A Review of Neuroimaging Studies in Persistent Postural-Perceptual Dizziness (PPPD)

Persistent postural-perceptual dizziness (PPPD) is a functional vestibular disease characterized by persistent dizziness, unsteadiness, and/or non-spinning vertigo, and is the most common vestibular syndrome in young adults. A stiffened postural control strategy, shift to reliance on visual over vestibular information, and hypervigilance to the environment have been suggested as possible pathophysiological mechanisms of PPPD. However, the exact mechanisms remain unclear. Recently, neuroimaging studies using magnetic resonance imaging and single photon emission computed tomography have provided pivotal insights into the pathophysiology of PPPD. The aim of this review was to evaluate and summarize the existing data on neuroimaging studies in PPPD. In summary, these studies fairly consistently reported decreased brain structure, function, and connectivity among the areas involved in multisensory vestibular processing and spatial cognition, and increased function and connectivity in the visual processing areas in patients with PPPD. The detected brain changes might reflect maladaptive and compensatory mechanisms including dysfunctional integration of multisensory vestibular information and visual dependence. Notably, various factors including personality traits (i.e., neuroticism), psychiatric comorbidities (i.e., anxiety and depression), and triggering factors (i.e., peripheral vestibular lesions) seem to modulate brain functional activity and connectivity patterns, possibly accounting for some differences across the results. Future studies should carefully control for these confounding effects in order to draw firm conclusions.     

Progressive brain changes in schizophrenia related to antipsychotic treatment? A meta-analysis of longitudinal MRI studies

Context

Antipsychotic treatment is the first-line treatment option for schizophrenia. Individual studies suggested they can significantly affect brain structure and account for progressive brain changes observed during the illness.

Objectives

To quantitatively examine the effect of antipsychotics as compared to illness related factors on progressive brain changes in schizophrenia.

Data sources

Electronic databases were searched until April 2012. All magnetic resonance imaging studies reporting progressive brain changes in schizophrenia subjects and antipsychotic exposure were retrieved.

Study selection

30 longitudinal MRI studies with antipsychotic administration in schizophrenia patients met the inclusion criteria.

Data extraction

Brain volumes before and after antipsychotic exposure, duration of illness, severity of psychotic symptoms as well as demographic, clinical, and methodological variables were extracted from each publication, or obtained directly from its authors.

Data synthesis

The overall sample was of 1046 schizophrenia patients and 780 controls for a median duration of follow-up of 72.4 weeks. At baseline, patients showed significant whole brain volume reductions and enlarged lateral ventricle (LV) volumes compared to controls. No baseline volumetric abnormalities were detected in the gray matter volumes (GMV), white matter volumes, cerebrospinal fluid and caudate nucleus. Longitudinally, there were progressive GMV decreases and LV enlargements in patients but not in controls. The GMV decreases were inversely correlated with cumulative exposure to antipsychotic treatments, while no effects were observed for duration of illness or illness severity.

Conclusions

Schizophrenia is characterized by progressive gray matter volume decreases and lateral ventricular volume increases. Some of these neuroanatomical alterations may be associated with antipsychotic treatment.     

4D-CT angiography differentiating arteriovenous fistula subtypes

Objective and methods

In the diagnostic work-up of patients suspected of a dural arteriovenous fistula (dAVF), imaging has a key role in order to diagnose the dAVF, assess its bleeding risk and choose optimal treatment strategy. Digital subtraction angiography (DSA) is the gold standard for the most detailed image of a dAVF. Nowadays four-dimensional CT angiography (4D-CTA) could possibly be an additional first-line tool in the work-up of a patient suspected of a dAVF. We describe three cases clinically suspected of a dAVF which had a diagnostic work-up with 4D-CTA as well as DSA. We evaluated the angioarchitecture of the dAVF both on 4D-CTA and DSA, with emphasis on the patterns of venous drainage as this is important in assessing the bleeding risk of a dAVF.

Results and conclusion

4D-CTA identified the dAVF, revealed its angioarchitecture and correctly differentiated different patterns of venous drainage (Borden type I, II and III) as confirmed on DSA. Although DSA has the advantage of higher spatial and temporal resolution, 4D-CTA seems to be a new useful non-invasive tool in the diagnostic work-up of a patient suspected of a dAVF.     

特发性正常压力脑积水的诊断研究进展

特发性正常压力脑积水(idiopathic normal pressure hydrocephalus,iNPH)是1965年最先提出的一种以步态异常、痴呆和尿失禁(又称Hakim三联征)为特征的交通性脑积水综合征.挪威流行病学调查估计iNPH在人群中的发病率为5.5/10万人口,患病率为21.9/10万人口[1].日本的研究表明iNPH主要发生于老年人,65岁以上患病率为1.4％～2.9％[2-3],被认为是痴呆的第一位可治性病因,脑脊液分流术可使半数以上患者症状改善[4-5].因iNPH的临床和影像学表现与其它疾病相似,早期诊断比较困难,但早期干预可获得好的疗效.随着研究深入,一些新的诊断依据不断发现,本文就有关研究进展做一综述.     

Hoarding disorder and obsessive–compulsive disorder show different patterns of neural activity during response inhibition

Although hoarding disorder (HD) has been historically conceptualized as a subtype or dimension of obsessive–compulsive disorder (OCD), preliminary evidence suggests that these two disorders have distinct neural underpinnings. The aim of the present study was to compare the hemodynamic responses of HD patients, OCD patients, and healthy controls (HC) during response inhibition on a high-conflict Go/NoGo task that has previously proved sensitive to OCD. Participants comprised 24 HD patients, 24 OCD patients, and 24 HCs who completed a Go/NoGo task during functional magnetic resonance imaging (fMRI). Although behavioral data showed no difference among the groups in Go/NoGo task performance, significant differences in hemodynamic activity were noted. During correct rejects (successful response inhibition), HD patients showed greater right precentral gyrus activation, whereas OCD patients exhibited greater right orbitofrontal activation, as assessed using a region of interest approach. During errors of commission (response inhibition failures), OCD patients, but not HD patients, were characterized by excessive activity in left and right orbitofrontal gyrus. The present results lend further support to the biological distinction between HD and OCD, and they are consistent with previous research suggesting frontal hypoactivity in HD patients during hoarding-unrelated tasks.     

A comparison of neural responses to appetitive and aversive stimuli in humans and other mammals

Distinguishing potentially harmful or beneficial stimuli is necessary for the self-preservation and well-being of all organisms. This assessment requires the ongoing valuation of environmental stimuli. Despite much work on the processing of aversive- and appetitive-related brain signals, it is not clear to what degree these two processes interact across the brain. To help clarify this issue, this report used a cross-species comparative approach in humans (i.e. meta-analysis of imaging data) and other mammals (i.e. targeted review of functional neuroanatomy in rodents and non-human primates). Human meta-analysis results suggest network components that appear selective for appetitive (e.g. ventromedial prefrontal cortex, ventral tegmental area) or aversive (e.g. cingulate/supplementary motor cortex, periaqueductal grey) processing, or that reflect overlapping (e.g. anterior insula, amygdala) or asymmetrical, i.e. apparently lateralized, activity (e.g. orbitofrontal cortex, ventral striatum). However, a closer look at the known value-related mechanisms from the animal literature suggests that all of these macroanatomical regions are involved in the processing of both appetitive and aversive stimuli. Differential spatiotemporal network dynamics may help explain similarities and differences in appetitive- and aversion-related activity.     

Neural Correlates of Failed Inhibitory Control as an Early Marker of Disordered Eating in Adolescents

BackgroundBinge eating and other forms of disordered eating behavior (DEB) are associated with failed inhibitory control. This study investigated the neural correlates of failed inhibitory control as a potential biomarker for DEB.MethodsThe study used prospective longitudinal data from the European IMAGEN study adolescent cohort. Participants completed baseline assessments (questionnaires and a brain scan [functional magnetic resonance imaging]) at 14 years of age and a follow-up assessment (questionnaires) at 16 years of age. Self-reported binge eating and/or purging were used to indicate presence of DEB. Neural correlates of failed inhibition were assessed using the stop signal task. Participants were categorized as healthy control subjects (reported no DEB at both time points), maintainers (reported DEB at both time points), recoverers (reported DEB at baseline only), and developers (reported DEB at follow-up only). Forty-three individuals per group with complete scanning data were matched on gender, age, puberty, and intelligence (N = 172).ResultsAt baseline, despite similar task performance, incorrectly responding to stop signals (failed inhibitory control) was associated with greater recruitment of the medial prefrontal cortex and anterior cingulate cortex in the developers compared with healthy control subjects and recoverers.ConclusionsGreater recruitment of the medial prefrontal and anterior cingulate regions during failed inhibition accords with abnormal evaluation of errors contributing to DEB development. As this precedes symptom onset and is evident despite normal task performance, neural responses during failed inhibition may be a useful biomarker of vulnerability for DEB. This study highlights the potential value of prospective neuroimaging studies for identifying markers of illness before the emergence of behavior changes.