Cerebral amyloid angiopathy-related inflammation (CAA-ri) is an important diagnosis to reach in clinical practice because many patients with the disease respond to immunosuppressive therapy. Reliable noninvasive diagnostic criteria for CAA-ri would allow some patients to avoid the risk of brain biopsy. To test the sensitivity and specificity of clinical and neuroimaging-based criteria for CAA-ri. We modified the previously proposed clinicoradiological criteria and retrospectively analyzed clinical medical records and magnetic resonance imaging fluid-attenuated inversion recovery and gradient-echo scans obtained from individuals with CAA-ri and noninflammatory CAA. At 2 referral centers between October 1, 1995, and May 31, 2013, and between January 1, 2009, and December 31, 2011, participants included 17 individuals with pathologically confirmed CAA-ri and 37 control group members with pathologically confirmed noninflammatory CAA. The control group was further divided into those with past lobar intracerebral hemorrhage (ICH) (n = 21) and those with cerebral microbleeds only and no history of ICH (n = 16). The dates of our analysis were September 1, 2012, to August 31, 2015. The sensitivity and specificity of prespecified criteria for probable CAA-ri (requiring asymmetric white matter hyperintensities extending to the subcortical white matter) and possible CAA-ri (not requiring the white matter hyperintensities to be asymmetric). The 17 patients in the CAA-ri group were a mean (SD) of 68 (8) years and 8 (47%) were women. In the CAA-ri group, 14 of 17 (82%) met the criteria for both probable and possible CAA-ri. In the control group having noninflammatory CAA with lobar ICH, 1 of 21 (5%) met the criteria for possible CAA-ri, and none met the criteria for probable CAA-ri. In the control group having noninflammatory CAA with no ICH, 11 of 16 (69%) met the criteria for possible CAA-ri, and 1 of 16 (6%) met the criteria for probable CAA-ri. These findings yielded a sensitivity and specificity of 82% and 97%, respectively, for the probable criteria and a sensitivity and specificity of 82% and 68%, respectively, for the possible criteria. Our data suggest that a reliable diagnosis of CAA-ri can be reached from basic clinical and magnetic resonance imaging information alone, with good sensitivity and excellent specificity.

Background and Objectives The goal of this work was to investigate the natural history and outcomes after treatment for spontaneous amyloid-related imaging abnormalities (ARIA)-like in cerebral amyloid angiopathy–related inflammation (CAA-ri). Methods This was a multicenter, hospital-based, longitudinal, prospective observational study of inpatients meeting CAA-ri diagnostic criteria recruited through the Inflammatory Cerebral Amyloid Angiopathy and Alzheimer9s Disease βiomarkers International Network from January 2013 to March 2017. A protocol for systematic data collection at first-ever presentation and at subsequent in-person visits, including T1-weighted, gradient recalled echo–T2*, fluid-suppressed T2-weighted (fluid-attenuated inversion recovery), and T1 postgadolinium contrast-enhanced images acquired on 1.5T MRI, was used at the 3-, 6-, 12-, and 24-month follow-up. Centralized reads of MRIs were performed by investigators blinded to clinical, therapeutic, and time-point information. Main outcomes were survival, clinical and radiologic recovery, intracerebral hemorrhage (ICH), and recurrence of CAA-ri. Results The study enrolled 113 participants (10.6% definite, 71.7% probable, and 17.7% possible CAA-ri). Their mean age was 72.9 years; 43.4% were female; 37.1% were APOEε4 carriers; 36.3% had a history of Alzheimer disease; and 33.6% had a history of ICH. A history of ICH and the occurrence of new ICH at follow-up were more common in patients with cortical superficial siderosis at baseline (52.6% vs 14.3%, p < 0.0001 and 19.3% vs 3.6%, p < 0.009, respectively). After the first-ever presentation of CAA-ri, 70.3% (95% confidence interval [CI] 61.6%–78.5%) and 84.1% (95% CI 76.2%–90.6%) clinically recovered within 3 and 12 months, followed by radiologic recovery in 45.1% (95% CI 36.4%–54.8%) and 77.4% (95% CI 67.7%–85.9%), respectively. After clinicoradiologic resolution of the first-ever episode, 38.3% (95% CI 22.9%–59.2%) had at least 1 recurrence within the following 24 months. Recurrence was more likely if IV high-dose corticosteroid pulse therapy was suddenly stopped compared to slow oral tapering off (hazard ratio 4.68, 95% CI 1.57–13.93; p = 0.006). Discussion These results from the largest longitudinal cohort registry of patients with CAA-ri support the transient and potentially relapsing inflammatory nature of the clinical-radiologic acute manifestations of the disease and the effectiveness of slow oral tapering off after IV corticosteroid pulse therapy in preventing recurrences. Our results highlight the importance of differential diagnosis for spontaneous ARIA-like events in β-amyloid–driven diseases, including treatment-related ARIA in patients with Alzheimer disease exposed to immunotherapy drugs.

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels control neuronal excitability and their dysfunction has been linked to epileptogenesis but few individuals with neurological disorders related to variants altering HCN channels have been reported so far. In 2014, we described five individuals with epileptic encephalopathy due to de novo HCN1 variants. To delineate HCN1-related disorders and investigate genotype-phenotype correlations further, we assembled a cohort of 33 unpublished patients with novel pathogenic or likely pathogenic variants: 19 probands carrying 14 different de novo mutations and four families with dominantly inherited variants segregating with epilepsy in 14 individuals, but not penetrant in six additional individuals. Sporadic patients had epilepsy with median onset at age 7 months and in 36% the first seizure occurred during a febrile illness. Overall, considering familial and sporadic patients, the predominant phenotypes were mild, including genetic generalized epilepsies and genetic epilepsy with febrile seizures plus (GEFS+) spectrum. About 20% manifested neonatal/infantile onset otherwise unclassified epileptic encephalopathy. The study also included eight patients with variants of unknown significance: one adopted patient had two HCN1 variants, four probands had intellectual disability without seizures, and three individuals had missense variants inherited from an asymptomatic parent. Of the 18 novel pathogenic missense variants identified, 12 were associated with severe phenotypes and clustered within or close to transmembrane domains, while variants segregating with milder phenotypes were located outside transmembrane domains, in the intracellular N- and C-terminal parts of the channel. Five recurrent variants were associated with similar phenotypes. Using whole-cell patch-clamp, we showed that the impact of 12 selected variants ranged from complete loss-of-function to significant shifts in activation kinetics and/or voltage dependence. Functional analysis of three different substitutions altering Gly391 revealed that these variants had different consequences on channel biophysical properties. The Gly391Asp variant, associated with the most severe, neonatal phenotype, also had the most severe impact on channel function. Molecular dynamics simulation on channel structure showed that homotetramers were not conducting ions because the permeation path was blocked by cation(s) strongly complexed to the Asp residue, whereas heterotetramers showed an instantaneous current component possibly linked to deformation of the channel pore. In conclusion, our results considerably expand the clinical spectrum related to HCN1 variants to include common generalized epilepsy phenotypes and further illustrate how HCN1 has a pivotal function in brain development and control of neuronal excitability.

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed as four different isoforms (HCN1-4) in the heart and in the central and peripheral nervous systems. HCN channels are activated by membrane hyperpolarization at voltages close to resting membrane potentials and carry the hyperpolarization-activated current, dubbed If (funny current) in heart and Ih in neurons. HCN channels contribute in several ways to neuronal activity and are responsible for many important cellular functions, including cellular excitability, generation and modulation of rhythmic activity, dendritic integration, transmission of synaptic potentials and plasticity phenomena. Because of their role, defective HCN channels are natural candidates in the search for potential causes of neurological disorders in humans. Several data, including growing evidence that some forms of epilepsy are associated with HCN mutations, support the notion of an involvement of dysfunctional HCN channels in different experimental models of the disease. Additionally, some anti-epileptic drugs are known to modify the activity of the Ih current. HCN channels are widely expressed in the peripheral nervous system and recent evidence has highlighted the importance of the HCN2 isoform in the transmission of pain. HCN channels are also present in the midbrain system, where they finely regulate the activity of dopaminergic neurons, and a potential role of these channels in the pathogenesis of Parkinson’s disease has recently emerged. The function of HCN channels is regulated by specific accessory proteins, which control the correct expression and modulation of the neuronal Ih current. Alteration of these proteins can severely interfere with the physiological channel function, potentially predisposing to pathological conditions. In this review we address the present knowledge of the association between HCN dysfunctions and neurological diseases, including clinical, genetic and physiopathological aspects.

Epilepsy of infancy with migrating focal seizures (EIMFS) is a rare early-onset developmental epileptic encephalopathy resistant to anti-epileptic drugs. The most common cause for EIMFS is a gain-of-function mutation in the KCNT1 potassium channel gene, and treatment with the KCNT1 blocker quinidine has been suggested as a rational approach for seizure control in EIMFS patients. However, variable results on the clinical efficacy of quinidine have been reported. In the present study, we provide a detailed description of the clinical, genetic, in vitro, and in vivo electrophysiological profile and pharmacological responses to quinidine of 2 EIMFS unrelated patients with a heterozygous de novo KCNT1 mutation: c.2849G>A (p.R950Q) in patient 1 and c.2677G>A (p.E893K) in patient 2. When expressed heterologously in CHO cells, KCNT1 channels carrying each variant showed gain-of-function effects, and were more effectively blocked by quinidine when compared to wild-type KCNT1 channels. On the basis of these in vitro results, add-on quinidine treatment was started at 3 and 16 months of age in patients 1 and 2, respectively. The results obtained reveal that quinidine significantly reduced seizure burden (by about 90%) and improved quality of life in both patients, but failed to normalize developmental milestones, which persisted as severely delayed. Based on the present experience, early quinidine intervention associated with heart monitoring and control of blood levels is among the critical factors for therapy effectiveness in EIMFS patients with KCNT1 gain-of-function mutations. Multicenter studies are needed to establish a consensus protocol for patient recruitment, quinidine treatment modalities, and outcome evaluation, to optimize clinical efficacy and reduce risks as well as variability associated to quinidine use in such severe developmental encephalopathy.