Electrophysiological tests

Various neurophysiological tests have been investigated over the years to determine their possible usefulness as diagnostic tools in dementia. Abnormalities in evoked potentials and event-related potentials, in particular the P300, in Alzheimer’s disease (AD) and related disorders have been known for a long time.1-3 However, although these studies can provide a better understanding of the neurophysiological processes underlying cognitive dysfunction in AD, they have not been proven to be clinically useful at the level of individual patients. Perhaps a relatively new type of eventrelated potential, the mismatch negativity, will turn out to be more useful in this respect.4 Other attempts to apply new neurophysiological techniques to dementia assessment involve transcranial Doppler and transcranial magnetic stimulation (TMS).5-8 With TMS, changes in cortical excitability have been shown in Alzheimer’s disease.6 This approach might help to differentiate AD from frontotemporal dementias (FTD) and predict response to treatment with cholinesterase inhibitors.7, 8 Transcranial ultrasound has been used recently to differentiate Parkinson’s disease from atypical parkinsonian syndromes.9 However, although many of these new approaches are fascinating and promising, their clinical usefulness remains to be determined.