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Lewy body disease (LBD), manifesting as Parkinson’s disease and dementia (PDD) or dementia with Lewy bodies (DLB), is the second most common cause of neurodegenerative dementia, after Alzheimer’s disease (AD) (Chap. 431). Approximately 10% of patients with PD develop PDD per year, with the majority of PD patients developing PDD over time. The incidence of DLB is approximately 7 per 100,000 person-years. The prevalence of both PDD and DLB increases with aging, and both affect men more often than women.
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CLINICAL MANIFESTATIONS
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Most researchers conceptualize PDD and DLB as points on a spectrum of LBD pathology. Cognitively, PDD and DLB usually manifest with severe executive, attentional, and visuospatial deficits but preserved episodic memory. Cognitive decline in LBD affects performance of daily living activities beyond other PD symptoms. Early psychosis including well-formed visual hallucinations, fluctuating cognition, rapid eye movement sleep behavior disorder (RBD), and parkinsonism are the main diagnostic features in DLB. The sense of a presence behind the person may precede well-formed hallucinations. Delusions are less frequent than hallucinations and are usually related to misidentification, infidelity, theft, or persecution. Fluctuating attention and concentration are other characteristic features. Minor day-to-day variation in cognitive functioning is common across dementias, but in DLB these fluctuations can be marked, with short periods of confusion or severe lethargy that may rapidly resolve. Patients with PDD and DLB are highly sensitive to infectious or metabolic disturbances. The first manifestation of DLB in some patients is delirium, often precipitated by an infection, new medicine, or other systemic disturbance. Parkinsonism in DLB is usually associated with early postural instability and can present early or later in the course. RBD is a characteristic, often prodromal, feature. Normally, dreaming is accompanied by skeletal muscle paralysis, but patients with RBD enact dreams, often violently, leading to injuries to themselves or their bed partners. Both PDD and DLB may be accompanied or preceded by anosmia, constipation, RBD, depression, and anxiety.
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The symptom profile in DLB and PDD can provide clues for the differential diagnosis at the clinic. Clinically, the time interval between parkinsonism and dementia differentiate PDD and DLB. PDD presents in patients with long-standing PD, who manifest dementia often with visual hallucinations, fluctuating attention or alertness, and RBD. On the other hand, when the dementia and the neuropsychiatric symptoms precede or co-emerge with the parkinsonism, the patient is diagnosed with DLB. Patients with DLB, more frequently than those with PDD, also have AD co-pathology, making the prediction of underlying pathology challenging for clinicians. Episodic memory disturbance points to the diagnosis of comorbid AD. Orthostatic hypotension that can lead to syncopal events, erectile dysfunction, and constipation can be present early in DLB, at times making it challenging to differentiate DLB from multiple system atrophy (MSA). In MSA the autonomic disturbances occur early and are usually more severe than in DLB, and cognition is relatively preserved. Anosmia is also more characteristic of ...