Rasmussen syndrome, also known as Rasmussen's encephalitis, is a rare progressive autoimmune neurological disease. It is characterized by frequent and severe focal seizures, progressive neurological decline, hemiparesis (weakness on one side of the body), encephalitis, and unilateral cerebral atrophy. The disease primarily affects children under the age of 15, though adult cases have been reported. Originally described as a form of chronic focal motor epilepsy by Dr. A. Ya. Kozhevnikov in the 1880s and separately identified as focal seizures due to chronic localized encephalitis in the 1950s by Dr. Theodore Rasmussen. It is now classified to be a cytotoxic T-cell–mediated encephalitis.

Signs and symptoms

The hallmark symptoms are focal seizures, particularly epilepsia partialis continua (EPC), a form of epilepsy characterized by continuous or near-continuous clonic movements in a localized body part. Over time as the disease advances, patients develop hemiparesis, hemianopia (vision loss of one side of visual field), and cognitive deficits, involving learning, memory or language. In this phase, an MRI often reveals hemispheric swelling and beginning signs of atrophy.

The chronic or residual stage occurs after inflammation subsides. While the active immune damage lessens, the neurological deficits persist due to structural brain damage. Patients are often left with long-term epilepsy, paralysis/motor impairment, and cognitive dysfunction, although the severity varies.

Rasmussen's Encephalitis is most commonly diagnosed in children, with an average age of 6 years. However, approximately 10% of reported cases begin in adulthood.

Pathophysiology

Rasmussen's encephalitis is theorized as a T-cell-mediated autoimmune encephalitis, characterized by chronic, progressive inflammation limited to a single hemisphere of the brain. Recent research has identified auto antibodies against the anti-NDMA receptor subunit GluRepsilon2 (NR2A), these are not consistently present across cases and may represent a secondary epiphenomenon rather than a primary pathogenic mechanism. There is limited evidence for auto antibodies targeting the nicotinic acetylcholine receptor.

Rare associations with systemic autoimmune disorders, such as neurovisceral porphyria and acute intermittent porphyria, have been reported in isolated cases.

Diagnosis

thumb|[[Brain biopsy in Rasmussen's encephalitis showing lymphocytic infiltrates staining for CD8 on immunohistochemistry]]Early multidisciplinary diagnostic approach is essential as delayed diagnosis may lead to irreversible neurological decline. Other immunotherapies such as plasmapheresis, azathioprine, cyclophosphamide, mycophenolate mofetil, and tacrolimus have been used at varying success, though clinical trials are still in progress.

The RE Children's Project was founded in 2010 to increase awareness of Rasmussen's encephalitis. Its primary purpose is to support scientific research directed toward finding a cure for this disease.

References

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