Brief report
Olfactory sulcus morphology in established bipolar affective disorder

https://doi.org/10.1016/j.pscychresns.2014.02.005Get rights and content

Abstract

This MRI study examined the morphology of the olfactory sulcus, a potential marker of early neurodevelopment in 26 patients with bipolar I disorder and 24 matched controls. Bipolar patients had significantly shallower olfactory sulci bilaterally compared to controls, suggesting that neurodevelopmental abnormalities contribute to the neurobiology of bipolar disorder.

Introduction

A large number of studies suggest a close relationship between olfactory and affective information processing, with common underlying neural substrates including limbic structures (Soudry et al., 2011). Although olfactory function in bipolar disorder (BD) has not been well documented (Burón and Bulbena, 2013), several recent studies have demonstrated olfactory dysfunction in BD (Cumming et al., 2011, Hardy et al., 2012, Lahera et al., in press) or in a BD subgroup with psychotic symptoms (Striebel et al., 1999).

The olfactory sulcus appears during fetal development at around 16 weeks of gestation (Chi et al., 1977), and its depth has been related to olfactory function in healthy subjects (Hummel et al., 2003). For psychiatric disorders, an abnormally shallow olfactory sulcus has been reported in schizophrenia (Turetsky et al., 2009a, Takahashi et al., 2013), supporting the notion that olfactory dysfunction is a prominent feature of schizophrenia and may represent a marker of early neurodevelopmental abnormalities (Brewer et al., 2001, Turetsky et al., 2009b, Kamath et al., 2014). In addition to clinical and biological commonality between BD and schizophrenia (Whalley et al., 2012, Tamminga et al., 2013), some neuroimaging (e.g., Takahashi et al. (2010)) and post-mortem studies suggest a possible embryonic developmental etiology also in BD (reviewed by Sanches et al. (2008)). Furthermore, BD patients and their unaffected first-degree relatives are likely to share brain morphologic changes related to olfactory processing (e.g., anterior-limbic structures) (Matsuo et al., 2012, Nery et al., 2013), suggesting that abnormalities in the olfactory structures may be at least partly associated with vulnerability to BD. It remains largely unknown, however, whether BD patients exhibit morphologic changes of the olfactory sulcus.

This magnetic resonance imaging (MRI) study investigated the olfactory sulcus morphology in BD patients and matched controls. Based on previous olfactory ability findings in BD and the potential role of olfactory sulcus depth as a marker of early neurodevelopment, we predicted a shallower olfactory sulcus in BD patients compared with controls. We also investigated the association between olfactory sulcus morphology and clinical features of BD.

Section snippets

Participants

Twenty-six patients with DSM-IV bipolar I disorder and 24 age- and gender-matched healthy controls participated in this study (Table 1). Patients were recruited through advertisement and via a dedicated specialist bipolar disorder clinic based in Sydney, Australia. Diagnoses were made by a research psychiatrist (GM) using the Structured Clinical Interview for DSM-IV (SCID-IV-P) (First et al., 1998), supplemented by case note review. The majority of patients were euthymic at the time of

Results

ANCOVA of the sulcus depth revealed significant main effects for diagnosis [F(1, 44)=51.55, P<0.001] and hemisphere [F(1, 46)=83.14, P<0.001] but no interaction between these factors; the BD patients had a shallower sulcus than controls, and the sulcus was deeper in the right than in the left hemisphere (Table 1, Fig. 2). There was no group difference in the sulcus length, but the olfactory sulcus was longer in the right hemisphere [F(1, 46)=6.88, P=0.012] (Table 1). No significant effect

Discussion

To our knowledge, this is the first MRI study to report the morphologic changes of the olfactory sulcus in established bipolar I disorder. The BD patients had significantly shallower olfactory sulci bilaterally compared with controls, but there was no group difference in its anterior-posterior length. Illness duration, number of affective episodes, and medication status did not affect the sulcus depth of the patients, suggesting that it might be a static illness marker reflecting abnormal

Acknowledgements

This research was supported in part by Grants-in-Aid for Scientific Research (C) (no. 22591275, 24591699) and Grants-in-Aid for Scientific Research (B) (no. 24390281) from the Japanese Society for the Promotion of Science, Health and Labour Sciences Research Grants (Comprehensive Research on Disability, Health and Welfare, H23-Seishin-Ippan-002 and H23-Seishin-Ippan-009), a Grant from Research Group For Schizophrenia, Japan, and a Research Grant from the JSPS Asian Core Program. Prof. Christos

References (28)

  • W.J. Brewer et al.

    Impairment of olfactory identification ability in individuals at ultra-high risk for psychosis who later develop schizophrenia

    American Journal of Psychiatry

    (2003)
  • E. Burón et al.

    Olfaction in affective and anxiety disorders: a review of the literature

    Psychopathology

    (2013)
  • J.G. Chi et al.

    Gyral development of the human brain

    Annals of Neurology

    (1977)
  • A.G. Cumming et al.

    Olfactory identification and preference in bipolar disorder and schizophrenia

    European Archives of Psychiatry and Clinical Neurosciences

    (2011)
  • Cited by (0)

    View full text