conduct a detailed review of the patient’s medical history along with a neurological examination^[5].

Several diagnostic tests may be used^[5][6]:

• Magnetic resonance imaging (MRI): An MRI can show the shrinking (atrophy) and loss of brain tissue on one side of the brain. At the beginning of the disease, the MRI may be normal, but over time it shows progressive changes^[6].
• Electroencephalogram (EEG): This test records electrical activity in the brain and can identify unusual electrical activity patterns. An EEG is the most useful tool for understanding seizures^[5]. It can reveal how the brain is slowing or causing seizures in a localized area, one region, or an entire side, depending on the stage of disease^[6].
• CT scan: A CT scan may be conducted to produce a detailed map of the brain^[5].
• Blood tests may be used to look for signs of infection or to check how the body is functioning^[8].
• A lumbar puncture (spinal tap) may help diagnose encephalitis^[8].

Stages of the Disease

Rasmussen encephalitis progresses through three stages^[6]:

Prodromal stage: During this stage, a child experiences focal seizures intermittently, meaning the seizures are not frequent. The child often has no neurological problems at this point^[6]. This stage may last a few months^[4].

Acute stage: During this stage, which may last between four to eight months, the inflammation is active and symptoms worsen progressively^[4]. The seizures often become more frequent. The affected side of the brain loses volume (it shrinks), leading to problems with brain function in the region where seizures originate^[6]. Children may develop weakness, vision changes, and abnormal speech^[6].

Residual (chronic) stage: During this stage, the active immune damage lessens and there are fewer seizures. However, there is often significant shrinking in parts of the brain^[6]. While inflammation subsides, the neurological problems persist due to structural brain damage. Patients are often left with long-term epilepsy, paralysis or motor impairment, and cognitive difficulties, although the severity varies^[4].

Treatment Options

There is no cure for Rasmussen encephalitis, but certain treatments can help manage symptoms^[1]. Treatment focuses on managing symptoms and supporting the patient^[8].

Medications: Anti-seizure medications can help control seizures in some cases, but these medications are not helpful for most patients with Rasmussen encephalitis^[8][7]. The seizures are typically drug-resistant, meaning they fail to respond to antiseizure medications^[6]. Some research suggests that medications that reduce inflammation may help. Doctors may prescribe medications to help suppress the immune system, such as steroids and intravenous immunoglobulin, in some cases^[7].

Surgery: Surgery may be the only option to stop seizures and brain damage^[8]. A type of brain surgery called hemispherectomy or hemispherotomy may help treat some children with Rasmussen encephalitis^[7]. This procedure surgically disconnects the affected side of the brain from the unaffected side. The goal is to help decrease further damage and prevent seizures^[7]. Doctors will help families weigh the benefits and risks of this major surgery^[7].

Supportive care: When a patient has experienced brain damage, lifestyle changes and other supportive services may be needed. These can include breathing assistance, physical therapy, occupational therapy, and speech therapy^[8].

Outlook and Prognosis

The inflammation associated with Rasmussen encephalitis is thought to get progressively worse, peak, and then subside, leaving stable function but permanent brain damage^[5]. The neurological damage from the condition is permanent^[1].

Early diagnosis and treatment may lessen long-term disability in some cases^[4]. Despite the permanent effects of the condition, many patients can achieve improvements in quality of life with appropriate rehabilitation and support. A multidisciplinary approach involving neurologists, neurosurgeons, neuropsychologists, therapists, and other specialists is important for comprehensive care^[7].

Over time, frequent seizures lead to a decline in academic abilities and other neurological functions^[6]. However, with surgery and rehabilitation, some patients have been able to adapt and achieve significant functional improvements, even learning to walk again and returning to academic pursuits^[18].