What’s Up Doc column: Is Lewy body dementia the same thing as Alzheimer’s?
Columns share an author’s personal perspective.
Question: Is Lewy body dementia the same thing as Alzheimer’s?
Answer: Dementia is a fairly generic term for changes in mentation including social, memory, language, problem-solving and other thinking issues that may interfere with daily life. Alzheimer’s disease is the most common cause of dementia in older people, followed by vascular dementia. Dementia with Lewy bodies is a separate condition that is overall the third most common cause of dementia in the elderly, accounting for up to 15% to 30% of all patients diagnosed with dementia and affecting almost 1.5 million Americans.
DLB is thought to be from a disruption in the flow of neurological electrical signals to and from certain areas of the brain, although the cause of this is not known. On autopsy, brains of DLB have some abnormal intracytoplasmic inclusions (balloonlike clumps of proteins called Lewy bodies after Dr. Frederick Lewy who identified these on autopsy of several patients in 1914). Up to 40% of AD and most Parkinson’s disease patients may also have some Lewy bodies on autopsy (although not necessarily in the areas of the brain where DLB patients have their Lewy bodies), indicating that there may be some overlap of these conditions.
Both AD and DLB are progressive dementias, but certain clinical features lead to a diagnosis of DLB rather than AD:
• Cognitive function fluctuates with varying degrees of alertness and attention in DLB (for example, cognitive function may be very compromised when the patient is even slightly tired).
• DLB patients commonly have excessive daytime drowsiness and sleep changes.
• Visual hallucinations (as well as other types of hallucinations) are a common symptom of DLB.
• Anterograde memory loss (inability to form new memories) is a very common symptom of AD but is not so common in DLB.
• DLB patients often develop movement disorders similar to PD patients. In PD, the movement disorders commonly occur a year or more before the onset of dementia and other neuropsychiatric symptoms, whereas in DLB the dementia occurs earlier or may precede the development of PD-like movement symptoms.
• DLB patients very commonly develop adverse effects from certain antipsychotic medications.
Other symptoms of DLB may include frequent falls, syncope, autonomic dysfunction (such as changes in blood pressure upon standing) and others.
There is no definitive test for DLB. For a dementia patient with suspicion of DLB, the diagnosis is made by:
• Ruling out other possible causes: so certain blood tests and imaging tests (some which may increase suspicion of AD, multi-infarct dementia and/or PD with dementia) are ordered.
• Evaluating the patient’s specific clinical symptoms, specifically looking for hallucinations, rapid eye movement (REM), sleep disorder and/or PD-like movement disorder, as well as consideration of the timing of when these symptoms manifested. A scoring system has been developed to aid in making the final diagnosis.
Presently, there are no specific treatments for DLB. Certain symptoms, such as the PD-like movement issues and some of the neuropsychiatric symptoms (for example agitation and hallucinations, which are often the most troubling symptoms of DLB), may have some improvement from certain medications.
As with AD, DLB is a progressive disease. Patients eventually die of complications caused by the immobility, eating issues, swallowing issues, breathing issues, etc. secondary to the progression of their condition. On average, the life expectancy after diagnosis of DLB is about seven to eight years, a bit less than the nine to 10-year average life expectancy after diagnosis with AD.
Jeff Hersh, Ph.D., M.D., can be reached at DrHersh@juno.com.