Workshop Report: consensus on biomarkers of cerebral involvement in myotonic dystrophy, 2–3 December 2014, Milan, Italy

Available online at www.sciencedirect.com

ScienceDirect Neuromuscular Disorders 25 (2015) 813–823 www.elsevier.com/locate/nmd

Workshop report

Workshop Report: consensus on biomarkers of cerebral involvement in myotonic dystrophy, 2–3 December 2014, Milan, Italy G. Bosco, S. Diamanti, G. Meola * on behalf of the DM-CNS Group ☆ Department of Biomedical Sciences for Health, IRCCS Policlinico San Donato, University of Milan, Milan, Italy Received 15 July 2015

1. Introduction A workshop on the central nervous system involvement in myotonic dystrophy type 1 took place in Milan on 2nd and 3rd December 2014. Twenty-four clinicians, scientists and delegates from pharmaceutical industries convened to debate the most relevant issues on cognitive impairment and potential brain-related biomarkers in myotonic dystrophy. As Myotonic Dystrophy (DM) is a multisystemic disease, as explored previously during the Consensus conference [1], this workshop focused especially on cognitive dysfunction in DM patients, with the aim of establishing uniform guidelines for cognitive assessment. This Consensus confirmed the importance of a multidisciplinary approach, based on the collaboration among specialists that integrate data from neuroimaging, clinical evaluation, molecular studies on human models and mouse models, neuropathological results and neuropsychological assessments in order to enhance the understanding of CNS alteration in DM1 patients. This document reports on the major themes that were discussed during this two-day meeting, providing an overview of the latest achievements, new proposals and future goals of the investigation on CNS dysfunction in myotonic dystrophy. 2. Session description 2.1. Theme 1: perspectives of the Canadian and European DM CNS task force; Chairs: Mr. MacKenzie and Dr. Meola Dr. Meola launched the Consensus presenting the main objectives of the workshop: to establish uniform protocols on neuroimaging, neuropathology and neuropsychology; to understand the extent of disease progression over time by longitudinal studies [2]; to propose neuroimaging, CSF and * Corresponding author. Department of Biomedical Sciences for Health, IRCCS Policlinico San Donato, University of Milan, Piazza E. Malan 1, 20097 San Donato Mil, Milan, Italy. Tel.: +39 02 52774480; fax: +39 02 5274717. E-mail address: [email protected] (G. Meola). ☆ See participants’ list in the Appendix. http://dx.doi.org/10.1016/j.nmd.2015.07.016 0960-8966/© 2015 Elsevier B.V. All rights reserved.

plasma biomarkers; to create a biobank and a network for tissue collection and sharing; to select gold standard neuropsychological tests for the evaluation of cognitive deficits at time of diagnosis and over time; to correlate the neuroimaging findings with the corresponding neuropsychological deficits during longitudinal studies, with the aim of clarifying if brain abnormalities are stable or progressive; to improve on the knowledge of molecular aspects of myotonic dystrophies and the relationship between clinical features and alterations in cellular function; to establish inclusion criteria for patients suitable for clinical trials based on neuropsychological features; to reach a consensus on classification of DM1 forms in relation to pediatric subgroups; to introduce additional CNS parameters in the registries that can account for the characteristics of each form of DM1; and to define the most significant parameters for the evaluation of the condition of patients during clinical trials. 2.2. Theme 2: consensus on gold standard in cognitive testing in adult, childhood and in congenital forms; Chairs: Drs. Ekström and Bosco Dr. Bosco started the session listing the major cognitive alterations reported in each form of DM1: in the congenital form, delayed motor development, behavioral abnormalities such as autism and ADHD (Attention Deficit Hyperactivity Disorder) and mild to severe mental retardation have been reported [3]; in the childhood form, learning disabilities and psychiatric disorders including phobias, mood disorders such as anxiety and depression, and ADHD have been documented [4]; in the adult form, global intelligence scores are within the norm, but patients show frontal lobe dysfunction, specific personality patterns, excessive daytime sleepiness and emotional problems related to an impairment of facial emotion recognition [5]. From the neuropsychological point of view, Dr. Bosco explained that in the adult form of DM1, WAIS (Wechsler Adult Intelligence Scale) and MMSE (Mini Mental Scales Examination) results are within the norm, although patients are affected by visuo-spatial impairment, attention deficits and a dysexecutive syndrome [6]. As reported in the previous

814

G. Bosco et al. / Neuromuscular Disorders 25 (2015) 813–823

Consensus, only the Trail Making test A and B, the Color Word Stroop Test, the FAS test (oral word association) and the WAIS Block design subtest were found to have sensitivity suitable for clinical trials. In DM2 patients, QI and MMSE scores are found to be within the norm, but cognitive deficits, similar to those seen in DM1, regarding visuospatial, attention and global memory impairment, have been documented, although these abnormalities appear to be milder than in DM1. The scores of executive tests are lower for DM1 than for DM2 patients, except in the case of the Cambridge Neuropsychological Test in which results were found to be equivalently abnormal for both DM1 and DM2 patients. DM1 individuals also showed a reduced ability to understand nonverbally expressed emotion, for example subnormal facial and emotional recognition, that correlates with the size of CTG expansion, but not with cognitive abilities. These alterations may contribute to their complex personality and low cooperativeness. According to the neuropsychiatric interviews, apathy, reduced initiative, inactivity, personality patterns including obsessive compulsive trait and avoidant or passive aggressive behavior are more pronounced in DM1 than in DM2 subjects [7]. Moreover, the DM1 population appears to be scarcely concerned about its condition and tends to ignore its symptoms. From the neuropathological point of view, DM1 individuals showed cell loss in dorsal raphe nucleus, brainstem nuclei, superficial layer of frontoparietal and occipital cortex and basal ganglia [8]. Hydrophilic inclusion bodies and Tau protein aggregates have been detected in thalamic nuclei and basal ganglia, together with neurofibrillary degeneration similar to those seen in AD, without any link to amyloid plaques. Neuroimaging studies showed cortical atrophy predominantly in frontal and temporal lobes and white matter hyperintense lesions, which do not seem to correlate with the severity of cognitive impairment. The DTI MR technique detected diffuse microstructural changes in white matter and a hypoperfusion in frontal and temporal lobes. White matter alterations can range from mild and diffuse to confluent lesions or to severe brain atrophy. Voxel based morphometry showed regional gray matter loss in DM1 patients, especially in frontoparietal lobes, but also in occipital lobes, superior and middle temporal gyrus [9]. PET studies highlighted a global reduced glucose uptake. fMRI showed increased functional connectivity in the bilateral posterior cingulate and left parietal lobes in DM1 patients and such alterations seem to correlate with personality trait disorders. Dr. Bosco reinforced the need to reach a better understanding of CNS dysfunction in myotonic dystrophy, as cognitive impairment strongly affects the quality of life of DM patients; she underlined the need to find instruments to monitor the possible beneficial effects of new therapeutic approaches on CNS symptoms. The elaboration of a standard protocol for cognitive assessment should consider factors that can influence DM performances. Moreover, the neuropsychological test battery should be divided into two sessions in order to avoid fatigue that can negatively influence the results of the tests. Dr. Ekström focused primarily on most severe neurodevelopment impairments in DM1 patients and the

challenges in assessing their abilities and disabilities. Severe cognitive impairment is present in most of the individuals classified as congenital DM1 but can be documented also in a large portion of individuals with the childhood form. The evaluation tools, such as intelligence tests and behavioral scales, are standardized on a large sample of children in the population over a long period of time and scores from the sample assessment are distributed along a bell-shaped curve. As the sample of the population with moderate to severe mental retardation is rather small, there are some uncertainties in the normative data in this population. The method used for psychometric assessment is usually the Wechsler scales providing measures of global intellectual ability – the full scale IQ (FSIQ) and the subscores of verbal and performance IQ (VIQ; PIQ). Furthermore, the WISC and the WAIS provide subtests and the results are given as raw scores which are transformed into scale scores for comparison with age-related normative data. However, in the population of individuals with moderate and severe neurodevelopment impairments there are individuals that will not be able to perform any tests standardized for their chronological age. Therefore Dr. Ekström pointed out that for these individuals we should use assessment methods based on developmental age and functioning rather than on chronological age. According to the DSM-IV, mental retardation (MR) is defined as significantly subaverage mental function shown by an IQ ≤ 70 on an individually administered IQ test with concurrent deficits or impairments in the present adaptive functioning in at least two of areas of: communication, self-care, home living, social-interpersonal skills, use of community resources, self-direction, functional academic skills, work, leisure or health and safety, and onset of the condition before the age of 18. From a statistical perspective, the diagnostic criteria of having a score of 70 or below on instruments that assess intelligence and adaptive behavior imply that scores must be more than two standard deviations below the mean on test that yield standard scores with a mean of 100 and a standard deviation of 15. The definition of intelligence levels usually applied is as follows: normal when IQ is 85 or above; borderline if 70 < IQ < 85, mild mental retardation if 50 < IQ < 69, moderate MR if 45 < IQ < 49, severe MR if 20 < IQ < 45 and profound MR if IQ < 20. The expression mental retardation has been replaced by intellectual disability (ID) in DSM-V [10] and the severity of ID has now increased the importance and value of adaptive functioning together with standardized IQ testing scores. The need for suitable adaptive instruments is crucial: one of the instruments that is well validated and widely used to assess the adaptive functioning is the VABS (Vineland Adaptive Behavior Scales) [11]. It explores four domains and several subdomains. The main domains are Communication (subdomains: Receptive, Expressive, Written), Socialization (subdomains: Interpersonal relationship, Play and Leisure time, Coping skills), Motor skills (subdomains: Gross motor, Fine motor) and Daily living skills (subdomains: Personal, Domestic, Community). Each subdomain consists of five descriptive levels (High, Moderately high, Adequate, Moderately low and Low). The VABS is a valid instrument to assess cognitive level especially in individuals with profound and severe intellectual disability. In our previous

G. Bosco et al. / Neuromuscular Disorders 25 (2015) 813–823

study we have demonstrated that almost all individuals with DM1 scored lower regarding adaptive level as opposed to intellectual level [3]. The task of measuring changes in cognitive abilities in atypical developing individuals in longitudinal studies is a methodological challenge. Due to increased age, most individuals could not be assessed with the same intelligence test, making the comparison of test results sometimes impossible except for VABS. As already known, higher functioning individuals with DM1 have deficits in executive function. The assessment of executive function in individuals with ID is often difficult and in individuals with DM1 and ID even more difficult due to the different range of developmental level, limitations in motor and verbal abilities, variable behavior problems and the medical conditions associated with the disorder. Therefore Dr. Ekström suggested the administration of the Behavior Rating Inventory of Executive Function (BRIEF) that is a questionnaire with normative data designed to assess executive function behaviors at home and at school [12]. Different BRIEF parental and teachers rating versions are available from the pre-school (2–5 years old) and to the adult age and is an option to study individuals affected by CDM and the childhood form of DM1. There is also a self-report version for patients 11–18 years of age. The BRIEF rating scale has already been used in assessing executive dysfunction in several developmental neurological conditions including Intellectual Disabilities, Tourette Disorders, ADHD, Autism and Obsessive–Compulsive disorders. Another important neurodevelopmental disorder affecting individuals with DM1 is autism spectrum disorders (ASD). According to DSM-IV [13], ASD is characterized by the inability of an individual to communicate or interact with others; it covers a wide spectrum of symptoms that vary greatly in nature and severity. The spectrum includes four different diagnoses: Autistic Disorders, Asperger Syndrome, Pervasive Developmental Disorder and Childhood Disintegrative disorder. In DSM-V [10] these four entities have been replaced by Autistic Spectrum Disorder (ASD) and the symptoms fall on a continuum that defines a single spectrum with significant individual variability. The severity is established according to three levels, based on the need of support. According to DSM-V, in the diagnostic procedure, the clinicians are encouraged to the describe the severity of the ASD symptoms, the pattern of onset and clinical course, the cognitive abilities (any level of intellectual disability), etiologic factors and any associated clinical condition (such as constipation, visual impairments, sleep disorders, etc). The diagnosis of ASD is a lengthy and time consuming process that requires suitable qualified personnel to assess behavioral, historical, and parent reported information. Parental interviews are crucial for the diagnosis of ASD, but parents of DM1 patients tends to recognize and report too few symptoms and problems. For this reason, several diagnostic tools should be used, both interviews as well as observational instruments, performed by experienced personnel, familiar with the diagnosis of ASD, intellectual disability as well as DM1. Dr. Ekström concluded by emphasizing the importance of making an accurate assessment of cognitive and adaptive skills as well as awareness of the possible comorbidity of ASD in individuals affected by

815

DM1 in order to develop optimum educational support and rehabilitation care. 2.3. Theme 3: childhood form of DM1 and autism: is there a comorbidity?; Chair: Dr. Angeard Dr. Angeard introduced the subject with a brief review on psychiatric disorders observed in congenital and childhood forms of DM1. The prevalent diagnosis includes ADHD, anxiety disorders and ASD, although for ASD there are some controversial results that may be explained by the different methods used for the diagnosis, the heterogeneity of the cohorts and the heterogeneity of the IQ level of the participants [14]. Therefore Dr. Angeard suggested to classify the results according to phenotypes and IQ levels, when studying the comorbidity between ASD and DM1. She proposed a comparison in cognitive and social functioning between patients affected by the childhood form of DM1 and those in the ASD population, with the aim of distinguishing between the aspects that are specific to each cognitive condition and those they have in common. The main characteristics of the cognitive profile in the childhood form of DM1 are: an IQ level around 70, visuo-spatial and constructive deficits and dissociation between the ability to remember a list of words as compared to the ability to remember visuo-spatial information. Dr. Angeard explained that visuo-spatial and constructive deficit is to be attributed to a problem in the integration of the visual information rather than memory impairment. Patients also show specific reading and spelling impairment, speed of processing impairment, short term visual memory and verbal working memory deficit, attention deficit, cognitive flexibility deficit and alexithymia. Facial emotion and recognition impairment has also been reported, indicating that social cognition is a sensitive domain; hence, Dr Angeard underlined the need to explore not only the frontal lobe but also the temporal functions during cognitive assessment. Later on, Dr. Angeard illustrated the characteristics of ASD, focusing on social cognitive development: the ASD population shows social cognition deficit and impaired processing of social information, executive functions impairment, reduced cognitive flexibility and atypical sensory processing, including high sensitivity to visual information with fixation on details rather than the global object. A comparison between DM1 and ASD then followed: from the neurofunctional point of view, DM1 patients show white matter abnormalities that correlate with IQ level, executive functioning and working memory deficits while individuals having ASD show an atypical pattern of connectivity which is responsible for deficits in integrative functions. In the domain of social communication, DM1 patients show social interaction deficit, contingent response, passivity without self-injurious behavior, few repetitive and stereotyped patterns of behavior and late acquisition of language. Individuals with ASD present absence of language, echolalia or delayed acquisition of sophisticated language and pragmatic language deficits. Concerning cognition, there is a heterogeneous spectrum from mild ID (Intellectual Disability) to borderline or normal IQ in DM1 and from severe ID to high level IQ in ASD. In conclusion, further studies must be performed to clarify if ASD

816

G. Bosco et al. / Neuromuscular Disorders 25 (2015) 813–823

can be considered as a comorbidity of DM1, comparing the cognitive, emotional, behavioral profiles in DM1 and ASD groups within the same IQ range. Three areas of interest were the focus of the first session of the conference. The first one was concerned with the correlation between ASD and DM1: Dr. Ekström explained that autistic symptoms can be observed in several genetic diseases and the phenotypic expression can vary in a wide spectrum, but the diagnosis of ASD is based on the symptoms and not on the etiology, and it can be reached only if the patient fulfills all the criteria established in DSM-V. Moreover, autistic symptoms can be observed both in adult and in children affected by DM1, being more pronounced in the childhood form than in the adult one. However the neuropsychological process underlying the autistic symptoms may be different. Second she emphasized how individuals affected by ASD or Asperger Syndrome show poor facial recognition and that the same difficulty is present in DM1 patients. Therefore Dr. Meola and Dr. Angeard reaffirmed the importance of exploring facial recognition in childhood and congenital forms of DM1. The third theme dealt with the effort to obtain reliable information from the parents of children affected by DM1: healthy parents are capable of recognizing symptoms, psychiatric alterations and learning difficulties of their children, while affected parents are not, maybe because they consider these aspects as normal, as they are affected by the same characteristics. 2.4. Theme 4: neuroimaging in DMI-DM2; Chairs: Drs. Bozzali, Kornblum, Minnerop Dr. Kornblum opened the session with an overview on previous neuroimaging studies in DM1 and DM2 and illustrated general neuroimaging findings concerning white matter (WM) and gray matter (GM), detected by various techniques including conventional morphological MRI, Voxel Based Morphometry (VBM), Diffusion Tensor Imaging (DTI), and Positron Emission Tomography/Single Photon Emission Computed Tomography (PET/SPECT) techniques. Recent functional imaging studies revealed glucose hypometabolism in frontal and temporal lobes in DM1 and, to a lower extent, in DM2 patients; cerebral perfusion studies showed hypoperfusion in frontal and temporoparietal regions in DM1 patients and hypoperfusion in frontal and middle frontal cortex in DM2 patients. Structural alterations included ventricular enlargement and microcephaly especially in CDM, thickening of the scalp, diffuse brain atrophy and white matter changes in DM1 more than DM2 patients. GM abnormalities included GM reduction in diverse areas of the brain, mainly in the frontal lobes, parietal lobes, the pre-central and post-central gyrus in DM1. GM reduction in the cortical and subcortical regions seems to be more pronounced in adult than in juvenile forms of DM1, while adult DM2 patients showed less profound GM reduction compared to DM1 predominantly in cerebral midline structures. The white matter findings consisted of widespread alterations throughout the whole brain, the changes being particularly important in the limbic system. These abnormalities seem to be equally pronounced in congenital, juvenile and adult forms of DM1; atrophy of the corpus callosum is present in congenital and adult forms of

DM1 but also in DM2 patients. In general, WM lesions and microstructural white matter changes seem to be more severe and frequent in DM1 than in DM2. In conclusion, all previous studies showed morphological and functional brain affection that are more evident in DM1 than in DM2 patients; all studies showed comparable results with regard to the patterns of hypoperfusion and cerebral metabolite uptake changes in DM1 and in DM2 patients. WM tracts seem to be degraded in a ubiquitous manner in DM1 more than in DM2, and WM affection seems to be more pronounced compared to the GM one [15,16]. Further studies are necessary to clarify if WM and GM abnormalities produce relevant functional consequences, to find a precise correlation between neuropsychological and neuroimaging data, to establish if these abnormalities are stable or dynamic over time, to distinguish neurodevelopmental defects from neurodegenerative alterations and to establish which neuroimaging survey is the most sensitive. Based on these questions, longitudinal studies have been initiated. Dr. Minnerop and Dr. Kornblum presented first data of a longitudinal study on DM1 and DM2 patients based on VBM and DTI techniques: white matter microstructural integrity and GM have been evaluated over time in DM1 and DM2 patients and the results have been compared to those of healthy controls. The longitudinal study has been designed to determine the natural history of morphological brain affection in DM1 and DM2 patients, to establish if MRI changes are stable or progressive over time and if they are more pronounced in DM patients compared to healthy controls. Data analysis is currently underway and might present new insights into the nature of structural MRI alterations. Dr. Bozzali presented a neuroimaging study using the VBM technique for the detection of microscopic and macroscopic abnormalities in the brain structure and to assess GM and WM atrophy in DM1 patients [17]. The result of this study revealed a correlation between WM lesions and the extension of CTG repeats, and an inverse correlation between CTG repeats and GM alteration, confirming a strict association between the patient level of cognitive efficiency and the genetic background. The current hypothesis is that WM disease takes place first and its alteration produces a secondary degeneration of the GM tissue. Dr. Bozzali confirmed MRI as an invaluable tool for detecting specific structural and functional brain abnormalities in DM1 patients, as already demonstrated by consistent results across independent studies. Dr. Bozzali suggested also to introduce a connectomics analysis for brain functioning investigation in DM1 patients: this approach consists of mapping the neural connections and networks using neuroimaging techniques [18] in order to reach a major understanding of the pathophysiological processes that affect cognitive functioning in DM1 patients. 2.5. Theme 5: DM registries focused on CNS aspects; Chairs: Drs. Bassez, Fossati, Wood Dr. Fossati presented on the Italian experience with the National Registries for DM patients. The project was launched by the National Institute of Health and consists of a multicenter study led by the I.R.C.C.S. Policlinico San Donato and coordinated by Dr. Meola. This organization is an operative network involving

G. Bosco et al. / Neuromuscular Disorders 25 (2015) 813–823

eighteen Centers specialized in diagnosis and treatment of neuromuscular diseases and is distributed all over Italy. The DM registry is an online database that collects information on symptoms, quality of life, demographic distribution and genetic data concerning DM patients. The current objective is to enroll one thousand individuals by December 2015. The registry contains two sections: one is accessible to patients, who are invited to input their personal data; the second one is accessible to physicians only, who update the instrumental exams and clinical evaluations. Dr. Fossati illustrated the preliminary results of the project that began operating over one year ago: at present, 118 individuals (97 DM1 and 21 DM2 patients) have been enrolled. The data collected so far are consistent with the data found in the literature: in particular 87.1% having a mean age of 49.8 are affected by DM1, 62.3% of these are male, the paternal transmission is present in 49.2% of the DM1 subgroup. 16.7% of the DM1 individuals earned a University degree while only 9% of DM2 individuals did. 52.5% of DM1 subjects are employed and 41% of them report that the disease affects their performance at work. 12.8% of the population is affected by DM2 with a mean age of 60.8, all of them had a maternal inheritance of the disease. Concerning symptoms, the majority of DM1 patients manifested myotonia or weakness as the onset symptom, while DM2 patients manifested hyposthenia more frequently than myotonia. Cramps and muscle pain are more frequent in DM2 than in DM1 patients. No subjects showed cardiac involvement as an early symptom. The lag between the onset of symptoms and diagnosis in both DM1 and DM2 patients is significant: 8.8 and 12.9 years respectively, which is consistent with the results published in the literature [19]. All DM2 patients are affected by hyposthenia, whereas only 16.8% of DM1 are. Both populations report a high occurrence of hypersomnia, while the percentage of cataracts is significantly different, being 66.7% and 27.9% in DM2 and DM1 patients respectively. Myotonia mainly affects hands, with 74.1% of DM1 and 25% DM2 patients having grip myotonia. All patients reported an improvement of their myotonia condition following treatment with Mexiletine. Cardiac involvement is more frequent in DM1 than in DM2 patients [20,21]; it mainly manifests itself as a prolonged PR interval and a widened QRS. Dr. Fossati concluded by underlining how myotonic dystrophy represents a continuous challenge for patients, with long lasting disabilities. Even though knowledge on the disease has increased over the last few years, for the time being, no treatment is available and therefore the best that a physician can do is to provide care and clinical follow-up with psychological assistance. Ms. Wood from the University of Newcastle presented the UK Myotonic Dystrophy Registry (http://www.dm-registry.org/uk), an online, patient centered database containing two sections: one in which patients input their data and another which allows physicians to access and elaborate that data; patients are invited to enroll themselves, provide their personal information and select their neuromuscular specialist. An email is automatically sent to the selected physician and each patient receives all of their clinical information via a personal account. Patients are periodically informed of progress in research by newsletters, and the registry has been successful in recruiting patients into

817

a number of academic research studies. Data items collected include all of the mandatory and highly encouraged items agreed at the 2009 TREAT-NMD/Marigold Foundation workshop held in Naarden [22]. In the first two years 410 DM1 and 13 DM2 patients had registered; therefore, the data represent only the DM1 population. There is a broad range of ages represented from 1 to 81 years old (mean 43.41) and an even spread is seen across genders (214 female 196 male). From the clinical point of view, fatigue, myotonia and dysphagia (swallowing difficulties) are the main symptoms reported by the individuals affected by the adult form of DM1; myotonia is less frequent in early onset DM1 (onset before the age of 3) than in adult form, with a similar prevalence concerning other symptoms. Only a few parameters concerning CNS involvement have been considered in the UK Registry, and these include daytime sleepiness and fatigue. Fatigue/daytime sleepiness is the most frequent symptom in the early onset, childhood (onset between 3 and 16 years) and adult form. This does not appear to be related to the respiratory function in the majority of cases. Current treatment strategies include Modafinil and non-invasive ventilation both but do not eliminate the problem. Additional data were presented from the Newcastle in-patient sleep study, which supported these registry findings. Dr. Bassez presented results achieved in France with the DM Registry, focusing on the potential contribution of registries to the CNS research: they constitute a broad source of information for epidemiological investigation, natural history understanding, comparison of the clinical features according to gender and evaluation of genotype–phenotype correlation. This registry called DM-scope International Registry is the widest DM database with collection of information from 1962 French patients and could shed light on clinical classification. Open issues are: to select cognitive tests according to each form of DM1; to develop a standard protocol for neuroimaging and to outline common guidelines for cognitive assessment in order to establish potential outcome measures. For instance, recent findings suggest that brain alterations progress slower than muscle–skeletal degeneration. The current objectives of the registries are to validate multinational and reliable outcome measures for the baseline characterization of cognitive impairment in DM1 and DM2 and to track changes throughout a period of time. Dr. Bassez suggested using fatigue assessment and cognitive impairment tested by neuropsychological battery to measure change over time. Dr. Bassez reaffirmed the need to reach a worldwide consensus on DM1 classification and to establish a common and harmonized nomenclature: he suggested an additional clinical sub-classification for Congenital DM1 to classify cases by severity. Dr. Bassez also invited physicians to avoid the term “Classical” when referring to Adult DM1, considering this nomenclature inappropriate for a disease with such a wide spectrum of possible forms. Very recently, according to French National registry, it has been shown a “gender effect” on the natural history of DM1 (presented at IDMC9-International Myotonic Dystrophy Consortium 2011, San Sebastian, Spain). During the session, two aspects were explored: the first focused on the importance of integrating all the registries into an international database. The second one regarded the protocol

818

G. Bosco et al. / Neuromuscular Disorders 25 (2015) 813–823

for administration of Modafinil to reduce daily sleepiness: Dr. Eymard proposed that a feasible strategy may consist of first attempting to reduce OSAS with assisted nigh-time ventilation and to offer to Modafinil only where patients continue to suffer from persistent daily sleepiness. 2.6. Theme 6: disease models and neurochemistry; Chairs: Drs. Sonnino and Gomes-Pereira Dr. Sonnino presented on ganglioside altered composition and concentration in the plasma membranes of DM1 and DM2 patients. Gangliosides are strongly associated with the brain system and functioning, although their specific role has not been completely clarified. Ganglioside content is ten-fold higher in cerebral than in extra-neuronal tissue and it is one of the principal components of the plasma membrane, being associated with the outer layer. Gangliosides are amphiphilic compounds that consist of a hydrophilic moiety and a lipid moiety called ceramide. Ceramide is constituted by fatty acids and sphingosine that forms a network of hydrogen bonds with other ceramides, resulting in reduced membrane fluidity and promoting interaction with cholesterol. Thanks to this property, gangliosides tend to segregate, reducing the interactions with other molecules. Therefore they are not distributed homogeneously, but are aggregated in specific areas of the plasma membrane. These areas show a decreased fluidity and a scarce concentration of proteins compared to other parts of the plasma membrane. These proteins act as receptors involved in cell signaling. Therefore glycosphingolipids are implicated in the modulation of cell signaling in neurons. The segregation of glycosphingolipids and the interaction between sphingolipids and proteins influence the stability of the myelin and the interaction between axon and myelin. Dr. Sonnino illustrated the analysis of DM1 and DM2 myoblast membrane composition after labeling the sphingolipids with a radioactive marker: numerous gangliosides have been detected, with GM3 being the most representative one. The analysis by mass spectrophotometry evidenced a shift from short to long fatty acids in the lipid moiety that determines membrane fluidity modification. Furthermore DM1 and DM2 myoblasts showed a different glycosphingolipid composition than that found in cells obtained from healthy individuals. This observation may be explained by an alteration of the enzymatic cascade implicated in the membrane organization and composition. A recent analysis evidenced a reduced activity of these enzymes in DM1 and in DM2 senescent cells. As a consequence, glycoside ceramides are not transformed into their final compounds and result in being more concentrated in the plasma membrane, leading to an alteration of the segregation process and the molecular interaction. Further studies are needed to better characterize cellular processing in DM1 and DM2 cells. In particular the analysis of the brain tissue may represent the starting point for a new research. Dr. Gomes-Pereira presented on a French model of transgenic mouse named DMSXL that has been created with the objective of assessing RNA toxicity, notably in the CNS. DMSXL mice express an expanded DMPK gene carrying a CTG sequence that ranges from 1000 to 3000 repetitions [23], whose transcription

induces the accumulation of toxic RNA foci in several tissues, including muscle and brain. The DMPK gene is expressed in multiple CNS regions and abundant foci of toxic RNA have been observed in both neurons and astrocytes, with the higher content being in astrocytes. The main consequences of this toxic accumulation on mouse behavior and cognition are novelty inhibition, increased anxiety, visuospatial memory deficit and anhedonia, which resemble the neurological manifestations observed in DM1 patients. Electrophysiological studies showed deficits in PPF (Pared Pulse Facilitation), a sign of impaired short-term synaptic plasticity [24]. The increased expression of RAB3A and hyperphosphorylation of SYN1, with consequent alteration of constitutive exocytosis, have been documented in the frontal cortex [24]. RAB3A is a protein associated with the outer surface of synaptic vesicles; it interacts with other proteins, hence contributing to the fusion of the vesicle and synaptic membranes and the release of vesicular content to the synaptic cleft. The overexpression of RAB3A causes spontaneous exocytosis, and this protein plays a role in spatial learning, sleep control and synaptic plasticity [25]. SYN1 interacts with the synaptic vesicles and the cytoskeleton and in a phosphorylation-dependent manner: when dephosphorylated, it fastens the vesicle to the cytoskeleton; when phosphorylated, it presents a reduced affinity for actin, facilitating the detachment of the vesicle from the cytoskeleton and its migration toward the synaptic membrane [26]. Hyperphosphorylation of SYN1 determines the alteration of short term synaptic plasticity [27]. Further studies are needed to clarify the mechanisms of synaptic protein dysregulation and the functional consequences on synaptic vesicle dynamics and disease neuropathogenesis. Interestingly, DMSXL mice show behavioral and electrophysiological signs of cerebellar dysfunction, associated with great foci content in this brain region. Global proteomics and transcriptomics approaches will help elucidate the molecular mechanisms behind cerebellum dysfunction in DMSXL mice. These data point to a possible involvement of the cerebellum in DM1 neuropathology, and call for the clinical and molecular assessment of human patients and post-mortem cerebellum samples. 2.7. Theme 7: molecular aspects and the linking of these to CNS manifestation; Chair: Dr. Sergeant Dr. Sergeant opened the session with an overview of the principal anatomopathological findings detected in several neurodegenerative diseases, focusing on neurofibrillary degeneration (NFD), Tau aggregates and amyloid plaques. Neurofibrillary degeneration (NFD) or neurofibrillary tangle (NFT) is a pathological hallmark characterized by the fibrillization of abnormally and hyperphosphorylated Tau isoforms are associated with neurofibrillary tangles composed of hyperphosphorylated Tau proteins [28]; it has been observed in both neurons and astrocytes of patients affected by numerous neurological disorders, but also in elder healthy individuals together merged under the denomination of Tauopathies. Recent studies evidenced NFD affecting the brainstem, locus coeruleus, amygdala and temporo-insular region of DM1 and DM2 patients, even though for these patients no amyloid plaques and scarce

G. Bosco et al. / Neuromuscular Disorders 25 (2015) 813–823

Lewy bodies had been observed [29]. The accumulation of Tau proteins in the hippocampus, insula and temporal cortex of DM patients has also been evidenced [30] and biochemical analysis on Tau aggregates revealed that a single Tau isoform lacking the encoded sequences of exons 2, 3 and 10 is the most prevalent isoform to aggregate. The pattern of distribution of Tau aggregates suggested the hypothesis of a “prion-like propagation” of the TAU-pathology: a neuron-to-neuron, homotypic seeding of a wild type Tau protein through a transsynaptic mechanism that disseminates along cortical connections, with a propagation pattern that depends on the Tau isoform. The capability of associating clinical manifestations to the Tau-pathology is still insufficient and hence demands further investigation. However, measuring Tau isoform in CSF or the plasma of DM1 patients could be indicative of the brain involvement and helpful for any theranostic purpose. What are the modifiers of the disease in DM remain unclear but, considering the multiple polymorphisms of MBNL1 and their potential role in determining the severity of the symptoms, Dr. Sergeant hypothesized that these polymorphisms may influence also the response to therapy. Hence, Dr. Sergeant suggested considering MBNL1 and MBNL2 as valuable biomarkers. Additional reliable biomarkers may be represented by Tau isoforms expressed in the brain and measured in CSF and in blood, although in reality, most of the compounds detected in CSF are only fragments of Tau proteins. Amyloid beta (Abeta) species may also represent interesting biomarkers: the transport of Abeta from the brain to the blood is under active transport through the blood–brain barrier (BBB). An ancillary study, conducted on a group of 53 DM1 patients and 53 healthy controls, whose concentration of all the species of Abeta have been measured in residual plasma samples obtained with informed consent for genetic diagnosis, evidenced increased levels of Abeta40 and Abeta42 in DM1 patients with respect to controls. As already stated, no amyloid pathology is present in myotonic dystrophy [31,32]; therefore, these results do not represent amyloid accumulation in the brain. They may however reflect an alteration of the permeability of the BBB. Hence, Abeta42 and Abeta40 may represent suitable markers of increased permeability of the BBB in patients affected by myotonic dystrophy. Further studies are required to establish a correlation between cognitive deficits assessed by neuropsychological tests and plasma concentrations of Abeta. 2.8. Theme 8: nomenclature in DM and OMMYD strategy; Chairs: Drs. Gallais and Meola Dr. Gallais highlighted the wide heterogeneity of terms and criteria currently in use and the discrepancies in phenotype classification that can be found in the literature to emphasize the need to reach a consensus among specialists concerning the nomenclature and classification of DM1 phenotypes. A common terminology and phenotype classification will be needed in order to be able to compare studies, share results and better define criteria required for each investigation. The classification of DM1 phenotypes is based on the OMMYD initiative, in which the objective is to define feasible outcome measures and scales and identify relevant health outcome domains. According

819

to one literature review, the range of CTG repeat, age at onset, age of diagnosis and specific clinical manifestations have been the main criteria adopted to classify patients, but the features of these criteria vary widely from one study to another. For example, in adult phenotype CTG expansion, ranges from 50 to 1000 repetitions were used in some studies and from 150 to 1000 in others. Dr. Gallais pointed out that the homogeneity in the selection of specific features for each phenotype is necessary. Therefore, when considering the classification of phenotypes in different investigations, only some characteristics are comparable, while others are not. In conclusion, the selection of consensual criteria for the definition of a harmonized classification of DM1 phenotypes is still an ongoing process and based on the clinician and researcher experts’ point of view. 2.9. Theme 9: consensus on multiple biomarkers of CNS involvement; Chairs: Drs. Eymard, Meola, Sergeant, Turner, Van Engelen Dr. Meola opened the morning session focusing on the need to reach a consensus on neuropsychological assessment, neuroimaging biomarkers and plasma biomarkers in DM patients. Dr. Meola proposed a collaboration between neuroradiologists to establish a standard neuroimaging protocol and to select the most convenient techniques, with VBM and DTI being the most valuable techniques to date, as emerged during the discussion among the participants of the Congress. Furthermore, a decision should be taken whether to apply a standardized protocol to all DM1 patients or only to subgroups of these. The correlation between neuroradiological findings and neuropsychological tests should be better clarified, with the objective of establishing a common strategy of intervention. He also encouraged the planning of additional longitudinal studies, with large patient numbers and an extended period of follow-up in order to better evaluate change over time, in accordance with the slow progression of the disease. Neuropsychological tests should be also selected for pediatric assessment. Dr. Meola suggested also a collaboration between physicians involved in the organization of registries to decide which CNS parameters and neuropsychological tests should be included in the registries. An additional issue concerned the need to create a biobank and to establish which tissues and what information should be collected in order to monitor patients during clinical trials. Emphasis was placed on the opportunity to collect either blood or CSF or both and on determining which biomarkers should be investigated in both samples. Dr. Turner discussed clinical, neuroradiological and neuropathological biomarkers, explaining that biomarkers meaningful for brain neuropathology may not only come from the brain but also from CSF, muscular tissue, fibroblasts and blood, and that these extracerebral biomarkers could correlate with cognitive impairment or with cognitive improvement during clinical trials. As already stated, myotonic dystrophy is a slowly progressing disease and changes require many years to be detected. How progressive the phenotype actually is, however, still remains unclear and the domains that should be tested to

820

G. Bosco et al. / Neuromuscular Disorders 25 (2015) 813–823

evaluate changes are fully defined. Dr. Turner underlined the need to establish a Global Cognitive Scale using neuropsychometric tests with the aim of developing a unified DM scale. Concerning biochemical markers, he invited physicians to undertake a broad investigation on serum and to apply further screening tests in order to identify other biomarkers, additionally to Abeta. 2.10. Theme 10: optimistic study; Chair: Dr. Van Engelen OPTIMISTIC is the first international and multicentre clinical trial carried out in Europe on DM1 [33]: it was launched in October of 2012, with patient enrollment starting in April of 2014. It consists of an observational, prolonged trial using a tailored intervention on severely fatigued patients affected by myotonic dystrophy type 1. The approach consists of a cognitive behavioral therapy (CBT) associated with a specific exercise therapy. CBT is designed to improve several symptoms, including fatigue and reduced initiative, thus influencing the quality of life of the affected patients. Participation begins with a baseline evaluation: patients undergo a physical examination, they are asked to complete a questionnaire that evaluates their quality of life and then blood and urine samples are taken. A randomized selection of patients that will receive CBT and exercise therapy or conventional care then follows. After being treated for 10 months, patients undergo a second global examination and a comparison between the two cohorts is performed. The objectives of OPTIMISTIC are to evaluate the effectiveness of a tailored program of CBT to induce behavioral changes and the capability of exercise therapy to improve physical performance; create clinical guidelines for CBT based on observational data; combine an evidence-based with a mechanism-based approach; and identify biomarkers of disease progression for clinical trials. 2.11. Theme 11: clinical research and preparedness; Chairs: Drs. Eymard, Turner, Van Engelen Dr. Eymard illustrated the main issues concerning clinical research and preparedness, focusing on numerous themes, including the choice of the best tools for clinical research; the problem of a proper classification of DM1; the identification of biomarkers; the need of longitudinal, multimodal and standardized studies to understand the decline in cognitive defects; the identification of CNS features that would be meaningful for monitoring response to therapy; the importance of deciding what are the optimal conditions for a trial in terms of duration, single or multiple center studies and the choice of patients; and finally the necessity to adapt the evaluation tools for clinical trials when testing motor functions. Dr. Eymard underlined the importance of integrating information coming from evaluations on animal models with that obtained from humans, trying to verify in humans those hypothesis derived from mouse models. Dr. Eymard then focused on Childhood DM1, describing the difficulties to obtain consensus from families when investigating their children for DM1, especially in the case of patients for whom a parent has not been already diagnosed

with DM1. Therefore the need emerges to elaborate a standardized protocol and to adopt a multidisciplinary approach. He reinforced the need for a standard neurocognitive evaluation protocol that includes exploration of social cognition, psycho-behavioral features, school adaptation, sleep, respiration. He also emphasized the importance of standardizing intervention for scholastic and socio-professional integration; establishing protocols for behavioral therapy and response of patients to treatments; developing school programs dedicated to children affected by DM1 and defining guidelines for administration of psycho-stimulant drugs. Dr. Meola emphasized the necessity of investing in the formation of specialists such as psychologists, neuropsychiatrists and neuropediatricians in order to provide the best care possible for Childhood DM1 patients, both in their family environment and at school and to obtain support from pharmaceutical industries in providing services to all DM patients. Dr. Eymard underlined the importance of developing a collaboration between pediatricians and neurologists to assure that a continuous health care from childhood to adulthood is provided. Dr. Turner remarked on the need to improve neuropsychiatric assistance and to invest resources to support adult patients in the process of social and professional integration. 2.12. Theme 12: biomarkers in animal models used in preclinical test; Chairs: Drs. Lopez and Gourdon Dr. Lopez presented on the translational approaches to neuromuscular disease developed by the biotechnology company Valentia Biopharma, focusing on Drosophila fly models for DM1. Drosophila is a convenient vehicle for studying muscular and cognitive involvement in myotonic dystrophy primarily because close to seventy percent of human genes are conserved in the genome of this fruit fly, which therefore shares with mammalians numerous molecular, cellular, functional and biological characteristics as well as several neurotransmitter systems and a Blood–Brain Barrier. Moreover, there are no ethical concerns associated with the utilization of this insect and the fast reproductive cycle ensures for timely results. CNS involvement can be globally investigated, thanks to the availability of 3D pictures and functional circuit maps on fly brains that allow for neurodegeneration studies in single cells and for the examination of neuronal connections. Drosophila flies exhibit a wide range of CNS functions and behaviors, similar to those of mammalians and they also respond in a similar manner to CNS drugs. There are many fly models for DM1, most of which are characterized by CTG expansions of different lengths in the genome. Consequently, Drosophila has been used to develop numerous studies on RNA toxicity, miRNA deregulation, research on therapeutic compounds, some of which are now being developed by Valentia Biopharma. Ongoing studies are being conducted with the objective of developing DM2 models while other studies are finalized to the creation of knocked down models for MBNL proteins. In conclusion, valuable Drosophila samples for muscular and cognitive DM1 impairment are currently available, while further experiments are being conducted to obtain models for cardiac involvement. Dr. Gourdon illustrated the pathogenesis of myotonic dystrophy starting from the expression of CTG expansion in the DMPK

G. Bosco et al. / Neuromuscular Disorders 25 (2015) 813–823

gene, whose translation in CUG repeats produces toxic RNA that accumulates in the nucleus, sequestering MBNL, upregulating CELF, proteins involved in the regulation of splicing processes, thus impairing the alternative splicing of numerous proteins and producing the clinical manifestations of the disease. Several therapeutic strategies have been identified, some of which act on MBNL proteins, restoring their normal level and reverting many of the abnormalities, while other approaches target toxic CUG repeats using molecules able to destroy the RNA or to release proteins retained by RNA. Dr. Gourdon briefly illustrated the mouse models currently used recalling that MBNL2 is the most important protein conditioning brain alterations, while MBNL1 is mostly relevant in muscle tissue; this distinction is particularly important when considering the feasible biomarkers for therapeutic strategies. Dr. Gourdon suggested that valuable biomarkers of CNS involvement would be represented by foci of RNA in cell nuclei, by products of altered splicing processes (although splicing patterns differ from one brain region to another) synaptic proteins such as RAB3A and SYN1. Finally, Dr. Gourdon proposed launching longitudinal studies on mice models to better investigate behavior abnormalities,

821

electrophysiological alterations and define which gender is the easiest to work with. 2.13. Theme 13: therapeutic strategy in the pharmaceutical industry; Chair: Dr. Dent Dr. Dent presented a general framework about drug development illustrating the opportunities and challenges associated with the development of drugs for rare diseases as well as challenges and opportunities for developing compounds for CNS disorders. It takes 10–20 years to develop a compound and the production of drugs for the treatment of rare diseases is quite similar to the production of drugs for treating highly prevalent diseases. However, there are major difficulties that need to be overcome concerning achieving in-depth understanding of the natural history of the disease and the identification of biomarkers that are crucially important to verify the efficacy of the therapy. Dr. Dent then illustrated the challenges associated with developing drugs for the treatment of CNS diseases: some of the obstacles are represented by the higher difficulty in achieving approval for the utilization of drugs for CNS disorders as

Table 1 Key point and proposals for future studies and measures. Theme Theme 1.

Theme 2.

Theme 3. Theme 4. Theme 5. Theme 6. Theme 7.

Theme 8. Theme 9. Theme 10.

Theme 11.

Theme 12. Theme 13.

Key point - Improve on the knowledge of molecular aspects of myotonic dystrophies and the relationship between clinical features and cellular functioning alterations - Establish inclusion criteria for patients suitable for clinical trials - Select appropriate tools to monitor the beneficial effects of new therapeutic approaches on CNS symptoms - Elaborate a standard neurocognitive evaluation protocol that includes exploration of social cognition, psycho-behavioral features, school adaptation, sleep, respiration - Make an accurate assessment of cognitive and adaptive skills in individuals affected by DM1 - Explore facial recognition in childhood and congenital forms of DM1 - Carry out effort to obtain reliable information from the parents of children affected by DM1 - Introduce connectomics analyses for brain functioning investigation in DM1 patients - Develop longitudinal, multimodal and standardized studies to understand the decline in cognitive defects - Outline common guidelines for cognitive assessment in order to establish potential outcome measures - Integrate information collected in the registries to track changes throughout a period of time - Study mouse models of the disease to clarify the mechanisms of synaptic protein dysregulation and the functional consequences on synaptic vesicle dynamics - Identify the modifiers of the disease in DM pathogenesis - Investigate reliable biomarkers of CNS involvement in CSF and in the blood - Selection of consensual criteria for the definition of a harmonized classification of DM1 phenotypes - Start a collaboration between neuroradiologists to establish a standardized neuroimaging protocol and to select the most convenient techniques - Create a biobank and establish which tissue and what information should be collected in order to monitor patients during clinical trials - Start a collaboration between physicians involved in the organization of registries to decide which CNS parameters and neuropsychological tests should be included in the registries - Evaluate the effectiveness of a tailored program of CBT to induce behavioral changes and the capability of exercise therapy to improve physical performance - Create clinical guidelines for CBT based on observational data - Combine evidence-based medicine with mechanism-based approach and identify biomarkers of disease progression for clinical trials - Standardize intervention for scholastic and socio-professional integration - Establish protocols for behavioral therapy and response of patients to treatments - Develop school programs dedicated to children affected by DM1 - Define guidelines for administration of psycho-stimulant drugs - Launch new longitudinal studies on mice models to better investigate behavior abnormalities and electrophysiological alterations - Clarify disease mechanisms, pathogenesis and manifestations by collecting data to understand the natural history of CNS dysfunction - Conceptualize treatment benefits and to select outcome measures - Develop tools to assess CNS clinical endpoints - Form a partnership between academia, pharmaceutical industries and advocacy groups

822

G. Bosco et al. / Neuromuscular Disorders 25 (2015) 813–823

compared to what can be seen for other disorders, the longer application time for approval of CNS than for non-CNS drugs and the decreased chance of success in phase III during clinical trials. Clinical trials for a pharmacological treatment require the presentation of a road map for patient-focused outcome measures. Therefore, clinicians are asked to clarify disease mechanisms, pathogenesis and manifestations, to conceptualize treatment benefits and to select outcome measures. Concerning myotonic dystrophy, opportunities to advance therapeutics consist of collecting data to understand the natural history of CNS dysfunction, publishing as many results as possible to strengthen the academic position on CNS dysfunction, developing tools to assess CNS clinical endpoints and forming a partnership between academia, pharmaceutical industries and advocacy groups. 3. Conclusions The workshop focused primarily on CNS involvement in myotonic dystrophy: the most recent clinical, molecular, neuroradiological and neuropsychological findings have been presented and discussed. Further investigation is being conducted and more will be needed in the future and there are high expectations for the results of these studies. New proposals and future objectives were consolidated during the meeting (Table 1) and this event constituted a major opportunity for specialists in the field to debate on common grounds, share objectives and consolidate their collaboration. Acknowledgements The workshop was supported by the Marigold Foundation and by FMM – Fondazione Malattie Miotoniche, Milan, Italy. Appendix Workshop participants (all members of DM-CNS Group, including invited guests*) Nathalie Angeard (France) Guillaume Bassez (France) Anne-Berit Ekström (Sweden) Giovanna Bosco (Italy) Marco Bozzali (Italy) Rosanna Cardani (Italy) Gersham Dent (USA, Biogen IDEC)* Susanna Diamanti (Italy) Bruno Eymard (France) Barbara Fossati (Italy) Benjamin Gallais (Canada) Mario Gomes-Pereira (France) Geneviève Gourdon (France) Cornelia Kornblum (Germany) Arturo Lopez (Spain, Valentia Biopharma)* Don MacKenzie (Canada, Marigold) Giovanni Meola (Italy) Martina Minnerop (Germany) Jatin Pattni (UK) Nicolas Sergeant (France)

Sandro Sonnino (Italy) Chis Turner (UK) Baziel Van Engelen (The Netherlands) Libby Wood (UK) References [1] Bugiardini E, Meola G, on behalf of the DM-CNS Group. Consensus on cerebral involvement in myotonic dystrophy: workshop report: May 24–27, 2013, Ferrere (AT), Italy. Neuromuscl Disord 2014;24:445–52. [2] Gagnon C, Meola G, Hébert LJ, et al. Report of the second outcome measures in myotonic dystrophy type 1 (OMMYD-2) international workshop San Sebastian, Spain, October 16, 2013. Neuromuscul Disord 2015;25(7):603–16. doi:10.1016/j.nmd.2015.01.008. pii: S09608966(15)00027-9. [3] Ekström AB, Hakenäs-Plate L, Tulinius M, et al. Cognition and adaptive skills in myotonic dystrophy type 1: a study of 55 individuals with congenital and childhood forms. Dev Med Child Neurol 2009;51: 982–90. [4] Douniol M, Jacquette A, Cohen D, et al. Psychiatric and cognitive phenotype of childhood myotonic dystrophy type 1. Dev Med Child Neurol 2012;54:905–11. [5] Winblad S, Hellström P, Lindberg C, et al. Facial emotion recognition in myotonic dystrophy type 1 correlates with CTG repeat expansion. J Neurol Neurosurg Psychiatry 2006;77:219–23. [6] Peric S, Mandic-Stojmenovic G, Stefanova E, et al. Frontostriatal dysexecutive syndrome: a core cognitive feature of myotonic dystrophy type 2. J Neurol 2015;262:142–8. [7] Meola G, Sansone V. Cerebral involvement in myotonic dystrophies. Muscle Nerve 2007;36:294–306. [8] Ono S, Kanda F, Takahashi K, et al. Neuronal loss in the medullary reticular formation in myotonic dystrophy: a clinicopathological study. Neurology 1996;46:228–31. [9] Antonini G, Mainero C, Romano A, et al. Cerebral atrophy in myotonic dystrophy: voxel based morphometric study. J Neurol Neurosurg Psychiatry 2004;75:1611–13. [10] American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 5th ed. Washington, DC: American Psychiatric Association; 2013. [11] Sparrow SS, Balla DA, Cicchetti DV. Vineland adaptive behavior scales. Circle Pines, MN: American Guidance Service; 1984. [12] Gioia GA, Isquith PK, Guy SC, Kenworthy L. Test review: behavior rating inventory of executive function. Child Neuropsychol 2000;6:235–8. [13] American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 4th ed. Washington, DC: American Psychiatric Association; 1994. [14] Huerta E, Jacquette A, Cohen D, et al. Childhood form of myotonic dystrophy type 1 and autism spectrum disorders: is there a comorbidity? Neuropsychiatr Enfance Adolesc 2015;63(2):91–8. [15] Minnerop M, Weber B, Schoene-Bake JC, et al. The brain in Myotonic Dystrophy 1 and 2: evidence for a predominant white matter disease. Brain 2011;134:3530–46. [16] Wozniak JB, Mueller BA, Bell CJ, et al. Diffusion tensor imaging reveals widespread white matter abnormalities in children and adolescents with myotonic dystrophy type 1. J Neurol 2013;260:1122–31. [17] Serra L, Silvestri G, Petrucci A, et al. Abnormal functional brain connectivity and personality traits in myotonic dystrophy type 1. JAMA Neurol 2014;71:603–11. [18] Sporns O. The human connectome: origins and challenges. Neuroimage 2013;80:53–61. [19] Hilbert JE, Ashizawa T, Day JW, Moxley RT 3rd. Diagnostic odyssey of patients with myotonic dystrophy. J Neurol 2013;260:2497–504. [20] Lindqvist P, Morner S, Olofsson BO, et al. Ventricular dysfunction in type 1 myotonic dystrophy: electrical, mechanical, or both? Int J Cardiol 2010;143:378–84. [21] Petri H, Vissing J, Witting N, et al. Cardiac manifestations of myotonic dystrophy type 1. Int J Cardiol 2011;160:82–8.

G. Bosco et al. / Neuromuscular Disorders 25 (2015) 813–823 [22] Thompson R, Schoser B, Monckton DG, et al. Patient registries and trial readiness in myotonic dystrophy – TREAT-NMD/marigold international workshop report. Neuromuscl Disord 2009;19:860–6. [23] Gomes-Pereira M, Cooper TA, Gourdon G. Myotonic dystrophy mouse models: towards rational therapy development. Trends Mol Med 2011;17:506–17. [24] Hernández-Hernández O, Guiraud-Dogan C, Sicot G, et al. Myotonic dystrophy CTG expansion affects synaptic vesicle proteins, neurotransmission and mouse behaviour. Brain 2013;136:957–70. [25] D’Adamo P, Wolfer DP, Kopp C, et al. Mice deficient for the synaptic vesicle protein Rab3a show impaired spatial reversal learning and increased explorative activity but none of the behavioral changes shown by mice deficient for the Rab3a regulator Gdi1. Eur J Neurosci 2004;19:1895–905. [26] Fdez E, Hilfiker S. Vesicle pools and synapsins: new insights into old enigmas. Brain Cell Biol 2006;35:107–15. [27] Tallent MK, Varghis N, Skorobogatko Y, et al. In vivo modulation of O-GlcNAc levels regulates hippocampal synaptic plasticity through interplay with phosphorylation. J Biol Chem 2009;284:174–81.

823

[28] Oyamada R, Hayashi M, Katoh Y, et al. Neurofibrillary tangles and deposition of oxidative products in the brain in cases of myotonic dystrophy. Neuropathology 2006;26:107–14. [29] Maurage CA, Udd B, Ruchoux MM, et al. Similar brain Tau pathology in DM2/PROMM and DM1/Steinert disease. Neurology 2005;65:1636–8. [30] Caillet-Boudin ML, Fernandez-Gomez FJ, Tran H, et al. Brain pathology in myotonic dystrophy: when Tauopathy meets spliceopathy and RNAopathy. Front Mol Neurosci 2014;6(57):1–20. doi:10.3389/fnmol.2013.00057. [31] Winblad S, Månsson JE, Blennow K, et al. Cerebrospinal fluid Tau and amyloid beta42 protein in patients with myotonic dystrophy type 1. Eur J Neurol 2008;15:947–52. [32] Peric S, Mandic-Stojmenovic G, Markovic I. Cerebrospinal fluid biomarkers of neurodegeneration in patients with juvenile and classic myotonic dystrophytype 1. Eur J Neurol 2014;21:231–7. [33] Van Engelen B, OPTIMISTIC Consortium. Cognitive behaviour therapy plus aerobic exercise training to increase to activity in patients with myotonic dystrophy type 1 (DM1) compared to usual care (OPTIMISTIC): study protocol for randomised controlled trial. Trials 2015;16(224):1–19.