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The role of the cerebellum in schizophrenia has been highlighted by Andreasen's hypothesis of “cognitive dysmetria,” which suggests a general dyscoordination of sensorimotor and mental processes. Studies in schizophrenic patients have brought observations supporting a cerebellar impairment: high prevalence of neurological soft signs, dyscoordination, abnormal posture and propioception, impaired eyeblink conditioning, impaired adaptation of the vestibular-ocular reflex or procedural learning tests, and lastly functional neuroimaging studies correlating poor cognitive performances with abnormal cerebellar activations. Despite those compelling evidences, there has been, to our knowledge, no recent review on the clinical, cognitive, and functional literature supporting the role of the cerebellum in schizophrenia. We conducted a Medline research focusing on cerebellar dysfunctions in schizophrenia. Emphasis was given to recent literature (after 1998). The picture arising from this review is heterogeneous. While in some domains, the role of the cerebellum seems clearly defined (ie, neurological soft signs, posture, or equilibrium), in other domains, the cerebellar contribution to schizophrenia seems limited or indirect (ie, cognition) if present at all (ie, affectivity). Functional models of the cerebellum are proposed as a background for interpreting these results.

Clozapine is associated with significant weight gain and metabolic disturbances. This multicentre, randomized study comprised a double-blind, placebo-controlled treatment phase of 16 wk, and an open-label extension phase of 12 wk. Outpatients who met DSM-IV-TR criteria for schizophrenia, who were not optimally controlled while on stable dosage of clozapine for > or =3 months and had experienced weight gain of > or =2.5 kg while taking clozapine, were randomized (n=207) to aripiprazole at 5-15 mg/d or placebo, in addition to a stable dose of clozapine. The primary endpoint was mean change from baseline in body weight at week 16 (last observation carried forward). Secondary endpoints included clinical efficacy, body mass index (BMI) and waist circumference. A statistically significant difference in weight loss was reported for aripiprazole vs. placebo (-2.53 kg vs. -0.38 kg, respectively, difference=-2.15 kg, p<0.001). Aripiprazole-treated patients also showed BMI (median reduction 0.8 kg/m(2)) and waist circumference reduction (median reduction 2.0 cm) vs. placebo (no change in either parameter, p<0.001 and p=0.001, respectively). Aripiprazole-treated patients had significantly greater reductions in total and low-density lipoprotein (LDL) cholesterol. There were no significant differences in Positive and Negative Syndrome Scale total score changes between groups but Clinical Global Impression Improvement and Investigator's Assessment Questionnaire scores favoured aripiprazole over placebo. Safety and tolerability were generally comparable between groups. Combining aripiprazole and clozapine resulted in significant weight, BMI and fasting cholesterol benefits to patients suboptimally treated with clozapine. Improvements may reduce metabolic risk factors associated with clozapine treatment.

Schizophrenia is a heterogeneous disease involving genetic and environmental factors. The frequency of structural brain abnormalities or physical anomalies supports a neurodevelopmental etiology, especially in early onset schizophrenia. Brain-Derived-Neurotrophic-Factor (BDNF) is involved in the neurodevelopment of dopaminergic (DA)-related systems and interacts with the meso-limbic DA systems, involved in the therapeutic response to antipsychotic drugs and substance abuse. In addition, BDNF promotes and maintains dopamine D3 receptor (DRD3) expression. In a French Caucasian population, we found no statistical difference in allele or genotype distribution of the BDNF gene dinucleotide repeat polymorphism (166-174 bp) between the whole group of schizophrenic patients and controls. By contrast, an excess of the 172-176 bp alleles was found in patients with late onset, in neuroleptic-responding patients and in non-substance-abusing patients. BDNF gene variants thus appear to be associated with developmental features of schizophrenia. In addition, this association with good treatment responding was independent from the association found with the DRD3 Ball gene polymorphism in the same population. These results suggest an independent contribution of each gene to a treatment-sensitive form of schizophrenia.

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