Understanding brain resilience in superagers: a systematic review.

PURPOSE: Superagers are older adults presenting excellent memory performance that may reflect resilience to the conventional pathways of aging. Our contribution aims to shape the evidence body of the known distinctive biomarkers of superagers and their connections with the Brain and Cognitive Reserve and Brain Maintenance concepts. METHODS: We performed a systematic literature search in PubMed and ScienceDirect with no limit on publication date for studies that evaluated potential biomarkers in superagers classified by validated neuropsychological tests. Methodological quality was assessed using the QUADAS-2 tool. RESULTS: Twenty-one studies were included, the majority in neuroimaging, followed by histological, genetic, cognition, and a single one on blood plasma analysis. Superagers exhibited specific regions of cortical preservation, rather than global cortical maintenance, standing out the anterior cingulate and hippocampus regions. Both superagers and controls showed similar levels of amyloid deposition. Moreover, the functional oscillation patterns in superagers resembled those described in young adults. Most of the quality assessment for the included studies showed medium risks of bias. CONCLUSION: This systematic review supports selective cortical preservation in superagers, comprehending regions of the default mode, and salience networks, overlapped by stronger functional connectivity. In this context, the anterior cingulate cortex is highlighted as an imaging and histologic signature of these subjects. Besides, the biomarkers included pointed out that the Brain and Cognitive Reserve and Brain Maintenance concepts are independent and complementary in the superagers' setting.

Accuracy of unenhanced, non-sedated MRI in the diagnosis of acute appendicitis in children.

BACKGROUND: Children with suspected appendicitis generally undergo an ultrasound (most commonly) or a CT scan (rarely) as the first imaging study. At our hospital, patients with non-diagnostic ultrasound or CT scan results undergo a non-contrast (unenhanced), non-sedated MRI. We aimed to determine the accuracy of this study for this purpose in a large cohort of children. METHODS: A retrospective review of all unenhanced, non-sedated MRIs done for suspected appendicitis was performed from January 2014 to December 2018. MRI reports were correlated with pathology reports in cases that underwent appendectomy, and with clinical outcomes if no operation was done (clinical follow up: 30d). No patient was treated for appendicitis non-operatively. RESULTS: Three hundred fifty unenhanced, non-sedated MRIs were done and reviewed with median age: 12 (3 to 18) years. Sixty-five (18.6%) MRIs were positive for appendicitis, and 62 of those underwent appendectomy (3 excluded clinically). Pathology was positive in 59/62 cases. 256 (73.1%) MRIs were negative for appendicitis. Six cases underwent appendectomy (persistent symptoms). Pathology was positive in 2/6 cases. The overall diagnostic accuracy was: sensitivity 96.7% (95% CI: 88.6-99.6), specificity 97.7% (95% CI: 95.0-99.1), PPV: 90.8% (95% CI: 81.6-95.6; false positives 6/65), and NPV: 99.2% (95% CI: 97.0-99.8; false negatives 2/254). Twenty-nine (8.3%) MRIs were non-diagnostic. None of those 29 cases had appendicitis (4 negative pathology, 25 excluded clinically). CONCLUSIONS: The unenhanced, non-sedated MRI is highly accurate for the diagnosis of appendicitis in children. It should be considered as an alternative to CT in the work-up of patients with suspected appendicitis to eliminate the risks associated with ionizing radiation. LEVEL OF EVIDENCE: Level IV.