Clinical aspects of human spongiform encephalopathies, with the exception of iatrogenic forms

Human spongiform encephalopathies (HSEs) are transmissible diseases exclusively affecting the central nervous system. Sporadic Creutzfeldt-Jakob disease (CJD) constitute 85% of all forms of HSE. The origin of the disease is still unknown. A wide spectrum of diversely associated clinical symptoms are observed. Besides the typical rapidly progressive form which includes dementia, myoclonia, cerebellar ataxia, visual disturbances and periodic electroencephalography (EEG), other forms of the disease exist and may give rise to diagnostic difficulties. Periodic EEG or 14-3-3 protein detection in spinal fluid are helpful for diagnosis when clinical symptoms are present. Currently there is no presymptomatic test for diagnosis. Genetic CJD, Gerstmann-Straussler-Scheinker syndrome and Fatal Familial Insomnia are rarely observed and are always associated with a mutation or an insertion of the prion protein gene. The new variant of CJD is clinically characterized by psychiatric abnormalities, sensory symptoms and ataxia preceding dementia along with other features usually observed in sporadic CJD. Age of patient is abnormally low and duration of the illness is relatively long. Most of the cases are observed in the United Kingdom and a link with bovine spongiform encephalopathy is highly probable.