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Lewy Body Dementia

Diffuse Lewy body disease is a diagnosis that has gained in popularity in the 1990s. Lewy bodies are
microscopic structures present in the brains of patients with Parkinson's disease. At least one-third of
Alzheimer's patients also have clinical features of Parkinson's disease: tremor, slow movements,
rigidity of muscles, and difficulty in walking. Some of these patients have Lewy bodies in addition to
the typical Alzheimer's autopsy findings of neurofibrillary tangles and amyloid plaques. A British
group headed by Ian McKeith has led the charge in calling for a separate diagnostic category called
diffuse Lewy body disease, which has the clinical features of dementia, Parkinsonian signs,
fluctuating memory loss and confusion, hallucinations, and extreme sensitivity to antipsychotic
medications. Many cases previously called Alzheimer's are now called Lewy body disease; this topic
remains controversial.

Frontotemporal Dementia

Frontal or frontotemporal dementia is a less common subtype. Earlier, all such cases were thought to
have Pick's bodies, a specific type of microscopic abnormality, but many cases of frontotemporal
dementia do not show this lesion. The clinical features overlap with those of Alzheimer's disease, but
‘‘frontal lobe disinhibition” signs are more prominent: overeating, sleeping excessively,
hypersexuality, motor agitation, and impulsive and unpredictable behavior. Following damage to the
temporal and frontal lobes, impulsive behaviors are unleashed from lower parts of the brain, as in the
case of Phineas Gage, the railroad foreman whose frontal lobes were crushed by a tamping iron over
a hundred years ago. For example, I remember a patient of mine with frontal lobe dementia who
gained eighty pounds in one year and lost a hundred pounds in the next. These changes happened
without any conscious effort on her part to either diet or put on weight. It was as if the appetite center
in the hypothalamus (in a deep part of the brain) was receiving different inputs from the damaged
frontal lobes in different calendar years. Some patients with frontal lobe dementia develop complete
apathy and lethargy, a near vegetative existence. This can happen even when memory loss is only
mild to moderate in severity.

Currently, there is no specific, approved treatment for either Lewy body disease or frontotemporal
dementia.