Mieke C. E. Hermans

Intraepidermal nerve fiber density and its application in sarcoidosis

Background: Intraepidermal nerve fiber density (IENFD) is considered a good diagnostic tool for small fiber neuropathy (SFN). Objectives: To assess stratified normative values for IENFD and determine the reliability and validity of IENFD in sarcoidosis. Methods: IENFD was assessed in 188 healthy volunteers and 72 patients with sarcoidosis (n = 58 with SFN symptoms, n = 14 without SFN symptoms). Healthy controls were stratified (for age and sex), resulting in 6 age groups (20–29, 30–39, … up to ≥70 years) containing at least 15 men and 15 women. A skin biopsy was taken in each participant 10 cm above the lateral malleolus and analyzed in accordance with the international guidelines using bright-field microscopy. Interobserver/intraobserver reliability of IENFD was examined. In the patients, a symptoms inventory questionnaire (SIQ; assessing SFN symptoms) and the Vickrey Peripheral Neuropathy Quality-of-Life Instrument-97 (PNQoL-97) were assessed to examine the discriminative ability of normative IENFD values. Results: There was a significant age-dependent decrease of IENFD values in healthy controls, with lower densities in men compared with women. Good interobserver/intraobserver reliability scores were obtained (κ values ≥0.90). A total of 21 patients with sarcoidosis had a reduced IENFD score (<5th percentile; 19 [32.8%] in patients with SFN symptoms, 2 [14.3%] in patients without SFN symptoms). The validity of the normative IENFD values was demonstrated by distinguishing between the SIQ scores and various PNQoL-97 values for the different patient groups. Conclusion: This study provides clinically applicable distal intraepidermal nerve fiber density normative values, showing age- and sex-related differences.

Rasch-built Overall Disability Scale (R-ODS) for immune-mediated peripheral neuropathies

Objective: To develop a patient-based, linearly weighted scale that captures activity and social participation limitations in patients with Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), and gammopathy-related polyneuropathy (MGUSP). Methods: A preliminary Rasch-built Overall Disability Scale (R-ODS) containing 146 activity and participation items was constructed, based on the WHO International Classification of Functioning, Disability and Health, literature search, and patient interviews. The preliminary R-ODS was assessed twice (interval: 2–4 weeks; test-retest reliability studies) in 294 patients who experienced GBS in the past (n = 174) or currently have stable CIDP (n = 80) or MGUSP (n = 40). Data were analyzed using the Rasch unidimensional measurement model (RUMM2020). Results: The preliminary R-ODS did not meet the Rasch model expectations. Based on disordered thresholds, misfit statistics, item bias, and local dependency, items were systematically removed to improve the model fit, regularly controlling the class intervals and model statistics. Finally, we succeeded in constructing a 24-item scale that fulfilled all Rasch requirements. “Reading a newspaper/book” and “eating” were the 2 easiest items; “standing for hours” and “running” were the most difficult ones. Good validity and reliability were obtained. Conclusion: The R-ODS is a linearly weighted scale that specifically captures activity and social participation limitations in patients with GBS, CIDP, and MGUSP. Compared to the Overall Disability Sum Score, the R-ODS represents a wider range of item difficulties, thereby better targeting patients with different ability levels. If responsive, the R-ODS will be valuable for future clinical trials and follow-up studies in these conditions.

Hereditary muscular dystrophies and the heart

Cardiac disease is a common clinical manifestation of neuromuscular disorders, particularly of muscular dystrophies. Heart muscle cells as well as specialized conducting myocardial fibres may be affected by the dystrophic process. The incidence and nature of cardiac involvement vary with different types of muscular dystrophies. Some mainly lead to myocardial disease, resulting in cardiomyopathy and heart failure, while others particularly affect the conduction system, leading to arrhythmias and sudden death. As prognosis of muscular dystrophy patients may be directly related to cardiac status, surveillance and timely management of cardiac complications are important. However, recognition of cardiac involvement requires active investigation and remains challenging since typical signs and symptoms of cardiac dysfunction may not be present and progression is unpredictable. In this review, we present a comprehensive overview of hereditary muscular dystrophies associated with cardiac disease to provide an efficient strategy for the expertise and management of these diseases.

Modifying the Medical Research Council grading system through Rasch analyses

The Medical Research Council grading system has served through decades for the evaluation of muscle strength and has been recognized as a cardinal feature of daily neurological, rehabilitation and general medicine examination of patients, despite being respectfully criticized due to the unequal width of its response options. No study has systematically examined, through modern psychometric approach, whether physicians are able to properly use the Medical Research Council grades. The objectives of this study were: (i) to investigate physicians’ ability to discriminate among the Medical Research Council categories in patients with different neuromuscular disorders and with various degrees of weakness through thresholds examination using Rasch analysis as a modern psychometric method; (ii) to examine possible factors influencing physicians’ ability to apply the Medical Research Council categories through differential item function analyses; and (iii) to examine whether the widely used Medical Research Council 12 muscles sum score in patients with Guillain–Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy would meet Rasch models expectations. A total of 1065 patients were included from nine cohorts with the following diseases: Guillain–Barré syndrome (n = 480); myotonic dystrophy type-1 (n = 169); chronic inflammatory demyelinating polyradiculoneuropathy (n = 139); limb-girdle muscular dystrophy (n = 105); multifocal motor neuropathy (n = 102); Pompes disease (n = 62) and monoclonal gammopathy of undetermined related polyneuropathy (n = 8). Medical Research Council data of 72 muscles were collected. Rasch analyses were performed on Medical Research Council data for each cohort separately and after pooling data at the muscle level to increase category frequencies, and on the Medical Research Council sum score in patients with Guillain–Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy. Disordered thresholds were demonstrated in 74–79% of the muscles examined, indicating physicians’ inability to discriminate between most Medical Research Council categories. Factors such as physicians’ experience or illness type did not influence these findings. Thresholds were restored after rescoring the Medical Research Council grades from six to four options (0, paralysis; 1, severe weakness; 2, slight weakness; 3, normal strength). The Medical Research Council sum score acceptably fulfilled Rasch model expectations after rescoring the response options and creating subsets to resolve local dependency and item bias on diagnosis. In conclusion, a modified, Rasch-built four response category Medical Research Council grading system is proposed, resolving clinicians’ inability to differentiate among its original response categories and improving clinical applicability. A modified Medical Research Council sum score at the interval level is presented and is recommended for future studies in Guillain–Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy.

Structural and functional cardiac changes in myotonic dystrophy type 1: a cardiovascular magnetic resonance study

BackgroundMyotonic dystrophy type 1 (MD1) is a neuromuscular disorder with potential involvement of the heart and increased risk of sudden death. Considering the importance of cardiomyopathy as a predictor of prognosis, we aimed to systematically evaluate and describe structural and functional cardiac alterations in patients with MD1.MethodsEighty MD1 patients underwent physical examination, electrocardiography (ECG), echocardiography and cardiovascular magnetic resonance (CMR). Blood samples were taken for determination of NT-proBNP plasma levels and CTG repeat length.ResultsFunctional and structural abnormalities were detected in 35 patients (44%). Left ventricular systolic dysfunction was found in 20 cases, left ventricular dilatation in 7 patients, and left ventricular hypertrophy in 6 patients. Myocardial fibrosis was seen in 10 patients (12.5%). In general, patients had low left ventricular mass indexes. Right ventricular involvement was uncommon and only seen together with left ventricular abnormalities. Functional or structural cardiac involvement was associated with age (p = 0.04), male gender (p < 0.001) and abnormal ECG (p < 0.001). Disease duration, CTG repeat length, severity of neuromuscular symptoms and NT-proBNP level did not predict the presence of myocardial abnormalities.ConclusionsCMR can be useful to detect early structural and functional myocardial abnormalities in patients with MD1. Myocardial involvement is strongly associated with conduction abnormalities, but a normal ECG does not exclude myocardial alterations. These findings lend support to the hypothesis that MD1 patients have a complex cardiac phenotype, including both myocardial and conduction system alteration.

Rasch-built myotonic dystrophy type 1 activity and participation scale (DM1-Activ)

We describe the development of an outcome measure of activity and participation for patients with myotonic dystrophy type 1 using the Rasch measurement model. A 49-item questionnaire was completed by 163 DM1 patients. Data were subsequently analyzed with Rasch software to design the item set to fit model expectations. Through systematic investigation of response category ordering, model fit, item bias, and local response dependency, we succeeded in constructing a 20-item unidimensional scale of activity and participation (DM1-Activ). High internal consistency (PSI=0.95) and good test-retest reliability values of item difficulty hierarchy and patient location were demonstrated. Patient measures had acceptable correlations with MRC sum scores and MIRS grades (ICC=0.69 and 0.71, respectively), indicating good external construct validity. DM1-Activ is a practical, reliable and valid outcome measure that fulfils all clinimetric requirements. Further evaluation of this scale is needed to provide a nomogram for clinical use.

Fatigue and daytime sleepiness scale in myotonic dystrophy type 1

Introduction: Fatigue and excessive daytime sleepiness are frequent complaints in myotonic dystrophy type 1 (DM1) that often overlap. We aimed to construct a combined fatigue and daytime sleepiness rating scale for DM1 using the Rasch measurement model. Methods: Questionnaires, including the Epworth Sleepiness Scale, Fatigue Severity Scale, and Daytime Sleepiness Scale, were completed by 354 patients. Data were subjected to Rasch analyses and tested for required measurement issues such as appropriate response categories, absence of item bias, local independence, and unidimensionality. Results: The initial 22 items did not meet Rasch model expectations. After rescoring and removing misfitting items, the final 12‐item scale showed good model fit and unidimensionality. High internal consistency (person separation index = 0.80) and validity were demonstrated. Conclusions: The Rasch‐built Fatigue and Daytime Sleepiness Scale, developed specifically for DM1 patients, provides interval measures on a single continuum. Its use is suggested for future clinical trials and therapeutic follow‐up. Muscle Nerve, 2013

Peripheral neuropathy in myotonic dystrophy type 1

Myotonic dystrophy 1 (DM1) is characterized by a wide range of clinical features. We aimed to verify the presence of peripheral nerve involvement in a large cohort of DM1 patients and to determine clinical consequences. A total of 93 patients underwent detailed neurological examination and nerve conduction studies. Additionally, balance impairment was assessed with the Berg Balance Scale and health status was evaluated with the SF‐36 health survey. Sensory symptoms were not reported and mild sensory signs were found in six patients. Electrophysiological abnormalities consistent with a diagnosis of neuropathy were found in 16 patients (17%). Peripheral nerve involvement was significantly associated with decreased muscle strength (p = 0.001) and absence of Achilles‐tendon reflexes (p = 0.003), but not with age or duration of neuromuscular symptoms. It had no significant effect on balance, mental or physical health. In conclusion, peripheral nerve involvement may be one of the multisystemic manifestations of DM1, but is usually subclinical. Other causes should be excluded when sensory symptoms or signs are severe.