Unusual presentations are not rare in subacute sclerosing panencephalitis. Five patients initially diagnosed with pseudotumor cerebri were ultimately determined to have pseudotumor cerebri secondary to subacute sclerosing panencephalitis. The present study retrospectively reviewed 56 cases history, neurologic symptoms, and clinical and laboratory data, as well as the outcomes. On admission, five patients (group 1) presenting with pseudotumor cerebri exhibited bilateral papilledema, and in each of them cranial magnetic resonance imaging revealed small lateral ventricles, effacement of the subarachnoid space, and no mass lesion. On admission, 51 patients (group 2) had no pseudotumor cerebri findings. The year of original measles infection, the interval between measles and onset of subacute sclerosing panencephalitis, and initial neurologic symptoms were similar, but length of symptoms before diagnosis of subacute sclerosing panencephalitis was shorter in group 1, and the clinical stage of subacute sclerosing panencephalitis on admission was more advanced in group 2. Cerebrospinal fluid mean open pressure was 378 +/- 22 H(2)O in group 1 and 146 +/- 28 H(2)O in group 2; cerebrospinal fluid antibody was 2038 +/- 768 U/L in group 1 and was 664 +/- 214 U/L in group 2. Only three of the five patients with pseudotumor cerebri had typical periodic discharges on electroencephalographic examination. These findings suggest that subacute sclerosing pariencephalitis can cause pseudotumor cerebri. (C) 2009 by Elsevier Inc. All rights reserved.