Relation between motor function and cerebellar structure in psychosis

Recent research suggests that psychotic disorders are linked to abnormalities in both the structure and function of the cerebellum. Motor dysfunction seems to be an intrinsic trait of psychosis, being present in individuals previous to diagnosis and naive to antipsychotics. Given the cerebellum's role in motor coordination, it raises questions about whether these changes contribute to the motor alterations seen in individuals with the disorder. To explore these ideas, we studied 19 patients diagnosed with schizophrenia, bipolar or schizoaffective disorder. We assessed neurological soft signs (NSS) in all eligible patients using the Neurological Evaluation Scale and magnetic resonance imaging (MRI) was used to measure cerebellar volumes. Additionally, antipsychotic medication was studied as a potential confounding variable. The pharmacological therapy data was collected during hospital admission or follow-ups at the time of the neurological evaluation and transformed into chlorpromazine equivalents. Our findings revealed that higher scores in the subsequent subgroups of NSS correlated with significantly smaller cortical cerebellar volumes for both hemispheres. However, we did not observe this relation between NSS and white matter cerebellar volume. We also did not find any associations between cerebellar gray matter volumes and antipsychotic treatment, or between cerebellar volumes and NSS total score. These results lend support to the hypothesis implicating the cerebellum in psychosis and suggest that these alterations are linked to NSS, independently of antipsychotic treatment. Therefore, the cerebellum, and as this study shows, particularly the cerebellar cortex can be part of the pathological basis for NSS and subsequently of the psychopathology of this spectrum of disorders.
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