Neuroimaging as a diagnostic tool in dementia with Lewy bodies.

Due to similar presenting symptoms, many physicians find it difficult to distinguish cases of dementia with Lewy bodies (DLB) from Alzheimer's disease or Parkinson's disease with dementia. The pathologic diagnosis of DLB has improved because of the discovery of probes for alpha-synuclein, a protein found in Lewy bodies. However, pathologic diagnosis can be employed postmortem only, and therefore diagnostic techniques that can be employed to guide patient management are still needed. Consensus criteria have been developed for establishing a clinical diagnosis of DLB, but they lack sensitivity. Therefore, a review of the recent literature was conducted to establish whether neuroimaging studies are useful diagnostic tools to help differentiate these syndromes. At least six types of tests can be used to image the brain of patients with dementia. Structural studies (x-ray, magnetic resonance imaging and computerized tomography) can disclose the presence of stroke sequelae and other lesions, whereas functional studies (magnetic resonance spectroscopy, positron emission tomography and single-photon emission computed tomography) can disclose metabolic and blood flow alterations that may be characteristic for different types of dementia. Although more formal studies are needed to confirm that these imaging techniques are reliable diagnostic tools for DLB and permit the establishment of guidelines for their use, neuroimaging techniques currently are being employed in practice to differentiate dementia types as a guide to treatment.