La schizophrénie, le trouble schizophréniforme et le trouble psychotique bref constituent l’essentiel des psychoses fonctionnelles non affectives de la quatrième édition du Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). Tels que définis, il est difficile de les différencier au début de la maladie. Les auteurs ont évalué la possibilité d’en faire le diagnostic différentiel au moyen de tests neuropsychologiques.

La population étudiée était composée de 70 schizophrènes, de 68 patients avec trouble psychotique bref et de 50 avec trouble schizophréniforme, tous Congolais, recrutés au centre neuro-psychopathologique de l’université de Kinshasa et au centre de santé mentale « Téléma » de Kinshasa, du 5 août 2003 au 14 mars 2005. Les performances des trois groupes de patients à une batterie conventionnelle de tests neuropsychologiques pour schizophrènes ont été comparées. Pour ce faire, une analyse des variances « one way » complétée par le test post-hoc de Tukey et une analyse discriminante multivariée ont été appliquées.

L’analyse discriminante multivariée a été concluante (F=2,55 ; df=2 ; p=0,0055). Cependant le risque d’erreur totale était très élevé (53 %) et il n’a pas été possible de dégager un profil neuropsychologique solide spécifique à chacune des trois affections. Seule la mémoire verbale – et non les fonctions du lobe frontal ni l’attention – a manifesté un certain pouvoir discriminant.

Les tests neuropsychologiques utilisés ne pourraient être recommandés avec assurance au diagnostic différentiel des affections étudiées. Toutefois les 15 mots de Rey retiennent l’attention à ce sujet.

Schizophrenia, Schizophreniform Disorder and Brief Psychotic Disorder constitute the main part of non-affective functional psychoses of the forth edition of Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). The DSM-IV primarily recognizes the same symptoms in them; it differentiates them only by the disease duration. It is thus difficult to make the differential diagnosis of the three affections at the beginning of the disease. However, they do not have the same prognosis and Schizophrenia, famous for its poor prognosis, requires energetic and early treatment which requires an early positive diagnosis. Hence the need to lay out tools for differential diagnosis other than symptoms. The authors studied the possibility to make the differential diagnosis of the three affection through neuropsychological assessment.

The sample comprised 70 schizophrenics, 68 patients with Brief Psychotic Disorder and 50 with Schizophreniform Disorder, all Congolese people, recruited in “Centre neuro-psychopathologique” of the university of Kinshasa and the mental health center “Téléma” in Kinshasa, from 5 August 2003 to 14 March 2005. Neuropsychological performances of the three patients groups at a conventional neuropsychological battery for schizophrenics were compared. A principal components analysis provided the cognitive factors used to compare the three patients groups. The comparison based on the one way analysis of variances (ANOVA), Tukey’s test and multivariate discriminant analysis, whilst controlling for demographic variables, clinical syndromes and neuroleptics side effects.

Five cognitive factors were identified: factor 1 with high loadings on tests of frontal functions, nonverbal memory and nonverbal general intelligence, factor 2 with high loadings on tests measuring the time and speed of execution of mental tasks, factor 3 measuring frontal controlled processes, factor 4 measuring verbal memory and factor 5 measuring attention. The multivariate discriminant analysis was conclusive (F=2.55; df=2; P=0.0055). However the overall error count estimate was too high (53%) and no convincing neuropsychological profile specific to each of the three affections could be released. Only verbal memory – not frontal functions nor attention – affirmed some discriminant power. Clinical variables showed more important differences between the patients groups. The founded differences showed that Brief Psychotic Disorder was different from Schizophrenia and Schizophreniform Disorder. The discrimination between Schizophrenia and Schizophreniform Disorder was less obvious; we failed especially to identify patients with Schizophreniform Disorder.

The used neuropsychological tests could not be used without caution in making differential diagnosis of the studied affections, however the importance of the 15 words of Rey, measuring verbal memory is highlighted. Other types of variables, e.g. the clinical one, could be more recommended to make the differential diagnosis between the three affections.