Xenomelia is the oppressive feeling that one or more limbs of one's body do not belong to one's self. We present the results of a thorough examination of the characteristics of the disorder in 15 males with a strong desire for amputation of one or both legs. The feeling of estrangement had been present since early childhood and was limited to a precisely demarcated part of the leg in all individuals. Neurological status examination and neuropsychological testing were normal in all participants, and psychiatric evaluation ruled out the presence of a psychotic disorder. In 13 individuals and in 13 pair-matched control participants, magnetic resonance imaging was performed, and surface-based morphometry revealed significant group differences in cortical architecture. In the right hemisphere, participants with xenomelia showed reduced cortical thickness in the superior parietal lobule and reduced cortical surface area in the primary and secondary somatosensory cortices, in the inferior parietal lobule, as well as in the anterior insular cortex. A cluster of increased thickness was located in the central sulcus. In the left hemisphere, affected individuals evinced a larger cortical surface area in the inferior parietal lobule and secondary somatosensory cortex. Although of modest size, these structural correlates of xenomelia appear meaningful when discussed against the background of some key clinical features of the disorder. Thus, the predominantly right-sided cortical abnormalities are in line with a strong bias for left-sided limbs as the target of the amputation desire, evident both in our sample and in previously described populations with xenomelia. We also propose that the higher incidence of lower compared with upper limbs (∼80% according to previous investigations) may explain the erotic connotations typically associated with xenomelia, also in the present sample. These may have their roots in the proximity of primary somatosensory cortex for leg representation, whose surface area was reduced in the participants with xenomelia, with that of the genitals. Alternatively, the spatial adjacency of secondary somatosensory cortex for leg representation and the anterior insula, the latter known to mediate sexual arousal beyond that induced by direct tactile stimulation of the genital area, might play a role. Although the right hemisphere regions of significant neuroarchitectural correlates of xenomelia are part of a network reportedly subserving body ownership, it remains unclear whether the structural alterations are the cause or rather the consequence of the long-standing and pervasive mismatch between body and self.

Objective: Xenomelia, that is, the nonacceptance of one's own limb, is an intriguing but little understood condition. We sought to further test the most prominent neuroscientific hypothesis that suggests xenomelia results from a breakdown in multisensory integration for the affected body part. Method: A "rubber foot illusion" paradigm was developed and tested in healthy participants and in individuals with a desire for left foot amputation (xenomelia). Behavioral and physiological responses quantified illusory ownership of a fake foot after synchronous and asynchronous stroking of a visible rubber foot and the subject's own hidden foot. Results: Healthy participants (n = 15) showed a rubber foot illusion similar to the well-known rubber hand illusion. Individuals with xenomelia (n = 9) experienced the rubber foot illusion in a way comparable to healthy controls. The only difference in the individuals with xenomelia was an increase in the vividness of the illusion for the undesired limb. This vividness of the illusion correlated positively with the strength of amputation desire. Conclusion: These findings might reflect the malleable sense of the body in xenomelia and suggest a weakened representation of the affected body part. These findings may support the use of multisensory stimulation in therapeutic settings. Objective: Xenomelia -i.e. the non-acceptance of one's own limb -is an intriguing but littleunderstood condition. This study aimed to further test the most prominent neuroscientific hypothesis that suggests it results from a breakdown in multisensory integration for the affected body part. Method:A "rubber foot illusion" paradigm was developed and tested both in healthy participants as well as in individuals with a desire for left foot amputation (xenomelia). Questionnaire, behavioral and physiological responses quantified illusory ownership of a fake foot after synchronous and asynchronous stroking of a seen rubber foot and the hidden own foot.Results: Healthy participants (n=15) showed a rubber foot illusion similar to the known rubber hand illusion. Furthermore, individuals with xenomelia (n=9) experienced the rubber foot illusion in a comparable way to healthy controls. The only difference was an increased vividness of the illusion for the undesired limb. This vividness of the illusion was further positively correlated to the strength of amputation desire. Conclusions:These findings might reflect the malleable sense of the body in xenomelia and suggest a weakened representation specifically of the affected body part. They might further pave the way for the use of multisensory stimulation in therapeutic settings.Keywords: Body image identity disorder (BIID), multisensory integration, amputation desire, xenomelia, neuropsychiatryXenomelia designates the non-acceptance of one or several limbs by non-psychotic individuals (McGeoch et al., 2011). Usually first noticed in childhood, the failure to integrate the limb into one's bodily self typically gets stronger during puberty and may culminate i...

Body integrity identity disorder (BIID), or xenomelia, is a failure to integrate a fully functional limb into a coherent body schema. It manifests as the desire for amputation of the particular limb below an individually stable 'demarcation line.' Here we show, in five individuals with xenomelia, defective temporal order judgments to two tactile stimuli, one proximal, the other distal of the demarcation line. Spatio-temporal integration, known to be mediated by the parietal lobes, was biased towards the undesired body part, apparently capturing the individual's attention in a pathologically exaggerated way. This finding supports the view of xenomelia as a parietal lobe syndrome.

IntroductionXenomelia 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.MethodsWe 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.ResultsWe 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.ConclusionsOur 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.

Body integrity identity disorder (BIID) is characterised by profound experience of incongruity between the biological and desired body structure. The condition manifests in "non-belonging" of body parts, and the subsequent desire to amputate, paralyse or disable a limb. Little is known about BIID; however, a neuropsychological model implicating right fronto-parietal and insular networks is emerging, with potential disruption to body representation. We argue that, as there is scant systematic research on BIID published to date and much of the research is methodologically weak, it is premature to assume that the only process underlying bodily experience that is compromised is body representation. The present review systematically investigates which aspects of neurological processing of the body, and sense of self, may be compromised in BIID. We argue that the disorder most likely reflects dysregulation in multiple levels of body processing. That is, the disunity between self and the body could arguably come about through congenital and/or developmental disruption of body representations, which, together with altered multisensory integration, may preclude the experience of self-attribution and embodiment of affected body parts. Ulimately, there is a need for official diagnostic criteria to facilitate epidemiological characterisation of BIID, and for further research to systematically investigate which aspects of body representation and processing are truly compromised in the disorder.

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.

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Study design and objectives: Case report and review of supernumerary phantom limbs in patients suffering from spinal cord injury (SCI). Setting: SCI rehabilitation centre. Case report: After a ski accident, a 71-year-old man suffered an incomplete SCI (level C3; AIS C, central cord syndrome), with a C3/C4 dislocation fracture. From the first week after injury, he experienced a phantom duplication of both upper limbs that lasted for 7 months. The supernumerary limbs were only occasionally related to painful sensation, specifically when they were perceived as crossed on his trunk. Although the painful sensations were responsive to pain medication, the presence of the illusory limb sensations were persistent. During neurological recovery, the supernumerary limbs gradually disappeared. A rubber hand illusion paradigm was used twice during recovery to monitor the patient's ability to integrate visual, tactile and proprioceptive stimuli. Conclusion: Overall, the clinical relevance of supernumerary phantom limbs is not clear, specific treatment protocols have not yet been developed, and the underlying neural mechanisms are not fully understood. Supernumerary phantom limbs have been previously reported in patients with (sub)cortical lesions, but might be rather undocumented in patients suffering from traumatic SCI. For the appropriate diagnosis and treatment after SCI, supernumerary phantoms should be distinguished from other phantom sensations and pain syndromes after SCI.