What is the treatment approach for a pediatric patient with Rasmussen seizures?

Treatment of Rasmussen Encephalitis (Rasmussen Seizures)

Hemispheric surgery (hemispherectomy or hemispherotomy) is the only definitive treatment for controlling intractable seizures in Rasmussen encephalitis, though it should be viewed as palliative rather than curative, with 68% seizure freedom at 1 year declining to 22% at 10 years. 1

Understanding the Disease

Rasmussen encephalitis (RE) is a rare, severe immune-mediated brain disorder causing unilateral hemispheric atrophy, progressive neurological dysfunction, and drug-resistant seizures. 2 The condition predominantly affects children and is characterized by:

• Frequent, medically refractory seizures 3
• Progressive unilateral hemispheric atrophy 3, 2
• Progressive neurological deficits including hemiparesis and cognitive decline 4

The pathogenesis involves cytotoxic CD8+ T lymphocytes, activated microglia, and possible immune-mediated mechanisms, though no definitive viral or antigenic cause has been confirmed. 3

Diagnostic Confirmation

[18F]FDG PET and perfusion SPECT imaging are critical for early diagnosis and surgical planning, particularly when MRI findings are inconclusive. 5

• During early disease stages, functional imaging detects both hypermetabolism and hypometabolism depending on seizure status at examination 5
• The most crucial role of [18F]FDG PET is excluding bilateral hemispheric involvement, which fundamentally changes prognosis and surgical candidacy 5
• Functional imaging may identify abnormalities before structural MRI changes become apparent 5

Treatment Algorithm

Medical Management (Initial/Temporizing)

Immunotherapy may partially slow disease progression in early stages but does not provide definitive seizure control. 3

• Antiepileptic medications are uniformly ineffective for long-term seizure control 3, 4
• Immunotherapy targets initial T-cell and microglial-mediated brain damage 3
• Medical management should be viewed as a bridge to surgery, not definitive treatment 3, 2

Surgical Management (Definitive Treatment)

Surgery is the only effective method to control seizures in RE patients. 4

Surgical Options and Outcomes:

Anatomical hemispherectomy provides longer time to seizure recurrence compared to functional hemispherectomy (HR 0.078, p = 0.03). 1

• 80% of patients achieve Engel Class I outcomes (seizure freedom or rare disabling seizures) 4
• At 1 year post-surgery: 68% seizure freedom 1
• At 5 years post-surgery: 48% seizure freedom 1
• At 10 years post-surgery: 22% seizure freedom 1
• Median time to first seizure recurrence: 39 weeks (IQR 11-355 weeks) 1

Surgical Techniques Include:

• Anatomical hemispherectomy (preferred for durability) 1
• Functional hemispherectomy 4, 1
• Hemispherotomy 4
• Less extensive options (multilobar resection, selective resection) show no statistical difference in seizure outcomes compared to complete hemispherectomy 1

Functional Outcomes Post-Surgery:

• All patients show improved cognitive abilities after surgery (except those with bilateral RE) 4
• 68% can ambulate independently 1
• 84% retain speech ability 1
• Fine motor hand movements are typically lost on the affected side 4
• Most patients can walk independently post-operatively 4

Special Considerations for Adult-Onset RE

Adult-onset Rasmussen encephalitis progresses more slowly with more variable neurological deficits. 6

• Occipital lobe involvement is more common than in childhood-onset 6
• Atypical features include bilateral involvement, temporal lobe epilepsy patterns, or movement disorders 6
• Hemispheric disconnection surgery is generally NOT indicated in adults due to unacceptable functional consequences 6
• Medical immunotherapy becomes the primary treatment approach for adult-onset cases 6

Critical Pitfalls to Avoid

• Do not delay surgical evaluation while pursuing prolonged medical management - antiepileptic drugs are ineffective for long-term control 3, 4
• Always exclude bilateral hemispheric involvement before proceeding with hemispherectomy using [18F]FDG PET 5
• Do not present hemispheric surgery as curative - counsel families that this is palliative treatment with high likelihood of eventual seizure recurrence 1
• Recognize that anatomical hemispherectomy, while more invasive, provides superior durability compared to functional approaches 1
• Postoperative hydrocephalus can occur and requires monitoring 4

Timing of Surgery

Early surgical intervention is recommended once diagnosis is confirmed and medical management fails, as the disease causes progressive neurological deterioration. 2, 4 The optimal timing balances seizure control against inevitable functional deficits, though delaying surgery allows continued hemispheric damage without preventing ultimate functional loss. 4