Reduction in the volume of the front part of the hippocampus in schizophrenics with hyponatremia on hospital admission

Purpose: Evaluation of the volume of the front part of hippocampi in schizophrenics with hyponatremia on psychiatric ward admission.

Methods: Hippocampal volumes were compared across a group of 11 schizophrenics with hyponatremia and 22 patients with normonatremia, in the whole groups and in 11 couples matched in terms of gender, age and the disease duration. The groups were characterised in terms of demographic (gender, age) and clinical (course of illness, pharmacotherapy, tobacco smoking) features. All the participants were right-handed. The hippocampal volumes were manually measured on the basis of the magnetic resonance imaging (MRI), using manual contouring, separately and jointly for the right and left hippocampus, then the obtained results were standardised for the maximum transverse brain diameter (MTBD), the maximum trans-pineal inner table diameter (LTID) or the height.

Results: No relation was found between hyponatremia and the MTBD. In patients with hyponatremia, a smaller volume of the left hippocampus was observed, both using direct measurement and after standardisation for the MTBD. The analysis of regression indicates a relation model, in which the reduction in the left hippocampus is explained by the covariance of hyponatremia and MTBD values.

Conclusions: Dependency of reduction in the volume of the left hippocampus on hyponatremia observed in patients with schizophrenia encourages a number of pathogenic hypotheses whose interpretation, however, urges caution as the phenomenon itself is complex, and methodological limitations of the undertaken research are present.