Lewy body dementias include two clinical diagnoses, dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD), which share essentially the same array of symptoms. (To view this chart in a printable .pdf, click here.)
DLB Diagnostic Criteria
The diagnostic criteria for probable DLB require:
- The presence of dementia
- At least two of three core features:
- fluctuating attention and concentration,
- recurrent well-formed visual hallucinations, and
- spontaneous parkinsonian motor signs.
Suggestive clinical features include:
- Rapid eye movement (REM) sleep behavior disorder
- Severe neuroleptic sensitivity
- Low dopamine transporter uptake in basal ganglia demonstrated by SPECT or PET imaging
In the absence of two core features, the diagnosis of probable DLB can also be made if dementia plus at least one suggestive feature is present with one core feature.
Possible DLB can be diagnosed with the presence of dementia plus one core or suggestive feature.
Supportive clinical features include repeated falls, syncope, a transient loss of consciousness, severe autonomic dysfunction, depression, systematized delusions, or hallucinations in other sensory and perceptual modalities.While these features may support the clinical diagnosis, they lack diagnostic specificity and can be seen in other neurodegenerative disorders.
These criteria have a sensitivity of 83% (17% clinical false negative rate) and a specificity of 95% (clinical false positive rate of only 5%) for the presence of neocortical Lewy bodies (LBs) at autopsy, the current diagnostic gold standard. However, these criteria are more predictive of autopsied cases with the relatively rare “pure” form of LBD rather than the much more common cases with a mixture of LBD and the pathology of AD. The criteria cannot reliably differentiate between the two clinical entities. The DLB criteria tangentially address PDD as very similar to DLB with the exception of temporal appearance of extrapyramidal signs. (i.e., in PDD the motor symptoms precede the onset of dementia by at least one year.)
The current absence of radiological or biological markers that can reliably aid in the diagnosis of DLB has led to a search for clinical measures that can serve as markers for pathology or predictors of disease progression. Moreover, there is also an absence of effective treatment for DLB, except for drugs that offer modest control of the cognitive and behavioral symptoms. There are yet no therapies that have proven to alter or delay disease progression. Early clinical detection of dementia or the identification of pre- clinical markers of different dementia pathologies may provide insight into early disease mechanisms and pave the way for the development of disease modifying therapy, which of necessity must be initiated at the earliest possible juncture, ideally before symptoms have developed.
The importance of early, aggressive treatment is supported by recent data suggesting that LBD patients might have better responses to cholinesterase inhibitors than AD patients. In addition, an early diagnosis of LBD implies that treating physicians will know to avoid medications that can aggravate the clinical picture, such as the traditional neuroleptics. It is estimated that almost 60% of LBD patients may exhibit exaggerated extrapyramidal signs, sedation, immobility, or neuroleptic malignant syndrome (NMS) with fever, generalized rigidity and muscle breakdown following exposure to neuroleptics. NMS is a life-threatening condition and the higher prevalence in LBD suggests that traditional neuroleptics such as haloperidol, fluphenazine or thioridazine should be avoided.
Early diagnosis will also allow families and caregivers the time to plan for the expected decline. Preventive steps to improve safety in the home environment should be taken, given the tendency to recurrent falls and rapid attentional fluctuations. Families will also have time to develop a better understanding of their role in patient care, including assistance with daily activities and provision of social and cognitive stimulation.
PDD Diagnostic Criteria
A consensus statement by a task force from the Movement Disorder Society for the diagnosis of PDD has just been published, providing criteria for probable and possible PDD.
A diagnosis of probable PDD requires the core features (Table 1) and a typical presentation of clinical features which is defined as having deficits in at least two out of four cognitive domains (below). There may or may not be behavioral symptoms, although their presence would support a diagnosis of probable PDD. There must not be any features present from groups III and IV, as the abnormalities and conditions described in these categories can cause too much uncertainty in a potential diagnosis.
A diagnosis of possible PDD also requires the core features, but can have a more non-characteristic pattern of symptoms in at least one of the cognitive domains. There may or may not be any behavioral symptoms. One or more features of group III may be present, and none in Group IV.
Group I - The core feature requires a prior diagnosis of Parkinson’s disease, and dementia causing a decline in function severe enough to impair the patient in daily activities and in at least one cognitive domain.
Group II - The clinical features include both the cognitive and behavioral domains described below:
Group III - The third category includes two features that will not rule out a diagnosis of PDD, but may make the diagnosis more uncertain:
Group IV - The last domain contains two features which suggest that other existing conditions impair the patient’s cognitive functioning to such an extent that reliable diagnosis of PDD becomes impossible.
Source: "Current Issues in LBD Diagnosis, Treatment and Research" by James E. Galvin, MD, Bradley F. Boeve, MD, John E. Duda, MD, Douglas R. Galasko, MD, Daniel Kaufer, MD, James B. Leverenz, MD, Carol F. Lippa, MD, Oscar L. Lopez, MD, representing the Scientific Advisory Council of the Lewy Body Dementia Association. May, 2008