Creutzfeldt-Jakob disease is a transmissible spongiform encephalopathy caused by an accumulation of an abnormal isoform of host-encoded cellular prion protein. The progressive neurodegeneration and early visual symptoms supported by EEG are characteristic of the Heidenhain variant of CJD. The EEG is an essential part of the diagnosis1. Non-specific findings such as diffuse slowing of the background or FIRDA may be apparent initially. By the mid-stage of CJD the classic generalized periodic sharp wave complexes are noted in 2/3rds of cases. Periodic complexes appear with a sensitivity of 64%, specificity of 91% (also rarely reported in other dementias), a positive predictive value of 95%, and negative predictive value of 49% according to one study2. In the Heidenhain variant of CJD (above), the periodic sharp waves are localized to the occipital region but occurred without seizures despite their epileptiform morphology.
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