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Journal of Psychiatry and Brain Science 2016;1(1):3; DOI:10.20900/jpbs.20160003

Article

Gray Matter Volume Decrease in Treatment-refractory Schizophrenia Patients

Xiaomeng Shi1 , Xijia Xu1 * , Eugene Chao2, Xiaolan Wang1, Jing Sun1, Hui Yao1,

1 Department of Psychiatry, Affiliated Nanjing Brain Hospital of Nanjing Medical University, Nanjing 210029, P.R. China;

2 Baylor College of Medicine, Huston, Texas, USA.

Correspondence: Xijia Xu. Email: xuxijia@aliyun.com.

Published: 4/25/2016 8:46:08 PM

ABSTRACT

Objective: To investigate gray matter alterations in treatment-refractory schizophrenia (TRS) patients and explore correlations between gray matter alterations and the clinical characteristics of these patients.

Methods: Voxel-based morphometry (VBM) in conjunction with statistical parametric mapping of TRS patient (n = 24) structural magnetic resonance images and healthy controls (n = 21) to assess differences in gray matter volumes (GMV) between the two groups.

Results: GMV decreased in the left olfactory, bilateral insula, and right anterior cingulate of TRS patients compared to healthy controls (p < 0.05, FWE corrected). No correlation between gray matter reduction and clinical characteristics in these patients was found.

Conclusion: TRS patients have GMV decreases in the left olfactory, bilateral insula, and right anterior cingulate.

Schizophrenia, characterized by delusions, hallucinations, formal thought disorder, personality disturbances, and cognitive dysfunction, is a complex neuropsychiatric disorder. The pathophysiology underlying it remains unknown. Schizophrenia has a lifetime risk of about 1 % is frequently chronic and socially disabling. A body of cohort studies indicate that 20 - 30 % of schizophrenia patients meet the criteria for treatment-refractory schizophrenia (TRS)[1]. TRS is defined by the following criteria: (1) at least three periods of treatment, in the preceding 5 years, with antipsychotic drugs (from at least two different chemical classes) at dosages equivalent to, or greater than, 600 mg / day of chlorpromazine for a period of 4 weeks, without significant symptomatic relief; or patients intolerance antipsychotic side effects, and; (2) no period of good functioning within the preceding 5 years[2, 3]. TRS has a strong impact on rehabilitation of social function and quality of life. It has been the focus and of psychiatrists.

A number of schizophrenia neuroimaging studies have provided overwhelming evidence that the disease is a disorder involving widespread brain structure abnormalities[4]. Structural abnormalities include enlargement of the lateral and third ventricles, and reduced lateral temporal cortical, medial temporal, and prefrontal lobe volumes in the schizophrenia patients compared to healthy control[5]. The neurobiological processes underlying these structural abnormalities are believed to be central to the pathophysiology of schizophrenia[6]. Few neuroimaging studies have been performed on TRS patient brain structures[7]. In this study, using voxel-based morphometry (VBM), we investigated gray matter volume (GMV) changes in TRS patients in order to explore TRS patient brain structure changes.

1 OBJECTS AND METHODS

1.1 Objects 1.1.1 Patient group

The TRS patients were recruited from the Department of Psychiatry, Affiliated Nanjing Brain Hospital of Nanjing Medical University between March 2013 and December 2014. Inclusion criteria: (1) conforming to the TRS diagnosis standard (Kane Standard); a patient who had no response to the treatment of two, or three kinds, of atypical antipsychotics at least for 4 - 6 weeks; (2) aged 18 - 50 years old; (3) subjects were fully informed about the measurement and MRI scanning in the study. Written informed consent forms were obtained from each subject or their legal guardian. The protocols used in this study were approved by the Ethics Committee of Nanjing Brain Hospital of Nanjing Medical University Review Board, No. KY44, 2011. Exclusion criteria are: (1) presence of organic brain diseases, infectious diseases, other chronic somatic diseases, history of psychoactive substance abuse; (2) constrained dications of magnetic resonance imaging examination. TRS patients were diagnosed by two professional psychiatrists.

1.1.2 Control group

Healthy subjects with matching age, gender, and average education were recruited as a control group. The criteria of healthy subjects included: (1) no mental disorder and current good state of mind; (2) no family history of psychosis in the past three generations. (3) aged 18 - 50. Exclusion criteria were: (1) presence of organic brain disease, infectious diseases, or other chronic somatic diseases; (2) contraindications of magnetic resonance imaging examination.

1.2 Methods 1.2.1 High-resolution

T1-weighted Imaging Acquisition Magnetic resonance imaging (MRI) was performed with a 3.0T Siemens MRI scanner (Verio, Siemens Medical System) at the Nanjing Brain Hospital of Nanjing Medical University. A standard birdcage head coil was used, along with foam pads for limiting head motion. High-resolution whole brain volume T1-weighted images were acquired sagittally with a 3D spoiled gradient echo pulse sequence. Scanning parameters were: repetition time (TR) = 2000 msec; echo time (TE) = 30 ms; flip angle = 8º; slice thickness = 1 mm; Gap = 0 mm; 1 NEX; FOV= 256 × 256 mm; matrix size = 256 × 256 mm; voxel size = 1 × 1 × 1 mm3; and, 176 slices.

1.2.2 MRI Data Analysis

All structural data were processed with the Statistical Parametric Mapping SPM8 software package (http://www.fil.ion.ucl.ac.uk/spm), with voxel-based morphometry toolbox (VBM8) (http://dbm.neuro.uni-jena.de/vbm). The VBM8 toolbox combines tissue segmentation, bias correction, and spatial normalization into a unified model[8] . A Hidden Markov Random Field (HMRF) model was used to introduce spatial constraints into the segmentation process to improve tissue segmentation accuracy[9]. In the spatial normalization step, a high-dimensional Dartel-normalization approach (VBM-Dartel) was chosen. Images were multiplied (modulated) by the Jacobian determinants from the normalization step to preserve volume information. Modulated gray matter images were smoothed with an 8 mm FWHM Gaussian kernel for statistical analyses.

1.2.3 Statistical Analyses

A voxel-wise two-sample t-test analysis was carried out in SPM8 to measure differences in regional GMV between groups. Total gray matter volume, age, gender, and years of education were set as confounding covariates. An absolute threshold mask of 0.1 was used to avoid possible edge effects around the border between gray matter and white matter. Clusters of 100 voxels (a cluster size equal to 1 × 1 × 1 mm3) or greater, surviving a family-wise error (FWE) corrected threshold of p < 0.05 were considered significant.

Statistical analyses of demographic data were conducted with SPSS 15.0 software (SPSS, Chicago, Illinois). Independent-sample t test and X2 test were used to compare demographic data between two groups. The mean volumes of clusters that had shown group differences in VBM analysis were extracted. Correlations between mean volumes of the clusters and clinical variables including PANSS scores (positive symptoms, negative symptoms, general psychopathology, total score), duration of illness, and chlorpromazine (CPZ) equivalent value were calculated by partial correlation analysis controlling for ROI GMV (p < 0.05).

2 RESULTS

2.1 Characteristics of research samples

After quality control, poor quality MRI data samples were eliminated. The final samples contained 24 TRS patients and 21 healthy controls. TRS and control subject demographics, course of disease, PANSS score, CPZ equivalent dose and other data appear in Table 1. .

TABLE 1
Table 1. Demographic and clinical characteristics of TRS patients and control subjects

PANSS:Positive and Negative Syndrome Scale

2.2 Brian maps of representative axial slices showing GMV differences between TRS group and control group

Results from the VBM analysis revealed that the GMV of left olfactory, bilateral anteriorinsular, and right cingulate was reduced in TRS group (Table 2.; Fig. 1).

TABLE 2
Table 2. Regions of reduced GMV of left olfactory, bilateral insula, and right anterior cingulate in TRS group compared to control group
FIGURE 1
Fig. 1 Brain maps showing GMV differences between TRS group and controls. Significance level: The FWE corrected p < 0.05, voxel >100
2.3 Region of interest (ROI) analysis

GMV decreased in the left olfactory, bilateral insula, and right anterior cingulate of TRS patients compared to healthy controls (p < 0.05, FWE corrected). No correlation was found between the mean ROI area of GMV in TRS patients with illness duration, education, CPZ equivalent dose, and, PANSS scores (positive symptoms, negative symptoms, general psychopathology, total score) (p > 0.05).

3 DISCUSSION

Considerable progress has been made in the treatment of schizophrenia with the use of second generation antipsychotic drugs. TRS treatment continues to be a challenge for clinicians. It has special characteristics of psychopathology and clinical symptoms and any underlying neurobiologic mechanism largely unknown.

Changes in TRS patient brain gray matter were observed by performing high resolution T1-weighted imaging. The results showed that TRS patients had general gray matter deficits including bilateral insula, left olfactory, and right anterior cingulate.

Insula plays important roles in emotional processing, sensory stimulation, and inner body state perception[10]. Several studies had reported that gray matter was reduced in the, unilateral, or bilateral insular of patients with chronic schizophrenia. The results suggest that GMV alteration of the insular may be degenerative[11, 12]. In this study, it was found that the volume of the TRS patient brain gray matter in the bilateral insula was significantly reduced. The results support the conclusion that the insula should be involved in pathophysiology of schizophrenia.

Anterior cingulate is the main component of the limbic system in the central nervous system. It mainly involves emotion, learning, and memory processing. Its role in schizophrenia remains largely unknown. Sheng et al. reported that first onset schizophrenia patients displayed gray matter defects in the anterior cingulated[13]. Velakoulis et al. found that gray matter volume decreased in the anterior cingulate of the patients suffering from chronic schizophrenia and it continued shrinking during the course of the disease[14]. Liu et al. demonstrated anterior cingulate abnormalities as manifested by reduced surface area may contribute to cognitive dysfunction in schizophrenia[15]. This study found that TRS patients also had GMV reduction in their right anterior cingulate. Taken together, the observations suggest that the continuous reduction of gray matter volume in the anterior cingulate may be responsible for the poor responses of schizophrenia patients to medication.

The olfactory bulb and the olfactory tract lay below the basal forebrain. Olfactory bulb mitral cell synapses with neuroepithelium, retrieve information throughout the olfactory tract to primary olfactory areas and other regions that play crucial roles in emotion regulation and executive planning. Olfactory functional impairment may be a biological marker of schizophrenia susceptibility[16]. Performing a meta-analysis on olfactory dysfunction in schizophrenia patients, high-risk groups and first-degree relatives, Moberg PJ et al. discovered that schizophrenia patients and high-risk individuals had a moderate degree of olfactory dysfunction and their first-degree relatives also had mild, or moderate, olfactory dysfunction[17].

Consistent with the olfactory functional impairment in schizophrenia, peripheral olfactory structures, including neuroepithelial dysfunctional processes, were found to be abnormal[18] and a significant decrease in olfactory bulb volume and shallower olfactory sulcus was found in schizophrenia patients.

These structural changes stablize over time and correlate with poor olfactory performance[19]. Results from other observations show that schizophrenia patients have normal orbital sulci[20]. Shallower olfactory sulcus, a structure occurring at early embryogenesis, is often disturbed during early development. However, the orbital sulcus, which does not develop until the third trimester, is relatively immune to early insults. The developmental differences of the two structures support a hypothesis that the defined temporal window, the first half of gestation, for neurodevelopment (at least for olfactory structures) is crucial for schizophrenia patients. This study found that gray matter volume in the left olfactory cortex decreased in TRS patients. The result provides another piece of evidence about olfactory dysfunction in schizophrenia. Reports of abnormal olfactory cortexes in the study of common schizophrenia are rare and the findings may suggest that TRS is a more severe schizophrenia subgroup[21]. The results of this study implies that olfactory cortical gray matter damage may reflect a specific lesion in the brain of TRS patients.

Schizophrenia is characterized by progressive GMV decreases and lateral ventricular volume increases. Some of these neuroanatomical alterations may be associated with antipsychotic treatment. The putative mechanism of action for antipsychotics on GMV is unknown and can only be inferred in vivo from animal studies. It should be noted that association is not causation and thus GMV decreases being correlated with cumulative exposure to antipsychotic treatments should be interpreted cautiously. Antipsychotic treatment may not be the only factor associated with longitudinal GMV decreases in schizophrenia[22]. This is supported by the presence of progressive brain changes before onset and may in particular occur during the transition of psychosis in antipsychotic-naïve subjects.

In summary, this study suggests strongly that TRS patients have extensive decreases in gray matter and the defective areas include the left olfactory cortex, bilateral insula, and right anterior cingulate. Whether the defects are responsible for TRS patient poor response to medication needs further investigation.

DISCLOSURE STATEMENT

The authors do not have any actual or potential conflicts of interest.

ACKNOWLEDGMENTS

The authors thank the patients and their families, and the healthy control subjects, for their cooperation in this study. This study was supported by Nanjing Medical Science and Technique Development Foundation (QRX11121, ZKX08034), Jiangsu Provincial Commission of Health and Family Planning (H200875), State Key Clinical Specialty (Psychiatry, 2011 - 873, National Health and Family Planning Commission of the Peoples’s Republic of China), Provincial Medical Key Discipline (Psychiatry, 2011 - 12, Jiangsu Provincial Commission of Health and Family Planning), and National Clinical Research Center on Mental Disorders (2015BAI13B02).

The authors thank Shuiping Lu, Hong Lin, Yuan Li, Qing Cui (Department of Psychiatry, Affiliated Nanjing Brain Hospital of Nanjing Medical University, Nanjing, China) and Caoyong Xiao, Zonghong Li, Jun Hu, Chenlin Li (Department of Radiology, Affiliated Nanjing Brain Hospital of Nanjing Medical University, Nanjing, China) for the advises and assistance in sample collection and data acquisition of magnetic resonance imaging.

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