Mutations in VRK1 Associated With Complex Motor and Sensory Axonal Neuropathy Plus Microcephaly

Importance  Patients with rare diseases and complex clinical presentations represent a challenge for clinical diagnostics. Genomic approaches are allowing the identification of novel variants in genes for very rare disorders, enabling a molecular diagnosis. Genomics is also revealing a phenotypic expansion whereby the full spectrum of clinical expression conveyed by mutant alleles at a locus can be better appreciated.

Objective  To elucidate the molecular cause of a complex neuropathy phenotype in 3 patients by applying genomic sequencing strategies.

Design, Setting, and Participants  Three affected individuals from 2 unrelated families presented with a complex neuropathy phenotype characterized by axonal sensorimotor neuropathy and microcephaly. They were recruited into the Centers for Mendelian Genomics research program to identify the molecular cause of their phenotype. Whole-genome, targeted whole-exome sequencing, and high-resolution single-nucleotide polymorphism arrays were performed in genetics clinics of tertiary care pediatric hospitals and biomedical research institutions.

Main Outcomes and Measures  Whole-genome and whole-exome sequencing identified the variants responsible for the patients’ clinical phenotype.

Results  We identified compound heterozygous alleles in 2 affected siblings from 1 family and a homozygous nonsense variant in the third unrelated patient in the vaccinia-related kinase 1 gene (VRK1). In the latter subject, we found a common haplotype on which the nonsense mutation occurred and that segregates in the Ashkenazi Jewish population.

Conclusions and Relevance  We report the identification of disease-causing alleles in 3 children from 2 unrelated families with a previously uncharacterized complex axonal motor and sensory neuropathy accompanied by severe nonprogressive microcephaly and cerebral dysgenesis. Our data raise the question of whether VRK1 mutations disturb cell cycle progression and may result in apoptosis of cells in the nervous system. The application of unbiased genomic approaches allows the identification of potentially pathogenic mutations in unsuspected genes in highly genetically heterogeneous and uncharacterized neurological diseases.

JAMA 2013

Origin of Fasciculations in Amyotrophic Lateral Sclerosis and Benign Fasciculation Syndrome

Importance  Fasciculation potentials (FPs) may arise proximally or distally within the peripheral nervous system. We recorded FPs in the tibialis anterior using 2 concentric needle electrodes, ensuring by slight voluntary contraction and electrical nerve stimulation that each electrode recorded motor unit potentials innervated by different axons.

Observations  Time-locked FPs recorded from both electrodes, suggesting a spinal origin, were most frequent in benign fasciculation syndrome (44%) (P < .001) and amyotrophic lateral sclerosis without reinnervation (27%). Fewer time-locked FPs were found (14%) in the reinnervated tibialis anterior in amyotrophic lateral sclerosis (P < .001).

Conclusions and Relevance  We conclude that in chronic partial denervation FPs are more likely to arise distally and that FPs in benign fasciculation syndrome more frequently arise proximally.

JAMA 2013

Inherited neuropathies: Clinical overview and update

Inherited neuropathy is a group of common neurologic disorders with heterogeneous clinical presentations and genetic causes. Detailed neuromuscular evaluations, including nerve conduction studies, laboratory testing, and histopathologic examination, can assist in identification of the inherited component beyond family history. Genetic testing increasingly enables definitive diagnosis of specific inherited neuropathies. Diagnosis, however, is often complex, and neurologic disability may have both genetic and acquired components in individual patients. The decision of which genetic test to order or whether to order genetic tests is often complicated, and the strategies to maximize the value of testing are evolving. Apart from rare inherited metabolic neuropathies, treatment approaches remain largely supportive. We provide a clinical update of the various types of inherited neuropathies, their differential diagnoses, and distinguishing clinical features (where available). A framework is provided for clinical evaluations, including the inheritance assessment, electrophysiologic examinations, and specific genetic tests. 

Muscle Nerve 2013

Mutations in phospholipase DDHD2 cause autosomal recessive hereditary spastic paraplegia (SPG54)

Hereditary spastic paraplegias (HSP) are a genetically heterogeneous group of disorders characterized by a distal axonopathy of the corticospinal tract motor neurons leading to progressive lower limb spasticity and weakness. Intracellular membrane trafficking, mitochondrial dysfunction and myelin formation are key functions involved in HSP pathogenesis. Only recently defects in metabolism of complex lipids have been implicated in a number of HSP subtypes. Mutations in the 23 known autosomal recessive HSP genes explain less than half of autosomal recessive HSP cases. To identify novel autosomal recessive HSP disease genes, exome sequencing was performed in 79 index cases with autosomal recessive forms of HSP. Resulting variants were filtered and intersected between families to allow identification of new disease genes. We identified two deleterious mutations in the phospholipase DDHD2 gene in two families with complicated HSP. The phenotype is characterized by early onset of spastic paraplegia, mental retardation, short stature and dysgenesis of the corpus callosum. Phospholipase DDHD2 is involved in intracellular membrane trafficking at the golgi/ endoplasmic reticulum interface and has been shown to possess phospholipase A1 activity in vitro. Discovery of DDHD2mutations in HSP might therefore provide a link between two key pathogenic themes in HSP: membrane trafficking and lipid metabolism.

European Journal of Human Genetics 2013

Phenotypic spectrum of probable and genetically-confirmed idiopathic basal ganglia calcification

Idiopathic basal ganglia calcification is characterized by mineral deposits in the brain, an autosomal dominant pattern of inheritance in most cases and genetic heterogeneity. The first causal genes, SLC20A2 and PDGFRB, have recently been reported. Diagnosing idiopathic basal ganglia calcification necessitates the exclusion of other causes, including calcification related to normal ageing, for which no normative data exist. Our objectives were to diagnose accurately and then describe the clinical and radiological characteristics of idiopathic basal ganglia calcification. First, calcifications were evaluated using a visual rating scale on the computerized tomography scans of 600 consecutively hospitalized unselected controls. We determined an age-specific threshold in these control computerized tomography scans as the value of the 99th percentile of the total calcification score within three age categories: <40, 40–60, and >60 years. To study the phenotype of the disease, patients with basal ganglia calcification were recruited from several medical centres. Calcifications that rated below the age-specific threshold using the same scale were excluded, as were patients with differential diagnoses of idiopathic basal ganglia calcification, after an extensive aetiological assessment. Sanger sequencing of SLC20A2 and PDGFRB was performed. In total, 72 patients were diagnosed with idiopathic basal ganglia calcification, 25 of whom bore a mutation in either SLC20A2 (two families, four sporadic cases) or PDGFRB (one family, two sporadic cases). Five mutations were novel. Seventy-one per cent of the patients with idiopathic basal ganglia calcification were symptomatic (mean age of clinical onset: 39 ± 20 years; mean age at last evaluation: 55 ± 19 years). Among them, the most frequent signs were: cognitive impairment (58.8%), psychiatric symptoms (56.9%) and movement disorders (54.9%). Few clinical differences appeared between SLC20A2 and PDGFRB mutation carriers. Radiological analysis revealed that the total calcification scores correlated positively with age in controls and patients, but increased more rapidly with age in patients. The expected total calcification score was greater inSLC20A2 than PDGFRB mutation carriers, beyond the effect of the age alone. No patient with a PDGFRB mutation exhibited a cortical or a vermis calcification. The total calcification score was more severe in symptomatic versus asymptomatic individuals. We provide the first phenotypical description of a case series of patients with idiopathic basal ganglia calcification since the identification of the first causative genes. Clinical and radiological diversity is confirmed, whatever the genetic status. Quantification of calcification is correlated with the symptomatic status, but the location and the severity of the calcifications don’t reflect the whole clinical diversity. Other biomarkers may be helpful in better predicting clinical expression.

Brain 2013

A Dominant Mutation in FBXO38 Causes Distal Spinal Muscular Atrophy with Calf Predominance

Spinal muscular atrophies (SMAs) are a heterogeneous group of inherited disorders characterized by degeneration of anterior horn cells and progressive muscle weakness. In two unrelated families affected by a distinct form of autosomal-dominant distal SMA initially manifesting with calf weakness, we identified by genetic linkage analysis and exome sequencing a heterozygous missense mutation, c.616T>C (p.Cys206Arg), in F-box protein 38 (FBXO38). FBXO38 is a known coactivator of the transcription factor Krüppel-like factor 7 (KLF7), which regulates genes required for neuronal axon outgrowth and repair. The p.Cys206Arg substitution did not alter the subcellular localization of FBXO38 but did impair KLF7-mediated transactivation of a KLF7-responsive promoter construct and endogenous KLF7 target genes in both heterologously expressing human embryonic kidney 293T cells and fibroblasts derived from individuals with the FBXO38 missense mutation. This transcriptional dysregulation was associated with an impairment of neurite outgrowth in primary motor neurons. Together, these results suggest that a transcriptional regulatory pathway that has a well-established role in axonal development could also be critical for neuronal maintenance and highlight the importance of FBXO38 and KLF7 activity in motor neurons.

AJHG October 2013

Aggressive medical treatment with or without stenting in high-risk patients with intracranial artery stenosis (SAMMPRIS): the final results of a randomised trial

Background

Early results of the Stenting and Aggressive Medical Management for Preventing Recurrent stroke in Intracranial Stenosis trial showed that, by 30 days, 33 (14·7%) of 224 patients in the stenting group and 13 (5·8%) of 227 patients in the medical group had died or had a stroke (percentages are product limit estimates), but provided insufficient data to establish whether stenting offered any longer-term benefit. Here we report the long-term outcome of patients in this trial.

Methods

We randomly assigned (1:1, stratified by centre with randomly permuted block sizes) 451 patients with recent transient ischaemic attack or stroke related to 70—99% stenosis of a major intracranial artery to aggressive medical management (antiplatelet therapy, intensive management of vascular risk factors, and a lifestyle-modification programme) or aggressive medical management plus stenting with the Wingspan stent. The primary endpoint was any of the following: stroke or death within 30 days after enrolment, ischaemic stroke in the territory of the qualifying artery beyond 30 days of enrolment, or stroke or death within 30 days after a revascularisation procedure of the qualifying lesion during follow-up. Primary endpoint analysis of between-group differences with log-rank test was by intention to treat. This study is registered with ClinicalTrials.gov, number NCT 00576693.

Findings

During a median follow-up of 32·4 months, 34 (15%) of 227 patients in the medical group and 52 (23%) of 224 patients in the stenting group had a primary endpoint event. The cumulative probability of the primary endpoints was smaller in the medical group versus the percutaneous transluminal angioplasty and stenting (PTAS) group (p=0·0252). Beyond 30 days, 21 (10%) of 210 patients in the medical group and 19 (10%) of 191 patients in the stenting group had a primary endpoint. The absolute differences in the primary endpoint rates between the two groups were 7·1% at year 1 (95% CI 0·2 to 13·8%; p=0·0428), 6·5% at year 2 (—0·5 to 13·5%; p=0·07) and 9·0% at year 3 (1·5 to 16·5%; p=0·0193). The occurrence of the following adverse events was higher in the PTAS group than in the medical group: any stroke (59 [26%] of 224 patients vs 42 [19%] of 227 patients; p=0·0468) and major haemorrhage (29 [13%]of 224 patients vs 10 [4%] of 227 patients; p=0·0009).

Interpretation

The early benefit of aggressive medical management over stenting with the Wingspan stent for high-risk patients with intracranial stenosis persists over extended follow-up. Our findings lend support to the use of aggressive medical management rather than PTAS with the Wingspan system in high-risk patients with atherosclerotic intracranial arterial stenosis.

Extending the KCNQ2 encephalopathy spectrum

Objectives: To determine the frequency of KCNQ2 mutations in patients with neonatal epileptic encephalopathy (NEE), and to expand the phenotypic spectrum of KCNQ2 epileptic encephalopathy.

Methods: Eighty-four patients with unexplained NEE were screened for KCNQ2 mutations using classic Sanger sequencing. Clinical data of 6 additional patients with KCNQ2 mutations detected by gene panel were collected. Detailed phenotyping was performed with particular attention to seizure frequency, cognitive outcome, and video-EEG.

Results: In the cohort, we identified 9 different heterozygous de novo KCNQ2 missense mutations in 11 of 84 patients (13%). Two of 6 missense mutations detected by gene panel were recurrent and present in patients of the cohort. Seizures at onset typically consisted of tonic posturing often associated with focal clonic jerking, and were accompanied by apnea with desaturation. One patient diagnosed by gene panel had seizure onset at the age of 5 months. Based on seizure frequency at onset and cognitive outcome, we delineated 3 clinical subgroups, expanding the spectrum of KCNQ2 encephalopathy to patients with moderate intellectual disability and/or infrequent seizures at onset. Recurrent mutations lead to relatively homogenous phenotypes. One patient responded favorably to retigabine; 5 patients had a good response to carbamazepine. In 6 patients, seizures with bradycardia were recorded. One patient died of probable sudden unexpected death in epilepsy.

Conclusion: KCNQ2 mutations cause approximately 13% of unexplained NEE. Patients present with a wide spectrum of severity and, although rare, infantile epilepsy onset is possible

Neurology 2013

Quinacrine treatment trial for sporadic Creutzfeldt-Jakob disease

Objective: To determine whether oral quinacrine increases survival in sporadic Creutzfeldt-Jakob disease (sCJD).

Methods: This NIH/National Institute on Aging–funded, double-blinded, placebo-controlled, stratified randomization treatment trial was conducted at the University of California, San Francisco from February 2005 through May 2009 (ClinicalTrials.gov, NCT00183092). Subjects were randomized (50:50) to quinacrine (300 mg daily) or placebo with inpatient evaluations at baseline, and planned for months 2, 6, and 12. Subjects returning for their month-2 visit were offered open-label quinacrine. The primary outcome was survival from randomization to month 2.

Results: Of 425 patients referred, 69 subjects enrolled, 54 subjects were randomized to active drug or placebo, and 51 subjects with sCJD were included in survival analyses. Survival for the randomized portion of the trial (first 2 months) showed no significant difference between the 2 groups (log-rank statistic, p = 0.43; Cox proportional relative hazard = 1.43, quinacrine compared with placebo, 95% confidence interval = 0.58, 3.53). The quinacrine-treated group, however, declined less on 2 of 3 functional scales, the modified Rankin and Clinical Dementia Rating, than the placebo group during the first 2 months.

Conclusion: This interventional study provides Class I evidence that oral quinacrine at 300 mg per day does not improve 2-month survival of patients with sCJD, compared with placebo. Importantly, this study shows that double-blinded, placebo-controlled, randomized treatment trials are possible in prion disease. Furthermore, the quantitative data collected on the course of sCJD will be useful for future trials.

Classification of evidence: This study provides Class I evidence that quinacrine does not improve survival for people with sCJD when given orally at a dose of 300 mg per day for 2 months.

Neurology 2013

Classification and pathology of primary progressive aphasia

Objective: We aimed to determine the extent to which patients with progressive language impairment conform to 2011 primary progressive aphasia (PPA) classification and to examine clinicopathologic correlations within PPA variants.

Methods: Sixty-two consecutive patients with pathologically confirmed dementia who presented clinically with aphasia were identified. Patients with insufficient clinical information were excluded. PPA classifications were applied to anonymized clinical data taken from patients' initial assessment by raters who were blinded to clinical and pathologic diagnosis.

Results: The final cohort comprised 52 patients, 30 of whom met basic PPA criteria. Twenty-five patients met one of the 3 PPA classifications (13 logopenic, 8 nonfluent/agrammatic, and 4 semantic). Five patients did not meet the criteria for any of the PPA variants. All patients who met semantic variant PPA and 75% of patients who met nonfluent/agrammatic variant PPA classifications had frontotemporal lobar degeneration spectrum pathology. Pathologies were heterogeneous in patients who met logopenic variant PPA criteria (46% Alzheimer disease [AD], 8% AD mixed with dementia with Lewy bodies, 23% frontotemporal lobar degeneration, and 23% other).

Conclusion: The 2011 PPA recommendations classify a large proportion of patients who meet basic PPA criteria. However, some patients had aphasic syndromes that could not be classified, suggesting that the 2011 recommendations do not cover the full range of PPA variants. Classification of semantic variant PPA provides a good prediction of underlying pathology. Classification of logopenic variant does not successfully differentiate PPA due to AD from PPA due to other pathologies.

Neurology 2013

Episodic weakness due to mitochondrial DNA MT-ATP6/8 mutations

Objective: To report that homoplasmic deleterious mutations in the mitochondrial DNA MT-ATP6/8 genes may be responsible for acute episodes of limb weakness mimicking periodic paralysis due to channelopathies and dramatically responding to acetazolamide.

Methods: Mitochondrial DNA sequencing and restriction PCR, oxidative phosphorylation functional assays, reactive oxygen species metabolism, and patch-clamp technique in cultured skin fibroblasts.

Results: Occurrence of a typical MELAS (mitochondrial encephalopathy with lactic acidosis and stroke-like episodes) syndrome in a single member of a large pedigree with episodic weakness associated with a later-onset distal motor neuropathy led to the disclosure of 2 deleterious mitochondrial DNA mutations. The MT-ATP6 m.9185T>C p.Leu220Pro mutation, previously associated with Leigh syndrome, was present in all family members, while the MT-TL1 m.3271T>C mutation, a known cause of MELAS syndrome, was observed in the sole patient with MELAS presentation. Significant defect of complexes V and I as well as oxidative stress were observed in both primary fibroblasts and cybrid cells with 100% m.9185T>C mutation. Permanent plasma membrane depolarization and altered permeability to K⁺ in fibroblasts provided a link with the paralysis episodes. Screening of 9 patients, based on their clinical phenotype, identified 4 patients with similar deleterious MT-ATP6 mutations (twice m.9185T>C and once m.9176T>C or m.8893T>C). A fifth patient presented with an original potentially deleterious MT-ATP8 mutation (m.8403T>C). All mutations were associated with almost-normal complex V activity but significant oxidative stress and permanent plasma membrane depolarization.

Conclusion: Homoplasmic mutations in the MT-ATP6/8 genes may cause episodic weakness responding to acetazolamide treatment.

Neurology 2013

Classification of gait disturbances: Distinguishing between continuous and episodic changes

The increased awareness of the importance of gait and postural control to quality of life and functional independence has led many research groups to study the pathophysiology, epidemiology, clinical, and therapeutic aspects of these motor functions. In recognition of the increased awareness of the significance of this topic, the Movement Disorders journal is devoting this entire issue to gait and postural control. Leading research groups provide critical reviews of the current knowledge and propose future directions for this evolving field.

The intensive work in this area throughout the world has created an urgent need for a unified language. Because gait and postural disturbances are so common, the clinical classification should be clear, straightforward, and simple to use. As an introduction to this special issue, we propose a new clinically based classification scheme that is organized according to the dominant observed disturbance, while taking into account the results of a basic neurological exam. The proposed classification differentiates between continuous and episodic gait disturbances because this subdivision has important ramifications from the functional, prognostic, and mechanistic perspectives.

We anticipate that research into gait and postural control will continue to flourish over the next decade as the search for new ways of promoting mobility and independence aims to keep up with the exponentially growing population of aging older adults. Hopefully, this new classification scheme and the articles focusing on gait and postural control in this special issue of the Movement Disorders journal will help to facilitate future investigations in this exciting, rapidly growing area.

Movement DIsorders 2013

Clinical implications of genetic advances in Charcot–Marie–Tooth disease

Charcot–Marie–Tooth disease (CMT) refers to a group of inherited neuropathies with a broad range of phenotypes, inheritance patterns and causative genes. The number of disease genes identified in CMT has expanded rapidly over the past few decades, such that more than 60 CMT-associated genes have now been discovered. This rise in genetic discovery can be attributed to the development of next-generation sequencing (NGS) technology, which allows the entire exome or genome to be sequenced in a matter of days. In this Review, we discuss how NGS is being employed in the diagnostic evaluation of patients with CMT and how the genetic advances in CMT are influencing clinical practice. In particular, we explore how genetic advances have broadened the phenotype of CMT and related disorders and how NGS allows a large number of CMT genes to be screened simultaneously early in the evaluation of an unexplained neuropathy. Finally, we discuss the different methods of NGS that can be used in CMT and related disorders, and propose a simple diagnostic algorithm in which clinical assessment and neurophysiology are used to guide the application of phenotype specific 'panels'.

Nature Reviews Neurology 9, 562-571 (October 2013) 

Lysosomal storage diseases—the horizon expands

Since the discovery of the lysosome in 1955, advances have been made in understanding the key roles and functions of this organelle. The concept of lysosomal storage diseases (LSDs)—disorders characterized by aberrant, excessive storage of cellular material in lysosomes—developed following the discovery of α-glucosidase deficiency as the cause of Pompe disease in 1963. Great strides have since been made in understanding the pathobiology of LSDs and the neuronal ceroid lipofuscinoses (NCLs). The NCLs are neurodegenerative disorders that display symptoms of cognitive and motor decline, seizures, blindness, early death, and accumulation of lipofuscin in various cell types, and also show some similarities to 'classic' LSDs. Defective lysosomal storage can occur in many cell types, but the CNS and PNS are particularly vulnerable to LSDs and NCLs, being affected in two-thirds of these disorders. Most LSDs are inherited in an autosomal recessive manner, with the exception of X-linked Hunter disease, Fabry disease and Danon disease, and a variant type of adult NCL (Kuf disease). This Review provides a summary of known LSDs, and the pathways affected in these disorders. Existing therapies and barriers to development of novel and improved treatments for LSDs and NCLs are also discussed.

Nature Reviews Neurology 2013

Atherosclerotic intracranial arterial stenosis: risk factors, diagnosis, and treatment

Intracranial atherosclerosis is one of the most common causes of stroke worldwide and is associated with a high risk of recurrent stroke. New therapeutic approaches to treat this high-risk disease include dual antiplatelet treatment, intensive management of risk factors, and endovascular therapy. Early data from randomised trials indicate that aggressive medical therapy is better than stenting for prevention of recurrent stroke in high-risk patients with atherosclerotic stenosis of a major intracranial artery. Nevertheless, there are subgroups of patients who remain at high risk of stroke despite aggressive medical therapy. Further research is needed to identify these high-risk subgroups and to develop more effective treatments. Non-invasive vascular imaging methods that could be used to identify high-risk patients include fractional flow on magnetic resonance angiography (MRA), quantitative MRA, and high-resolution MRI of the atherosclerotic plaque. Alternative therapies to consider for future clinical trials include angioplasty alone, indirect surgical bypass procedures, ischaemic preconditioning, and new anticoagulants (direct thrombin or Xa inhibitors).

Lancet 2013

Prolonged release oxycodone—naloxone for treatment of severe restless legs syndrome after failure of previous treatment: a double-blind, randomised, placebo-controlled trial with an open-label extension

Background

Opioids are a potential new treatment for severe restless legs syndrome. We investigated the efficacy and safety of a fixed-dose combination of prolonged release oxycodone—naloxone for patients with severe restless legs syndrome inadequately controlled by previous, mainly dopaminergic, treatment.

Methods

This multicentre study consisted of a 12-week randomised, double-blind, placebo-controlled trial and 40-week open-label extension phase done at 55 sites in Austria, Germany, Spain, and Sweden. Patients had symptoms for at least 6 months and an International RLS Study Group severity rating scale sum score of at least 15; patients with severe chronic obstructive pulmonary disease or a history of sleep apnoea syndrome were excluded. Patients were randomly assigned (1:1) to either study drug or matched placebo with a validated interactive response technology system in block sizes of four. Study drug was oxycodone 5·0 mg, naloxone 2·5 mg, twice per day, which was up-titrated according to investigator's opinion to a maximum of oxycodone 40 mg, naloxone 20 mg, twice per day; in the extension, all patients started on oxycodone 5·0 mg, naloxone 2·5 mg, twice per day, which was up-titrated to a maximum of oxycodone 40 mg, naloxone 20 mg, twice per day. The primary outcome was mean change in severity of symptoms according to the International RLS Study Group severity rating scale sum score at 12 weeks. This study is registered with ClinicalTrials.gov (number NCT01112644) and with EudraCT (number 2009-011107-23).

Findings

We screened 495 patients, of whom 306 were randomly assigned and 276 included in the primary analysis (132 to prolonged release oxycodone—naloxone vs 144 to placebo). 197 patients participated in the open-label extension. Mean International RLS Study Group rating scale sum score at randomisation was 31·6 (SD 4·5); mean change after 12 weeks was −16·5 (SD 11·3) in the prolonged release oxycodone—naloxone group and −9·4 (SD 10·9) in the placebo group (mean difference between groups at 12 weeks 8·15, 95% CI 5·46—10·85; p<0·0001). After the extension phase, mean sum score was 9·7 (SD 7·8). Treatment-related adverse events occurred in 109 of 150 (73%) patients in the prolonged release oxycodone—naloxone group and 66 of 154 (43%) in the placebo group during the double-blind phase; during the extension phase, 112 of 197 (57%) had treatment-related adverse events. Five of 306 (2%) patients had serious treatment-related adverse events when taking prolonged release oxycodone—naloxone (vomiting with concurrent duodenal ulcer, constipation, subileus, ileus, acute flank pain).

Interpretation

Prolonged release oxycodone—naloxone was efficacious for short-term treatment of patients with severe restless legs syndrome inadequately controlled with previous treatment and the safety profile was as expected. Our study also provides evidence of open-label long-term efficacy of this treatment. Opioids can be used to treat patients with severe restless legs syndrome who have had no benefit with first-line drugs.

Lancet Neurology 2013

COX10 Mutations Resulting in Complex Multisystem Mitochondrial Disease That Remains Stable Into Adulthood.

IMPORTANCE Isolated cytochrome-c oxidase (COX) deficiency is one of the most frequent respiratory chain defects seen in human mitochondrial disease. Typically, patients present with severe neonatal multisystem disease and have an early fatal outcome. We describe an adult patient with isolated COX deficiency associated with a relatively mild clinical phenotype comprising myopathy; demyelinating neuropathy; premature ovarian failure; short stature; hearing loss; pigmentary maculopathy; and renal tubular dysfunction. OBSERVATIONS Whole-exome sequencing detected 1 known pathogenic and 1 novel COX10 mutation: c.1007A&gt;T; p.Asp336Val, previously associated with fatal infantile COX deficiency, and c.1015C&gt;T; p.Arg339Trp. Muscle COX holoenzyme and subassemblies were undetectable on immunoblots of blue-native gels, whereas denaturing gels and immunocytochemistry showed reduced core subunit MTCO1. Heme absorption spectra revealed low heme aa3 compatible with heme A:farnesyltransferase deficiency due to COX10 dysfunction. Both mutations demonstrated respiratory deficiency in yeast, confirming pathogenicity. A COX10 protein model was used to predict the structural consequences of the novel Arg339Trp and all previously reported substitutions. CONCLUSIONS AND RELEVANCE These findings establish that COX10 mutations cause adult mitochondrial disease. Nuclear modifiers, epigenetic phenomenon, and/or environmental factors may influence the disease phenotype caused by reduced COX activity and contribute to the variable clinical severity related to COX10 dysfunction.

JAMA Neurology 2013

ERBB4 Mutations that Disrupt the Neuregulin-ErbB4 Pathway Cause Amyotrophic Lateral Sclerosis Type 19

Amyotrophic lateral sclerosis (ALS) is a devastating neurological disorder characterized by the degeneration of motor neurons and typically results in death within 3–5 years from onset. Familial ALS (FALS) comprises 5%–10% of ALS cases, and the identification of genes associated with FALS is indispensable to elucidating the molecular pathogenesis. We identified a Japanese family affected by late-onset, autosomal-dominant ALS in which mutations in genes known to be associated with FALS were excluded. A whole- genome sequencing and parametric linkage analysis under the assumption of an autosomal-dominant mode of inheritance with incomplete penetrance revealed the mutation c.2780G>A (p. Arg927Gln) in ERBB4. An extensive mutational analysis revealed the same mutation in a Canadian individual with familial ALS and a de novo mutation, c.3823C>T (p. Arg1275Trp), in a Japanese simplex case. These amino acid substitutions involve amino acids highly conserved among species, are predicted as probably damaging, and are located within a tyrosine kinase domain (p. Arg927Gln) or a C-terminal domain (p. Arg1275Trp), both of which mediate essential functions of ErbB4 as a receptor tyrosine kinase. Functional analysis revealed that these mutations led to a reduced autophosphorylation of ErbB4 upon neuregulin-1 (NRG-1) stimulation. Clinical presentations of the individuals with mutations were characterized by the involvement of both upper and lower motor neurons, a lack of obvious cognitive dysfunction, and relatively slow progression. This study indicates that disruption of the neuregulin-ErbB4 pathway is involved in the pathogenesis of ALS and potentially paves the way for the development of innovative therapeutic strategies such using NRGs or their agonists to upregulate ErbB4 functions.

 American Journal of Human Genetics 2013

NEVER STOP FIGHTING AGAINST ALS

Intravenous immunoglobulin for treatment of neuromuscular disease

Intravenous immunoglobulin (IVIg) has been widely used in the treatment of autoimmune neuromuscular diseases. Compared to other treatment modalities, such as corticosteroids and chemotherapy for autoimmune disorders, IVIg has relatively few side effects and favorable therapeutic outcomes in certain neuromuscular diseases. There is Class I evidence for IVIg as an initial treatment for patients with Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating polyneuropathy (CIDP), and multifocal motor neuropathy. It is as effective as plasma exchange in GBS and CIDP. In myasthenia gravis, IVIg is used for myasthenic crisis and exacerbations, though it is also helpful as maintenance therapy, particularly in patients with a suboptimal response or contraindications to prednisone or other immunosuppressive agents. IVIg has been demonstrated to be beneficial in placebo-controlled, double-blind, randomized studies in dermatomyositis and Lambert-Eaton syndrome. IVIg has also been beneficial in select patients with polymyositis and other autoimmune peripheral neuropathies. Clinical trials in amyotrophic lateral sclerosis, inclusion body myositis, and anti–myelin-associated glycoprotein neuropathy have been negative.

Neurology 2013

Discovering new drugs: Vortioxetine

Vortioxetine (Brintellix, Takeda Pharmaceuticals and Lundbeck), an investigational multimodal antidepressant thought to work through a combination of 2 pharmacologic modes of action ― serotonin (5-HT) receptor activity modulation and 5-HT reuptake inhibition ― has been approved by the US Food and Drug Adminstration (FDA) for major depressive disorder in adults.

The approval was based on safety and efficacy data from 6 multicenter, randomized, double-blind, parallel group trials of adult patients testing doses of vortioxetine ranging from 5 to 20 mg/day compared with placebo.

Some of these data from 4 trials were recently presented at the American Psychiatric Association's 2013 Annual Meeting andreported by Medscape Medical News at that time. In those studies, 3 of the 4 met the primary efficacy endpoint, as measured by the change from baseline of the Montgomery-Åsberg Depression Rating Scale (MADRS) total score at week 8.

The 20-mg dose had the most consistent effect in relation to placebo.

One of the studies did not meet the primary endpoint. However, the manufacturer noted that all of the trials provided additional information regarding the drug's safety profile.

The most common side effects, which lead researcher Madhukar Trivedi, MD, told Medscape Medical News was "not outside the realm of what is normally seen with antidepressants," included nausea, headache, diarrhea, dizziness, constipation, vomiting, fatigue, and viral upper respiratory infection.

"Major depressive disorder can be disabling and can keep a person from functioning normally. Since medications affect everyone differently, it is important to have a variety of treatment options available for patients who suffer from depression," Mitchell Mathis, MD, acting director of the Division of Psychiatry Products in the FDA's Center for Drug Evaluation and Research, said in a release.

Like other antidepressant medications, Brintellix has an FDA boxed warning and a medication guide alerting patients and healthcare professionals that antidepressants can increase the risk for suicidal thought and behavior in children, adolescents, and young adults aged 18 to 24 years during initial treatment.

Discovering rare diseases: Madelung Disease

http://onlinelibrary.wiley.com/doi/10.1002/mus.20406/full

We report a 51-year-old alcoholic man with a 10-year history of cervical lipomas and progressive symmetrical sensory neuropathy, initially diagnosed with Madelung's disease, an idiopathic syndrome often attributed to chronic alcoholism. The eventual development of proximal weakness led to pathological and genetic testing which identified a A8344G mutation in the mitochondrial tRNA lysine gene, associated with MERRF (myoclonic epilepsy with ragged-red fibers). This case demonstrates how the varied terminology for this syndrome has resulted in a lack of consistent recognition and assessment for mitochondrial cytopathy. 

Muscle Nerve, 2005

Mutations in B4GALNT1 (GM2 synthase) underlie a new disorder of ganglioside biosynthesis

Glycosphingolipids are ubiquitous constituents of eukaryotic plasma membranes, and their sialylated derivatives, gangliosides, are the major class of glycoconjugates expressed by neurons. Deficiencies in their catabolic pathways give rise to a large and well-studied group of inherited disorders, the lysosomal storage diseases. Although many glycosphingolipid catabolic defects have been defined, only one proven inherited disease arising from a defect in ganglioside biosynthesis is known. This disease, because of defects in the first step of ganglioside biosynthesis (GM3 synthase), results in a severe epileptic disorder found at high frequency amongst the Old Order Amish. Here we investigated an unusual neurodegenerative phenotype, most commonly classified as a complex form of hereditary spastic paraplegia, present in families from Kuwait, Italy and the Old Order Amish. Our genetic studies identified mutations in B4GALNT1 (GM2 synthase), encoding the enzyme that catalyzes the second step in complex ganglioside biosynthesis, as the cause of this neurodegenerative phenotype. Biochemical profiling of glycosphingolipid biosynthesis confirmed a lack of GM2 in affected subjects in association with a predictable increase in levels of its precursor, GM3, a finding that will greatly facilitate diagnosis of this condition. With the description of two neurological human diseases involving defects in two sequentially acting enzymes in ganglioside biosynthesis, there is the real possibility that a previously unidentified family of ganglioside deficiency diseases exist. The study of patients and animal models of these disorders will pave the way for a greater understanding of the role gangliosides play in neuronal structure and function and provide insights into the development of effective treatment therapies.

Brain 2013

A regenerative approach to the treatment of multiple sclerosis

Progressive phases of multiple sclerosis are associated with inhibited differentiation of the progenitor cell population that generates the mature oligodendrocytes required for remyelination and disease remission. To identify selective inducers of oligodendrocyte differentiation, we performed an image-based screen for myelin basic protein (MBP) expression using primary rat optic-nerve-derived progenitor cells. Here we show that among the most effective compounds identifed was benztropine, which significantly decreases clinical severity in the experimental autoimmune encephalomyelitis (EAE) model of relapsing-remitting multiple sclerosis when administered alone or in combination with approved immunosuppressive treatments for multiple sclerosis. Evidence from a cuprizone-induced model of demyelination, in vitro and in vivo T-cell assays and EAE adoptive transfer experiments indicated that the observed efficacy of this drug results directly from an enhancement of remyelination rather than immune suppression. Pharmacological studies indicate that benztropine functions by a mechanism that involves direct antagonism of M1 and/or M3 muscarinic receptors. These studies should facilitate the development of effective new therapies for the treatment of multiple sclerosis that complement established immunosuppressive approaches.

Nature 2013

Neuro-oncology: Glioblastoma prognosis linked to neuronal PD-L1 expression in tumour-adjacent tissue

Expression of programmed death ligand 1 (PD-L1) by neurons surrounding glioblastoma tissue increases neuronal killing of tumour cells and is associated with prolonged survival, a new study has shown. The results shed light on the dynamic influence of the microenvironment on tumour growth.

Nature Reviews Neurology 2013

Neurodegenerative disease: PDK1—a common therapeutic target for AD and prion disease?

Researchers in France have identified a possible role for 3-phosphoinositide-dependent protein kinase 1 (PDK1) in progression of prion disease and Alzheimer disease (AD), indicating that this enzyme could be targeted therapeutically in both of these conditions. Inhibition of PDK1 leads to an increase in α-secretase activity at the neuronal surface, causing cellular prion protein (PrP^C) and amyloid precursor protein (APP) to be cleaved into nonpathogenic forms.

Nature Reviews Neurology 2013

Imaging in sepsis-associated encephalopathy—insights and opportunities

Sepsis-associated encephalopathy (SAE) refers to a clinical spectrum of acute neurological dysfunction that arises in the context of sepsis. Although the pathophysiology of SAE is incompletely understood, it is thought to involve endothelial activation, blood–brain barrier leakage, inflammatory cell migration, and neuronal loss with neurotransmitter imbalance. SAE is associated with a high risk of mortality. Imaging studies using MRI and CT have demonstrated changes in the brains of patients with SAE that are also seen in disorders such as stroke. Next-generation imaging techniques such as magnetic resonance spectroscopy, diffusion tensor imaging and PET, as well as experimental imaging modalities, provide options for early identification of patients with SAE, and could aid in identification of pathophysiological processes that represent possible therapeutic targets. In this Review, we explore the recent literature on imaging in SAE, relating the findings of these studies to pathological data and experimental studies to obtain insights into the pathophysiology of sepsis-associated neurological dysfunction. Furthermore, we suggest how novel imaging technologies can be used for early-stage proof-of-concept and proof-of-mechanism translational studies, which may help to improve diagnosis in SAE.

Nature Reviews Neurology 2013

C9ORF72 repeat expansions in cases with previously identified pathogenic mutations

ABSTRACT

Objective: To identify potential genetic modifiers contributing to the phenotypic variability that is detected in patients with repeat expansions in chromosome 9 open reading frame 72 (C9ORF72), we investigated the frequency of these expansions in a cohort of 334 subjects previously found to carry mutations in genes known to be associated with a spectrum of neurodegenerative diseases.

Methods: A 2-step protocol, with a fluorescent PCR and a repeat-primed PCR, was used to determine the presence of hexanucleotide expansions in C9ORF72. For one double mutant, we performed Southern blots to assess expansion sizes, and immunohistochemistry to characterize neuropathology.

Results: We detected C9ORF72 repeat expansions in 4 of 334 subjects (1.2% [or 1.8% of 217 families]). All these subjects had behavioral phenotypes and also harbored well-known pathogenic mutations in either progranulin (GRN: p.C466LfsX46, p.R493X, p.C31LfsX35) or microtubule-associated protein tau (MAPT: p.P301L). Southern blotting of one double mutant with a p.C466LfsX46 GRN mutation demonstrated a long repeat expansion in brain (>3,000 repeats), and immunohistochemistry showed mixed neuropathology with characteristics of both C9ORF72 expansions and GRN mutations.

Conclusions: Our findings indicate that co-occurrence of 2 evidently pathogenic mutations could contribute to the pleiotropy that is detected in patients with C9ORF72 repeat expansions. These findings suggest that patients with known mutations should not be excluded from further studies, and that genetic counselors should be aware of this phenomenon when advising patients and their family members.

Neurology 2013