ATLANTA – In the not-so-distant past, neurologists viewed dementia with Lewy bodies as a disorder primarily of the brain, but it turned out to be far more complex than that.
Dr. Bradley F. Boeve
At the annual meeting of the American Neurological Association, Bradley F. Boeve, MD, described dementia with Lewy bodies (DLB) as a systemic neurologic disorder affecting the brain, including brain stem, spinal cord, and peripheral nervous system, especially the autonomic nervous system. “This leads to the complex array of clinical manifestations, which are quite different from patient to patient cross-sectionally and longitudinally,” said Dr. Boeve, the Little Family Foundation Professor of Lewy Body Dementia in the department of neurology at the Mayo Clinic, Rochester, Minn.
, he said. The four core clinical features are Parkinsonism unrelated to medications; recurrent, fully-formed visual hallucinations; fluctuations in cognition and/or arousal; and rapid eye movement (REM) sleep behavior disorder. “This is the most predictive of all four features,” Dr. Boeve said. He described REM sleep behavior disorder as a parasomnia manifested by the tendency to repeatedly “act out one’s dreams.” The dreams tend to contain a chasing/attacking theme, and behaviors mirror dream content. Injuries to the patient and bed partner can occur.
Typically, patients will present with REM sleep behavior disorder in their 50s and 60s, and sometimes in their 30s and 40s, “decades before cognitive changes begin,” he said. “This is usually followed by Parkinsonism and visual hallucinations. That’s the prototypical DLB [case], but there are many examples where this is not followed. Prominent neuropsychiatric features can also begin before any cognitive changes.”
Neuropsychological features of DLB often include impairment of executive functions and visuospatial functions. “Early in the course of Alzheimer’s disease, typically performance on memory measures – especially delayed recall – are down and the other measures are borderline or mildly impaired,” Dr. Boeve noted. “By contrast, in DLB, attention, executive function, and visuospatial measures are down, but memory is often pretty good. What’s remarkable is that in the office setting, when you take a history the person often says, ‘I’m very forgetful,’ yet in the testing environment people tend to rise to the occasion pretty well.”
Imaging isn’t always helpful in establishing a diagnosis of DLB. MRI scans, for example, “can look pretty normal, including the hippocampi,” he said. “This is really the norm in DLB and it seems to be a disconnect. The person can have significant symptoms yet their MRI scan can be pretty normal.”
In Alzheimer’s disease, 18F-fluorodeoxyglucose-PET (FDG-PET) shows temporal, parietal, and frontal hypometabolism, sparing of the sensory-motor strip and sparing of the primary occipital cortex, while in DLB, FDG-PET shows marked deficits in the occipital regions with relative sparing of the frontal and temporal lobes. Another key neuroimaging sign of DLB is the posterior cingulate island sign, which is characterized by sparing of the posterior cingulate cortex relative to the precuneus plus cuneus on FDG-PET.
In 2017, the Dementia with Lewy Bodies Consortium published updated recommendations on the diagnosis and management of the disease (Neurology. 2017;89[1]:88-100). In its consensus report, the consortium defines probable DLB as dementia plus two or more clinical features or one core clinical feature plus one or more indicative biomarker. These biomarkers include reduced dopamine transport uptake in basal ganglia by SPECT or PET; abnormal (low uptake) meta-iodobenzylguanidine (MIBG) myocardial scintigraphy, and/or polysomnographic confirmation of REM sleep without atonia.
“Neuropathologically, limbic with or without neocortical Lewy bodies and Lewy neurites are the defining characteristics of pathologically-proven DLB,” added Dr. Boeve, a member of the DLB consortium. “The classic DLB phenotype can occur in limbic-predominant DLB. Lewy bodies in the neocortex are not necessary to cause a dementia syndrome.”
He characterized management of DLB as “very complicated. Consider symptoms as they relate to cognitive impairment, neuropsychiatric features, motor features, sleep disorders, and autonomic dysfunction.” He often asks the patient/family to prioritize the three most troublesome issues they seek to change, and develops a plan based on their input.
There is no Food and Drug Administration–approved medication for DLB, but the standard of care is an acetylcholinesterase inhibitor such as donepezil. “There is evidence that memantine can provide a modest benefit,” Dr. Boeve said. “Hypersomnia is quite prominent in DLB and worthy of assessing and treating.” Clinicians must weigh the pros and cons of pharmacotherapy with each patient. “For example, in the atypical neuroleptic class [of drugs], there may be a benefit to the hallucinations and delusions in DLB but hypersomnia can worsen,” he said. “Selecting agents is challenging but worth the effort.”
Survival is lower and more rapid with DLB, compared with Alzheimer’s. Most people pass away from primary DLB-related features or failure to thrive. The second most common is pneumonia or aspiration. Median survival was 4 years after diagnosis in one study, and end-of life discussions occurred in less than half of all patients. “This is a frustrating reminder that we as clinicians are not very good at discussing important topics such as end-of-life care with patients and their families,” Dr. Boeve said. Resources that he recommends for education and support include the Lewy Body Dementia Association and The Lewy Body Society.
At the 2016 Alzheimer’s Disease-Related Dementias Summit, clinicians formed a list of DLB research priorities (Neurology 2017;89[23]:2381-91). Among them were recommendations to “initiate clinical trials in diverse populations using therapies that address symptoms that have the greatest effect on patient function and caregiver burden” and “identify novel common and rare genetic variants, epigenetic changes, and environmental influences that affect the risk for and clinical features of” the disease.
Meanwhile, several research protocols are under way, including the development of a DLB module by the U.S. Alzheimer’s Research Disease Centers and a number of DLB-focused projects from the National Institute of Neurological Disorders and Stroke (NINDS) Parkinson’s Disease Biomarkers Program. In addition, the Lewy Body Dementia Association Research Centers of Excellence program is focused on optimizing clinical care and setting up the infrastructure for clinical trials, while the North American Prodromal Synucleinopathy Consortium is conducting longitudinal studies in those with REM sleep behavior disorder.
Dr. Boeve disclosed that he has been an investigator for clinical trials sponsored by GE Healthcare, Axovant, and Biogen. He is a member of the scientific advisory board for the Tau Consortium and has received research support from the National Institute on Aging, the NINDS, the Mangurian Foundation, and the Little Family Foundation.