Congenital stationary night blindness: An analysis and update of genotype–phenotype correlations and pathogenic mechanisms

Congenital stationary night blindness (CSNB) refers to a group of genetically and clinically heterogeneous retinal disorders. Seventeen different genes with more than 360 different mutations and more than 670 affected alleles have been associated with CSNB, including genes coding for proteins of the phototransduction cascade, those important for signal transmission from the photoreceptors to the bipolar cells or genes involved in retinoid recycling in the retinal pigment epithelium. This article describes the phenotypic characteristics of different forms of CSNB that are necessary for accurate diagnosis and to direct and improve genetic testing. An overview of classical and recent methods used to identify specific CSNB genotypes is provided and a meta-analysis of all previously published and novel data is performed to determine the prevalence of disease-causing mutations. Studies of the underlying molecular pathogenic mechanisms based on cell culture techniques and animal studies are outlined. The article highlights how the study of CSNB has increased understanding of the mechanisms of visual signalling in the retina, likely to prove important in developing future treatments for CSNB and other retinal disorders.     

La vasodilatation a-t-elle un rôle dans la migraine ? Oui

The role of vasodilatation in migraine pathophysiology is still debated with three hypotheses. The first is that vasodilatation of meningeal or intracranial arteries are the primary cause of pain. The second is that vasodilatation is secondary to neuronal activation, but can sustain or increase pain through sensitized perivascular nociceptors. The third is that vasodilatation is an epiphenomenon neither sufficient nor necessary for pain. We review in this part the arguments in favor of the old hypothesis that vasodilation is the primary cause of pain. Finally we show that there is a mild vasodilation during the attacks provoked by CGRP infusion.     

Mild parkinsonian features in dystonia: Literature review,mechanisms and clinical perspectives

Dystonia is a hyperkinetic movement disorder that can be highly stigmatizing and disabling. Substantial evidence from animal models, neuropathological, neurophysiological, neuroimaging and clinical studies emphasizes the role of dopaminergic dysfunction in the pathophysiology of dystonia, illustrating possible pathophysiological overlap with parkinsonism. Furthermore, basal ganglia dysfunction has been implicated in the pathogenesis of dystonia, and is well established to underlie the manifestations of Parkinson's disease. Clinically, parkinsonian features are a key characteristic of some combined dystonias, including dopa-responsive dystonia, and Parkinson's disease often presents with dystonia. Moreover, many treatments effective in Parkinson's disease, both medical and surgical, also offer some benefit in dystonia. Therefore, mild parkinsonian features might logically accompany idiopathic and inherited isolated dystonias. However, as the current literature is particularly scant, the present review aimed to investigate mild parkinsonism in idiopathic and inherited dystonia. We found limited evidence alluding to the presence of mildly reduced arm-swing, increased tone, and non-decremental bradykinesia in adult-onset focal dystonia. Tremor, with postures, action and rest, also occurs commonly in idiopathic isolated dystonia, and can simulate Parkinson's disease tremor and be a cause of ‘scans without evidence of dopaminergic deficit’. Parkinsonian features in monogenic isolated dystonias have been less well investigated, despite the potential benefit of correlating pathophysiological and clinical findings. The recognition and improved clinical characterization of parkinsonian features in idiopathic and inherited isolated dystonia extends the clinical spectrum of motor features in dystonia, which may help avoid incorrect diagnosis and inform therapeutic research.     

Gas Exchange and Ventilatory Efficiency During Exercise in Pulmonary Vascular Diseases

Background and ObjectiveVentilatory inefficiency (high V′_E/V′CO₂) and resting hypocapnia are common in pulmonary vascular disease and are associated with poor prognosis. Low resting PaCO₂ suggests increased chemosensitivity or an altered PaCO₂ set-point. We aimed to determine the relationships between exercise gas exchange variables reflecting the PaCO₂ set-point, exercise capacity, hemodynamics and V′_E/V′CO₂.MethodsPulmonary arterial hypertension (n = 34), chronic thromboembolic pulmonary hypertension (CTEPH, n = 19) and pulmonary veno-occlusive disease (PVOD, n = 6) patients underwent rest and peak exercise arterial blood gas measurements during cardiopulmonary exercise testing. Patients were grouped according to resting PaCO₂: hypocapnic (PaCO₂ ≤34 mmHg) or normocapnic (PaCO₂ 35–45 mmHg). The PaCO₂ set-point was estimated by the maximal value of end-tidal PCO₂ (maximal P_ETCO₂) between the anaerobic threshold and respiratory compensation point.ResultsThe hypocapnic group (n = 39) had lower resting cardiac index (3.1 ±0.8 vs. 3.7 ±0.7 L/min/m², p < 0.01), lower peak V′O₂ (15.8 ± 3.5 vs. 20.7 ± 4.3 mL/kg/min, p < 0.01), and higher V′_E/V′CO₂ slope (60.6 ± 17.6 vs. 38.2 ± 8.0, p < 0.01). At peak exercise, hypocapic patients had lower PaO₂, higher V_D/V_T and higher P_(a-ET)CO₂. Maximal P_ETCO₂ (r = 0.59) and V_D/V_T (r = −0.59) were more related to cardiac index than PaO₂ or PaCO₂ at rest or peak exercise. Maximal P_ETCO₂ was the strongest correlate of V′_E/V′CO₂ slope (r = −0.86), peak V′O₂ (r = 0.64) and peak work rate (r = 0.49).ConclusionsResting hypocapnia is associated with worse cardiac function, more ventilatory inefficiency and reduced exercise capacity. This could be explained by elevated chemosensitivity and lower PaCO₂ set-point. Maximal P_ETCO₂ may be a useful non-invasive marker of PaCO₂ setpoint and disease severity even with submaximal effort.     

Pain and Depression: A Neurobiological Perspective of Their Relationship

Remarkable progresses have been achieved regarding the understanding of the neurobiological bases of pain and depression. The principal role of neurotransmitters, neuromodulators, and neurohormones has been proposed in the development of pain and depression. With the progression of molecular biology, an intricate interaction among biological factors accountable to the development and management of pain and depression has been also shown in a numerous preclinical and clinical researches. This mini-review will briefly describe the current issues and future research direction for better understanding of the relationship between pain and depression.