Sanne Piepers

Correlates of outcome and response to IVIg in 88 patients with multifocal motor neuropathy

Reply from the Authors: We thank Dr. Nabbout et al. for their comments on our article, in which we described 13 probands, and one of their mothers, with epilepsy variably associated with mental retardation and autistic features in whom the PCDH19 gene was mutated.1 The epilepsy phenotype was variable. Seven patients exhibited DS and 6 had focal epilepsy. These figures confirm that PCDH19 mutations can cause an epileptic encephalopathy resembling DS in girls.2 Therefore, if screening for SCN1A gene mutations, deletions, amplification, or duplications yields negative results, PCDH19 should be screened. In our cohort, girls with PCDH19 mutations and focal epilepsy had early seizure onset and either normal cognitive skills or mental retardation and autistic features. The spectrum of phenotypes associated with PCDH19 mutations is broad, ranging from mild epilepsy to a severe epileptic encephalopathy. Such phenotypic diversity might be partially explained by the cosegregation of other genetic factors either rescuing or worsening the phenotype. Since our article was accepted for publication, we have observed 6 more girls with PCDH19 mutations, none having a phenotype evocative of DS (unpublished data). Another article reported 3 girls with seizure onset in infancy and varying degrees of cognitive impairment and autistic features.3 However, the core clinical features of PCDH19-related epilepsy phenotypes seem to be early onset of seizures occurring in clusters and precipitated by fever. The spectrum of associated cognitive and behavioral impairment is variable and its relationship with epilepsy severity is not obvious. PCDH19 is clearly emerging as a major epilepsy gene in females. Analysis of larger cohorts, with unbiased recruitment, will clarify the full range of phenotypes caused by alterations in this gene.

Multifocal motor neuropathy Association of anti-GM1 IgM antibodies with clinical features

Objective: To determine the prevalence and specificity of antibodies against single gangliosides and ganglioside complexes in serum from 88 patients with multifocal motor neuropathy (MMN) and to study the association with clinical features. Methods: ELISA was used to detect immunoglobulin (Ig)M, IgG, and IgA antibodies against GM1, GM2, GD1a, GD1b, GM1b, GT1a, GT1b, GQ1b, GalNAc-GD1a, and the glycolipid SGPG; absorption studies were performed to study cross-reactivity. Presence of antibodies against ganglioside complexes consisting of any of combinations of GM1, GM2, GD1a, GD1b, GT1b, and GQ1b was also tested. Results: Anti-GM1 IgM, IgG, and IgA antibodies were detected in serum from 43%, 1%, and 5% of patients with MMN. Anti-GM2 IgM antibodies were detected in 6% and anti-GD1b IgM antibodies in 9% of patients. Patients with MMN with anti-GM1 IgM antibodies had more severe weakness (p < 0.01), more disability (p < 0.01), and more axon loss (p = 0.05) than patients without anti-GM1 IgM antibodies. Anti-GM1 IgM antibody titers correlated with Medical Research Council scores (correlation coefficient = 0.43; p < 0.0001). Anti-GD1b IgM antibody activity was associated with reduced vibration sense (p < 0.01). Absorption studies showed that anti-GD1b and anti-GM2 IgM antibodies cross-reacted with GM1. Antibodies against ganglioside complexes were not detected. Complexes containing GD1a, GD1b, GT1b, or GQ1b with GM1 lowered antibody activity against GM1. Conclusion: Anti-ganglioside IgM antibodies in MMN display limited specificity and are associated with severity and clinical characteristics. Results of this study suggest that anti-GM1 IgM antibodies may play a role in MMN pathogenesis.

Randomized sequential trial of valproic acid in amyotrophic lateral sclerosis

To determine whether valproic acid (VPA), a histone deacetylase inhibitor that showed antioxidative and antiapoptotic properties and reduced glutamate toxicity in preclinical studies, is safe and effective in amyotrophic lateral sclerosis (ALS) using a sequential trial design.

IVIg inhibits classical pathway activity and anti-GM1 IgM-mediated complement deposition in MMN

The effects of intravenous immunoglobulins (IVIg) on anti-GM1 IgM titer and function, classical complement pathway activity, and antibody-complement interaction were investigated in 62 patients with multifocal motor neuropathy (MMN). In vitro, IVIg decreased complement deposition by anti-GM1 IgM antibodies. First IVIg treatment (2 g/kg) decreased C1q and C4 concentrations and classical pathway activity in serum. In sera from patients receiving IVIg maintenance therapy (0.4 g/kg) C4 concentrations and classical pathway activity were generally lower at higher IgG concentrations. The beneficial effects of IVIg in MMN may be explained by reduced antibody-mediated complement deposition in nerves amplified by a systemically attenuated classical pathway.

A natural history study of late onset spinal muscular atrophy types 3b and 4.

BackgroundSpinal muscular atrophy (SMA) is caused by a homozygous deletion of the survival motor neuron (SMN)1 gene. The nearly identical SMN2 gene plays a disease modifying role. SMA is classified into four different subtypes based on age of onset and clinical course (SMA types 1–4). The natural history of early onset SMA types 1–3a has been studied extensively. Late onset SMA is rare and disease course has not been studied in detail.ObjectiveTo perform a prospective study on the clinical course and the correlation with SMN2 copy numbers of late onset SMA.MethodsPatients fulfilling the diagnostic criteria for late onset SMA (types 3b and 4) were included in the study. At inclusion and follow-up, muscle strength, respiratory function, functional status and quality of life were assessed. SMN2 copy number was determined in all patients.ResultsTwelve patients were identified and included. Six patients were siblings from one family, two patients were brothers from a second family and four patients were sporadic cases. All patients carried four copies of the SMN2 gene. Median age of disease onset was 22.2 years (10–37). Age of disease onset in patients from family one was lower as compared to the other patients. None of the outcome measures changed after a follow-up of 2.5 years. Five patients reported an increase in fatigue and muscle weakness. None of the patients showed symptoms of respiratory insufficiency.ConclusionsThis study indicates that late onset SMA is not characterized by disease progression and that alternative or surrogate disease markers are required for the design of future trials. This study confirms the finding that SMN2 copy number is a SMA disease course modifier.

Pharmacokinetics of intravenous immunoglobulin in multifocal motor neuropathy

Background Multifocal motor neuropathy (MMN) is often responsive to treatment with intravenous immunoglobulin (IVIg), but the optimal dose and intervals of IVIg maintenance treatment have not been established. Increase in IgG concentration (ΔIgG) after IVIg infusion has recently been identified as determinant of outcome in Guillain-Barré syndrome. ΔIgG may therefore represent a potentially useful biomarker to optimise IVIg dosing in patients with MMN. Objective The aims of this study were to determine variability of IVIg pharmacokinetics in patients with MMN in relation to treatment response, and to establish whether interindividual differences in IVIg pharmacokinetics were associated with genetic polymorphisms of the endothelial IgG receptor (FcRn) which determines IgG half-life. Methods Twenty-three patients with MMN receiving their first IVIg treatment at a cumulative dose of 2.0 g/kg in 5 days were included. A good treatment response was defined as an increase in muscle strength of at least one Medical Research Council point in minimally two muscle groups. IgG concentrations in serum were determined at baseline, at day 1 and day 5 of the IVIg course, and 3 weeks after treatment. FcRn copy number variation and differences in repeat length of the variable number of tandem repeats in the FcRn gene were determined by quantitative PCR and Sanger sequencing. Results Seventeen patients (74%) had a good response to treatment. Total IgG and ΔIgG levels showed large variation between patients. Mean ΔIgG was higher in IVIg responders than in non-responders, with the largest difference on day 1 (11.1 g/L vs 4.5 g/L, p=0.06), but our study lacked power to show statistically significant differences. Genetic variation in the FcRn gene was not associated with ΔIgG levels or response to treatment. Conclusions IVIg pharmacokinetics varies in patients with MMN and may be associated with clinical response.

Effect of non-invasive ventilation on survival, quality of life, respiratory function and cognition: a review of the literature.

Symptoms of nocturnal hypoventilation may negatively influence the quality of life (QoL) of ALS patients long before respiratory failure ensues. Non‐invasive mechanical ventilation (NIV) is considered a treatment option for nocturnal hypoventilation. The primary objective of NIV is improving quality of life (QoL). It may also prolong life by several months. A systematic review of the literature was performed to analyse what is known of the effect of NIV on survival, QoL and other outcome measures. A computerized literature search was performed to identify controlled clinical trials and observational studies of treatment of ALS‐associated nocturnal hypoventilation from 1985 until May 2005. Twelve studies fulfilled the inclusion criteria. Four studies were retrospective, seven prospective and in one study randomization was used. All studies reported beneficial effects of NIV on all outcome measures. In seven studies NIV was associated with prolonged survival in patients tolerant for NIV, and five studies reported an improved QoL. In conclusion, studies on the use of NIV in ALS differ in study design and endpoint definitions. All studies suggest a beneficial effect on QoL and other outcome measures (Evidence level Class II‐III). Well‐designed randomized controlled trials comparing the effect on QoL and survival have not been performed.

Quantification of SMN protein in leucocytes from spinal muscular atrophy patients: effects of treatment with valproic acid

Background Spinal muscular atrophy (SMA) is caused by the homozygous deletion of the survival motor neuron (SMN)1 gene. The nearly identical SMN2 gene produces small amounts of full-length mRNA and functional SMN protein, due to a point mutation in a critical splicing site. Increasing SMN protein production by histone deacetylase inhibiting drugs such as valproic acid (VPA) is an experimental treatment strategy for SMA. Objective To investigate whether an SMN-specific ELISA could detect changes in SMN protein expression in peripheral blood mononuclear cells (PBMCs) after treatment with VPA. Methods The authors developed a sensitive SMN-specific ELISA. Six patients with SMA types 2 and 3 participated in the study. Recombinant SMN calibration curves were used to calculate SMN protein levels in PBMCs before and after 4 months of VPA treatment. Results The SMN ELISA was able to detect small differences in SMN protein concentrations, and differences in SMN protein levels in Epstein–Barr virus immortalised lymphocyte cell lines from SMA type 1 and 2 patients, carriers and healthy individuals (p<0.05). The mean SMN protein level in PBMCs from SMA patients was 22% (SD 15%) of the value in a healthy control. VPA treatment resulted in significantly increased SMN protein levels in five out of six SMA patients compared with baseline values (p<0.05), but did not restore SMN levels to normal values. Conclusions SMN protein quantification by this SMN ELISA is a useful additional tool for evaluating the effects of experimental treatment in SMA.

No benefits from experimental treatment with olfactory ensheathing cells in patients with ALS

Abstract Cell based therapies may be promising options for treating ALS. These therapies aim at neuronal replacement or they may prevent dysfunctional motor neurons from dying. Conflicting results on transplantation of olfactory ensheathing cells (OECs) in ALS mouse models indicate that this technique is not yet ready to progress to clinical trials. A Chinese group has nevertheless treated ALS patients with OECs. We carried out a prospective study of seven patients who underwent OEC treatment in China, following them from four months before departure until one year after treatment. Muscle strength, level of daily functioning and respiratory capacity were measured at regular intervals. Three patients reported subjective positive effects directly after treatment. No individual objective improvement was measured, and outcome measures gradually declined in all patients. Two patients had severe side-effects. Based on our findings in these ALS patients who underwent experimental OEC treatment, we conclude that there are no indications that this treatment is beneficial.

Increased frequency of HLA-DRB1*15 in patients with multifocal motor neuropathy

Objectives: The favorable response to treatment with IV immunoglobulins and the presence of IgM antibodies to the glycolipid GM1 are indications that inflammation underlies multifocal motor neuropathy (MMN) pathogenesis. We investigated the association of MMN with human leukocyte antigen (HLA) class I and II antigens. Methods: HLA class I and II antigens of 74 Dutch patients with MMN and 700 controls were determined in a case-control study. Associations of HLA types with MMN disease characteristics were investigated. Results: Compared with controls, patients with MMN had higher frequencies of HLA-DRB1*15 (41 vs 24%, p = 0.0017). Disease characteristics were not associated with specific HLA types. Conclusions: Similar associations were found in patients with multiple sclerosis and women with chronic immune-mediated demyelinating neuropathy, which may suggest that these demyelinating disorders share pathogenic mechanisms.