Carcinomatous meningitis: Yet another cause for rapidly progressive dementia and triphasic waves in electroencephalograph!

We report a 65-year-old woman who manifested with progressive cognitive impairment, abnormal behavior, slurred speech, inability to carry out activities with right upper limb, gait disturbances, emotional liability, and double incontinence that evolved progressively over the last 8 months. A clinical syndrome of “rapidly progressive dementia” was considered. The MRI of brain was unremarkable except for small para third ventricular enhancing lesion was detected in the left thalamic region. There was bi/tri-phasic sharp waves in the routine scalp EEG occurring at periodically 1.5–2.0 Hz, mimicking Creutzfeldt–Jakob disease (CJD). She was later diagnosed to have carcinomatous meningitis based on cerebrospinal fluid (CSF) cytology. This case is being discussed for rarity and interesting EEG observations in patients with carcinomatous meningitis and to highlight the importance of CSF cytology in an appropriate clinical setting. One needs to be careful in concluding CJD as possible diagnosis in such scenario.