It must not be reproduced or copied without the permission of the Editor of Brain Pathology . The core feature of DLB is a progressive dementia. Clinically, this condition can present as a dementia which is often initialy diagnosed as either Alzheimer's disease or vascular dementia. Alternatively, many patients start with classical Parkinson's disease and later go on to develop dementia. Only a minority of patients present with the simultaneous onset of both dementia and parkinsonism A combination of key clinical features has allowed workers in many centres to diagnose this condition and distinguish it from other causes of dementia.
Most patients initially complain of impaired recent memory.
In other patients the main problem is behavioural disturbance with preserved memory. Features, such as inattention, mental inflexibility, indecisiveness and lack of judgement, together with loss of insight, may also develop in the early stages of the disease and are useful in suggesting the possibility of a non-Alzheimer form of dementia. An important feature which helps to distinguish DLB from Alzheimer's disease is the presence of striking fluctuations in cognitive performance during the early stages of the disease. By way of example, one day a patient may be able to hold a sustained conversation, the next they may be drowsy, inattentive and almost mute. The basis of these fluctuations is not clear.