Alzheimer's disease and senile dementia of Alzheimer type. A comparative study.

Clinical and neuropsychological findings, EEG, and several blood and CSF parameters were investigated in 36 patients with Alzheimer's disease (AD) and 35 patients with senile dementia of Alzheimer type (SDAT). There were more women among senile patients and more familial cases among presenile patients. The average duration of the symptoms was longer in presenile patients (6.1 years) than in senile patients (3.9 years). This could be due to the lower resistance to the disease process in the senile group. Extrapyramidal signs, especially rigidity, were found in over 60% of all patients and in practically all patients with advanced dementia. Tremor was found in three patients only. Four presenile (11%) and two senile (6%) patients had epileptic seizures. All patients had abnormal EEG recordings, mainly in form of diffuse slowing. A positive correlation was found between the EEG abnormality and the severity of dementia in AD but not in SDAT. However, the difference between the correlation coefficients in AD and SDAT was insignificant. Between EEG and the duration of the disease there was no correlation. EEG was not more abnormal in very severe dementia than in severe dementia. Other findings were similar in AD and SDAT. It is concluded that it is artificial to separate AD and SDAT at the age of 65 and that they clinically compose a single entity. This entity could well be called Alzheimer's disease.