Rasmussen encephalitis (RE), also known as chronic focal encephalitis (and not to be confused with a Rasmussen aneurysm), is a chronic inflammatory disease of unknown origin, usually affecting one brain hemisphere.
Children of ten years or younger age group are affected in 85% cases 1. However, disease detection rate in adults is increasing with routine MRI investigations in intractable seizure patients 5.
Pathologic features are similar to viral encephalitis, with lymphocytes around round cells and diffuse proliferation of microglia. However, later spongiform degeneration and cortical atrophy sets in.
The observed inflammatory changes in RE include perivascular cuffing, microglial nodules, T lymphocytic infiltration gliosis, meningeal inflammation, and neuronal injury or loss 9,10.
Autoimmune mechanism has also been proposed describing antibodies against GluR3 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor in a few patients 11.
Exact cause of the disease is unknown, however various viral (SSPE like, EBV or CMV), or inflammatory episodes have been implicated by different authors 3, 4, 6.
Patients frequently have episodes of epilepsia partialis continua and, much less frequently, generalized status epilepticus. The seizures are intractable despite aggressive medical management 1.
Apart from seizures, patient may have hemiparesis and speech disturbances, as well as hemianopia (pertaining to unilateral cerebral involvement). Mental deterioration over time may also be seen, especially in patient presenting later in younghood.
CT may not show any specific feature in early imaging, however patchy hypodense attenuation areas (similar to viral encephalitis) may be seen. Late stage disease may show unilateral cortical atrophy. CT perfusion may show decreased cerebral blood flow (CBF) 1.
- T1: unilateral cortical atrophy with ex-vacuo ventricular dilatation
- T2: hyperintense signal areas in the affected hemisphere
- DWI: restricted diffusion may be seen in altered signal areas
- T1 C+ (Gd): no significant post-contrast enhancement
Treatment with high-dose methylprednisolone and intravenous immunoglobulin 12 has been successful further supporting the autoimmune nature of the disease.
Functional hemispherectomy is the only definitive treatment in refractory cases 12.
History and etymology
It was first described by American neurologist Theodore Brown Rasmussen (1910-2002) in 1958 2.
General imaging differential considerations include:
- Dyke-Davidoff-Masson syndrome
- Sturge Weber syndrome
- unilateral megalencephaly
hemiconvulsion-hemiplegia epilepsy syndrome (HHE)
- HHE syndrome usually shows a seizure free interval of months to years from initial presentation 7-8
- 1. Tien RD, Ashdown BC, Lewis DV et-al. Rasmussen's encephalitis: neuroimaging findings in four patients. AJR Am J Roentgenol. 1992;158 (6): 1329-32. AJR Am J Roentgenol (abstract) - Pubmed citation
- 2. Rasmussen T, Olszewski J, Lloyd Smith D. Focal seizures due to chronic localized encephalitis. Neurology. 2000;8 (6): 435-45. Pubmed citation
- 3. Rasmussen T, Andermann F. Update on the syndrome of "chronic encephalitis" and epilepsy. Cleve Clin J Med. 1989;56 Suppl Pt 2 : S181-4. - Pubmed citation
- 4. Farrell MA, Cheng L, Cornford ME et-al. Cytomegalovirus and Rasmussen's encephalitis. Lancet. 1991;337 (8756): 1551-2. Lancet (link) - Pubmed citation
- 5. Mclachlan RS, Girvin JP, Blume WT et-al. Rasmussen's chronic encephalitis in adults. Arch. Neurol. 1993;50 (3): 269-74. Arch. Neurol. (link) - Pubmed citation
- 6. Atkins MR, Terrell W, Hulette CM. Rasmussen's syndrome: a study of potential viral etiology. Clin. Neuropathol. 14 (1): 7-12. - Pubmed citation
- 7. Oguni H, Andermann F, Rasmussen TB. The syndrome of chronic encephalitis and epilepsy. A study based on the MNI series of 48 cases. Adv Neurol. 1992;57: 419-33. Pubmed citation
- 8. Sethi NK, Tenney JR. Child Neurology: Hemiconvulsion-hemiplegia-epilepsy syndrome. Neurology. 2012;79 (24): 2367. doi:10.1212/01.wnl.0000424157.07211.bf - Pubmed citation
- 9. Rasmussen T, Olszewski J, Lloydsmith D. Focal seizures due to chronic localized encephalitis. Neurology. 2000;8 (6): 435-45. Pubmed citation
- 10. Bien CG, Bauer J, Deckwerth TL et-al. Destruction of neurons by cytotoxic T cells: a new pathogenic mechanism in Rasmussen's encephalitis. Ann. Neurol. 2002;51 (3): 311-8. Pubmed citation
- 11. Rogers SW, Andrews PI, Gahring LC et-al. Autoantibodies to glutamate receptor GluR3 in Rasmussen's encephalitis. Science. 1994;265 (5172): 648-51. Pubmed citation
- 12. Bien CG, Granata T, Antozzi C et-al. Pathogenesis, diagnosis and treatment of Rasmussen encephalitis: a European consensus statement. Brain. 2005;128 (3): 454-71. doi:10.1093/brain/awh415 - Pubmed citation
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Rasmussen encephalitis (RE)||✗|
|Rasmussen's encephalitis (RE)||✗|