Background
Alzheimer’s disease (AD) prevalence is rapidly growing as worldwide populations grow older. Available treatments have failed to slow down disease progression, thus increasing research focus towards early or preclinical stages of the disease. Subjective cognitive decline (SCD) is known to increase the risk of developing AD and several other negative outcomes. However, it is still very scarcely characterized and there is no neurophysiological study devoted to its individual classification which could improve targeted sample recruitment for clinical trials.
Methods
Two hundred fifty-two older adults (70 healthy controls, 91 SCD, and 91 MCI) underwent a magnetoencephalography scan. Alpha relative power in the source space was employed to train a LASSO classifier and applied to distinguish between healthy controls and SCD. Moreover, MCI participants were used to further validate the previously trained algorithm.
Results
The classifier was significantly associated to SCD with an AUC of 0.81 in the whole sample. After randomly splitting the sample in 2/3 for discovery and 1/3 for validation, the newly trained classifier was also able to correctly classify SCD individuals with an AUC of 0.75 in the validation sample. The regions selected by the algorithm included medial frontal, temporal, and occipital areas. The algorithm trained to select SCD individuals was also significantly associated to MCI diagnostic.
Conclusions
According to our results, magnetoencephalography could be a useful tool for distinguishing individuals with SCD and healthy older adults without cognitive concerns. Furthermore, our classifier showed good external validity, being not only successful for an unseen SCD sample, but also in a different population with MCI cases. This supports its utility in the context of preclinical dementia. These findings highlight the potential applications of electrophysiological techniques to improve sample recruitment at the individual level in the context of clinical trials.
Electronic supplementary material
The online version of this article (10.1186/s13195-019-0502-3) contains supplementary material, which is available to authorized users.
Background
Two main genetic risks for sporadic Alzheimer’s disease (AD) are a family history and ɛ4 allele of apolipoprotein E. The brain and retina are part of the central nervous system and share pathophysiological mechanisms in AD.
Methods
We performed a cross-sectional study with 30 participants without a family history of sporadic AD (FH−) and noncarriers of ApoE ɛ4 (ApoE ɛ4−) as a control group and 34 participants with a family history of sporadic AD (FH+) and carriers of at least one ɛ4 allele (ApoE ɛ4+). We analyzed the correlations between macular volumes of retinal layers and thickness of the peripapillary retinal nerve fiber layer (pRNFL) measured by optical coherence tomography (OCT) with the brain area parameters measured by magnetic resonance imaging (MRI) in participants at high genetic risk of developing AD (FH+ ApoE ɛ4+).
Results
We observed a significant volume reduction in the FH+ ApoE ɛ4+ group compared with the control group in some macular areas of (i) macular RNFL (mRNFL), (ii) inner plexiform layer (IPL), (iii) inner nuclear layer (INL), and (iv) outer plexiform layer (OPL). Furthermore, in the FH+ ApoE ɛ4+ group, the retinal sectors that showed statistically significant volume decrease correlated with brain areas that are affected in the early stages of AD. In the same group, the peripapillary retinal nerve fiber layer (pRNFL) did not show statistically significant changes in thickness compared with the control group. However, correlations of these sectors with the brain areas involved in this disease were also found.
Conclusions
In cognitively healthy participants at high genetic risk of developing sporadic forms of AD, there are significant correlations between retinal changes and brain areas closely related to AD such as the entorhinal cortex, the lingual gyrus, and the hippocampus.
SUMMARYJoubert syndrome and related disorders comprise a subgroup of ciliopathies defined by the presence of the 'molar tooth sign', a midbrain-hindbrain malformation identifiable by neuroimaging. Characteristically, the corticospinal tract and superior cerebellar peduncles do not decussate. Epileptic seizures are uncommon. We present a case of a 28-year-old man with a background of Leber's congenital amaurosis with nephronophthisis, requiring kidney transplantation, and mental retardation, who developed epileptic seizures consisting of a short muffled cry and involuntary shaking movements of the extremities beginning in the left upper limb; these episodes lasted several seconds and occurred in clusters. Simultaneous video-EEG recording showed an ictal pattern in the left frontal lobe. Brain MRI revealed the pathognomonic 'molar tooth sign'; diffusion tensor imaging (DTI)-tractography showed a lack of decussation of both corticospinal tracts. To the best of our knowledge, this is the first time that DTI-tractography has been used to uncover the anatomical substrate underlying the semiology of epileptic seizures.
BACKGROUND
Introduction The evaluation of red flags is crucial for the accurate the diagnosis of headache disorders, especially for thunderclap headache. We analysed if secondary headache disorders were adequately ruled out in patients that presented to the emergency room with thunderclap headache. Methods In this retrospective cohort study, we screened all patients that visited the emergency room for headache, including those that described thunderclap headache. We measured the frequency with which secondary causes were not adequately ruled out. We analysed the order of the exams, the final diagnosis, and the time elapsed between arrival, initial request for imaging, and the completion of the imaging. Results We screened 2132 patients, and 42 (1.9%) fulfilled eligibility criteria. Mean age was 43.1 ± 17.1 years, and 57% of patients were female. For 22 (52.4%) patients, the work-up was incomplete. Vascular study was missing in 16 (38.1%) patients, cerebrospinal fluid evaluation in nine (21.4%), and magnetic resonance imaging in seven (16.7%), with multiple assessments missing in six (14.3%). There were ten different combinations in which the exams were performed, with the most frequent being the second exam’s cerebral spinal fluid evaluation in 18 (52.9%) and the computed tomography angiogram in 10 (29.4%). A secondary cause of thunderclap headache was found in 16 (38.1%) patients, and four (9.5%) had a primary headache diagnosis after an adequate and complete study. Conclusions Thunderclap onset was described in one of every 50 patients that visited the emergency room for headache. More than half of these patients were not adequately managed. More than a third of thunderclap headache patients had a secondary cause.
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