The need for diagnosis in dementia

Dr Macleod has written a timely, comprehensive and humane article about the thorny issues of management in end-stage dementia.¹ But while the precise cause of the catastrophic brain failure that characterises late dementia may at that stage no longer be of direct relevance to management, I was nonetheless puzzled that Dr Macleod gave just passing reference to diagnosis and only mentioned Alzheimer’s disease, the most common cause, in his last paragraph.

As he states, dementia is a progressive, life-limiting syndrome. It is not a diagnosis in itself, but diagnosis is important. Occasionally, apparently profound dementia may have reversible causes such as hypothyroidism or severe, undiagnosed depressive disorder. Sometimes specific treatments may be indicated in the subtypes of neurodegenerative disorder that most commonly underly dementia. As they become better defined, it is increasingly likely that the associated genetic abnormalities will become of vital interest to relatives of sufferers. Precise diagnosis is also a necessary aspect of research.

In contemporary New Zealand practice, a diagnosis of the type of disorder causing dementia is usually made on clinical grounds by an experienced medical specialist, but not all patients see specialists. Psychometric testing is sometimes useful and imaging may provide a more definitive diagnosis, but both are constrained by the resources available. Postmortem brain examination is rarely done. The lack of a definitive diagnosis, supported by imaging or pathology, in many cases of dementia is regrettable, albeit that it may not contribute a great deal to the management of advanced cases.