Brain weight refers to the basic mass measurement of a post-mortem brain, either at time of autopsy (‘fresh’) or after formalin fixation (‘fixed’). Its ease of collection means it is a routine measurement at autopsy and has become a widely used tool for insight into brain integrity. If brain weight is altered, this provides a non-specific indication of neuropathology. It is often a presumed equivalent of the MRI findings of decreased brain volume.

What is the evidence for brain weight?

Moderate quality evidence suggests the brain of a person with schizophrenia is significantly lower in weight than a healthy brain. Moderate quality evidence suggests that male brain weight is significantly inversely correlated with age at disease onset, such that an earlier age at onset indicated a heavier brain weight.

October 2020

The post Brain weight appeared first on NeuRA Library.

CT imaging is a method for visualising the structural organisation of the brain using the attenuation of X-rays to generate image contrast. Tissues in regions of interest are highlighted based on their X-ray absorption properties, as dense tissues attenuate X-rays more than soft tissues, and air attenuates the least. Three-dimensional images are generated from a series of two-dimension X-ray images taken around a single axis of rotation.

What is the evidence for CT brain structure?

Moderate quality evidence suggests reduced temporal lobe volume in people with schizophrenia. Moderate to low quality evidence is unclear as to the utility of structural imaging as a means of identifying individual structural abnormalities in patients following a first episode of psychosis.

October 2020

The post Computed tomography appeared first on NeuRA Library.

DTI is a specialised imaging technique that uses MRI technology to investigate the movement of water within tissues of interest. By applying a magnetic field, the movement (“diffusivity”) of water molecules can be visualised in vivo. The diffusion of water is influenced by the cellular structure of the surrounding tissues, and measures such as fractional anisotropy (FA) were derived as an approximate measurement for the freedom of movement. In areas of high structural coherence such as white matter, FA is highest, indicating that water is moving in relatively fixed directions. It is lower in grey matter, and close to zero in cerebrospinal fluid, indicating that water is moving freely. Consequently, changes in FA values are interpreted to be representing alterations in the structural integrity of the regional white matter.

What is the evidence for DTI brain structure?

Compared to controls, moderate quality evidence finds white matter reductions in people with schizophrenia in the anterior commissure, corpus callosum, fornix, internal capsule, bilateral arcuate fasciculus, bilateral cingulum, bilateral cortico-ponto-cerebellum tract, bilateral cortico-spinal tract, bilateral inferior fronto-occipital fasciculus, bilateral inferior longitudinal fasciculus, bilateral inferior cerebellar penduculus, bilateral optic radiation, bilateral anterior and posterior segment of the arcuate fasciculus, bilateral superior longitudinal fasciculus 1, 2 and 3, bilateral superior cerebellar penduculus, and bilateral uncinate fasciculus. There was reduced white matter in the left, but not the right, arcuate fasciculus in people with schizophrenia who are experiencing auditory hallucinations.

Moderate quality evidence finds similar decreases in white matter integrity in people with schizophrenia and people with bipolar disorder in the genu of the corpus callosum extending to anterior thalamic radiation/cingulum fibres/inferior fronto-occipital fasciculus, and in left posterior cingulum fibres.

Moderate to high quality evidence found decreased whole brain white matter was associated with a small decrease in positive and general symptoms, and a small increase in negative symptoms. Review authors state these relationships could be explained by older age, which was associated with decreased whole brain white matter. This is because older age has been associated with less severe positive symptoms and more prominent negative symptoms.

High quality evidence found similar reductions in white matter in the genu, but not splenium, of the corpus callosum of male and female patients compared to controls. Although not significant, the reductions were slightly larger in females than in males.

January 2020

The post Diffusion tensor imaging appeared first on NeuRA Library.

MRI is a used to visualise the structure of the brain and other regions of the body. It uses the magnetic properties inside cells (such as protons) to create a 3D image of the target region. Understanding structural brain alterations in people with schizophrenia may help understand changes in brain development associated with the illness onset or progression, and may help to inform future treatment strategies.

What is the evidence for MRI brain structure?

Moderate to high quality evidence found grey matter reductions in bilateral frontal lobe, anterior and posterior cingulate gyri, superior and medial temporal gyrus, inferior parietal gyrus, corpus callosum, cerebellum, thalamus (particularly mediodorsal, and an absent adhesio interthalamica), insula, amygdala, hippocampus, and parahippocampus in people with schizophrenia compared to controls. Volume increases were found in the caudate, putamen, right globus pallidus, cerebrospinal fluid, and ventricles (lateral, third, and fourth, and a large cavum septum pellucidum). There were white matter reductions in bilateral frontal lobe, anterior commissure, corpus callosum, fornix, internal capsule, left anterior segment of the arcuate fasciculus, left long segment of the arcuate fasciculus, bilateral arcuate fasciculus, bilateral cingulum, bilateral cortico-ponto-cerebellum tract, bilateral cortico spinal tract, bilateral inferior fronto-occipital fasciculus, bilateral inferior longitudinal fasciculus, bilateral inferior cerebellar penduculus, bilateral optic radiation, bilateral posterior segment of the arcuate fasciculus, bilateral superior longitudinal fasciculus 1, 2 and 3, bilateral superior cerebellar penduculus, and bilateral uncinate fasciculus. Moderate to low quality evidence found an absence of normal leftward asymmetry in the planum temporale and Sylvian fissure, and an excess rightward asymmetry in the superior temporal gyrus (particularly posterior). There was also a higher frequency of abnormal (reversed) asymmetry in the frontal and occipital lobes in people with schizophrenia than controls.

Moderate to high quality evidence found auditory hallucinations were associated with grey matter volume reductions in the left superior temporal gyrua, and lower quality evidence also found associations with reductions in insula grey matter volume. Patients with persistent negative symptoms showed reductions in bilateral medial frontal gyrus, left precentral gyrus, left middle frontal gyrus, left caudate nucleus (caudate head), bilateral parahippocampal gyri, left anterior cingulate, thalamus, and insula.

Moderate quality evidence found similar patterns of grey matter abnormalities in antipsychotic-naïve and treated first-episode patients (compared to controls) in the frontal (gyrus rectus), superior temporal, left hippocampal, and insula cortex. Grey matter in the left supramarginal gyrus and left middle temporal gyrus were increased in antipsychotic-naive patients, but decreased in treated patients, while left median cingulate/paracingulate gyri and right hippocampus grey matter were decreased in antipsychotic-naive patients, but increased in treated patients. There was also reduced grey matter volume in the cerebellar vermic lobule IV/V/VII, left cerebellar lobule IV/V, and left cerebellar Crus I in antipsychotic-naïve patients. Increased antipsychotic dose over time (>2 years) was associated with small decreases in parietal and occipital lobe volume, and small increases in basal ganglia volume.

Moderate quality evidence found regions of structural and functional overlap in drug-free patients compared to controls. There was decreased grey matter volume and decreased functional activity in the left medial posterior cingulate/paracingulate gyrus, right temporal pole/superior temporal gyrus, left fusiform gyrus, left inferior parietal gyrus, and left caudate nucleus. There was decreased grey matter volume and increased functional activity in the left superior temporal gyrus, right superior temporal gyrus, left fusiform gyrus, and right lingual gyrus. There was increased grey matter volume and decreased functional activity in the left cerebellum, right gyrus rectus, and right inferior parietal gyrus. There was increased grey matter volume and increased functional activity in the left insula and left cerebellum (lobule IX).

Compared to people with bipolar disorder, moderate to high quality evidence found small reductions in the amygdala, left insula, bilateral hippocampal regions in people with schizophrenia. There was a distinct region of the pregenual cingulate cortex (anterior Brodmann area 24) where grey matter reduction was detected in bipolar disorder and not schizophrenia. Compared to people with an autism spectrum disorder, moderate to low quality evidence found overlapping grey matter volume decreases in the right posterior cingulate cortex, right parahippocampus, and right putamen, and to a lesser extent the right insula and left thalamus.

Moderate quality evidence found people at high genetic risk for schizophrenia showed reduced hippocampus, anterior cingulate, left basal ganglia/claustrum, left thalamus/putamen, right superior frontal gyrus, left insula, left inferior temporal gyrus, and right inferior network, as well as increased left medial frontal gyrus and third ventricle volume compared to controls. People at high clinical risk for schizophrenia showed decreases in the parahippocampus, hippocampus, right anterior cingulate, insula, right middle/superior temporal gyrus, right inferior frontal gyrus, and right frontal gyrus compared to controls. People at high clinical risk showed decreases in the bilateral anterior cingulate compared to people at high genetic risk, and people at high genetic risk showed decreases in the left parahippocampus, insula, and right superior temporal gyrus compared to people at high clinical risk. Moderate to low quality evidence found high risk individuals who transitioned to psychosis had greater pituitary volumes compared to controls and reduced grey matter in the insula, cingulate cortex, superior temporal gyrus, prefrontal cortex, and cerebellum compared to high risk individuals who did not transition to psychosis.

October 2020

The post Magnetic resonance imaging appeared first on NeuRA Library.

Most neurons have a cell body, an axon, and dendrites. Neurons communicate with other cells over synapses, or gaps between the neurons. Usually, axons send out signals and dendrites receive signals across the synapse, although synapses can also connect an axon to another axon or a dendrite to another dendrite. This process is partly electrical and partly chemical and can be excitatory or inhibitory. A group of connected neurons is called a neural circuit, involving sensory, motor, and interneurons.

Studies have shown grey matter reductions in people with schizophrenia, which may involve a loss of neurons and/or changes in synaptic density. This topic presents the results of studies assessing changes in neuronal structure.

What is the evidence for changes in neurons in people with schizophrenia?

Moderate to high quality evidence finds a small to medium-sized effect of decreased density of postsynaptic elements in people with schizophrenia, mainly in cortical regions and in dendritic spine density. There is also a small effect of reduced parvalbumin interneuron density in the pre-frontal cortex of people with schizophrenia.

October 2020

The post Neuronal changes appeared first on NeuRA Library.

OCT is an imaging technology that assesses the thickness of the peripapillary retinal nerve fibre layer, macular thickness, and volume. It has been used to assess neurologic diseases such as multiple sclerosis, Alzheimer’s disease, and Parkinson’s disease, and more recently, schizophrenia.

What is the evidence for OCT?

Moderate quality evidence finds a medium-sized effect of thinner overall peripapillary retinal nerve fibre layer thickness in people with schizophrenia compared to controls. There were small effects of thinner nasal and temporal peripapillary retinal nerve fibre layers as well as thinner ganglion cell + inner plexiform layers in patients. There were no significant differences in superior or inferior retinal nerve fibre layers or in choroidal or macula thickness and volume.

February 2021

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