Benign infantile seizures and paroxysmal dyskinesia caused by an SCN8A mutation

Objective

Benign familial infantile seizures (BFIS), paroxysmal kinesigenic dyskinesia (PKD), and their combination—known as infantile convulsions and paroxysmal choreoathetosis (ICCA)—are related autosomal dominant diseases. PRRT2 (proline-rich transmembrane protein 2 gene) has been identified as the major gene in all 3 conditions, found to be mutated in 80 to 90% of familial and 30 to 35% of sporadic cases.

Methods

We searched for the genetic defect in PRRT2-negative, unrelated families with BFIS or ICCA using whole exome or targeted gene panel sequencing, and performed a detailed cliniconeurophysiological workup.

Results

In 3 families with a total of 16 affected members, we identified the same, cosegregating heterozygous missense mutation (c.4447G>A; p.E1483K) in SCN8A, encoding a voltage-gated sodium channel. A founder effect was excluded by linkage analysis. All individuals except 1 had normal cognitive and motor milestones, neuroimaging, and interictal neurological status. Fifteen affected members presented with afebrile focal or generalized tonic–clonic seizures during the first to second year of life; 5 of them experienced single unprovoked seizures later on. One patient had seizures only at school age. All patients stayed otherwise seizure-free, most without medication. Interictal electroencephalogram (EEG) was normal in all cases but 2. Five of 16 patients developed additional brief paroxysmal episodes in puberty, either dystonic/dyskinetic or “shivering” attacks, triggered by stretching, motor initiation, or emotional stimuli. In 1 case, we recorded typical PKD spells by video-EEG-polygraphy, documenting a cortical involvement.

Interpretation

Our study establishes SCN8A as a novel gene in which a recurrent mutation causes BFIS/ICCA, expanding the clinical–genetic spectrum of combined epileptic and dyskinetic syndromes. 

Ann Neurol 2016

Multicenter prospective longitudinal study of magnetic resonance biomarkers in a large duchenne muscular dystrophy cohort

Objective

The aim of this study was to describe Duchenne muscular dystrophy (DMD) disease progression in the lower extremity muscles over 12 months using quantitative magnetic resonance (MR) biomarkers, collected across three sites in a large cohort.

Methods

A total of 109 ambulatory boys with DMD (8.7 ± 2.0 years; range, 5.0–12.9) completed baseline and 1-year follow-up quantitative MR imaging (transverse relaxation time constant; MRI-T₂), MR spectroscopy (fat fraction and ¹H₂O T₂), and 6-minute walk test (6MWT) measurements. A subset of boys completed additional measurements after 3 or 6 months.

Results

MRI-T₂ and fat fraction increased significantly over 12 months in all age groups, including in 5- to 6.9-year-old boys. Significant increases in vastus lateralis (VL) fat fraction were observed in 3 and 6 months. Even in boys whose 6MWT performance improved or remained stable over 1 year, significant increases in MRI-T₂ and fat fraction were found. Of all the muscles examined, the VL and biceps femoris long head were the most responsive to disease progression in boys with DMD.

Interpretation

MR biomarkers are responsive to disease progression in 5- to 12.9-year-old boys with DMD and able to detect subclinical disease progression in DMD, even within short (3–6 months) time periods. The measured sensitivity of MR biomarkers in this multicenter study may be critically important to future clinical trials, allowing for smaller sample sizes and/or shorter study windows in this fatal rare disease. 

Ann Neurol 2016

Clinical Trial Simulations Based on Genetic Stratification and the Natural History of a Functional Outcome Measure in Creutzfeldt-Jakob Disease

Importance  A major challenge for drug development in neurodegenerative diseases is that adequately powered efficacy studies with meaningful end points typically require several hundred participants and long durations. Prion diseases represent the archetype of brain diseases caused by protein misfolding, the most common subtype being sporadic Creutzfeldt-Jakob disease (sCJD), a rapidly progressive dementia. There is no well-established trial method in prion disease.

Objective  To establish a more powerful and meaningful clinical trial method in sCJD.

Design, Setting, and Participants  A stratified medicine and simulation approach based on a prospective interval-cohort study conducted from October 2008 to June 2014. This study involved 598 participants with probable or definite sCJD followed up over 470 patient-years at a specialist national referral service in the United Kingdom with domiciliary, care home, and hospital patient visits. We fitted linear mixed models to the outcome measurements, and simulated clinical trials involving 10 to 120 patients (no dropouts) with early to moderately advanced prion disease using model parameters to compare the power of various designs.

Main Outcomes and Measures  A total of 2681 assessments were done using a functionally orientated composite end point (Medical Research Council Scale) and associated with clinical investigations (brain magnetic resonance imaging, electroencephalography, and cerebrospinal fluid analysis) and molecular data (prion protein [PrP] gene sequencing, PrPSc type).

Results  Of the 598 participants, 273 were men. The PrP gene sequence was significantly associated with decline relative to any other demographic or investigation factors. Patients with sCJD and polymorphic codon 129 genotypes MM, VV, and MV lost 10% of their function in 5.3 (95% CI, 4.2-6.9), 13.2 (95% CI, 10.9-16.6), and 27.8 (95% CI, 21.9-37.8) days, respectively (P < .001). Simulations indicate that an adequately powered (80%; 2-sided α = .05) open-label randomized trial using 50% reduction in Medical Research Council Scale decline as the primary outcome could be conducted with only 120 participants assessed every 10 days and only 90 participants assessed daily, providing considerably more power than using survival as the primary outcome. Restricting to VV or MV codon 129 genotypes increased power even further. Alternatively, single-arm intervention studies (half the total sample size) could provide similar power in comparison to the natural history cohort.

Conclusions and Relevance  Functional end points in neurodegeneration need not require long and very large clinical studies to be adequately powered for efficacy. Patients with sCJD may be an efficient and cost-effective group for testing disease-modifying therapeutics. Stratified medicine and natural history cohort approaches may transform the feasibility of clinical trials in orphan diseases.

JAMA Neurology 2016

Cognitive Decline in a Colombian Kindred With Autosomal Dominant Alzheimer Disease A Retrospective Cohort Study

Importance  Data from an autosomal dominant Alzheimer disease (ADAD) kindred were used to track the longitudinal trajectory of cognitive decline associated with preclinical ADAD and explore factors that may modify the rate of cognitive decline.

Objectives  To evaluate the onset and rate of cognitive decline during preclinical ADAD and the effect of socioeconomic, vascular, and genetic factors on the cognitive decline.

Design, Setting, and Participants  We performed a retrospective cohort study from January 1, 1995, through June 31, 2012, of individuals from Antioquia, Colombia, who tested positive for the ADAD-associated PSEN1 E280A mutation. Data analysis was performed from August 20, 2014, through November 30, 2015. A mixed-effects model was used to estimate annual rates of change in cognitive test scores and to mark the onset of cognitive decline.

Main Outcomes and Measures  Memory, language, praxis, and total scores from the Consortium to Establish a Registry for Alzheimer Disease test battery. Chronologic age was used as a time scale in the models. We explore the effects of sex; educational level; socioeconomic status; residence area; occupation type; marital status; history of hypertension, diabetes mellitus, and dyslipidemia; tobacco and alcohol use; and APOE ε4 on the rates of cognitive decline.

Results  A total of 493 carriers met the inclusion criteria and were analyzed. A total of 256 carriers had 2 or more assessments. At the time of the initial assessment, participants had a mean (SD) age of 33.4 (11.7) years and a mean (SD) educational level of 7.2 (4.2) years. They were predominantly female (270 [54.8%]), married (293 [59.4%]), and of low socioeconomic status (322 [65.3%]). Word list recall scores provided the earliest indicator of preclinical cognitive decline at 32 years of age, 12 and 17 years before the kindred’s respective median ages at mild cognitive impairment and dementia onset. After the change point, carriers had a statistically significant cognitive decline with a loss of 0.24 (95% CI, −0.26 to −0.22) points per year for the word list recall test and 2.13 (95% CI, −2.29 to −1.96) points per year for total scores. Carriers with high educational levels had an increase of approximately 36% in the rate of cognitive decline after the change point when compared with those with low educational levels (−2.89 vs −2.13 points per year, respectively). Onset of cognitive decline was delayed by 3 years in individuals with higher educational levels compared with those with lower educational levels. Those with higher educational level, middle/high socioeconomic status, history of diabetes and hypertension, and tobacco and alcohol use had a steeper cognitive decline after onset.

Conclusions and Relevance  Preclinical cognitive decline was evident in PSEN1 E280A mutation carriers 12 years before the onset of clinical impairment. Educational level may be a protective factor against the onset of cognitive impairment.

JAMA Neurology 2016

The Role of APOE in the Occurrence of Frontotemporal Dementia in Amyotrophic Lateral Sclerosis F

Importance  Amyotrophic lateral sclerosis (ALS) is a heterogeneous disease with a wide spectrum of involvement of cognitive functions. The mechanisms of this heterogeneity are still largely unknown, but genetic variants may account for this variability.

Objective  To assess the influence of the apolipoprotein E (APOE) and C9ORF72 genotypes on cognitive impairment in a population-based series of Italian patients with ALS.

Design, Setting, and Participants  All 504 patients with ALS living in Piemonte, Italy, diagnosed between January 1, 2009, and December 31, 2013, and identified through the Piemonte and Valle d’Aosta register for ALS, were eligible to participate in the study. Controls were 223 age- and sex-matched individuals identified through the patients’ general practitioners. Data analysis was performed from June 1 to December 31, 2014.

Main Outcomes and Measures  The presence of APOE and C9ORF72 genotypes was assessed. Patients were cognitively classified as having ALS with normal cognition, ALS with frontotemporal dementia (FTD), ALS with executive or nonexecutive impairment, and ALS with behavioral impairment.

Results  Of the 504 patients with incident ALS, 357 (70.8%) were included in the study; 154 were women, 203 were men, they had a mean (SD) age at onset of 64.8 (10.2) years, and 37 of them carried a C9ORF72repeat expansion. Cognitive testing revealed that 184 patients (51.5%) had ALS with normal cognition, 51 (14.3%) had ALS with FTD, 103 (28.9%) had ALS with executive or nonexecutive impairment, and 19 (5.3%) had ALS with behavioral impairment. Distribution of APOE haplotypes did not significantly differ between patients and controls or among patients with different levels of cognitive impairment. According to multivariate logistic regression, the presence of C9ORF72 repeat expansions was the strongest determinant of FTD (odds ratio, 13.08; 95% CI, 4.75-36.02; P < .001); however, the presence of an APOE ε2 allele significantly increased the risk of FTD (odds ratio, 2.61; 95% CI, 1.14-6.10; P = .03). Presence of an APOE ε4 allele was ineffectual.

Conclusions and Relevance  C9ORF72 repeat expansions have a primary role in increasing the risk of cognitive impairment in patients with ALS; the APOE ε2 allele, to a lesser extent, also increases the risk of FTD. These study findings highlight the importance of considering the genetic background of patients with ALS when analyzing the putative effect of genetic modifiers.

JAMA Neurology 2016

CCDC88A mutations cause PEHO-like syndrome in humans and mouse

Progressive encephalopathy with oedema, hypsarrhythmia and optic atrophy (PEHO) syndrome is a rare Mendelian phenotype comprising severe retardation, early onset epileptic seizures, optic nerve/cerebellar atrophy, pedal oedema, and early death. Atypical cases are often known as PEHO-like, and there is an overlap with ‘early infantile epileptic encephalopathy’. PEHO is considered to be recessive, but surprisingly since initial description in 1991, no causative recessive gene(s) have been described. Hence, we report a multiplex consanguineous family with the PEHO phenotype where affected individuals had a homozygous frame-shift deletion in CCDC88A (c.2313delT, p.Leu772*ter). Analysis of cDNA extracted from patient lymphocytes unexpectedly failed to show non-sense mediated decay, and we demonstrate that the mutation produces a truncated protein lacking the crucial C-terminal half of CCDC88A (girdin). To further investigate the possible role of CCDC88A in human neurodevelopment we re-examined the behaviour and neuroanatomy of Ccdc88a knockout pups. These mice had mesial-temporal lobe epilepsy, microcephaly and corpus callosum deficiency, and by postnatal Day 21, microcephaly; the mice died at an early age. As the mouse knockout phenotype mimics the human PEHO phenotype this suggests that loss of CCDC88A is a cause of the PEHO phenotype, and that CCDC88A is essential for multiple aspects of normal human neurodevelopment

Brain 2016

Liver transplant in ethylmalonic encephalopathy: a new treatment for an otherwise fatal disease

Ethylmalonic encephalopathy is a fatal, rapidly progressive mitochondrial disorder caused by ETHE1mutations, whose peculiar clinical and biochemical features are due to the toxic accumulation of hydrogen sulphide and of its metabolites, including thiosulphate. In mice with ethylmalonic encephalopathy, liver-targeted adeno-associated virus-mediated ETHE1 gene transfer dramatically improved both clinical course and metabolic abnormalities. Reasoning that the same achievement could be accomplished by liver transplantation, we performed living donor-liver transplantation in an infant with ethylmalonic encephalopathy. Unlike the invariably progressive deterioration of the disease, 8 months after liver transplantation, we observed striking neurological improvement with remarkable achievements in psychomotor development, along with dramatic reversion of biochemical abnormalities. These results clearly indicate that liver transplantation is a viable therapeutic option for ETHE1 disease.

Brain 2016

Inherited erythromelalgia due to mutations in SCN9A: natural history, clinical phenotype and somatosensory profile

Inherited erythromelalgia, the first human pain syndrome linked to voltage-gated sodium channels, is widely regarded as a genetic model of human pain. Because inherited erythromelalgia was linked to gain-of-function changes of sodium channel Nav1.7 only a decade ago, the literature has mainly consisted of reports of genetic and/or clinical characterization of individual patients. This paper describes the pattern of pain, natural history, somatosensory profile, psychosocial status and olfactory testing of 13 subjects with primary inherited erythromelalgia with mutations of SCN9A, the gene encoding Nav1.7. Subjects were clinically profiled using questionnaires, quantitative sensory testing and olfaction testing during the in-clinic phase of the study. In addition, a detailed pain phenotype for each subject was obtained over a 3-month period at home using diaries, enabling subjects to self-report pain attacks, potential triggers, duration and severity of pain. All subjects reported pain and heat in the extremities (usually feet and/or hands), with pain attacks triggered by heat or exercise and relieved mainly by non-pharmacological manoeuvres such as cooling. A large proportion of pain attacks (355/1099; 32%) did not involve a specific trigger. There was considerable variability in the number, duration and severity of pain attacks between subjects, even those carrying the same mutation within a family, and within individuals over the 12–13 week observation period. Most subjects (11/13) had pain between attacks. For these subjects, mean pain severity between pain attacks was usually lower than that during an attack. Olfaction testing using the Sniffin’T test did not demonstrate hyperosmia. One subject had evidence of orthostatic hypotension. Overall, there was a statistically significant correlation between total Hospital Anxiety and Depression Scale scores (P = 0.005) and pain between attacks and for Hospital Anxiety and Depression Scale Depression scores and pain between attacks (P = 0.001). Hospital Anxiety and Depression Scale scores for five subjects were below the threshold for mild anxiety or depression and none of the 13 subjects were severely anxious and/or depressed. Quantitative sensory testing revealed significantly increased detection thresholds for cold and warm stimuli at affected, compared to unaffected sites. By contrast, significantly decreased cold and heat pain thresholds were found at unaffected sites. Sensory profiles varied considerably between affected and unaffected sites, suggesting the existence of small fibre neuropathy in symptomatic sites. This in-depth clinical characterization of a well-defined inherited erythromelalgia population indicates the importance of characterizing the pain phenotype in individuals before undertaking clinical trials, given the inherent variability of pain both between and within inherited erythromelalgia subjects, even those within a family who carry the same mutation.

Brain 2016

A randomized trial of mexiletine in ALS Safety and effects on muscle cramps and progression

Objective: To determine the safety and tolerability of mexiletine in a phase II double-blind randomized controlled trial of sporadic amyotrophic lateral sclerosis (SALS).

Methods: Sixty participants with SALS from 10 centers were randomized 1:1:1 to placebo, mexiletine 300 mg/d, or mexiletine 900 mg/d and followed for 12 weeks. The primary endpoints were safety and tolerability. Secondary endpoints were pharmacokinetic study from plasma and CSF, ALS Functional Rating Scale–Revised (ALSFRS-R) score, slow vital capacity (SVC), and muscle cramp frequency and severity.

Results: The only serious adverse event among active arm participants was one episode of imbalance. Thirty-two percent of participants receiving 900 mg of mexiletine discontinued study drug vs 5% on placebo (p = 0.026). Pharmacokinetic study demonstrated a peak plasma concentration 2 hours postdose and strong correlation between plasma and CSF (p < 0.001). Rates of decline of ALSFRS-R and SVC did not differ from placebo. Analysis of all randomized patients demonstrated significant reductions of muscle cramp frequency (300 mg: rate = 31% of placebo,p = 0.047; 900 mg: 16% of placebo, p = 0.002) and cramp intensity (300 mg: mean = 45% of placebo, p = 0.08; 900 mg: 25% of placebo, p = 0.005).

Conclusions: Mexiletine was safe at both doses and well-tolerated at 300 mg/d but adverse effects at 900 mg/d led to a high rate of discontinuation. Mexiletine treatment resulted in large dose-dependent reductions in muscle cramp frequency and severity. No effect on rate of progression was detected, but clinically important differences could not be excluded in this small and short-duration study.

Classification of evidence: This study provides Class I evidence that mexiletine is safe when given daily to patients with amyotrophic lateral sclerosis at 300 and 900 mg and well-tolerated at the lower dose.

Neurology 2016

Neuroinflammation in treated HIV-positive individuals A TSPO PET study

Objective: To explore the effects of microglial activation on brain function and structure, and its relationship with peripheral inflammatory markers, in treated, HIV-positive individuals, using in vivo [¹¹C]PBR28 PET (to measure the 18 kDa translocator protein [TSPO]).

Methods: Cognitively healthy HIV-positive individuals on suppressive antiretroviral therapy and HIV-negative individuals (controls) underwent brain [¹¹C]PBR28 PET and MRI. HIV-positive patients completed neuropsychological testing and CSF testing for chemokines. The concentration of bacterial ribosomal 16sDNA in plasma was measured as a marker of microbial translocation.

Results: HIV-positive individuals showed global increases in TSPO expression compared to controls (corrected p < 0.01), with significant regional increases in the parietal (p = 0.001) and occipital (p = 0.046) lobes and in the globus pallidus (p = 0.035). TSPO binding in the hippocampus, amygdala, and thalamus were associated with poorer global cognitive performance in tasks assessing verbal and visual memory (p < 0.05). Increased TSPO binding was associated with increased brain white matter diffusion MRI mean diffusivity in HIV-positive individuals, a lower CD4/CD8 ratio, and both high pretreatment HIV RNA and plasma concentration ribosomal 16s DNA (p < 0.05).

Conclusions: Cognitively healthy HIV-positive individuals show evidence for a chronically activated brain innate immune response and elevated blood markers of microbial translocation despite effective control of plasma viremia. Increased brain inflammation is associated with poorer cognitive performance and white matter microstructural pathology, suggesting a possible role in cognitive impairments found in some HIV-positive patients despite effective treatment.

Neurology 2016

Statin pretreatment is associated with better outcomes in large artery atherosclerotic stroke

Objective: Even though statin pretreatment is associated with better functional outcomes and lower risk of mortality in acute ischemic stroke, there are limited data evaluating this association in acute ischemic stroke due to large artery atherosclerosis (LAA), which carries the highest risk of early stroke recurrence.

Methods: Consecutive patients with acute LAA were prospectively evaluated from 7 tertiary-care stroke centers during a 3-year period. Statin pretreatment, demographics, vascular risk factors, and admission and discharge stroke severity were recorded. The outcome events of interest were neurologic improvement during hospitalization (quantified as the relative decrease in NIH Stroke Scale score at discharge in comparison to hospital admission), favorable functional outcome (FFO) (defined as modified Rankin Scale score of 0–1), recurrent stroke, and death at 1 month. Statistical analyses were performed using univariable and multivariable Cox regression models adjusting for potential confounders. All analyses were repeated following propensity score matching.

Results: Statin pretreatment was documented in 192 (37.2%) of 516 consecutive patients with LAA (mean age: 65 ± 13 years; 60.8% men; median NIH Stroke Scale score: 9 points, interquartile range: 5–18). Statin pretreatment was associated with greater neurologic improvement during hospitalization and higher rates of 30-day FFO in unmatched and matched (odds ratio for FFO: 2.44; 95% confidence interval [CI]: 1.07–5.53) analyses. It was also related to lower risk of 1-month mortality and stroke recurrence in unmatched and matched analyses (hazard ratio for recurrent stroke: 0.11, 95% CI: 0.02–0.46; hazard ratio for death: 0.24, 95% CI: 0.08–0.75).

Conclusion: Statin pretreatment in patients with acute LAA appears to be associated with better early outcomes regarding neurologic improvement, disability, survival, and stroke recurrence.

Neurology 2016

Diagnostic markers of axonal degeneration and demyelination in sensory nerve conduction

Introduction

The aim of this study was to formulate diagnostic hallmarks of axonal degeneration and demyelination in sensory nerve conduction studies (NCS).

Methods

We compared nerve conduction data obtained with surface electrode (SE) NCS and on-nerve needle (ONN) NCS in 50 cases of demyelination and 22 cases of axonal degeneration as assessed by sural nerve biopsy.

Results

The overall diagnostic sensitivities of sensory nerve conduction were 26% by SE-NCS and 69% by ONN-NCS. The most helpful marker for demyelination was negative-peak nerve conduction velocity (NP-NCV), using a 36% decrease from the means in both techniques. Dispersion was also helpful in identifying demyelination. Low amplitude and absence of compound nerve action potential were indicative of general pathology in SE-NCS but of axonal degeneration in ONN-NCS.

Conclusion

Although diagnostic sensitivity is low, NP-NCV and dispersion can be used for diagnosis of demyelination in sensory NCS. 

Muscle Nerve, 2016