CSF Aβ1-42 combined with neuroimaging biomarkers in the early detection, diagnosis and prediction of Alzheimer's disease

The development of validated, qualified, and standardized biomarkers for Alzheimer's disease (AD) that allow for an early presymptomatic diagnosis and discrimination (classification) from other types of dementia and neurodegenerative diseases is warranted to accelerate the successful development of novel disease-modifying therapies. Here, we focus on the value of the 42-residue-long amyloid β isoform (Aβ1-42) peptide in the cerebrospinal fluid as the core, feasible neurobiochemical marker for the amyloidogenic mechanisms in early-onset familial and late-onset sporadic AD. We discuss the role and use of Aβ1-42 in combination with evolving neuroimaging biomarkers in AD detection and diagnosis. Multimodal neuroimaging techniques, directly providing structural-functional-metabolic aspects of brain pathophysiology, are supportive to predict and monitor the progression of the disease. Advances in multimodal neuroimaging provide new insights into brain organization and enable the detection of specific proteins and/or protein aggregates associated with AD. The combination of biomarkers from different methodologies is believed to be of incrementally added risk-value to accurately identify asymptomatic and prodromal individuals who will likely progress to dementia and represent rational biomarker candidates for preventive and symptomatic pharmacological intervention trials.

Relevance of magnetic resonance imaging for early detection and diagnosis of Alzheimer disease

Hippocampus volumetry currently is the best-established imaging biomarker for AD. However, the effect of multicenter acquisition on measurements of hippocampus volume needs to be explicitly considered when it is applied in large clinical trials, for example by using mixed-effects models to take the clustering of data within centers into account. The marker needs further validation in respect of the underlying neurobiological substrate and potential confounds such as vascular disease, inflammation, hydrocephalus, and alcoholism, and with regard to clinical outcomes such as cognition but also to demographic and socioeconomic outcomes such as mortality and institutionalization. The use of hippocampus volumetry for risk stratification of predementia study samples will further increase with the availability of automated measurement approaches. An important step in this respect will be the development of a standard hippocampus tracing protocol that harmonizes the large range of presently available manual protocols. In the near future, regionally differentiated automated methods will become available together with an appropriate statistical model, such as multivariate analysis of deformation fields, or techniques such as cortical-thickness measurements that yield a meaningful metrics for the detection of treatment effects. More advanced imaging protocols, including DTI, DSI, and functional MRI, are presently being used in monocenter and first multicenter studies. In the future these techniques will be relevant for the risk stratification in phase IIa type studies (small proof-of-concept trials). By contrast, the application of the broader established structural imaging biomarkers, such as hippocampus volume, for risk stratification and as surrogate end point is already today part of many clinical trial protocols. However, clinical care will also be affected by these new technologies. Radiologic expert centers already offer “dementia screening” for well-off middle-aged people who undergo an MRI scan with subsequent automated, typically VBM-based analysis, and determination of z-score deviation from a matched control cohort. Next-generation scanner software will likely include radiologic expert systems for automated segmentation, deformation-based morphometry, and multivariate analysis of anatomic MRI scans for the detection of a typical AD pattern. As these developments will start to change medical practice, first for selected subject groups that can afford this type of screening but later eventually also for other cohorts, clinicians must become aware of the potentials and limitations of these technologies. It is decidedly unclear to date how a middle-aged cognitively intact subject with a seemingly AD-positive MRI scan should be clinically advised. There is no evidence for individual risk prediction and even less for specific treatments. Thus, the development of preclinical diagnostic imaging poses not only technical but also ethical problems that must be critically discussed on the basis of profound knowledge. From a neurobiological point of view, the main determinants of cognitive impairment in AD are the density of synapses and neurons in distributed cortical and subcortical networks. MRI-based measures of regional gray matter volume and associated multivariate analysis techniques of regional interactions of gray matter densities provide insight into the onset and temporal dynamics of cortical atrophy as a close proxy for regional neuronal loss and a basis of functional impairment in specific neuronal networks. From the clinical point of view, clinicians must bear in mind that patients do not suffer from hippocampus atrophy or disconnection but from memory impairment, and that dementia screening in asymptomatic subjects should not be used outside of clinical studies.

Brain involvement in glaucoma: advanced neuroimaging for understanding and monitoring a new target for therapy

On the basis of a large body of experimental data the notion that glaucoma damages retinal ganglion cells and central areas of the visual system has been put forward. The mechanisms underlying glaucomatous involvement of the central areas are not known: the most likely hypothesis is that this event is the result of an anterograde transynaptic neurodegeneration triggered by ganglion cells' death. However, it is possible that in some cases it may be the consequence of a neurodegenerative disease of the central nervous system. In any event, novel mechanisms leading to cell demise might be implicated. The development of powerful neuroimaging techniques in conjunction with sophisticated analysis has recently provided compelling support to the involvement of central stations of the visual pathway in patients suffering of glaucoma. Diffusion Tensor-MRI allows the central damage associated with glaucoma to be assessed and therapeutic efficacy of novel neuroprotective interventions to be quantified.

Brain hemodynamic changes associated with chronic cerebrospinal venous insufficiency are not specific to multiple sclerosis and do not increase its severity

PURPOSE

To investigate the relationship between chronic cerebrospinal venous insufficiency (CCSVI) and cerebral hemodynamic parameters and to disclose any possible involvement in the pathophysiology of multiple sclerosis (MS).

MATERIALS AND METHODS

The study was approved by the institutional review board, and written informed consent was obtained from all participants. The diagnosis of CCSVI was assigned by using specific color Doppler ultrasonographic criteria. Cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time were assessed with dynamic susceptibility contrast material-enhanced magnetic resonance imaging in normal-appearing white matter (NAWM) in 39 patients with MS. Of these, 25 had CCSVI and 14 did not. Twenty-six healthy control subjects were also evaluated, and of these, 14 had CCSVI and 12 did not. Two-way analysis of variance testing was used for statistical analysis, with Bonferroni correction for multiple comparisons. Correlation analysis was performed by calculating Spearman coefficients.

RESULTS

Individuals with CCSVI showed cerebral hemodynamic anomalies, such as decreased CBF and CBV, as compared with individuals without CCSVI, without any delay in mean transit time. No significant interaction between MS and CCSVI was found for any hemodynamic parameters. Furthermore, no correlations were found between CBV and CBF values in NAWM or for severity of disability in patients with MS. The MS group showed prolonged mean transit time in the periventricular NAWM, as compared with the control group, and positive correlation was found between mean transit time values and disability scales in patients with MS.

CONCLUSION

The data support a role of CCSVI in cerebral hemodynamic changes, such as a decrease of CBV and CBF, regardless of the presence of MS. CCSVI had no effect on neurologic function and disability progression in patients with MS.

Long-term cognitive and behavioral therapies, combined with augmentative communication, are related to uncinate fasciculus integrity in autism

Recent evidence points to white-matter abnormalities as a key factor in autism physiopathology. Using Diffusion Tensor Imaging, we studied white-matter structural properties in a convenience sample of twenty-two subjects with low-functioning autism exposed to long-term augmentative and alternative communication, combined with sessions of cognitive and behavioral therapy. Uncinate fasciculus structural properties correlated significantly with therapy length and early onset, as well as to clinical outcome, independently from IQ, age or symptoms severity at therapy onset. Moreover, adherence to therapy was linked with better clinical outcome and uncinate fasciculus structural integrity. The results point to the capability of a long-term rehabilitation of subjects with low-functioning autism to produce white-matter structural modifications, which could thus play a role in the rehabilitative outcome.

Cryptogenic stroke in hanging. A case report

This paper reports the unique neuroimaging findings of a 37-year-old woman who attempted suicide by hanging. To our knowledge, this is the first reported case describing neuroimaging findings of unilateral lesions instead of the well-documented bilateral lesions after a hanging event. Computed tomography demonstrated a low density area in the right thalamus and no hemorrhage. 3.0 T Magnetic resonance revealed a hyperintense area on both T2-weighted and FLAIR images on the right thalamus. Diffusion weighted images demonstrated no area of diffusivity restriction. Another smaller lesion with the same signal characteristics was found in the left cerebellum. A second relevant point of this report is the observation that the most probable cause of the documented unilateral lesions was an ischemic-arterial event.

White matter reduced streamline coherence in young men with autism and mental retardation

BACKGROUND AND PURPOSE

It has been proposed that white matter alterations might play a role in autistic disorders; however, published data are mainly limited to high-functioning autism. The goal of this study was to apply diffusion tensor imaging (DTI) and fiber tractography (FT) to study white matter in low-functioning autism and the relationship between white matter and cognitive impairment.

METHODS

Ten low-functioning males with autism (mean age: 19.7 +/- 2.83 years) and 10 age-matched healthy males (mean age: 19.9 +/- 2.64 years) underwent DTI-MRI scanning. fractional anisotropy (FA) maps were analyzed with whole brain voxel-wise and tract-of-interest statistics. Using FT algorithms, white matter tracts connecting the orbitofrontal cortex (OFC) with other brain regions were identified and compared between the two groups. FA mean values of the autistic group were correlated with intelligence quotient (IQ) scores.

RESULTS

Low-functioning autistic subjects showed a reduced tract volume and lower mean FA values in the left OFC network compared with controls. In the autistic group, lower FA values were associated with lower IQ scores.

CONCLUSIONS

We showed evidence of OFC white matter network abnormalities in low-functioning autistic individuals. Our results point to a relationship between the severity of the intellectual impairment and the extent of white matter alterations.

Optic nerve and optic radiation neurodegeneration in patients with glaucoma: in vivo analysis with 3-T diffusion-tensor MR imaging

PURPOSE

To evaluate, with high-field-strength diffusion-tensor (DT) magnetic resonance (MR) imaging, the axonal architecture of the optic nerves and optic radiations in patients with glaucoma and determine whether DT MR imaging-derived parameters correlate with disease severity.

MATERIALS AND METHODS

The study was approved by the institutional review board. All participants provided written informed consent. Sixteen patients with primary open-angle glaucoma were examined. Glaucoma severity was clinically assessed with use of a six-stage system based on static threshold visual field parameters. Ten healthy individuals served as control subjects. DT MR imaging was performed with a 3-T MR unit. Mean diffusivity (MD) and fractional anisotropy (FA) maps were automatically created. Regions of interest were positioned on the MD and FA maps, and mean MD and mean FA values were calculated for each optic nerve and each optic radiation.

RESULTS

The optic radiations and optic nerves of patients with glaucoma, as compared with control subjects, had significantly higher MD and significantly lower FA. The mean MD values for the optic nerves and the glaucoma stages varied consistently (r = 0.8087, P < .0001). A negative correlation between mean FA for the optic nerves and glaucoma stage (r = -0.7464, P < .0001) was observed.

CONCLUSION

Glaucoma is a complex neurologic disease that affects optic nerves and optic radiations. The finding that DT MR imaging-derived MD and FA in the optic nerves correlate with glaucoma severity suggests that these parameters could serve as complementary indicators of disease severity.

Sixty-four-section CT cerebral perfusion evaluation in patients with carotid artery stenosis before and after stenting with a cerebral protection device

BACKGROUND AND PURPOSE

Brain tissue viability depends on cerebral blood flow (CBF) that has to be kept within a narrow range to avoid the risk of developing ischemia. The aim of the study was to evaluate by 64-section CT (VCT) the cerebral perfusion modifications in patients with severe carotid stenosis before and after undergoing carotid artery stent placement (CAS) with a cerebral protection system.

MATERIALS AND METHODS

Fifteen patients with unilateral internal carotid stenosis (>or=70%) underwent brain perfusional VCT (PVCT) 5 days before and 1 week after the stent-placement procedure. CBF and mean transit time (MTT) values were measured.

RESULTS

Decreased CBF and increased MTT values were observed in the cerebral areas supplied by the stenotic artery as compared with the areas supplied by the contralateral patent artery (P < .001). A significant normalization of the perfusion parameters was observed after the stent-placement procedure (mean pretreatment MTT value, 5.3 +/- 0.2; mean posttreatment MTT value, 4.3 +/- 0.18, P < .001; mean pretreatment CBF value, 41.2 mL/s +/- 2.1; mean posttreatment CBF value, 47.9 mL/s +/- 2.9, P < .001).

CONCLUSIONS

PVCT is a useful technique for the assessment of the hemodynamic modifications in patients with severe carotid stenosis. The quantitative evaluation of cerebral perfusion makes it a reliable tool for the follow-up of patients who undergo CAS.

Variations of Neck Structures after Supracricoid Partial Laryngectomy: A Multislice Computed Tomography Evaluation

BACKGROUND

Surgery of laryngeal cancer used to profoundly alter the anatomy of the cervical region. Accurate anatomo-embryologic studies and repeated surgical trials allowed recognition of the cricoarytenoid complex as the smallest anatomofunctional unit able to maintain all the laryngeal functions.

OBJECTIVES

The aim of this study was to determine whether significant variations of neck anatomical parameters exist after partial laryngectomy, and to analyze whether some of these parameters are associated with a positive functional outcome.

METHODS

Out of 48 patients treated with a surgical technique according to Mayer-Piquet (cricohyoidoepiglottopexy, CHEP) over a 6-year period, 18 patients were enrolled in the study. Patients were all males with a mean age of 60 years. Cervical structures and their relationships were measured by computed tomography, and the measurements before and after surgery were compared.

RESULTS

Our data showed that hyoid bone is modified, both in morphology and position during CHEP. More specifically the relation of the hyoid bone to other neck structures (identified by the alpha-angle) is modified. The neolarynx and trachea undergo a caudocranial shift. All diameters of the cricoid cartilage remain unchanged after surgery. The position of the epiglottis after CHEP, in particular its relation with the arytenoid cartilage, is closely related to swallowing function outcome and recovery time.

CONCLUSIONS

Our study showed that these structures, and more specifically the relations among them, undergo significant variations after CHEP. Our results identify some parameters, i.e. the alpha-angle, width of the hyoid bone and position of the epiglottis, that may predispose to a positive functional outcome after surgery.

A diffusion longitudinal MR imaging study in normal-appearing white matter in untreated relapsing-remitting multiple sclerosis

BACKGROUND AND PURPOSE

Our aim was to evaluate the hypothesis that water diffusion alterations are present in normal-appearing white matter of patients with relapsing-remitting multiple sclerosis (RRMS) and to assess their change with time.

MATERIALS AND METHODS

Fifty-four subjects with clinically diagnosed RRMS, with disease duration of less than 12 months and an expanded disability status scale (EDSS) score of <3.5, underwent a diffusion 3T MR imaging study. The apparent diffusion coefficient (ADC) maps generated were compared with those of 18 control subjects. Eighteen of the 54 patients underwent MR imaging assessment at 3 and 6 months after baseline evaluation. Remitting patients were clinically and MR imaging stable for the 2 months before the study. All patients were drug-free for the 3 months before the study, and in the relapsing patients, the MR imaging was always performed before beginning treatment.

RESULTS

Mean ADC values showed significant differences when relapsing, remitting, and control patients were compared. The relapsing or remitting phase showed significant difference when compared both with controls (P < .01) and between them (P < .05). Comparing mean ADC values of patients with clinical disability (EDSS <2 versus EDSS >/=2) also provided significant differences with the control group (P < .01). The data of patients showing a relapsing episode during the longitudinal part of the study showed a significant difference compared with data from their remitting phase (P < .01).

CONCLUSION

Brain microstructural changes can be detected and correlate with clinical impairment during the stages of MS. These changes modify with time in the relapsing group.

Evaluation of basal ganglia haemodynamic changes with perfusion–weighted magnetic resonance imaging in patients with Parkinson’s disease

PURPOSE

The aim of our study was to assess the regional cerebral blood flow (rCBF) of basal ganglia and thalami in patients with Parkinson's disease (PD) using perfusion-weighted magnetic resonance imaging (PW-MRI).

MATERIAL AND METHODS

Twenty subjects affected by idiopathic PD according to the United Kingdom Brain Bank criteria were enrolled in the study. Twenty normal subjects matched for age and gender were included as controls. After 20-day therapy withdrawal, the PD patients underwent PW-MRI. The rCBF was calculated both in patients and in controls. The regions of interest were manually positioned on rCBF maps over the caudate nucleus, the putamen, the external and internal globus pallidus, and over the ventrolateral nucleus of the thalamus. Data were normalised with those obtained from parieto-occipital white matter (POWM). Statistical analysis was performed using a parametric ANOVA test.

RESULTS

Patients showed a significant (p<0.01) interhemispheric asymmetry; rCBF values were higher on the more severely affected side. Controls showed no interhemispheric asymmetry.

CONCLUSION

Our study suggests that PW-MRI is a valuable tool for assessing haemodynamic changes in PD patients. Haemodynamic change pattern may be useful in the early diagnosis of PD.

Increased Brain Apparent Diffusion Coefficient in Tuberous Sclerosis

PURPOSE

To evaluate the water diffusivity of normal-appearing white matter (NAWM) in patients with tuberous sclerosis complex compared with that in control subjects.

MATERIALS AND METHODS

Diffusion and conventional magnetic resonance (MR) imaging examinations were performed in 18 patients with clinically established tuberous sclerosis complex (10 male and eight female patients; mean age, 20.1 years; range, 12-30 years), as well as in 18 age-matched control subjects (nine male and nine female; mean age, 20.2 years; range, 11-28 years). Apparent diffusion coefficients (ADCs) were generated, and small elliptic regions of interest were manually placed both in perilesional NAWM and in six anatomic locations of NAWM remote from hamartomatous lesions. Perilesional ADCs were compared with those at the same anatomic site on the contralateral side of the brain (generalized linear regression analysis). ADCs from the predetermined sites in patients were compared with those in control subjects (generalized linear regression analysis).

RESULTS

Supratentorial ADCs were higher in patients with tuberous sclerosis complex than in control subjects, and statistically significant differences were observed in the occipital white matter, frontal white matter, centrum semiovale, parietal white matter, and corona radiata (for each location, P <.001). Significant increases were also seen in the perilesional NAWM compared with NAWM at the same anatomic locations on the contralateral side (P <.001). Infratentorial ADCs were normal.

CONCLUSION

Significant ADC increases were measured in the supratentorial NAWM.

[Non-invasive assessment of epiaortic vessels. Comparison of magnetic resonance angiography with gadolinium, spiral computerized tomography angiography, and digital angiography]

PURPOSE

The aim of the study was to compare gadolinium-enhanced MRA (Gd-MRA), Computed Tomography angiography (CTA) and digital subtraction angiography (DSA) in the evaluation of carotid stenosis.

MATERIAL AND METHODS

Thirty patients with US-proven internal carotid artery stenosis over 50%, underwent Gd-MRA, CTA and DSA. Gd-MRA was acquired using the keyhole technique.

RESULTS

The overall agreement was 90% for Gd-MRA and 93% for CTA. Gd-MRA and CTA overestimated 5 and 4 cases of mild stenosis and 1 case each of moderate stenosis, respectively. Gd-MRA better delineated ulcerated plaques, tandem lesions and pseudo-occlusions.

DISCUSSION AND CONCLUSIONS

Because of the high speed acquisition breath-hold is no longer necessary for Gd-MRA and more delayed phases were analysed when necessary. The main limitation of Gd-MRA was represented by insufficient volume coverage that allowed the visualisation of supraaortic vessels from the arch only in 57% of the cases. Calcified plaques were very well detected by CTA and not by Gd-MRA. In our experience Gd-MRA represents the second step non invasive tool in patients with US-proven carotid stenosis. This leads to avoid conventional angiography in most cases.