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. Another very characteristic clinical feature is the presence of visual hallucinations . The hallucinations are typically complex and detailed. For example, patients may see images of people or animals that they recognise.
Some patients see coloured patterns or shapes.
In many patients visual hallucinations are accompanied by delusions which tend to have a persecutory theme. A third characteristic clinical feature is the presence of clinical features of parkinson's disease . These develop spontaneously in most patients who have initially presented with dementia, and may be relatively mild. The typical features are a flexed posture a shuffling gait reduced armswing a tendency to falls. Myoclonus, is common.