Rasmussen encephalitis: A clinicopathologic and immunohistochemical study of seven patients

Richard A. Prayson, John L. Frater

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We retrospectively reviewed the clinicopathologic features and immunohistochemical profiles of 7 patients with Rasmussen encephalitis (age range, 3.5-15 years at surgery). All had medically intractable seizures (6 months' to 7 years' duration); all but 1 developed unilateral hemiparesis. Histologically, all cases were characterized by leptomeningeal and parenchymal perivascular chronic inflammation consisting primarily of T lymphocytes (CD3+, CD5+, CD7+). In all but 1 case, a predominance of CD8+ T-cytotoxic/suppressor lymphoid cells over CD4+ cells was observed. All cases had rare B lymphocytes (CD79a+, CD20+). Rare CD1O+ and no CD56+ cells were noted. All cases were marked by diffuse proliferation of microglial cells, highlighted on CD68 immunostaining. Focal microglial nodule formations were observed in 4 cases and focal cortical atrophy in 5 cases. Viral inclusions were not noted. There was no evidence of Epstein-Barr virus by LMP-1 antibody immunostaining. The histologic findings of Rasmussen encephalitis resemble those of viral meningoencephalitis. The pathologic findings may be only focally present, and missed, if diagnosis is made or confirmed with biopsy alone. Most lymphoid cells have a T-cell immunophenotype, with a predominance of CD8+ cells in most cases.

Original languageEnglish
Pages (from-to)776-782
Number of pages7
JournalAmerican journal of clinical pathology
Issue number5
StatePublished - 2002


  • Chronic encephalitis
  • Epilepsy
  • Epstein-Barr virus
  • Rasmussen encephalitis


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