“…While this has been reported by others in preclinical models where 29–40% rats did not develop neuropathic syndrome after sciatic or spinal nerve injury ( Cui et al, 2000 , Dean et al, 2017 , Gemes et al, 2009 , Kupers et al, 1992 ), such distinctions have rarely been previously described after nerve trauma, likely due to grouping of all data ( Decosterd and Woolf, 2000 , DeLeo and Rutkowski, 2000 , Dominguez et al, 2009 , Kupers et al, 1992 , LaCroix-Fralish et al, 2005 , Roytta et al, 1999 ). The reasons for variability in, or lack of, development of pain behavior is currently not known but have been attributed to biological, psychosocial, environmental, and genetic factors in humans that are largely absent or controlled in animal studies ( Bushnell et al, 2015 , Main, 2013 , Mogil, 2012 , Paller et al, 2009 ). The variations identified in the present study are unlikely to be due to genetic variation as all the rats were of the same strain, although epigenetic difference may be present, and pharmacologic and anatomic differences in analgesic mechanisms have been noted for identical strains obtained from different vendors ( Clark et al, 1992 ) The observation of individual differences raises the possibility that there are subtypes of temporal patterns of response to injury that are dictated by underlying differences in pathogenic mechanisms.…”