Traumatic brain injury and Alzheimer's: deficit profile similarities and the impact of normal ageing.

Research has suggested that sustaining a traumatic brain injury (TBI) may increase one's risk of developing Dementia of the Alzheimer's Type (DAT) later in life. Several neuropathological models have been proposed to explain the association between TBI and DAT and studies using a neuropsychological deficit profile methodology suggest that the pattern and extent of cognitive decline associated with these conditions are similar. This paper presents a new conceptual model, derived from deficit profile methodology, regarding the relationship between TBI and DAT. This model proposes that, for some individuals, TBI may not lead to true DAT neuropathology, but rather produces a profile of neuropsychological deficits similar to DAT, which increasingly mimics the symptoms of true DAT as the TBI survivor ages. Understanding how TBI may contribute to the development of DAT has important social and medical implications, influencing the direction of prevention efforts and contributing to one's understanding of DAT.

Assessment of anosmia after traumatic brain injury: performance characteristics of the University of Pennsylvania Smell Identification Test.

OBJECTIVE: To examine the performance characteristics of two forms of the University of Pennsylvania Smell Identification Test (UPSIT) in a sample of persons with traumatic brain injury (TBI). DESIGN: Analysis of consecutive admissions into a brain injury rehabilitation program. SETTING: Midwestern medical center. PARTICIPANTS: One hundred twenty-two adults diagnosed with TBI (49% severe TBI, 16% moderate TBI, 35% mild TBI). MAIN OUTCOME MEASURES: University of Pennsylvania Smell Identification Test (UPSIT; 3- and 40-item versions). RESULTS: Fifty-six percent of sample exhibited impaired olfaction on the full UPSIT; 40% of these patients were unaware of their deficits. Contrary to expectation, TBI patients detected dangerous odors (natural gas, gasoline, smoke) with high accuracy. Usefulness of a 3-item screening measure was examined: Missing even one item related to a 2:1 likelihood of being anosmic. CONCLUSIONS: These findings support past investigations indicating that anosmia, and unawareness of olfactory dysfunction, are common in persons with TBI and related to injury severity. The use of the 3-item screening measure as a gross indicator was supported, although caution is advised, because nearly 20% of patients performing perfectly on the 3-item screen scored in the anosmic range on the full UPSIT.