ELECTROENCEPHALOGRAPHIC CHARACTERISTICS IN CREUTZFELDT-JAKOB-DISEASE AND THEIR DIFFERENTIAL-DIAGNOSIS

Diagnosis:Although clinical electroencephalography is no longer as imp ortant as it used to be in differential diagnosis of a fair number of neurological and psychiatric diseases ever since imaging techniques ha ve been malting enormous strides, EEG is still an important diagnostic tool in dementias where specific morphological lesions are not im med lately or not at a II a ppa rent wh ich would otherwise be visible by imaging. Sporadic Creutzfeldt-Jakob disease is an important case in p oint. Although this is associated with some unspecific EEG findings, t ypical periodical sharp wave complexes (PSWC) become conspicuous in th e course of the disease. If these are meticulously studied and particu lar attention is paid to their periodicity, a sensitivity of 67% and a specificity of 86% are attained. With the exception of one familial v ariant of Creutzfeldt-Jakob disease PSWC are usually absent in all oth er human prion diseases. Hence, it is not likely that they are linked to the aetiology of sporadic Creutzfeldt-Jakob disease. We present a p athophysiological hypothesis on the development of PSWC basing on the assumption that the specific periodicity of PSWC results from a still functionally active but greatly impaired subcortical-cortical circuit of neuronal excitability. This specific pattern of neuronal degenerati on may obviously arise - albeit very rarely - also in other diseases i ndependent of their aetiology, so that the EEG patterns appear identic al. For this reason it is imperative to make complementary use of EEG and of recent clinical and laboratory data of Creutzfeldt-Jakob diseas e before PSWC can be considered a relevant diagnostic criterion. Conve rsely, clinical diagnosis of Creutzfeldt-Jakob disease should be recon sidered if repeated EEG recordings fail to reveal PSWC even under tech nically adequate conditions.