Now we will discuss the history and examination of the patient with cognitive deterioration, with an eye to recognizing syndromes of dementia that aren't Alzheimer's disease.
With respect to clinical history, there are certain signs and symptoms that are atypical for Alzheimer's disease and thus more suggestive of an atypical dementia rather than Alzheimer's disease.
With respect to history, there are some symptoms reported by the patient or their caregivers, such as sudden onset, that are not characteristic of a neurodegenerative disease such as Alzheimer's disease. Other symptoms such as presentation with a focal neurological finding—difficulty using one side of the body or one limb, difficulty with sensation, unilateral changes in visual perception —are also features that are atypical of Alzheimer's disease.
Seizures early in the course of illness, abnormal gait, and abnormal coordination are all atypical for Alzheimer's disease. Also, dementing disorders, which preserve memory function at an early point course of the disease, are inconsistent with typical Alzheimer's disease, which is preeminently a disorder of memory. That is not to say that there might not be rare cases in which this may not be the case, but overall, if memory is rather good and other cognitive functions more affected, the possibility of disorders other than Alzheimer's disease looms larger.
With regard to clinical signs, might there be aspects of the examination inconsistent with or not supportive of a diagnosis of Alzheimer's disease? Again, if memory is well preserved, even if there is a memory complaint, Alzheimer's disease is less likely.
Similarly, prominent behavioral, personality, and psychotic symptoms are inconsistent with Alzheimer's. Dr. Devanand talked about many of the psychotic symptoms in Alzheimer's disease, and you heard how many of them may be present even in the earlier stages of the disease. They may also be present in other dementias. In particular, certain frontotemporal dementias may be marked by prominent behavioral disinhibition or personality change at stages where cognition is otherwise relatively preserved.
Early parkinsonism, as you heard about from Dr. Devanand, may often be a side effect of neuroleptic drugs. But spontaneous parkinsonism is a sign to look for, often evident as early unexplained gait abnormalities not associated with neuroleptic use, and may be a sign of dementia with Lewy bodies. Other motor signs, sensory signs, and reflex asymmetries that are not explainable by a concomitant disorder the patient has—such as a stroke, myelopathy, or neuropathy—also should prompt a broader search for possible explanations of the disorder, other than that of Alzheimer's disease.
How can these atypical features be used to group the non-Alzheimer's dementias? They can be grouped in different ways, and there may be significant overlap. However, there are various Parkinsonian syndromes, various focal cortical syndromes, and there various vascular syndromes, all of which can be syndromes of dementia that are not attributable to Alzheimer's disease.
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