[Neurological soft signs in schizophrenia: correlations with age, sex, educational status and psychopathology]

Though the pathobiology of schizophrenia can be examined in multiple levels, the organic notion of brain disease suggests that neurological features will be present. One straightforward, inexpensive method of investigating brain dysfunction in schizophrenia is thought the bedside assessment of neurological abnormalities with a standard neurological examination. Neurological abnormalities are traditionally classified as "hard signs" (impairments in basic motor, sensory, and reflex behaviors, which do not appear to be affected in schizophrenia) and "soft signs", which refer to more complex phenomena such as abnormalities in motor control, integrative sensory function, sensorimotor integration, and cerebral laterality. Additionally, neurological soft signs (NSS) are minor motor and sensory abnormalities that are considered to be normal in the course of early development but abnormal when elicited in later life or persist beyond childhood. Soft signs also, have no definitive localizing significance but are indicative of subtle brain dysfunction. Most authors believe that they are a reflection not only of deficient integration between the sensory and motor systems, but also of dysfunctional neuronal circuits linking subcortical brain structures such as the basal ganglia, the brain stem, and the limbic system. Throughout the last four decades, studies have consistently shown that NSS are more frequently present in patients with schizophrenia than in normal subjects and non-psychotic psychiatric patients. However, the functional relevance of NSS remains unclear and their specificity has often been challenged, even though there is indication for a relative specificity with regard to diagnosis, or symptomatology. Many studies have considered soft signs as categorical variables thus hampering the evaluation of fluctuation with symptomatology and/or treatment, whereas other studies included insufficient number of assessed signs, or lacked a comprehensive assessment of extrapyramidal symptomatology. Factors such as sex, age or family history of schizophrenia, are said to influence the performance of neurological examination, whereas relative few studies have provided longitudinal follow-up data on neurological soft signs in a sufficient number of patients, in order to address a possible deterioration of neurological functions. Finally, one additional difficulty when analyzing the NSS literature lies in the diversity of symptoms that are evaluated in the studies and/or non-standardized procedures or scoring. We will review some basic issues concerning recurrent difficulties in the measurement and definition of soft signs, as well as controversies on the significance of these signs with respect to clinical subtyping of schizophrenia, and social and demographic variables.