Neuropsychological and neuroanatomical deficits in patients with polydipsia and hyponatremia in schizophrenia

The hippocampus has been implicated in various aspects of learning and memory. In patients with schizophrenia, reductions in hippocampal volume have been associated with such cognitive difficulties (Sanfilipo et al., 2002). Schizophrenia patients with polydipsia and hyponatremia (PHS) display hippocampal volume reductions (Luchins, Nettles, & Goldman, 1997) as well as pronounced behavioral and cognitive deficits. Given the factors that contribute to their symptoms, it was hypothesized that these patients would exhibit both hippocampal volume reductions as well as deficits in the following measures from the CVLT-II: Learning Over Trials, Retroactive Interference, Subjective Clustering, Semantic Clustering, and Serial Clustering. Hippocampal volumes were obtained for 7 polydipsic hyponatremic (PHS) patients, 9 nopolydipsic (NS) patients, 10 polydipsic normonatremic (PNS) patients, and 12 healthy controls (HC), with volumes and performance from least to greatest in that order. A slightly more encompassing sample was available for analysis of neuropsychological variables. The hypotheses were partially supported in that the PHS patients showed the smallest volumes, F&barbelow;(1,38) = -1.772, p&barbelow; = .096 and demonstrated poorest performance across a number of cognitive variables. Contrary to expectation, PNS patients had generally lower scores than NS patients. Overall, NS patients performed more poorly than controls, though poorer performance was not as consistent as for polydipsic groups, particularly those with polydipsia and hyponatremia. This study provides further evidence of hippocampal volume reductions and cognitive difficulties in patients with schizophrenia.