The role of hippocampal theta oscillations in working memory impairment in multiple sclerosis

Working memory (WM) problems are frequently present in people with multiple sclerosis (MS). Even though hippocampal damage has been repeatedly shown to play an important role, the underlying neurophysiological mechanisms remain unclear. This study aimed to investigate the neurophysiological underpinnings of WM impairment in MS using magnetoencephalography (MEG) data from a visual‐verbal 2‐back task. We analysed MEG recordings of 79 MS patients and 38 healthy subjects through event‐related fields and theta (4–8 Hz) and alpha (8–13 Hz) oscillatory processes. Data was source reconstructed and parcellated based on previous findings in the healthy subject sample. MS patients showed a smaller maximum theta power increase in the right hippocampus between 0 and 400 ms than healthy subjects (p = .014). This theta power increase value correlated negatively with reaction time on the task in MS (r = −.32, p = .029). Evidence was provided that this relationship could not be explained by a ‘common cause’ confounding relationship with MS‐related neuronal damage. This study provides the first neurophysiological evidence of the influence of hippocampal dysfunction on WM performance in MS.     

Reduced parenchymal cerebral blood flow is associated with greater progression of brain atrophy: The SMART-MR study

Global cerebral hypoperfusion may be involved in the aetiology of brain atrophy; however, long-term longitudinal studies on this relationship are lacking. We examined whether reduced cerebral blood flow was associated with greater progression of brain atrophy. Data of 1165 patients (61 ± 10 years) from the SMART-MR study, a prospective cohort study of patients with arterial disease, were used of whom 689 participated after 4 years and 297 again after 12 years. Attrition was substantial. Total brain volume and total cerebral blood flow were obtained from magnetic resonance imaging scans and expressed as brain parenchymal fraction (BPF) and parenchymal cerebral blood flow (pCBF). Mean decrease in BPF per year was 0.22% total intracranial volume (95% CI: –0.23 to –0.21). Mean decrease in pCBF per year was 0.24 ml/min per 100 ml brain volume (95% CI: –0.29 to –0.20). Using linear mixed models, lower pCBF at baseline was associated with a greater decrease in BPF over time (p = 0.01). Lower baseline BPF, however, was not associated with a greater decrease in pCBF (p = 0.43). These findings indicate that reduced cerebral blood flow is associated with greater progression of brain atrophy and provide further support for a role of cerebral blood flow in the process of neurodegeneration.     

A Post‐Hoc Comparison of the Utility of Sanger Sequencing and Exome Sequencing for the Diagnosis of Heterogeneous Diseases

The advent of massive parallel sequencing is rapidly changing the strategies employed for the genetic diagnosis and research of rare diseases that involve a large number of genes. So far it is not clear whether these approaches perform significantly better than conventional single gene testing as requested by clinicians. The current yield of this traditional diagnostic approach depends on a complex of factors that include gene‐specific phenotype traits, and the relative frequency of the involvement of specific genes. To gauge the impact of the paradigm shift that is occurring in molecular diagnostics, we assessed traditional Sanger‐based sequencing (in 2011) and exome sequencing followed by targeted bioinformatics analysis (in 2012) for five different conditions that are highly heterogeneous, and for which our center provides molecular diagnosis. We find that exome sequencing has a much higher diagnostic yield than Sanger sequencing for deafness, blindness, mitochondrial disease, and movement disorders. For microsatellite‐stable colorectal cancer, this was low under both strategies. Even if all genes that could have been ordered by physicians had been tested, the larger number of genes captured by the exome would still have led to a clearly superior diagnostic yield at a fraction of the cost.     

The influence of clan structure on the genetic variation in a single Ghanaian village

Socioeconomic and cultural factors are thought to have an important role in influencing human population genetic structure. To explain such population structure differences, most studies analyse genetic differences among widely dispersed human populations. In contrast, we have studied the genetic structure of an ethnic group occupying a single village in north-eastern Ghana. We found a markedly skewed male population substructure because of an almost complete lack of male gene flow among Bimoba clans in this village. We also observed a deep male substructure within one of the clans in this village. Among all males, we observed only three Y-single-nucleotide polymorphism (SNP) haplogroups: E1b1a*-M2, E1b1a7a*-U174 and E1b1a8a*-U209, P277, P278. In contrast to the marked Y-chromosomal substructure, mitochondrial DNA HVS-1 sequence variation and autosomal short-tandem repeats variation patterns indicate high genetic diversities and a virtually random female-mediated gene flow among clans. On the extreme micro-geographical scale of this single Bimoba village, correspondence between the Y-chromosome lineages and clan membership could be due to the combined effects of the strict patrilocal and patrilineal structure. If translated to larger geographic scales, our results would imply that the extent of variation in uniparentally inherited genetic markers, which are typically associated with historical migration on a continental scale, could equally likely be the result of many small and different cumulative effects of social factors such as clan membership that act at a local scale. Such local scale effects should therefore be considered in genetic studies, especially those that use uniparental markers, before making inferences about human history at large.     

Correction to: Dry mouth: saliva substitutes which adsorb and modify existing salivary condition films improve oral lubrication

Clinical Oral Investigations - After publication of this paper, the authors observed that that figure 6 appears before figure 5.     

Good Functional Recovery of Complex Elbow Dislocations Treated With Hinged External Fixation: A Multicenter Prospective Study

BackgroundAfter a complex dislocation, some elbows remain unstable after closed reduction or fracture treatment. Function after treatment with a hinged external fixator theoretically allows collateral ligaments to heal without surgical reconstruction. However, there is a lack of prospective studies that assess functional outcome, pain, and ROM.Questions/purposesWe asked: (1) In complex elbow fracture-dislocations, does treatment with a hinged external fixator result in reduction of disability and pain, and in improvement in ROM, function, and quality of life? (2) Does delayed treatment (7 days or later) have a negative effect on ROM after 1 year? (3) What are the complications seen after external fixator treatment?MethodsDuring a 2-year period, 11 centers recruited 27 patients 18 years or older who were included and evaluated at 2 and 6 weeks and at 3, 6, and 12 months after surgery as part of this prospective case series. During the study period, the participating centers agreed on general indications for use of the hinged external fixator, which included persistent instability after closed reduction alone or closed reduction combined with surgical treatment of associated fracture(s), when indicated. Functional outcome was evaluated using the Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH; primary outcome) score, the Mayo Elbow Performance Index (MEPI), the Oxford Elbow Score, and the level of pain (VAS). ROM, adverse events, secondary interventions, and radiographs also were evaluated. A total of 26 of the 27 patients (96%) were available for followup at 1 year.ResultsAll functional and pain scores improved. The median QuickDASH score decreased from 30 (25^th–75^th percentiles [P₂₅–P₇₅], 23–40) at 6 weeks to 7 (P₂₅–P₇₅, 2–12) at 1 year with a median difference of −25 (p < 0.001). The median MEPI score increased from 80 (P₂₅–P₇₅, 64–85) at 6 weeks to 100 (P₂₅–P₇₅, 85–100) at 1 year with a median difference of 15 (p < 0.001). The median Oxford Elbow Score increased from 60 (P₂₅–P₇₅, 44–68) at 6 weeks to 90 (P₂₅–P₇₅, 73–96) at 1 year with a median difference of 29 (p < 0.001). The median VAS decreased from 2.8 (P₂₅–P₇₅, 1.0–5.0) at 2 weeks to 0.5 (P₂₅–P₇₅, 0.0–1.9) at 1 year with a median difference of −2.1 (p = 0.001). ROM also improved. The median flexion-extension arc improved from 50° (P₂₅–P₇₅, 33°–80°) at 2 weeks to 118° (P₂₅–P₇₅, 105°–138°) at 1 year with a median difference of 63° (p < 0.001). Similarly, the median pronation-supination arc improved from 90° (P₂₅–P₇₅, 63°–124°) to 160° (P₂₅–P₇₅, 138°–170°) with a median difference of 75° (p < 0.001). At 1 year, the median residual deficit compared with the uninjured side was 30° (P₂₅–P₇₅, 5°–35°) for the flexion-extension arc, and 3° (P₂₅–P₇₅, 0°–25°) for the pronation-supination arc. Ten patients (37%) experienced a fixator-related complication, and seven patients required secondary surgery (26%). One patient reported recurrent instability.ConclusionsA hinged external elbow fixator provides enough stability to start early mobilization after an acute complex elbow dislocation and residual instability. This was reflected in good functional outcome scores and only slight disability despite a relatively high complication rate.

Level of Evidence

Level IV, therapeutic study.