Neurosurgery notes/Other specialities/Neurology/Neuroinflam/Rasmussen’s encephalitis

Rasmussen’s encephalitis

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Neuroinflam

Definition

  • A progressive disease with unihemispheric brain atrophy characterized by
    • Drug-resistant focal epilepsy
    • Progressive hemiplegia
    • Cognitive decline

Numbers

  • Rare
  • Affects mostly children or young adults.
  • 2·4 cases per 10 million people aged 18 years and younger per year

Aetiology

  • Unknown
  • May be due to CMV infection or antibodies to glutamate receptors

Pathophysiology

  • Antigen form from foreign (an infectious agent) or autoimmune → inflammation of one hemisphere
  • Microscopy: have reminiscent features of chronic viral encephalitis.
    • Presence of
      • Lymphocyte cuffs around blood vessels,
      • Widespread or clustered lymphocytes and microglia (or so called microglial nodules),
      • Neurophagia
    • These features are most often unilateral and located in the neocortex, hippocampus, subjacent white matter, and basal ganglia.
    • This is seen in addition to chronic leptomeningitis

Diagnostic criteria

  • Part A (all three) OR
    • Clinical
      • Focal seizures (with or without epilepsia partialis continua) and unilateral cortical deficits
    • Electroencephalogram
      • Unihemispheric slowing with or without epileptiform activity and unilateral seizure onset
    • MRI
      • Unihemispheric focal cortical atrophy and at least one of the following:
      • Grey or white matter T2/FLAIR hyperintense signal
      • Hyperintense signal or atrophy of the ipsilateral caudate head
  • Part B (two of three)
    • Clinical
      • Epilepsia partialis continua or progressive* unilateral cortical deficits
    • MRI
      • Progressive* unihemispheric focal cortical atrophy
    • Histopathology
      • T-cell-dominated encephalitis with activated microglial cells typically, but not necessarily, forming nodules and reactive astrogliosis;
      • Numerous parenchymal macrophages, B cells, or plasma cells or viral inclusion bodies exclude the diagnosis of Rasmussen’s encephalitis

Natural history

  • The disease might have a preceding prodromal stage with infrequent seizures, and presents with an acute stage of drug-resistant epilepsy.
  • The epilepsy is characterised by very frequent seizures of different semiologies in the same patient, often epilepsia partialis continua, with the emergence of a fluctuating then permanent hemiplegia (motor function) and concurrent progressive hemispheric volume loss on neuroimaging.
  • With the advent of immunotherapy, the natural clinical course seems to be changing.
    • The rate of motor function and hemispheric volume loss is slowed, and seizures decrease in frequency and plateau.
  • Cognitive deterioration is not shown because it is more variable, although usually becomes manifest during the acute phase.
    • EPC=epilepsia partialis continua.
  • Three disease stages of Rasmussen’s encephalitis
    • Prodromal stage
      • Non-specific, low seizure frequency, and mild hemiplegia
    • Acute stage
      • Frequent seizures, often epilepsia partialis continua; progressive hemiparesis, hemianopia, cognitive deterioration, and aphasia (if dominant hemisphere affected)
    • Residual stage
      • Permanent and stable neurological deficits and continuing seizures
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Clinical presentation

  • Children
    • Median age of onset is 6 years
    • Seizure
      • 50% have epilepsia partialis continua
        • A variant of simple focal motor status epilepticus in which frequent repetitive muscle jerks, usually arrhythmic, continue over prolonged periods of time.
      • As the disease progresses, different focal seizure semiologies emerge, suggesting newly affected areas of inflammation in the hemisphere
    • Untreated, children will develop hemiparesis, hemianopia, and cognitive decline within a year of epilepsy onset, and if the language-dominant hemisphere is affected, dysphasia.
  • Adolescent or adult
    • 10%
    • Vs children, adults have
      • Slower clinical course
      • Final deficits are not as severe
    • Semiology can be more characteristic of temporal lobe epilepsy
    • Unilateral movement disorders, including hemiathetosis and hemidystonia
Rasmussen's Encephalitis
 

Radiology

  • MRI brain scans of children with Rasmussen’s encephalitis, showing contrasting cases of radiological progression.
    • (A) Progressive right hemisphere atrophy, high signal and basal ganglia loss over 1 year (from left to right) in a child with Rasmussen’s encephalitis. The disease was mostly centred near the right Sylvian fissure (arrow).
    • (B) Slowly progressive disease with more subtle right hemisphere atrophy in a child on immunosuppressant treatment at 6 months (left), 18 months (centre), and 30 months (right) of disease course.
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Treatment

  • General
    • Antiepileptic drugs have a limited effect on seizures and disease progression in Rasmussen’s encephalitis.
    • Epilepsia partialis continua in particular tends to be refractory to antiepileptic drugs.
    • Realistic aim of antiepileptic drug therapy in Rasmussen’s encephalitis should be to protect the patient from the most severe seizures, namely bilateral convulsive seizures, rather than to achieve seizure freedom.
  • Aim
    • Reduce seizure severity and frequency
    • Improve the functional long-term outcome, as measured by both motor and cognitive performance.
  • Options
    • Botulinum toxin injected into the
      • Zygomaticus for facial myoclonus
      • Upper limb muscles for localised epilepsia partialis continua, reducing painful spasms and improving functional use of the limb
    • Future immunotherapy
    • Hemispherectomy (functional/anatomical)
      • Only effective surgery
      • To protect the contralateral normal hemisphere from repeated seizures and progressive neuropsychological loss

Management

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Reference