BACKGROUND: It remains unclear whether the four signs of Gerstmann syndrome are a cluster because the neuronal nets responsible for these symptoms are closer together, or because they shares a common networks. If the latter is correct, then with degenerative disorders such as Alzheimer's disease, each sign associated with Gerstmann syndrome should correlate with the other three signs more closely than they correlate with other cognitive dysfunctions. METHODS: Cluster and correlation analyses for various cognitive deficits including signs of Gerstmann syndrome were done among sixty-nine patients with probable Alzheimer's disease. RESULTS: The four signs of Gerstmann syndrome did not cluster together. With the exception of calculation and writing, other signs including right-left orientation and finger naming placed in other groups and did not significantly correlate each other. CONCLUSIONS: A detailed statistical analysis of the tetrad showed that Gerstmann syndrome was not attributable to a common neuronal network, and the phenomenological association of the four signs may be related to the anatomical proximity of the different networks mediating these functions.