Expanding the phenotypic spectrum of TUBB4A-associated hypomyelinating leukoencephalopathies

Objective: We performed whole-exome sequencing analysis of patients with genetically unsolved hypomyelinating leukoencephalopathies, identifying 8 patients with TUBB4A mutations and allowing the phenotypic spectrum ofTUBB4A mutations to be investigated.

Methods: Fourteen patients with hypomyelinating leukoencephalopathies, 7 clinically diagnosed with hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC), and 7 with unclassified hypomyelinating leukoencephalopathy, were analyzed by whole-exome sequencing. The effect of the mutations on microtubule assembly was examined by mapping altered amino acids onto 3-dimensional models of the αβ-tubulin heterodimer.

Results: Six heterozygous missense mutations in TUBB4A, 5 of which are novel, were identified in 8 patients (6/7 patients with H-ABC [the remaining patient is an atypical case] and 2/7 patients with unclassified hypomyelinating leukoencephalopathy). In 4 cases with parental samples available, the mutations occurred de novo. Analysis of 3-dimensional models revealed that the p.Glu410Lys mutation, identified in patients with unclassified hypomyelinating leukoencephalopathy, directly impairs motor protein and/or microtubule-associated protein interactions with microtubules, whereas the other mutations affect longitudinal interactions for maintaining αβ-tubulin structure, suggesting different mechanisms in tubulin function impairment. In patients with the p.Glu410Lys mutation, basal ganglia atrophy was unobserved or minimal although extrapyramidal features were detected, suggesting its functional impairment.

Conclusions: TUBB4A mutations cause typical H-ABC. Furthermore, TUBB4A mutations associate cases of unclassified hypomyelinating leukoencephalopathies with morphologically retained but functionally impaired basal ganglia, suggesting that TUBB4A-related hypomyelinating leukoencephalopathies encompass a broader clinical spectrum than previously expected. Extrapyramidal findings may be a key for consideration of TUBB4A mutations in hypomyelinating leukoencephalopathies.

Neurology 2014

Epilepsy and outcome in FOXG1-related disorders

FOXG1-related disorders are associated with severe intellectual disability, absent speech with autistic features, and epilepsy. Children with deletions or intragenic mutations of FOXG1 also have postnatal microcephaly, morphologic abnormalities of the corpus callosum, and choreiform movements. Duplications of 14q12 often present with infantile spasms, and have subsequent intellectual disability with autistic features. Long-term epilepsy outcome and response to treatment have not been studied systematically in a well-described cohort of subjects with FOXG1-related disorders. We report on the epilepsy features and developmental outcome of 23 new subjects with deletions or intragenic mutations of FOXG1, and 7 subjects with duplications.

Methods

Subjects had either chromosomal microarray or FOXG1 gene sequencing performed as part of routine clinical care. Development and epilepsy follow-up data were collected from medical records from treating neurologists and through telephone parental interviews using standardized questionnaires.

Results

Epilepsy was diagnosed in 87% of the subjects with FOXG1-related disorders. The mean age of epilepsy diagnosis in FOXG1duplications was significantly younger than those with deletions/intragenic mutations (p = 0.0002). All of the duplication FOXG1 children with infantile spasms responded to hormonal therapy, and only one required long-term antiepileptic therapy. In contrast, more children with deletions/intragenic mutations required antiepileptic drugs on follow-up (p < 0.0005). All subjects with FOXG1-related disorders had neurodevelopmental disabilities after 3 years of age, regardless of the epilepsy type or intractability of seizures. All had impaired verbal language and social contact, and three duplication subjects were formally diagnosed with autism. Subjects with deletion/intragenic mutations, however, had significantly worse ambulation (p = 0.04) and functional hand use (p < 0.0005).

Significance

Epilepsy and developmental outcome characteristics allow clinicians to distinguish among the FOXG1-related disorders. Further genotype–phenotype studies of FOXG1 may help to elucidate why children develop different forms of developmental epilepsy.

Epilepsia 2014

Dravet syndrome—From epileptic encephalopathy to channelopathy

Mutations in the gene encoding the α1 subunit of the voltage gated sodium channel (SCN1A) are associated with several epilepsy syndromes, ranging from relatively mild phenotypes found in families with genetic epilepsy with febrile seizures plus (GEFS+) to the severe infant-onset epilepsy Dravet syndrome. Evidence has emerged of the consequences of SCN1α dysfunction in different neuronal networks across the brain pointing toward a channelopathy model causing the neurologic features of Dravet syndrome that is beyond purely seizure related damage. A genetic change will present according to its severity, the genetic background of the individual, and environmental factors, and will affect a variety of neuronal networks according to channel distribution. This already-vulnerable system may be susceptible to secondary aggravating events such as status epilepticus. The channelopathy model implies that pharmacologic treatment and the restoration of impaired γ-aminobutyric acid (GABA)ergic neurotransmission might not only help prevent seizures but might affect the comorbidities of the syndrome. This critical review explores recent evidence relating to the pathogenicity of SCN1A mutations in Dravet syndrome and the effect these have on the wider disease phenotype and discusses whether knowledge of specific genotypes can influence clinical practice. Genetic technology is currently advancing at unprecedented speed and will increase our knowledge of new genes and interacting genetic networks. Clinicians and geneticists will have to work in close collaboration to guarantee good delivery and counseling of genetic testing results.

Epilepsia 2014

Ischaemic stroke in young adults: risk factors and long-term consequences

Contrary to trends in most other diseases, the average age of ischaemic stroke onset is decreasing, owing to a rise in the incidence of stroke among 'young' individuals (under 50 years of age). This Review provides a critical overview of the risk factors and aetiology of young ischaemic stroke and addresses its long-term prognosis, including cardiovascular risk, functional outcome and psychosocial consequences. We highlight the diminishing role of 'rare' risk factors in the pathophysiology of young stroke in light of the rising prevalence of 'traditional' vascular risk factors in younger age groups. Long-term prognosis is of particular interest to young patients, because of their long life expectancy and major responsibilities during a demanding phase of life. The prognosis of young stroke is not as favourable as previously thought, with respect either to mortality or cardiovascular disease or to psychosocial consequences. Therefore, secondary stroke prevention is probably a life-long endeavour in most young stroke survivors. Due to under-representation of young patients in past trials, new randomized trials focusing on this age group are needed to confirm the benefits of long-term secondary preventive medication. The high prevalence of poor functional outcome and psychosocial problems warrants further study to optimize treatment and rehabilitation for these young patients.

Nature Reviews Neurology 2014

Simvastatin in aneurysmal subarachnoid haemorrhage (STASH): a multicentre randomised phase 3 trial

Background

The benefit of statins in patients with acute aneurysmal subarachnoid haemorrhage is unclear. We aimed to determine whether simvastatin 40 mg could improve the long-term outcome in patients with this disorder.

Methods

In this international, multicentre, randomised, double-blind trial, we enrolled patients aged 18—65 years with confirmatory evidence of an aneurysmal subarachnoid haemorrhage and presenting less than 96 h from ictus from 35 acute neurosurgical centres in nine countries. Patients were randomly allocated (1:1) to receive either simvastatin 40 mg or placebo once a day for up to 21 days. We used a computer-generated randomisation code to randomise patients in every centre by blocks of ten (five simvastatin, five placebo). Participants and investigators were masked to treatment assignment. The primary outcome was the distribution of modified Rankin Scale (mRS) score obtained by questionnaire at 6 months. Analyses were done on the intention-to-treat population. This trial has been completed and is registered with Current Controlled Trials, number ISRCTN75948817.

Findings

Between Jan 6, 2007, and Feb 1, 2013, apart from the period between May 15, 2009, and Feb 8, 2011, when recruitment was on hold, 803 patients were randomly assigned to receive either simvastatin 40 mg (n=391) or placebo (n=412). All patients were included in the intention-to-treat population. 782 (97%) patients had outcome data recorded at 6 months, of whom 560 (72%) were classed as having a favourable outcome, mRS 0—2 (271 patients in the simvastatin group vs 289 in the placebo group). The primary ordinal analysis of the mRS, adjusted for age and World Federation of Neurological Surgeons grade on admission, gave a common odds ratio (OR) of 0·97, 95% CI 0·75—1·25; p=0·803. At 6 months, we recorded 37 (10%) deaths in the simvastatin group compared with 35 (9%) in the placebo group (log-rank p=0·592). 70 (18%) serious adverse events were reported in the simvastatin group compared with 74 (18%) in the placebo group. No suspected unexpected serious adverse reactions were reported.

Interpretation

The STASH trial did not detect any benefit in the use of simvastatin for long-term or short-term outcome in patients with aneurysmal subarachnoid haemorrhage. Despite demonstrating no safety concerns, we conclude that patients with subarachnoid haemorrhage should not be treated routinely with simvastatin during the acute stages.

Lancet Neurology 2014

Associations Between Cerebral Small-Vessel Disease and Alzheimer Disease Pathology as Measured by Cerebrospinal Fluid Biomarkers

Importance  It remains unclear if and how associations between cerebral small-vessel disease and Alzheimer disease (AD) pathology lead to cognitive decline and dementia.

Objective  To determine associations between small-vessel disease and AD pathology.

Design, Setting, and Participants  Cross-sectional study from January 2002 to December 2012 using the memory clinic–based Amsterdam Dementia Cohort. The study included 914 consecutive patients with available cerebrospinal fluid (CSF) and magnetic resonance imaging; 547 were patients diagnosed as having AD (54% female, mean [SD], 67 [8]; Mini-Mental State Examination score, mean [SD], 21 [5]), 30 were patients diagnosed as having vascular dementia (37% female, mean [SD], 76 [9]; Mini-Mental State Examination score, mean [SD], 24 [4]), and 337 were control participants with subjective memory complaints (42% female, mean [SD], 59 [59]; Mini-Mental State Examination score, mean [SD], 28 [2]). Linear regressions were performed with CSF biomarkers (log transformed) as dependent variables and magnetic resonance imaging measures (dichotomized) as independent, adjusted for sex, age, mediotemporal lobe atrophy, and diagnosis. An interaction term for diagnosis by magnetic resonance imaging measures was used for estimates per diagnostic group.

Main Outcomes and Measures  We examined the associations of magnetic resonance imaging white matter hyperintensities (WMH), lacunes, microbleeds with CSF β-amyloid 1-42 (Aβ42), total tau, and tau phosphorylated at threonine 181 (P-tau181) as well as for a subset of apolipoprotein E (APOE) ε4 carriers and noncarriers.

Results  Microbleed presence was associated with lower CSF Aβ42 in AD and vascular dementia (standardized beta = −0.09, P = .003; standardized beta = −0.30, P = .01), and higher CSF tau in controls (standardized beta = 0.10, P = .03). There were no effects for P-tau181. The presence of WMH was associated with lower Aβ42 in control participants and patients with vascular dementia (standardized beta = −0.18, P = .002; standardized beta = −0.32, P = .02) but not in patients with AD. There were no effects for tau or P-tau181. The presence of lacunes was associated with higher Aβ42 in vascular dementia (standardized beta = 0.17, P = .07) and lower tau in AD (standardized beta = −0.07, P = .05) but there were no effects for Aβ42 or P-tau181. Stratification for apolipoprotein E genotype revealed that these effects were mostly attributable to ε4 carriers.

Conclusions and Relevance  Deposition of amyloid appears aggravated in patients with cerebral small-vessel disease, especially in apolipoprotein E ε4 carriers, providing evidence for pathophysiological synergy between these 3 biological factors.

JAMA Neurology 2014

Immunophenotyping of Cerebrospinal Fluid Cells in Multiple Sclerosis In Search of Biomarkers

Importance  Cerebrospinal fluid (CSF) is the compartment in closest proximity to the central nervous system (CNS) parenchyma and might reflect immune pathology in inflammatory CNS disorders like multiple sclerosis (MS). Multiparameter flow cytometry is used to characterize immunological alterations in the CSF of patients with MS.

Objectives  To present a comprehensive review of the cellular alterations in CSF that distinguish MS from physiological conditions and other CNS disorders; integrate relevant findings into a model of leukocyte trafficking in the CNS; highlight treatment-related changes in leukocyte subsets; and evaluate the potential of CSF immunophenotyping in the search of novel biomarkers in MS.

Evidence Review  We searched MEDLINE articles published between 1980 and 2013 that include the flow cytometric characterization of leukocyte subsets in the CSF of patients with MS.

Findings  All of the articles have shown CSF pleocytosis in MS. Interesting results include CSF enrichment of helper T cells (subtypes TH1 and TH17) and regulatory T cells, as well as intrathecal B-cell differentiation resulting in the generation of antibody-producing plasmablasts and plasma cells. Other leukocyte populations, including natural killer cells, monocytes, and dendritic cells, show alterations as well. Characterization of CSF cells increases our understanding of MS pathogenesis and may provide useful biomarkers for individual prognosis and treatment decisions. However, validation in controlled settings is lacking in most cases.

Conclusions and Relevance  With the advent of more sophisticated approaches, immunophenotyping of CSF cells in MS might become increasingly important to correlate cellular subsets with different stages of disease activity and remission. An assessment of CSF cell numbers and composition should be incorporated into clinical trials.

JAMA Neurology 2014