Body dysmorphic disorder (BDD) is characterized by an often-delusional preoccupation with misperceived defects of appearance, causing significant distress and disability. Although previous studies have found functional abnormalities in visual processing, frontostriatal, and limbic systems, no study to date has investigated the microstructure of white matter connecting these systems in BDD. Participants comprised 14 medication-free individuals with BDD and 16 healthy controls who were scanned using diffusion-weighted magnetic resonance imaging (MRI). We utilized probabilistic tractography to reconstruct tracts of interest, and tract-based spatial statistics to investigate whole brain white matter. To estimate white matter microstructure, we used fractional anisotropy (FA), mean diffusivity (MD), and linear and planar anisotropy (cl and cp). We correlated diffusion measures with clinical measures of symptom severity and poor insight/delusionality. Poor insight negatively correlated with FA and cl and positively correlated with MD in the inferior longitudinal fasciculus (ILF) and the forceps major (FM). FA and cl were lower in the ILF and the inferior fronto-occipital fasciculus and higher in the FM in the BDD group, but differences were nonsignificant. This is the first diffusion-weighted MR investigation of white matter in BDD. Results suggest a relationship between impairments in insight, a clinically important phenotype, and fiber disorganization in tracts connecting visual with emotion/memory processing systems.
Body dysmorphic disorder (BDD) is a psychiatric disorder in which individuals are preoccupied with misperceived defects of their appearance (American Psychiatric Association, 2000). Believing that they look disfigured and ugly, they suffer significant distress and functional impairment. BDD affects approximately 0.7–2.4% of the population (Faravelli et al., 1997, Rief et al., 2006, Koran et al., 2008 and Buhlmann et al., 2010) and is associated with high lifetime rates of hospitalization (48%) (Phillips and Diaz, 1997) and suicide attempts (22–27.5%) (Veale et al., 1996, Phillips and Diaz, 1997 and Phillips et al., 2005). Insight is usually impaired and 36–60% of BDD patients are delusional (Gunstad and Phillips, 2003, Phillips et al., 2005b and Mancuso et al., 2010). Despite the severity of this disorder, knowledge of the underlying abnormalities in brain function and structure is still in its early stages.
An important symptom domain in BDD, for which there is emerging evidence, is distortion of visual perception. Distortion of self-perception of appearance may contribute to the conviction of disfigurement and ugliness, and subsequent poor insight or delusionality. Clinically, individuals with BDD focus on details of their appearance at the expense of global aspects. A neuropsychological study using the Rey–Osterrieth Complex Figure Test demonstrated that patients with BDD selectively recalled details instead of larger organizational design features (Deckersbach et al., 2000). Individuals with BDD may also have perceptual distortions for own-face processing; in one study they perceived distortions of digital images of their faces that were not actually present (Yaryura-Tobias et al., 2002).
A previous functional magnetic resonance imaging (fMRI) study (performed in the same participants as the current study) found that individuals with BDD demonstrated abnormalities in visual processing (striate and extrastriate visual cortex) and frontostriatal systems (orbitofrontal cortex and caudate) when viewing their face (Feusner et al., 2010a). There was also evidence of abnormalities in emotion processing systems. In addition, BDD symptom severity was correlated with frontostriatal activity and activity in extrastriate visual cortex. Abnormalities in visual systems may therefore represent early stage abnormalities (“bottom–up”) and/or may be the result of “top–down” modulation from emotional processing and/or prefrontal systems.
An earlier fMRI study in BDD using others' faces as stimuli also found a pattern of abnormal information processing, including left hemisphere hyperactivity in an extended face-processing network (Feusner et al., 2007). This pattern, in contrast to the generally right hemisphere-dominant pattern for healthy controls (Haxby et al., 1994), suggests greater detail in encoding and analysis relative to holistic and configural processing. Abnormal interhemispheric sharing of information may be involved, which may also contribute to aberrant visual processing.
The objective of the current study was to explore anatomical white matter connections involved in the neural systems that have been previously found to show abnormal activity in BDD. These white matter tracts include those likely involved in the integration of information between visual processing and the limbic as well as prefrontal systems, and those involved in interhemispheric sharing of information.
The only other studies in BDD that have investigated white matter include three small studies of volumetric brain morphometry. Two of these (Rauch et al., 2003 and Atmaca et al., 2010), but not the third (Feusner et al., 2009), found greater total white matter in the BDD group relative to healthy controls.
