Brain structural changes and neuropsychological impairments in male polydipsic schizophrenia

Tomohisa Nagashima,Soichiro Kitamura,Koji Okada,Jun Kosaka,Toshifumi Kishimoto,Kimihiko Kichikawa,Kuniaki Kiuchi,Toshiaki Taoka,Makoto Inoue,Naoko Kishimoto

doi:10.1186/1471-244x-12-210

Tomohisa Nagashima, Soichiro Kitamura + Show 8 more

Open Access

https://doi.org/10.1186/1471-244x-12-210

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Abstract

BackgroundPolydipsia frequently occurs in schizophrenia patients. The excessive water loading in polydipsia occasionally induces a hyponatremic state and leads to water intoxication. Whether polydipsia in schizophrenic patients correlates with neuropsychological impairments or structural brain changes is not clear and remains controversial.MethodsEight polydipsic schizophrenia patients, eight nonpolydipsic schizophrenia patients, and eight healthy controls were recruited. All subjects underwent magnetic resonance imaging (MRI) and neuropsychological testing. Structural abnormalities were analyzed using a voxel-based morphometry (VBM) approach, and patients’ neuropsychological function was assessed using the Brief Assessment of Cognition in Schizophrenia, Japanese version (BACS-J).ResultsNo significant differences were found between the two patient groups with respect to the clinical characteristics. Compared with healthy controls, polydipsic patients showed widespread brain volume reduction and neuropsychological impairment. Furthermore, the left insula was significantly reduced in polydipsic patients compared with nonpolydipsic patients. These nonpolydipsic patients performed intermediate to the other two groups in the neuropsychological function test.ConclusionsIt is possible that polydipsia or the secondary hyponatremia might induce left insula volume reduction. Furthermore, this structural brain change may indirectly induce more severe neuropsychological impairments in polydipsic patients. Thus, we suggest that insula abnormalities might contribute to the pathophysiology of polydipsic patients.

Highlights

We defined polydipsic schizophrenia (PS) as patients with a history of at least two hyponatremic states induced by polydipsia on available records, and who were continuously treated with water restrictions even on the day of testing because of their excessive fluid intake but who were not isolated from sources of water supply
PS had a longer duration of illness and higher chlorpromazine equivalent doses than did nonpolydipsic schizophrenia (NS), but there were no significant differences between these two patient groups
Psychopathological scores measured by Positive and Negative Syndrome Scale (PANSS) were not significantly different between these two patient groups

Summary

Introduction

The excessive water loading in polydipsia occasionally induces a hyponatremic state and leads to water intoxication. Whether polydipsia in schizophrenic patients correlates with neuropsychological impairments or structural brain changes is not clear and remains controversial. Schizophrenia affects about 1% of the population worldwide [1], and induces neuropsychological impairment [2], as well as structural brain changes [3]. Polydipsia occurs frequently among patients with schizophrenia and may be present in more than 20% of chronic psychiatric inpatients [4]. Neuroendocrine studies revealed that schizophrenia patients with hyponatremia secreted excess antidiuretic hormone (ADH) in a hypo-osmolemic serum state [5,6]. Excessive ADH secretion may accelerate a hyponatremic state and produce water intoxication [6,7]. The pathophysiology of polydipsia on the other hand remains to be elucidated

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