Is structural imaging useful in schizophrenia ? Acta Psych Scandi (Oct 2012)

03.10.2012

Peerlini and colleagues review the state of art in structural imaging in schizophrenia in this over view article. Imaging is helping to understand the biological substrate of this illness.But is it useful in day to day management of schizophrenia?

Image analysis (MRI)   follow two main methods 1. Region of interest (ROI) technique where  a chosen region is  studied by manual tracing  2. Voxel-based morphometry (VBM) a whole brain approach that compare brain gray matter local concentration (Grey matter tissue density, or volume (GMC or GMV) between different groups of subjects.

Computational neuroanatomical analyses  are also becoming important sources of information to classify the brain features of schizophrenia. one such technique is  ‘machine learning’ which can   potentially classify group of subjects (i.e., different clinical populations) by extracting brain features from MRI data.

Findings of the review:

ROI studies :In subjects with a long history of illness, the most replicated findings are ventricular enlargement ; cerebral atrophy ; limbic and paralimbic region anomalies (including amygdala, hippocampus, parahippocampal gyrus, anterior cingulate gyrus); volume differences in superior temporal gyrus [reduction , esp on left side), frontal lobe abnormalities,  (particularly in prefrontal and orbitofrontal subregions which represent the anatomical substrate of executive functions).

Studies strongly suggest that  volumetric anomalies often present at the early stages of the illness, may have progression over time and are influenced by age of onset, duration of illness,  treatment and outcome.

VBM studies: A recent meta-analysis (Ellison-Wright . Schizophr Res 2010; 117:1–12) of  VBM studies has shown GM decreases in patients suffering from schizophrenia compared to healthy controls in a large region including insula (bilaterally), thalamus, anterior cingulate, medial frontal gyrus, and posterior cingulate. By contrast, GM increase has been detected in the region extending from the right globus pallidus to the left caudate.  GMC reductions appeared to be generally larger and more consistent than GMV reduction.Effects of antipsychotic drugs on brain volume have been also reported, with greater changes associated with typical rather than atypical antipsychotics.

Computational analysis: In the long run, this technique might help clinicians in reliable and early detection of affected patients, potentially becoming a crucial tool. Dorsolateral prefrontal cortex (DLPFC) may be identified as a potential structural marker to classify subjects with schizophrenia. Cortical thickness as a reliable feature for pattern classification and thus as a possible diagnostic aid in schizophrenia.

Other imaging studies:

fMRI:  Most are based on BOLD (Blood oxygenation level dependent)  methods, measuring regional cerebral hemodynamics (i.e., blood flow and blood oxygenation) to make inferences about neural activity, indirectly ie what happenns during different sensory or cognitive activities.

Magnetic resonance spectroscopy (MRS) :   Enables the measurement of brain biochemistry ie  spatial distribution of metabolite concentrations  in white matter and gray matter tissues (i.e., glutamate and N-acetylaspartate)

DTI (Diffusion Tensor Imaging):  Study the micro structural organization of white matter and report the level of disruption.  Two measures of white-matter microstructure integrity  namely the apparent diffusion coefficient (ADC) and the fractional anisotropy (FA) are usually reported.

Authors hope that imaging could be added to the conventional diagnostic process as a complementary assessment for the evaluation of brain anatomy and morphometry .This could help in refining the diagnosis and identifying subgroups leading on to better selection of treatments.

Prof Stahl, in the accompanying editorial comment, considers how imaging and genomics will change the practice of psychiatry.He accepts that we  are still a long way from getting brain scans of patients to diagnose schizophrenia or to monitor their course illness over time.  In his opinion,   no structural, functional or genetic test will ever diagnose schizophrenia. How ever he thinks it will, in near future,give us information on what the odds may be in favor or against an individual responding to or tolerating a given drug.

This is the summary of the article:

Structural imaging techniques in schizophrenia. Perlini C, Bellani M, Brambilla P. Acta Psychiatr Scand. 2012 Oct;126(4):235-42:

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