Browsing by Author "Nachar, Rubén"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Quantitative Susceptibility Mapping MRI in Deep-Brain Nuclei in First-Episode Psychosis
    (2023) García Saborit, Marisleydis; Jara Vallejos, Alejandro Antonio; Muñoz Camelo, Néstor Andrés; Milovic, Carlos; Tepper, Angeles; Alliende Correa, Luz María; Mena, Carlos; Iruretagoyena Bruce, Bárbara Arantzazu; Ramírez Mahaluf, Juan Pablo; Diaz, Camila; Nachar, Rubén; Castaneda, Carmen Paz; Gonzalez, Alfonso; Undurraga, Juan; Crossley, Nicolás; Tejos Núñez, Cristián Andrés
    Background Psychosis is related to neurochemical changes in deep-brain nuclei, particularly suggesting dopamine dysfunctions. We used an magnetic resonance imaging-based technique called quantitative susceptibility mapping (QSM) to study these regions in psychosis. QSM quantifies magnetic susceptibility in the brain, which is associated with iron concentrations. Since iron is a cofactor in dopamine pathways and co-localizes with inhibitory neurons, differences in QSM could reflect changes in these processes. Methods We scanned 83 patients with first-episode psychosis and 64 healthy subjects. We reassessed 22 patients and 21 control subjects after 3 months. Mean susceptibility was measured in 6 deep-brain nuclei. Using linear mixed models, we analyzed the effect of case-control differences, region, age, gender, volume, framewise displacement (FD), treatment duration, dose, laterality, session, and psychotic symptoms on QSM. Results Patients showed a significant susceptibility reduction in the putamen and globus pallidus externa (GPe). Patients also showed a significant R2* reduction in GPe. Age, gender, FD, session, group, and region are significant predictor variables for QSM. Dose, treatment duration, and volume were not predictor variables of QSM. Conclusions Reduction in QSM and R2* suggests a decreased iron concentration in the GPe of patients. Susceptibility reduction in putamen cannot be associated with iron changes. Since changes observed in putamen and GPe were not associated with symptoms, dose, and treatment duration, we hypothesize that susceptibility may be a trait marker rather than a state marker, but this must be verified with long-term studies.
  • No Thumbnail Available
    Item
    Structural brain abnormalities in schizophrenia in adverse environments: Examining the effect of poverty and violence in six Latin American cities
    (2021) Crossley Karmelic, Nicolás Andrés; Zugman, Andre; Reyes-Madrigal, Francisco; Czepielewski, Leticia S.; Castro, Mariana N.; Díaz-Zuluaga, Ana M.; Pineda-Zapata, Julián A.; Reckziegel, Ramiro; Noto, Cristiano; Jackowski, Andrea; Alliende, Luz M.; Iruretagoyena, Bárbara; Ossandon, Tomás; Ramirez-Mahaluf, Juan P.; Castañeda, Carmen; González-Valderrama, Alfonso; Nachar, Rubén; León-Ortiz, Pablo; Undurraga, Juan; López-Jaramillo, Carlos; Guinjoan, Salvador; Gama, Clarissa; Fuente-Sandoval, Camilo de la; Bressan, Rodrigo
    Background: Social and environmental factors such as poverty or violence modulate the risk and course of schizophrenia. However, how they affect the brain in patients with psychosis remains unclear. Aims: We studied how environmental factors are related to brain structure in patients with schizophrenia and controls in Latin America, where these factors are large and unequally distributed. Method: This is a multicentre study of magnetic resonance imaging in patients with schizophrenia andcontrols fromsixLatinAmerican cities. Total and voxel-level grey matter volumes, and their relationship with neighbourhood characteristics such as average income and homicide rates, were analysed with a general linear model. Results: Atotal of 334 patients with schizophrenia and 262 controls were included. Income was differentially related to total grey matter volume in both groups (P=0.006). Controls showed a positive correlation between total grey matter volume and The risk of developing schizophrenia is modulated, among other factors, by the social and environmental context of where people live. Incidence rates of psychosis are different across countries,1 possibly reflecting variations in the environment. Proposed specific factors explaining this effect have included an urban upbringing,2 poverty3 and the neighbourhood crime rate.4 Where people live has also been related to recovery rates of schizophrenia, in the context of whether it is a low- or high-income country5 or experiencing periods of economic expansion or recession.6 Brain imaging studies have shown that many of these environmental factors are related to brain changes in healthy individuals. For example, young people raised in poverty in high-income countries show reductions in total brain grey matter.7 Exposure to childhood adversity and violence has also been related to differences in hippocampal and amygdala volumes.8 An unresolved question relates to how these environmental factors affect the biology of schizophrenia. Couldbraindifferences typically seen in patients with schizophrenia be accounted for by these environmental factors? How will the neuropathology of schizophrenia interact with brain changes related to the environment? Is there a double-hit situation, where * Joint last authors. 112 income(R=0.14, P=0.02). Surprisingly, this relationship was not present in patients with schizophrenia (R=−0.076, P=0.17). Voxel-level analysis confirmed that this interaction was widespread across the cortex. After adjusting for global brain changes, income was positively related to prefrontal cortex volumes only in controls. Conversely, the hippocampus in patients with schizophrenia, but not in controls, was relatively larger in affluent environments. There was no significant correlation between environmental violence and brain structure.
  • Thumbnail Image
    Item
    Uso de cannabis en jóvenes hospitalizados por un primer episodio de psicosis: un estudio caso-control
    (2020) Castañeda, Carmen Paz; Alliende Correa, Luz María; Iruretagoyena, Bárbara; Nachar, Rubén; Mancilla, Felipe; Diaz, Camila; Gallardo, Carlos; Mena, Cristian; Ramírez Mahaluf, Juan Pablo; Undurraga, Juan; González Valderrama, Alfonso; Crossley, Nicolás
    Background: Cannabis use among young people in Chile has increased significantly in the last years. There is a consistent link between cannabis and psychosis. Aim: To compare cannabis use in patients with a first episode of psychosis and healthy controls. Material and Methods: We included 74 patients aged 20 +/- 3 years (78% males) admitted to hospital with a first episode of psychosis and a group of 60 healthy controls aged 23 +/- 4 years (63% males). Cannabis consumption was assessed, including age of first time use and length of regular use. Results: Patients with psychosis reported a non-significantly higher frequency of life-time cannabis use. Patients had longer periods of regular cannabis use compared with healthy subjects (Odds ratio [OR] 2.4; 95% confidence intervals [CI] 1.14-5.05). Patients also used cannabis for the first time at an earlier age (16 compared with 17 years, p < 0.0). The population attributable fraction for regular cannabis use associated with hospital admissions due to psychosis was 17.7% (95% CI 1.2-45.5%). Conclusions: Cannabis use is related to psychosis in this Chilean group of patients. This relationship is stronger in patients with early exposure to the drug and longer the regular use. One of every five admissions due to psychosis is associated with cannabis consumption. These data should influence cannabis legislation and the public policies currently being discussed in Chile.