Terminology
Dementia refers to a change in intellectual function including a memory impairment, along with an additional cognitive deficit in at least one other area of function (such as language, attention, concentration, visuospatial skills, or problem solving). These impairments have to be of sufficient magnitude to affect the activities of daily living and are not thought to be due to a change in the sensorium, e.g. delirium. The Diagnostic and Statistical Manual IV criteria for dementia are outlined in Table 1.¹ The clinical diagnosis of AD is similar to that developed for dementia but adds the dimension of a presumed degenerative etiology. The most common research criteria for AD have been described by McKhann et al. (see Table 2). It is apparent that the dementia criteria were strongly influenced by AD, e.g. the requirement for a memory disorder to be present, and this aspect of the criteria is being reconsidered.² The American Academy of Neurology (AAN) concluded in a recent evidencebased medicine review of the literature that the clinical diagnoses of dementia and AD were actually quite accurate when compared with post-mortem findings.³ In spite of the lack of a biomarker for AD, clinicians are usually quite accurate. As previously mentioned, technology has assisted in making this diagnosis, meaning that some of these newer diagnostic techniques need to be reviewed.

Clinical Evaluation
The fundamental diagnosis of dementia or AD remains clinical, i.e. without a biomarker the ultimate diagnostic call is a clinical judgment. This can be accomplished with accuracy by following standard procedures.

History
A history from the patient and from someone who knows the patient well is of paramount importance. It is critical to inquire about daily activities, how well the person is performing activities of daily living, if performance of these activities is changed, and whether that change is secondary to an alteration in intellectual function. Since these disorders increase with age, it is important to determine that the changes in function are secondary to cognitive difficulties and are not due to medical co-morbidities. The typical course of the change is important to determine since AD is typically of insidious onset and gradual progression. Cognitive changes of a vascular etiology may appear in a more abrupt fashion, although vascular disorders involving certain types of vascular insults can progress slowly.

It is also important to inquire about non-cognitive behaviors.A personality change and other alterations in behavior can alert the clinician that the dementia may not be due to AD. Frontotemporal dementias typically present with an alteration of behavior with lack of insight into the clinical state and occasionally present with apathy. Inappropriate social behaviors may also be a feature of this disorder. It is also important to inquire about sleep habits. Individuals with dementia and Lewy body syndrome may be prone to snoring and may exhibit dream enactment behavior.This disorder is also frequently characterized by daytime hallucinations, which are often non-threatening, and wide fluctuations in behavioral performance. These features can be very useful in differentiating among the various dementias.

Examination
It is important to perform a medical and neurologic examination to determine any clues as to the etiology of the dementia syndrome.Typically, the general neurologic examination without a mental status examination component is largely normal in early AD. However, if there are subtle features of Parkinsonism, this may suggest a Lewy body component either leading to dementia with Lewy body syndrome or perhaps Parkinson’s disease with dementia.The examination can also reveal features that might suggest a vascular contribution such as asymmetrical reflexes, hemiparesis or a visual field defect. These features may direct a further investigation into the certain causes of the clinical findings.