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Pathophysiologic mechanisms underlying spatial disorientation in patients with Alzheimer's disease.

To the Editor. —In a recent issue, Henderson, Mack, and Williams reported that impaired drawing skill in patients with "probable" Alzheimer's disease (AD) was a significant predictor of spatial disorientation. 1 The authors concluded that the poor visuoconstructive performance exhibited in some patients' drawings implicates right inferior parietal lobe dysfunction. We commend this effort to understand the brain mechanisms responsible for a major clinical problem—wandering and getting lost in patients with AD—but we find it difficult to accept the authors' conclusions about the anatomic specificity of this deficit. Drawing tests are complex, multifactorial measures with a long history and demonstrated validity in the assessment of brain dysfunction. 2 Performance on these tests may suffer due to a variety of isolated or combined deficits in visual perception, visuospatial analysis/synthesis, or motor programming and execution. The same complexity of these tasks that makes them sensitive to brain dysfunction demands that valid interpretation