[Neurological soft signs in schizophrenic patients and their nonaffected siblings]

Neurological soft signs (NSS) are subtle neurological signs indicating non specific cerebral dysfunction. Several studies have found an excess of NSS in schizophrenic patients compared to healthy subjects. Although NSS have been consistently reported in schizophrenic patients, their clinical relevance and their relation to functional impairment and severity of this disease are not well-clarified. In addition, the presence of NSS in schizophrenic patient's relatives suggests that they could be associated with the genetic liability.

To determine the prevalence and scores of NSS in schizophrenic patients and their nonaffected siblings and to examine the clinical correlates of NSS in the schizophrenic patients.

Sixty-six schizophrenic patients (50 males and 16 females, mean age=31.16+/-7.17 years), were compared to 31 of their nonaffected siblings (22 males and nine females, mean age=32.19+/-5.88 years) and to 60 controls subjects (40 males and 20 females, mean age=30.70+/-6.54 years) without family psychiatric history. NSS were assessed with Krebs et al.'s neurological soft signs scale. It is a comprehensive and standardized scale consisting of 23 items comporting five factors: motor coordination, motor integration, sensory integration, quality of lateralization and involuntary movements or posture. The Simpson and Angus scale for extrapyramidal symptoms was also rated. Clinical assessment of the schizophrenic patients was conducted using the positive and negative syndrome scale (PANSS), clinical global impressions (CGI) and global functioning evaluation (GAF). Psychiatric disorders were ruled out among siblings of schizophrenic patients and control subjects by psychiatric review evaluation, according to the DSM-IV check list.

When the total NSS score of 11.5 was considered the cut-off point, the prevalence of NSS was 96.9% in the schizophrenic patients versus 35.5% in the nonaffected siblings (p<0.0001). Schizophrenic patients had also significantly higher NSS total score and subscores than the siblings and control groups. The NSS total score was 19.51+/-5.28 in the schizophrenic patients, 10.77+/-3.38 in their nonaffected siblings and 4.23+/-2.07 in control subjects (p<0.0001). The NSS total score and subscores in the siblings group were intermediate between those of the schizophrenic patients and those of the control subjects. The motor coordination, motor integration and sensory integration subscores were higher in schizophrenic patients and their nonaffected siblings. The NSS total score correlated positively with the negative (p<0.0001) and disorganization symptoms (p=0.001) subscores and total score of PANSS (p=0.004). The PANSS total score and negative and disorganization subscores also correlated positively with the motor integration and quality of laterality subscores of NSS. The NSS total score was significantly correlated with severity of illness (p<0.0001), lower educational level (p=0.002) and poor global functioning (p=0.003).

The association between NSS with negative and disorganization dimensions of schizophrenia supports that neurological dysfunction is an intrinsic characteristic of the illness and may distinguish a subgroup of patients with poor illness course and outcome. The NSS could be a trait marker useful in phenotypic characterization of schizophrenic patients and identification of vulnerability in genetically high-risk subjects.