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, here.
Journal: Journal of Neurosciences in Rural Practice