Abstract
BackgroundThe hippocampus has recently been identified to play a key role in the pathophysiology of adult obsessive-compulsive disorder (OCD). Surprisingly, there is only limited evidence regarding the potential relationships with symptom dimensions. Due to the heterogeneity of symptoms in OCD, we aimed at further examining, whether hippocampal volume differences might be related to symptom profiles instead of single symptom dimensions.MethodsIn order to find out more about the potential association between clinical symptom profiles and alterations in hippocampal volume we categorized a large sample of OCD patients (N = 66) into distinct symptom profile groups using K-means clustering. In addition, hippocampal volumes of the different symptom profile groups were compared with hippocampal volumes in a sample of 66 healthy controls.ResultsWe found significant differences in hippocampal volume between the different symptom profile groups which remained significant after correcting for age, sex, total intracranial volume, OCI-total score, depression, medication, disease duration and scanner. The patient group characterized by overall lower symptom scores and without high symptom severity in any specific domain showed the highest hippocampal volume. Finally, the comparison with healthy controls demonstrated significantly lower hippocampal volumes in those patients whose symptom profile was characterized by a high severity of ordering and checking symptoms.ConclusionsPresent results provide further confirmation for alterations in hippocampus structure in OCD and suggest that symptom profiles which take into account the multi-symptomatic character of the disorder should be given greater attention in this context.
Highlights
As a main finding the present analysis demonstrated that hippocampus volume differed significantly between the three groups with post-hoc tests indicating that cluster 2 had significantly smaller hippocampal volumes than cluster 3
Present findings extend recent results from the currently largest meta-analysis on structural alterations in obsessive-compulsive disorder (OCD) which revealed significantly smaller hippocampal volumes in adult OCD patients compared to healthy controls (Boedhoe et al, 2017)
Present findings corroborate the clinical relevance of hippocampal volume alterations in OCD as reported before (Honda et al, 2017) but strongly suggest that the interrelation of symptom dimensions should be taken into account in this regard
Summary
Despite increasing evidence for structural brain alterations in obsessive-compulsive disorder (OCD) the overall picture has to be considered as rather heterogeneous with findings reporting both increases and decreases in gray matter volume, thickness, surface area or gyrification (Fan et al, 2013; Kuhn et al, 2013; Nakamae et al, 2012; Piras et al, 2015; Rus et al, 2016; Shaw et al, 2015; Shin et al, 2007; Venkatasubramanian et al, 2012; Wobrock et al, 2010). There is strong reason to assume that hippocampal volume differences may be clinically relevant in OCD as well. The ENIGMA meta-analysis identified hippocampal volume differences to be larger in medicated patients, no relationship with symptoms was found. To find out more about the clinical relevance of the recently reported differences in hippocampal structure, the present study employs a cluster analysis approach on dimensional symptoms to reach a differentiation into distinct symptom composition profiles, comparing hippocampal volumes between the different symptom profile groups. We aimed at exploring whether taking into account the interrelation between different symptoms, i.e., patientssymptom composition profile, would be a valuable approach to relate structural alterations to clinically relevant features. If hippocampus volumes would not be related to symptom profiles, this would rather speak in favor of a clinically unspecific hippocampal involvement in the disease
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