History: An 81-year-old man, impreviously good health, suddenly developed c
onfusion and rapidly progressive severe tetraparesis.
Investigations: Peripheral blood and bone marrow revealed marked eosinophil
ia: allergic. parasitic, neoplastic or vasculitic causes were excluded. Mag
netic resonance imaging demonstrated multiple lesions in the cortical and s
ubcortical white matter.
Diagnosis, treatment and course: The findings indicated idiopathic hypereos
inophilic syndrome involving the central nervous system and treatment with
high doses of glucocorticoids was started. After a stormy course almost com
plete recovery occurred. Conclusion: Idiopathic hypereosinophilic syndrome
can rarely manifest itself a an isolated severe subacute encephalopathy.