Neurological Soft Signs (NSS) are minor neurological signs indicating non-specific cerebral dysfunction. They are divided into four categories: sensory integration, motor coordination, sequencing motor complex acts and primitive reflexes.
We sought to determine whether NSS were specifically related to schizophrenia.
1) To compare NSS scores between patients with schizophrenia, bipolar disorder and controls.
2) to assess the relationship of NSS scores with psychopathological measures and treatment (olanzapine equivalents).
We assessed neurological functioning by the Neurological Evaluation Scale (NES) in 67 patients diagnosed with schizophrenia (SCZ), 69 diagnosed with bipolar disorder (BD) and 50 healthy controls. Psychopathological dimension were assessed through the Positive and Negative Syndrome Scale (PANSS). Furthermore, we studied the correlation between NSS scores and psychopathological measures.Independent samples Student's t-tests and Post Hoc Tests were used to compute group differences. The correlations between NSS, treatment and PANSS scores were calculated using Pearson correlation coefficients.
Total NES and subscale scores were significantly higher in patients than in controls. SCZ patients performed worse than BD patients (p < 0,001). PANSS total scores were significantly related to NES scores (r = 0.63; p < 0,001). Antipsychotic treatment showed a significant correlation with PANSS total scores (p < 0,05), while no correlations was found with NES scores.
These findings support the hypothesis that neurological deficits measured through NSS could be a common endophenotype in schizophrenia and bipolar disorder, related to symptoms and independent from pharmacological treatment.