Structural and functional hyperconnectivity within the sensorimotor system in xenomelia.

INTRODUCTION: Xenomelia is a rare condition characterized by the persistent and compulsive desire for the amputation of one or more physically healthy limbs. We highlight the neurological underpinnings of xenomelia by assessing structural and functional connectivity by means of whole-brain connectome and network analyses of regions previously implicated in empirical research in this condition. METHODS: We compared structural and functional connectivity between 13 xenomelic men with matched controls using diffusion tensor imaging combined with fiber tractography and resting state functional magnetic resonance imaging. Altered connectivity in xenomelia within the sensorimotor system has been predicted. RESULTS: We found subnetworks showing structural and functional hyperconnectivity in xenomelia compared with controls. These subnetworks were lateralized to the right hemisphere and mainly comprised by nodes belonging to the sensorimotor system. In the connectome analyses, the paracentral lobule, supplementary motor area, postcentral gyrus, basal ganglia, and the cerebellum were hyperconnected to each other, whereas in the xenomelia-specific network analyses, hyperconnected nodes have been found in the superior parietal lobule, primary and secondary somatosensory cortex, premotor cortex, basal ganglia, thalamus, and insula. CONCLUSIONS: Our study provides empirical evidence of structural and functional hyperconnectivity within the sensorimotor system including those regions that are core for the reconstruction of a coherent body image. Aberrant connectivity is a common response to focal neurological damage. As exemplified here, it may affect different brain regions differentially. Due to the small sample size, our findings must be interpreted cautiously and future studies are needed to elucidate potential associations between hyperconnectivity and limb disownership reported in xenomelia.

Paralyzed by desire: a new type of body integrity identity disorder.

BACKGROUND: Body incongruity in body integrity identity disorder (BIID) manifests in the desire to have a healthy limb amputated. We describe a variant of the disorder: the desire to become paralyzed (paralysis-BIID). METHOD: Sixteen otherwise healthy participants, recruited through Internet-based forums, websites, or word of mouth, completed questionnaires about details of their desire and accompanying symptoms. RESULTS: Onset of the desire for paralysis typically preceded puberty. All participants indicated a specific level for desired spinal cord injury. All participants simulated paralysis through mental imagery or physical pretending, and 9 (56%) reported erotic interest in paraplegia and/or disability. Our key new finding was that 37.5% of paralysis-BIID participants were women, compared with 4.4% women in a sample of 68 individuals with amputation-BIID. CONCLUSIONS: BIID reflects a disunity between self and body, usually with a prominent sexual component. Sex-related differences are emerging: unlike men, a higher proportion of women desire paralysis than desire amputation, and, while men typically seek unilateral amputation, women typically seek bilateral amputation. We propose that these sex-related differences in BIID manifestation may relate to sex differences in cerebral lateralization, or to disruption of representation and/or processing of body-related information in right-hemisphere frontoparietal networks.