Lewy Body Dementias and Biomarkers
Whether in Lewy body dementias (LBD) or in any other neurological condition, an early and correct diagnosis best allows a patient to obtain the optimum course of disease management and quality of life. In LBD, there is a unique importance to an early correct diagnosis, given the wide-ranging nature of the disorder and the sometimes subtle differences between dementia with Lewy bodies (DLB), Parkinson’s disease dementia (PDD), and other dementias. In addition, a correct diagnosis allows not only more effective intervention but safer management of the disease. This can be especially important in LBD, with its high level of sensitivity to antipsychotic medications.
LBD Diagnostic Challenges
A diagnosis for early stage dementia with Lewy bodies (DLB) can be missed due to each individual's specific presentation of symptoms. For example, memory-based screening of DLB may fail to diagnose a person with cognitive changes that do not include reduced memory function. Similarly, those in late stage DLB will have a presentation similar to that of other late-stage dementias. It has therefore become clear that a more effective method is needed to diagnose and track LBD other than mainly relying on cognitive measures.
What are Biomarkers?
Biomarkers are biological indicators of the presence or severity of a disease. These measures can be obtained through physical examination, medical testing or imaging. A clear example of a biomarker would be the presence and size of a cancerous tumor, which would reflect the state of the disease, and the effectiveness of treatment to reduce the size of the tumor.
Biomarkers in LBD
In LBD, numerous studies have been conducted recently to find biomarkers. However, few have been found to be reliably show both a high specificity (accurate diagnosis) and sensitivity (ability to identify all affected individuals). Electroencephalograms (EEG) has been shown in some studies to differentiate between DLB and Alzheimer's disease, although it is not a reliable enough indicator, as results have not been consistent between studies. Genetic studies have likewise been conducted, although there are no current reliable genetic markers for LBD. Biomarkers based on cerebrospinal fluid (CSF) is a more promising field, with some studies showing the ability of specific proteins in CSF to distinguish DLB from individuals without DLB. However, further studies are still needed to confirm a high level of specificity and sensitivity.
Various neuroimaging techniques have been studied for the differential diagnosis of DLB, with varying results. Structural MRI imaging has shown some ability to distinguish DLB from AD, but only between groups of patients, and not between individual patients themselves. SPECT imaging, when used to measure blood flow in the brain, has shown some promise identifying DLB patients by specific patterns of blood flow. However, additional larger-scale studies are needed to establish its reliability as a biomarker. Another promising use of SPECT tracks the levels of dopamine transporter, a protein with markedly lower levels in specific regions of the brain of DLB patients. This method has shown particular use in distinguishing between DLB and AD, even in DLB patients who show little or no motor symptoms, who are often difficult to distinguish from AD.
Biomarker Meeting Slated for 2010
LBDA is planning a 2010 scientific meeting in collaboration with the National Institute on Neurological Disorders and Stroke (NINDS) to discuss the state of biomarkers for Lewy body disease -- the underlying disease process in the brain at the biological level of both Parkinson’s disease and Lewy body dementias. Representatives from governmental agencies and research groups will discuss and present their work. Specific goals of this symposium will include identifying the most promising areas of LBD biomarker research and establishing a forum to share progress among different governmental and research groups, as well as expanding LBD biomarker research and raising its visibility to other researchers and clinicians.