title: Xenomelia: a new right parietal lobe syndrome.
abstract: BACKGROUND
  Damage to the right parietal lobe has long been associated with various disorders of body image. The authors have recently suggested that an unusual behavioural condition in which otherwise rational individuals desire the amputation of a healthy limb might also arise from right parietal dysfunction.
  
  
  METHODS
  Four subjects who desired the amputation of healthy legs (two right, one left and one, at first, bilateral and then left only) were recruited and underwent magnetoencephalography (MEG) scans during tactile stimulation of sites above and below the desired amputation line. Regions of interest (ROIs) in each hemisphere (superior parietal lobule (SPL), inferior parietal lobule, S1, M1, insula, premotor cortex and precuneus) were defined using FreeSurfer software.
  
  
  RESULTS
  Analysis of average MEG activity across the 40-140 ms post-stimulation timeframe was carried out using an unpaired t test. This revealed significantly reduced activation only in the right SPL ROI for the subjects' affected legs when compared with both subjects' unaffected legs and that of controls.
  
  
  CONCLUSIONS
  The right SPL is a cortical area that appears ideally placed to unify disparate sensory inputs to create a coherent sense of having a body. The authors propose that inadequate activation of the right SPL leads to the unnatural situation in which the sufferers can feel the limb in question being touched without it actually incorporating into their body image, with a resulting desire for amputation. The authors introduce the term 'xenomelia' as a more appropriate name than apotemnophilia or body integrity identity disorder, for what appears to be an unrecognised right parietal lobe syndrome.
authors.affiliation: Center for Brain and Cognition, University of California, San Diego, La Jolla, CA 92093, USA. pmcgeoch@mac.com
authors.forename: Paul D
authors.initials: PD
authors.lastname: McGeoch
authors.forename: David
authors.initials: D
authors.lastname: Brang
authors.forename: Tao
authors.initials: T
authors.lastname: Song
authors.forename: Roland R
authors.initials: RR
authors.lastname: Lee
authors.forename: Mingxiong
authors.initials: M
authors.lastname: Huang
authors.forename: V S
authors.initials: VS
authors.lastname: Ramachandran
mesh_terms: D000328:Adult; D000368:Aged; D000671:Amputation, Surgical / Q000523:psychology*; D001828:Body Image; D007839:Functional Laterality / Q000502:physiology*; D059907:Functional Neuroimaging / Q000379:methods / Q000523:psychology* / Q000706:statistics & numerical data; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods / Q000523:psychology*; D008297:Male; D008875:Middle Aged; D010296:Parietal Lobe / Q000503:physiopathology*; D020886:Somatosensory Disorders / Q000503:physiopathology* / Q000523:psychology; D013577:Syndrome; D055698:Touch Perception / Q000502:physiology