Neurological soft signs in euthymic bipolar I patients: A comparative study with healthy siblings and controls

Neurological Soft Signs (NSS) are endophenotypic markers widely studied in schizophrenia and remain poorly evaluated in bipolar disorder. The aims of this paper were to determine the prevalence and scores of NSS in bipolar I patients, compared to healthy siblings and controls and to explore correlations with socio-demographic and clinical features of patients. This was a case-control study comparing 92 euthymic bipolar I patients, 44 of their healthy siblings and 60 control subjects. The neurological assessment was performed through the NSS scale validated by Krebs et al. (2000). Bipolar I patients were also assessed with the Bech-Rafaelsen Mania Scale (MAS), the Hamilton Depression Rating Scale (HDRS) and the Global Assessment of Functioning (GAF). The raters were not blinded to groups. The prevalence and the total score of NSS were significantly higher in bipolar I patients compared to their healthy siblings and controls. The sibling group had significantly higher NSS prevalence and total score than controls. No correlation was found between NSS total score and socio-demographic and clinical features of patients, except a negative correlation with the school level and the GAF score. In conclusion, bipolar I patients have motor and sensory signs, which are unrelated to their clinical features.