In-office testing of semantic memory may be an easy and quite sensitive early diagnostic tool for Alzheimer's disease, suggested Asmus Vogel, a Ph.D. student in the memory disorders research unit at Copenhagen University Hospital, and colleagues.
They concluded that semantic memory deficits occur even in predementia Alzheimer's patients, perhaps due to the early development of neurofibrillary tangles in the temporal neocortex. Short neuropsychological tests with semantic content may be a valuable tool for assessing patients with suspected AD, the investigators said (Dement. Geriatr. Cogn. Disord. 2005;19:75–81).
In their prospective study, the researchers administered five neuropsychological tests focusing on semantic memory to a total of 182 elderly subjects, including 58 healthy controls, 22 patients with predementia AD, and 102 patients with mild AD. The average age was 74 years.
The majority of mild AD patients had mild or moderate semantic impairment, and 25% had severe impairment (deficits on four of the five tests). Among predementia patients, 59% had below normal scores on at least one test, although only 9% were impaired on three or more tests.
The high frequency of semantic dysfunction in the earliest stages of AD has important clinical implications, they said. “First, semantic memory tests may be sensitive diagnostic tests in the assessment of patients suspected to have dementia. … Further, tests for semantic memory have been found to correlate strongly with patients' functional performance. This correlation highlights that assessment of semantic memory is important in early AD when trying to identify patients in need of professional assistance and care.”