Neurological soft signs in schizophrenia.

As  the  field  of  psychiatry  has  been  advancing  gradually  over  the  time,  the  concepts  of  the  etiopathogenesis of the various psychiatric illnesses have  also  been  evolving  gradually.  The  advent  of  new  age  imaging  techniques  and  other  advanced investigation  methodologies  has  helped  the  search  for  the ever alluring causes of the psychiatric illnesses beyond  anything. However,  the  debate  over  the  etiopathogenesis of schizophrenia, which has started  from the Kreplinian age, is still continuing. Over the years,  in  the  study  of  complex  psychiatric  diseases  such as schizophrenia, concept of certain  measurable components  has come  up,  that  is  apparently  invisible  to  the  naked  eyes  but  bridges  the  distal  genotype and the disease, such as  endophenotypes. Gottesman  and  Shields  in  1973 first  adapted  the  term  “endophenotype” and proposed four criteria to define it. Those being, “The  endophenotype should be associated with illness in the population, should be  heritable and primarily state‑independent (manifests in an individual whether or  not illness is active), and it  should  co‑segregate  with  a  psychiatric  illness.”  Leboyer etal. in 1998 suggested additional criteria that endophenotypes should be found at a higher rate in the family members of the affected rather than those of unaffected.

Assessment  of  brain  dysfunction  in  patients  of  schizophrenia took a new turn, when in 1988, Heinrichs and Buchanan reviewed the significance of neurological soft signs (NSSs) in the study of schizophrenia. NSS are “objectively  measured,  nonlocalizing abnormalities,  not related to impairment of a specific brain region, reflecting improper cortical‑subcortical and intercortical connections.” Numerous  scales  have  been  developed  such  as  the  Heidelberger  Scale, the  Cambridge  Neurological Inventory, and the Neurological Evaluation Scale (NES) to study brain dysfunction in schizophrenia through NSSs, as it is a much simpler, cost‑effective way of assessing. Over the last few decades, numerous studies have  been  conducted  to  see  the  prevalence of  NSS in  schizophrenia, and the most accepted range is 50–65%. The  possibility  of  NSS  as  an  endophenotype  in schizophrenia has been  studied  across  the  globe.  A meta‑analysis by Chan etal., in 2010, that included 33  relevant  and independent  studies from 1966  to  January 2008, concluded that “the substantial difference between  schizophrenia  patients  and controls  suggests  that  NSS meet  one  essential  criterion  (association  with  illness)  of  an  endophenotype  for  schizophrenia.” Among  the  latest  studies,  one Polish  study  conducted  in  2014  by  Kaluzynska  and  Rabe‑Jablonska also  concluded that “NSS still represent only candidates for an  endophenotype  of  schizophrenia,”  however,  they  recommended  the  need  for  further  studies about  the  usefulness of NSS as an endophenotype of schizophrenia.The validity of NSS as an endophenotype lies in the fact that it should be independent of all sociodemographic and illness variables. Here lies the importance of studies that are aimed at finding this association. Hence, with this aim  in  mind,  we  have  conducted  this  particular  study in the North‑Eastern part of India which not only targets at finding this association, but also the prevalence, pattern, and the intensity of NSS among patients with schizophrenia.

Read more about this research conducted by Dr. Subrata Naskar & colleagues, 

Journal: Journal of Neurosciences in Rural Practice