Peripheric and central olfactory measurements in patients with bipolar disorder

Background Bipolar disorder (BD) is a mental health disorder. Purpose To investigate the peripheric and central olfactory measurements in patients with BD using magnetic resonance imaging (MRI). Material and Methods This study was conducted retrospectively. Group 1 consisted of 27 euthymic patients with BD (14 men, 13 women) and Group 2 consisted of 27 healthy controls (14 men, 13 women). Olfactory bulb (OB) volume and olfactory sulcus (OS) depth (peripheric), and corpus amygdala and insular gyrus area (central) measurements were performed using cranial MRI. Results OB volume and OS depth value of the bipolar group were lower than the control group, but there were no significant differences between the groups (P > 0.05). The corpus amygdala and left insular gyrus area of the bipolar group were significantly lower than those in the control group (P < 0.05). There were positive correlations between OB volumes and OS depths, the insular gyrus areas, and the corpus amygdala areas (P < 0.05). As the number of depressive episodes and duration of illness increased in bipolar patients, the depth of the sulcus decreased (P < 0.05). Conclusion In the present study a correlation was detected between OB volumes and the structures, known as emotional processing (e.g. insular gyrus area, corpus amygdala), and clinical features. Accordingly, new treatment techniques, such as olfactory training, may be considered an option in the treatment of such patients with BD.

Automated summary

This study investigated the olfactory measurements in patients with bipolar disorder using MRI and found that the OB volume and OS depth were lower in the bipolar group compared to the control group. The corpus amygdala and left insular gyrus area were also significantly lower in the bipolar group. There were positive correlations between OB volumes and the insular gyrus areas, as well as the corpus amygdala areas. Therefore, new treatment techniques such as olfactory training may be considered for bipolar disorder patients.