Dementia: Update for the Practitioner

Recognition of Vascular Dementia, Dementia with Lewy Bodies, and Frontotemporal Dementia
Lawrence S. Honig, M.D., Ph.D.

The Spectrum of Lewy-Body Disease

Rather than using the term Lewy-body disease, I will refer to a Lewy-body spectrum, because there is a significant range of Lewy-body involvement in brains of people who are demented. At the extremes, the substantia nigra is normally dark or black in people with normal brains, and pale, with loss of pigment, in people with nigral pathology. This abnormal pallor is indicative of loss of the pigmented substantia-nigra neuronal cells. This loss is a major cause, but not the sole cause of parkinsonism.


	Lewy-Body Spectrum: Pathology


	The substantia nigra is normally dark or black in people with normal brains, and it is pale in people who have nigral pathology. Lewy-body disease is associated with the presence of Lewy bodies. Courtesy of Dr. Lawrence Honig

Many of the Parkinsonian disorders are associated with the neuropathological presence of certain neuronal cytoplasmic inclusions called Lewy bodies. As discussed earlier, there is a significant overlap between our definitions of Alzheimer's disease, Lewy-body dementia, and Parkinson's disease. We define Parkinson's disease as a motoric disorder that does not involve dementia early on. But in fact, many people with Parkinson's disease do get dementia later in their course. Many of them have concomitant Alzheimer's pathology, but those who do not are sometimes diagnosed with diffuse Lewy-body disease. However, this term is properly reserved for those persons who present with dementia and not persons with parkinsonism who years later become demented.

Although the neuropathology of a patient without Alzheimer's disease but who has Parkinson's disease and dementia is identical to the neuropathology of someone with dementia and parkinsonism early, we call them different names: Parkinson's disease with dementia and diffuse Lewy-body disease. However, this may not make sense since the pathology is indistinguishable. and the pathologist calls these the same disorder.


	Lewy-Body Dementia Spectrum


	The criteria for distinguishing among Lewy-body spectrum diseases overlap. Courtesy of Dr. Lawrence Honig

Pure Alzheimer's disease by definition has no Lewy bodies, but, as we discussed earlier, with modern sensitive techniques, some investigators have found Lewy bodies in as many as 65 percent of cases. Lewy-body variant of Alzheimer's disease is now more commonly termed dementia with Lewy bodies, which includes a mixture of pathologies, including those who have both some Alzheimer's pathology and some Parkinson's or Lewy-body pathology, and a few who have only Lewy-body pathology.

Various groups have tried to establish criteria for diagnosing the Lewy-body conditions clinically, much as we have clinical criteria for Alzheimer's and other disorders. Diagnosis of Lewy-body dementia presently requires both dementia and one or more of three putative hallmarks of Lewy-body involvement. These three features are recurrent, well-formed visual hallucinations; spontaneous parkinsonism, that is, increased tone, gait disorder, rest tremor, postural instability, and sometimes orthostatic hypotension; and fluctuations in cognition, including changes in attention and alertness, and even frank syncope, such as frequent fainting spells. Of these three sets of symptoms, the most difficult to specify is fluctuations in cognition. Anyone who treats dementia patients knows, that there may be good days and bad days. Furthermore, it is very difficult to rate fluctuations.


	Dementia with Lewy-Body Criteria Progressive cognitive decline (affecting function) frontal, subcortical, or visual dysfunction may be prominent Core features (probable (2 of 3); possible (1 of 3)) fluctuations in cognition: attention and alertness visual hallucinations: recurrent, well-formed, detailed Parkinsonism: spontaneous motoric features Supportive features falling, syncope, LOC, neuroleptic sensitivity, delusions, other hallucinations Exclusionary features strokes (clinical or imaged), other brain disorders

	A person has to have a dementia and one or more the hallmarks of Lewy-body involvement in Lewy-body dementia. Courtesy of Dr. Lawrence Honig

Various features are said to support a diagnosis of Lewy-body dementia. The International Consortium Consensus Criteria lists syncope, loss of consciousness, falling, neuroleptic sensitivity, delusions, and other hallucinatory experiences. There are also exclusionary criteria, but Alzheimer's disease is not one of them. Thus, one can meet Lewy-body dementia criteria and Alzheimer's criteria. In fact, the majority of cases of clinically diagnosed Lewy-body dementia also meet criteria for Alzheimer's disease. This is why some people use the term Lewy-body variant, although it is falling into disuse.

To summarize, Lewy-body disease represents a clinical and pathological spectrum, from pure Parkinson's disease with no dementia, and Lewy bodies in the brain but not outside the brain stem, to pure Alzheimer's disease, possibly with no Lewy bodies. In the middle between these extremes are large numbers of people who have the pathology of both Parkinson's and Alzheimer's diseases, and may present with dementia and parkinsonism.

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