Schizoaffective disorder: evidence for reversed cerebral asymmetry

Schizoaffective disorder--an ongoing challenge for psychiatric nosology

OBJECTIVE

Schizoaffective disorder is a common diagnosis in mental health services. The present article aims to provide an overview of diagnostic reliability, symptomatology, outcome, neurobiology and treatment of schizoaffective disorder.

METHOD

Literature was identified by searches in "Medline" and "Cochrane Library".

RESULTS

The diagnosis of schizoaffective disorder has a low reliability. There are marked differences between the current diagnostic systems. With respect to psychopathological symptoms, no clear boundaries were found between schizophrenia, schizoaffective disorder and affective disorders. Common neurobiological factors were found across the traditional diagnostic categories. Schizoaffective disorder according to ICD-10 criteria, but not to DSM-IV criteria, shows a more favorable outcome than schizophrenia. With regard to treatment, only a small and heterogeneous database exists.

CONCLUSION

Due to the low reliability and questionable validity there is a substantial need for revision and unification of the current diagnostic concepts of schizoaffective disorder. If future diagnostic systems return to Kraepelin's dichotomous classification of non-organic psychosis or adopt a dimensional diagnostic approach, schizoaffective disorder will disappear from the psychiatric nomenclature. A nosological model with multiple diagnostic entities, however, would be compatible with retaining the diagnostic category of schizoaffective disorder.

Is schizoaffective disorder a distinct categorical diagnosis? A critical review of the literature

Considerable debate surrounds the inclusion of schizoaffective disorder in psychiatric nosology. Schizoaffective disorder may be a variant of schizophrenia in which mood symptoms are unusually prominent but not unusual in type. This condition may instead reflect a severe form of either major depressive or bipolar disorder in which episode-related psychotic symptoms fail to remit completely between mood episodes. Alternatively, schizoaffective disorder may reflect the co-occurrence of two relatively common psychiatric illnesses, schizophrenia and a mood disorder (major depressive or bipolar disorder). Each of these formulations of schizoaffective disorder presents nosological challenges because the signs and symptoms of this condition cross conventional categorical diagnostic boundaries between psychotic disorders and mood disorders. The study, evaluation, and treatment of persons presently diagnosed with schizoaffective may be more usefully informed by a dimensional approach. It is in this context that this article reviews and contrasts the categorical and dimensional approaches to its description, neurobiology, and treatment. Based on this review, an argument for the study and treatment of this condition using a dimensional approach is offered.

Aberrant functional organization and maturation in early-onset psychosis: evidence from magnetoencephalography

Studies of the location of somatosensory and auditory cortical responses have shown anomalous hemispheric asymmetries in a variety of neurodevelopmental disorders. To date, abnormal asymmetries in the somatosensory region have shown greater specificity, being reported only in psychotic adults. This study examines the functional organization of the somatosensory cortices using magnetoencephalography in adolescents with childhood-onset psychotic disorders. Eighteen young outpatients with history of psychotic illness and 15 healthy adolescents participated. Both groups underwent stimulation of the index finger as magnetoencephalography was acquired from the contralateral hemisphere. Neural generators of the M50 somatosensory response were modeled using an equivalent current dipole for each hemisphere, and later investigated for systematic variation with diagnosis. Consistent with adult psychosis data, adolescent patients showed hemispheric symmetry in the anterior-posterior dimension. In controls, a reversed pattern of hemispheric asymmetry was observed relative to previous findings in normal adults [Reite, M., Teale, P., Rojas, D.C., Benkers, T.L., Carlson, J., 2003. Anomalous somatosensory cortical localization in schizophrenia. American Journal of Psychiatry 160, 2148-2153], but trend-level correlations suggested source location became more adult-like during the transition from adolescence to adulthood. Source parameters also exhibited robust inter-hemispheric correlations only in adolescent controls. In sum, source locations, patterns of cerebral lateralization, and inter-hemispheric correlations all distinguish patients from their normally developing cohort. These findings suggest aberrant maturation underlies the reduction in cerebral laterality associated with psychosis.

P50 sensory gating: Impact of high vs. low schizotypal personality and smoking status

Sensory gating deficits are seen in individuals with schizophrenia and schizotypal disorders, yet smoking influence, regional or lateral difference effects are rarely assessed. We examined sensory gating in smokers and non-smokers within university-level high and low schizotypal personality (HiS and LoS) groups using [Raine, A., 1991. The Schizotypal Personality Questionnaire (SPQ): A measure of schizotypal personality based on DSM-III-R criteria. Schizophr. Bull. 17, 555-564] Schizotypal Personality Questionnaire. Among 39 (18 men; 19 smokers) right-handed undergraduates, a paired-tone paradigm (40 pairs; 10 s ISI; 70 dB, 1000 Hz) was presented in two conditions (smokers while abstaining and after smoking). Sensory gating [S2(P50-N40)/S1(P50-N40)] was assessed at frontal, fronto-central, central, centro-parietal, and parietal midline and lateralized sites. Sensory gating was better at (1) midline than left/right hemispheric sites, and (2) fronto-central and central midline sites. At fronto-central/central lateral sites, (1) among non-smokers, better sensory gating occurred in LoS than HiS, (2) among smokers, better sensory gating occurred in HiS than LoS, and (3) among LoSs, smokers showed less sensory gating than non-smokers. No acute smoking effects emerged. Unlike schizophrenia studies, smoking did not impact sensory gating. Differences among smokers and non-smokers in LoS and HiS groups reinforce need to evaluate both smoking and schizotypal characteristics, as well as midline and lateral sites in anterior to posterior regions, in sensory gating studies.

Tonotopy of the Auditory-Evoked Field Component N100m in Patients with Schizophrenia

Abstract A number of clinical studies on the auditory neuromagnetic evoked field (AEF) component N100m have reported an altered lateralization in schizophrenic patients. This study addresses the problem of a possible functional reorganization of the temporal cortex in schizophrenia by examining the tonotopic organization of the N100m. Thirty-two patients with schizophrenia and 33 healthy controls of both sexes took part. Two tone frequencies (1000 and 5000 Hz tone) were applied for auditory stimuli, and AEF were recorded over both hemispheres successively using a 31-channel biomagnetometer. The comparison of N100m dipole location and orientation between hemispheres revealed no alterations in male or female patients. Between tone frequencies highly significant differences were found for N100m peak latency, mean global field power, dipole orientation, and dipole location in the anterior-posterior direction. Although the main effects of frequency were found to be the same in patients and controls, the balance between hemispheres was altered in patients with schizophrenia, with respect to the dependence between frequency and dipole location in the anterior-posterior direction as well as between frequency and latency. In patients, the influence of frequency on these variables was more pronounced in the right hemisphere and less pronounced in the left, compared to controls.