Parkinson’s Disease Dementia versus Dementia with Lewy Bodies
Differentiating between Parkinson’s disease dementia (PDD) and dementia with Lewy bodies (DLB) is a difficult issue for many clinicians. To date, these diseases share most of their clinical, neuropathological, and management features. Therefore, PDD and DLB are considered by some authors to be the two extremities of a single spectrum disease named Lewy body diseases. Nevertheless, specific diagnostic criteria now exist for each disease and specific diagnosis remains of interest in clinical practice. In this article, we summarize features and diagnostic criteria of both PDD and DLB, compare them, and examine their treatment options.
Key words: Parkinson’s disease dementia, dementia with Lewy bodies, Lewy body disease, movement disorders, dementia, treatment.
Introduction
Parkinsonism is a neurological syndrome characterized by three main symptoms: hypokinesia (slow or diminished movement of body not linked to muscle strength decrement or apraxia); extrapyramidal “lead-pipe” rigidity; and rest tremor. Several diseases may present with parkinsonism and cognitive disturbances (Table 1). Dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD) are the most frequent, and currently differentiating between them can be especially difficult. Even though some authors have proposed that DLB and PDD are the two extremities of the single spectrum of Lewy body disease (LBD), to date these conditions remain considered two different entities with specific diagnostic criteria. However, because of the clinical and neuropathological overlap between the two illnesses, distinguishing between DLB and PDD can be difficult in clinical settings. In this article, we report the main features of both diseases, underline the clinical differentiation between them, and summarize the main considerations of management.
Parkinson’s Disease Dementia
Parkinson’s disease has been primarily considered a motor disorder. Currently, cognitive disorders in Parkinson’s disease are increasingly recognized, partly because of the longer life expectancy provided by recent therapeutic advances. Estimates of the overall prevalence of dementia among patients with Parkinson’s disease vary, but a figure of about 30% is generally accepted. The mean duration of Parkinson’s disease before dementia occurs is about 10 years, but wide variations may be observed.1 Identified risk factors for PDD include older age, akinetic-rigid form, and early hallucinations.1,2 The main impaired cognitive functions in PDD are attention, executive, and visuospatial functions.1 Memory may also be impaired, but it is not a mandatory feature and, when disturbed, the degree of impairment is usually less than that seen in Alzheimer’s disease.1,3
Diagnostic Criteria
In 2007, the Movement Disorders Society Task Force proposed formalized diagnostic criteria for PDD.3 These criteria are separated in two levels. The first level requires no special neuropsychological skills to use and is thus usable by any clinician. The second level is more descriptive and is suitable for use in research and longitudinal follow-up. Diagnosis of PDD at level 1 requires that the patient fulfill five criteria (Table 2). First, a diagnosis of Parkinson’s disease must have been made according to the Queen Square Brain Bank criteria (except for the lack of dementia). Second, Parkinson’s disease must have developed prior to dementia. Third, cognitive deficiency must be severe enough to impair activities of daily living. As an alternative to a caregiver interview, the authors propose using the Pill Questionnaire, which assesses the