Signes neurologiques mineurs chez les patients schizophrènes et leurs apparentés non malades

Objectifs

Comparer la prévalence et les scores des signes neurologiques mineurs (SNM) chez un groupe de patients schizophrènes par rapport à leurs apparentés non malades et à des témoins sains et rechercher les corrélations avec les caractéristiques cliniques de la schizophrénie.

Méthodologie

C’est une étude cas-témoins, portant sur 66 patients schizophrènes comparés à 31 de leurs apparentés non malades et à 60 témoins sains sans antécédents psychiatriques familiaux. Les trois groupes étaient appariés en fonction de l’âge et du sexe. Les SNM ont été évalués par l’échelle de Krebs et al. Les patients schizophrènes ont été cliniquement évalués par le positive and negative syndrome scale (PANSS), les impressions cliniques globales (CGI) et l’échelle d’évaluation globale du fonctionnement (EGF).

Résultats

La prévalence des NSS était de 96,9 % chez les patients schizophrènes versus 35,5 % chez leurs apparentés (p<0,0001). Le score total moyen des SNM était significativement plus élevé chez les patients schizophrènes (19,51±5,28 versus 10,77±3,38 chez leurs apparentés et 4,23±2,07 chez les témoins sains, p<0,0001). Le score total des SNM était significativement corrélé au sous-type désorganisé de la schizophrénie (p=0,006), aux dimensions négative (p<0,0001) et de désorganisation de la PANSS (p=0,001), à une symptomatologie globale sévère à la PANSS (p=0,004), à une sévérité importante de la maladie à la CGI-sévérité (p<0,0001), à un bas niveau scolaire (p=0,002) et à un bas niveau de fonctionnement global à l’EGF (p=0,003).

Conclusions

Les SNM permettent une meilleure caractérisation phénotypique des patients schizophrènes et sont utiles dans l’identification de la vulnérabilité chez leurs apparentés. Les corrélations trouvées avec les dimensions négative et de désorganisation de la schizophrénie évoquent l’existence d’une base physiopathologique commune.

Background

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 patientʼs relatives suggests that they could be associated with the genetic liability.

Objectives

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.

Method

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.ʼs 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.

Results

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).

Conclusions

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 highy-risk subjects.