Rasmussen's Encephalitis

🧠 Standard of Care & Symptoms

Rasmussen's Encephalitis (RE) is a rare, progressive chronic inflammatory disease of the brain that selectively affects a single cerebral hemisphere, leading to severe seizures and motor deficits.

• Presentation: Focal seizures, motor weakness, and cognitive decline.
  • Epilepsia Partialis Continua (EPC): The diagnostic hallmark. Rhythmic, continuous focal muscle jerking, typically involving one hand, arm, or half of the face. These jerks persist for hours, days, or weeks, and are highly resistant to standard anti-seizure drugs.
  • Hemiparesis: Progressive weakness or paralysis affecting the side of the body contralateral to the inflamed hemisphere.
  • Cognitive and Language Decline: Severe regression in intellectual abilities and language loss (Aphasia) if the dominant hemisphere is involved.

🧬 Diagnostics & CD8+ Cytotoxic Damage

Diagnosis combines structural brain imaging, electrophysiology, and histopathological analysis of biopsied tissue.

• Brain MRI: Demonstrates progressive, unilateral cortical atrophy, widening of the sulci, and expansion of the ipsilateral lateral ventricle. T2/FLAIR hyperintensity is typically visible in the subcortical white matter.
• Electroencephalogram (EEG): Documents unilateral slowing and multifocal epileptiform discharges over the affected hemisphere.
• Histopathology: Shows a chronic encephalitic process concentrated in one hemisphere. Key findings include:
  • CD8+ T-Cell Infiltration: Cytotoxic T-lymphocytes cluster around neurons and glial cells.
  • Microglial Nodules: Microglial aggregates surround and ingest dying neurons (**neuronophagia**).
  • Reactive Gliosis: Severe astrogliosis replacing necrotic cortical areas.

Pathogenesis & Granzyme-Mediated Apoptosis

The progressive brain tissue destruction in Rasmussen's Encephalitis is driven by an auto-aggressive cellular immune response:

• Cytotoxic T-Cell Targeting: Clonal expansions of cytotoxic **CD8+ T-lymphocytes** target unknown antigens on neurons and astrocytes within one cerebral hemisphere.
• Granzyme-B and Perforin Release: Upon contact, CD8+ T cells excrete perforin to form pores in the cell membrane, allowing **granzyme-B** to enter. Granzyme-B cleaves intracellular substrates, activating the caspase cascade and inducing apoptosis in healthy neurons.
• Microglial Aggregation: Activated microglia aggregate into **microglial nodules** to clear the apoptotic debris (neuronophagia). This localized destruction drives progressive cortical necrosis, leading to tissue loss and hemispheric atrophy.

💊 Immunotherapy & Functional Hemispherectomy

Management utilizes immunomodulation in early stages to delay decline, followed by surgical disconnection to cure intractable seizures.

Immunotherapy Protocols

• Corticosteroids & IVIG: High-dose intravenous methylprednisolone followed by monthly immunoglobulin (IVIG) infusions or plasma exchange can temporarily slow down the inflammatory destruction.
• Rituximab & Tacrolimus: Rituximab (anti-CD20) or oral tacrolimus is used in early stages to inhibit T-cell and B-cell activation, preserving cognitive function and slowing hemiparesis.

Surgical Cure: Functional Hemispherectomy

• Disconnection Surgery: The only definitive cure for the intractable seizures. The surgeon disconnects the diseased hemisphere from the healthy one (functional hemispherectomy) while leaving the tissue in place. This surgery halts seizures in > 80% of patients and prevents further cognitive decline. However, it leaves a permanent contralateral hemiparesis (loss of fine motor control in one hand) and homonymous hemianopia.

🔬 Active Clinical Trials

Clinical trials are currently evaluating Rituximab efficacy in slowing pediatric cognitive decline, advanced digital seizure-detection wearables for EPC, and postoperative physical rehabilitation models.

🗺️ Next Steps After Diagnosis

If you or a child have recently been diagnosed with Rasmussen's Encephalitis, establish these care pathways:

1. Perform Serial Brain MRIs: Compare scans over 3-6 months to document progressive, unilateral cortical atrophy.
2. Consult an Epilepsy Neurosurgeon: Establish contact early to evaluate if a functional hemispherectomy is indicated.
3. Discuss Immunotherapies: Ask your neurologist about starting IVIG, Rituximab, or Tacrolimus to help preserve brain function before surgery.
4. Initiate Physical Therapy: Focus on maintaining range of motion and core strength to manage progressive hemiparesis.

❓ Patient FAQ

Q: What is Epilepsia Partialis Continua (EPC)?
A: Epilepsia Partialis Continua (EPC) is a specific type of focal seizure characterized by continuous, rhythmic muscle jerking in a localized part of the body, such as one hand, arm, or face. Unlike typical seizures that end after a few minutes, EPC jerking goes on for hours, days, or even weeks. It does not affect awareness but is highly resistant to standard anti-seizure medications.

Q: Will my child recover motor function after a hemispherectomy?
A: Disconnecting half of the brain (functional hemispherectomy) cures the seizures but causes a permanent weakness on the opposite side of the body (hemiparesis) and loss of side vision (hemianopia). However, children have remarkable brain plasticity. With intensive physical therapy, most children learn to walk independently, run, and talk normally, though they will lose fine motor control in the affected hand.