What are the Earliest Symptoms of Dementia with Lewy Bodies?
Abstract & Commentary
By Norman R. Relkin, MD, PhD, Associate Professor of Clinical Neurology and Neuroscience, NewYork-Presbyterian Hospital, Cornell Campus. Dr. Relkin is on the speaker's bureau for Pfizer, Eisai, and Athena Diagnostics, and does research for Pfizer and Merck.
Synopsis: Visual hallucinations, extrapyramidal motor signs, and visuoconstructional impairments at time of presentation are strongly suggestive of a diagnosis of dementia with Lewy bodies.
Source: Tiraboschi P, et al. What Best Differentiates Lewy Body from Alzheimer's Disease in Early-Stage Dementia? Brain. 2006;129:729-735.
Early and accurate diagnosis of dementia with Lewy bodies (DLB) is desirable because DLBs course and response to treatment can be quite different from that of Alzheimer's (AD) or Parkinson's disease (PD). To assist in early diagnosis, researchers at the UCSD School of Medicine reviewed the clinical features present at first examination in 23 pathologically proven cases of DLB compared to 93 age-matched AD controls. They selected signs and symptoms of DLB that could be readily determined by examination, and excluded features that could not be reliably measured in clinical practice.
The study revealed that a finding of visual hallucinations at the first visit was highly correlated with a definite DLB diagnosis, but only 22% of subjects had such hallucinations on initial presentation. Extrapyramidal symptoms (EPS) were also more prevalent in DLB than AD, but were detectable in only 26% of patients at first visit. The most sensitive predictor of DLB was the presence of isuoconstructional impairments (eg, difficulty with drawing tasks) which were found on presentation in 74% of subjects with DLB but only 45% of AD patients. Tiraboschi and colleagues concluded that visuoconstructional impairment may be one of the most sensitive early features of DLB, while visual hallucinations and EPS were among the most specific.
International consensus criteria have made DLB a better-defined entity than was the case a decade ago, but diagnostic sensitivity and specificity remains low in practice. DLB is under-recognized and frequently confused with other dementing disorders. This is one of the first autopsy-correlated studies to focus on signs and symptoms of DLB present at the first physician visit, as distinct from those that become evident in the first few years of the disease. The low prevalence of visual hallucinosis and EPS in this study, both considered by consensus to be core features of DLB, highlights one of the difficulties facing clinicians attempting to identify DLB by its clinical features alone.
One of the shortcomings of this study is its failure to examine all of the clinical features previously associated with DLB. For example, fluctuating cognitive and motor impairments are recognized to occur in DLB and can contribute to its diagnosis. Fluctuations were excluded from this study because Tiraboschi et al felt they could not be reliably assessed in clinical practice on an initial visit. However, evidence of fluctuations can bolster a DLB diagnosis. Other features, such as the presence of REM sleep behavior disorder, neuroleptic sensitivity, and occipital hypometabolism on an FDG PET can add to diagnostic sensitivity and specificity.
Another shortcoming of this study is its failure to include a control group with Parkinson's disease. Although AD is the most prevalent form of dementia and a frequent confounder in the diagnosis of DLB, dementia in PD overlaps that in DLB in a number of ways. For example, the visuoconstructional deficits that were found to be frequently associated with DLB in this study are also common in PD.
This study confirms that the symptoms that are considered to be core features of DLB are sometimes present at the time of initial examination. However, a practical method for diagnosing DLB with high sensitivity and specificity on an initial visit remains elusive.