Rasmussen syndrome

Overview

Rasmussen syndrome, also known as Rasmussen's encephalitis, is a rare, chronic inflammatory neurological disorder that primarily affects one hemisphere of the brain. It typically begins in childhood, most commonly between the ages of 2 and 10, but can occasionally present in adolescents and adults. The condition is characterized by frequent and severe seizures, progressive neurological decline, and loss of motor skills and speech due to ongoing inflammation and deterioration of brain tissue in the affected hemisphere.

First described by Dr. Theodore Rasmussen in the 1950s, this syndrome is particularly challenging due to its aggressive progression and resistance to anti-seizure medications. While rare, its debilitating nature demands early diagnosis and, in many cases, surgical intervention to preserve quality of life.

Causes

The exact cause of Rasmussen syndrome is not fully understood, but it is believed to be an autoimmune disorder. In this condition, the body's immune system mistakenly attacks healthy brain tissue, leading to inflammation, neuronal loss, and brain atrophy in one hemisphere.

Potential causes or contributing factors include:

• Autoimmune reaction: The presence of specific autoantibodies and cytotoxic T-cells attacking brain tissue supports an immune-mediated mechanism

• Genetic susceptibility: Though no single gene has been conclusively identified, genetic predisposition may play a role

• Viral triggers: Some researchers speculate that a viral infection could initiate the autoimmune response, but no specific pathogen has been confirmed

Symptoms

The symptoms of Rasmussen syndrome often develop in three phases: prodromal, acute, and residual. The most prominent and early symptom is intractable focal seizures, which progressively worsen over time.

Prodromal Phase

• Occasional seizures

• Mild weakness on one side of the body (hemiparesis)

• Subtle cognitive or behavioral changes

Acute Phase

• Frequent seizures, including epilepsia partialis continua (continuous focal motor seizures)

• Progressive weakness and paralysis on the opposite side of the affected hemisphere

• Loss of speech and language skills (aphasia), if the dominant hemisphere is involved

• Cognitive decline

Residual Phase

• Permanent neurological deficits such as hemiplegia (paralysis)

• Seizures may stabilize but often remain difficult to control

• Intellectual impairment and learning difficulties

Seizures in Rasmussen syndrome are often resistant to standard antiepileptic drugs and may be frequent and disabling.

Diagnosis

Diagnosis of Rasmussen syndrome involves a combination of clinical assessment, neuroimaging, electroencephalography (EEG), and sometimes brain biopsy. Key diagnostic tools include:

• Magnetic Resonance Imaging (MRI): Shows progressive atrophy and inflammation in one cerebral hemisphere

• EEG: Reveals unilateral epileptic activity, often consistent with epilepsia partialis continua

• Neurological examination: Identifies progressive motor and cognitive decline on the contralateral side

• CSF analysis: May show signs of inflammation, though not always conclusive

• Brain biopsy: Occasionally performed to confirm diagnosis and rule out other inflammatory or infectious causes

Rasmussen syndrome is a clinical diagnosis supported by imaging and EEG findings. Early detection is critical to improve outcomes and consider timely surgical treatment.

Treatment

Treatment of Rasmussen syndrome focuses on controlling seizures and slowing neurological decline. It typically involves a combination of medical and surgical approaches:

Medical Treatment

• Antiepileptic drugs (AEDs): Used to reduce seizure frequency, although often ineffective in fully controlling seizures

• Immunomodulatory therapies: Aim to suppress the autoimmune response and include:

  • Corticosteroids (e.g., prednisone)

  • Intravenous immunoglobulin (IVIG)

  • Plasmapheresis (plasma exchange)

  • Immunosuppressive drugs (e.g., tacrolimus, azathioprine)

Surgical Treatment

If seizures remain uncontrolled and neurological decline continues, surgical intervention may be necessary:

• Functional hemispherotomy or hemispherectomy: A major surgical procedure that disconnects or removes the affected hemisphere to stop seizure activity

While surgery results in permanent loss of function on the affected side of the body, it often leads to a significant reduction or complete cessation of seizures and can prevent further cognitive decline.

Prognosis

The prognosis for Rasmussen syndrome varies depending on how early it is diagnosed and how effectively it is treated. Without treatment, the condition leads to progressive neurological deterioration, severe disability, and lifelong epilepsy.

With timely surgical intervention, especially hemispherotomy, many patients experience significant seizure reduction and improved quality of life, although they often retain hemiparesis and other deficits. Lifelong rehabilitation and special education services are typically needed to support developmental and functional outcomes.

While there is currently no cure, ongoing research into immunotherapies and neuroprotective strategies offers hope for improved management of this challenging condition.