The diagnosis and evaluation of dementia and mild cognitive impairment with emphasis on SPECT perfusion neuroimaging

Abstract

As the world population ages, the incidence of dementing illnesses will dramatically increase. The number of people afflicted with dementia is expected to quadruple in the next 50 years. Since the neuropathology of the dementias precedes clinical symptoms often by several years, earlier detection and intervention could be key steps to mitigating the progression and burden of these diseases. This review will explore methods of evaluating, differentiating, and diagnosing the multiple forms of dementia. Particular emphasis will be placed on the diagnosis of mild cognitive impairment-the precursor to dementia. Anatomical imaging; cerebrospinal fluid markers; functional neuroimaging, such as positron emission tomography and single photon emission tomography; and molecular imaging, such as amyloid marker imaging, will be assessed in terms of sensitivity and specificity. Cost will also be a consideration, as the growing population afflicted with dementia represents an increasingly large financial encumbrance to the healthcare systems of every nation. In the face of expensive new markers and limited availability of cyclotrons, single photon emission computer tomography (SPECT) provides relatively high sensitivity and specificity at a comparatively low overall cost.

Clinical Utility of SPECT Neuroimaging in the Diagnosis and Treatment of Traumatic Brain Injury: A Systematic Review

“…Changes in brain structure represent a late change in most neurological disorders, such as dementia, when pathological cascades are often too advanced to optimize treatment [35]. As a consequence, structural changes may be insensitive to earliest changes seen in disease progression [36]. In TBI, this principle was illustrated in a recent study showing how changes in cerebral blood flow, a metric of brain function preceded changes in diffusion tensor imaging indicators of brain structure [37].…”

“…Functional imaging methods such as Single Photon Emission Computed Tomography (SPECT) can identify early changes in neurological diseases such as dementia by imaging regional cerebral blood flow, thus providing a predictive indicator of damage [42]. SPECT is of particular interest for such use because: i) it is a well-studied modality that has been previously utilized in such neurological disorders as epilepsy [43] and dementia [36]; ii) it has continuously seen hardware improvements from one head to three head cameras and from analog to digital detector components and; iii) it gains additional post-processing power with 3-D renderings and statistical analysis. Whether SPECT can yield such utility in the complex clinical setting of TBI is a question of great interest.…”

Functional Neuroimaging in Psychiatry—Aiding in Diagnosis and Guiding Treatment. What the American Psychiatric Association Does Not Know

“…First, numerous published, peer-reviewed studies by independent investigators show that both fluorodeoxyglucose positron emission tomography (FDG-PET) and SPECT meet the criteria set by the APA in diagnosing Alzheimer's disease (122). FDG-PET and SPECT both have sensitivity and specificity in the diagnosis of Alzheimer's disease between 82% and 89% (122). Moreover, FDG-PET and SPECT are superior to amyloid imaging in the differential diagnosis of the various forms of dementia (24,122).…”

“…FDG-PET and SPECT both have sensitivity and specificity in the diagnosis of Alzheimer's disease between 82% and 89% (122). Moreover, FDG-PET and SPECT are superior to amyloid imaging in the differential diagnosis of the various forms of dementia (24,122). To be specific, a positive amyloid scan can reliably be considered evidence of Alzheimer's disease or its precursor (sensitivity = 89%; specificity = 87%) (123).…”

“…To be specific, a positive amyloid scan can reliably be considered evidence of Alzheimer's disease or its precursor (sensitivity = 89%; specificity = 87%) (123). However, the non-specific binding in amyloid scans increases dramatically with age to over 40% in patients over 80 years (122,124). Thus, the specificity of amyloid imaging declines dramatically with age.…”