…an understanding of the diagnosis and management of muscle diseases is essential for all neurologists, as myopathies can be encountered in all neurologic settings… whether as primary myopathic disorders or as complications of the treatment of other neurologic or systemic diseases.
Despite what is likely a common inclination toward relegation to the subspecialist, an understanding of the diagnosis and management of muscle diseases is essential for all neurologists, as myopathies can be encountered in all neurologic settings (both general and subspecialty practices), whether as primary myopathic disorders or as complications of the treatment of other neurologic or systemic diseases. In this issue, Guest Editor Hannah R. Briemberg, MD, FRCPC, clinical associate professor of neurology at the University of British Columbia, and a member of the Continuum Editorial Board, has assembled a group of world-class experts to provide us with the most up-to-date understanding of the clinical features, increasingly characterized disease mechanisms, and diagnosis and management of our patients with muscle diseases and our patients with disorders of the neuromuscular junction.
Drs Laura K. Rosow and Anthony A. Amato open the issue with an extensive overview of electrodiagnostic testing, the most current and evolving aspects of magnetic resonance and ultrasound imaging, and the role of muscle biopsy in the investigation of our patients with muscle disease. Next, Dr Shannon L. Venance reviews the approach to the patient with hyperCKemia, a common clinical scenario for which our neurologic expertise is requested in both inpatient and outpatient settings. Drs Hans D. Katzberg and Charles D. Kassardjian then discuss the muscle diseases that occur because of various endocrinopathies, as well as from toxicity, particularly from some commonly encountered medications. Dr Mark A. Tarnopolsky next provides a detailed overview of the molecular pathophysiology of the metabolic myopathies as a framework to his discussion of the clinical features and distinct diagnostic and management issues with regard to glycogen-storage diseases, fatty acid oxidation defects, and mitochondrial myopathies.
Dr Andrew L. Mammen then reviews the most current diagnostic and management considerations relating to the autoimmune myopathies, particularly dermatomyositis, immune-mediated necrotizing myopathy, antisynthetase syndrome, and (the currently felt to be rare) polymyositis. Dr Steven A. Greenberg then provides an overview of the unique clinical aspects of inclusion body myositis and the growing understanding of its pathophysiologic underpinnings, including a recently discovered autoantigen biomarker associated with this disorder, supporting its status as an autoimmune myopathy.
Dr Valeria A. Sansone next discusses the unique clinical, diagnostic, and management considerations with regard to the myotonic dystrophies (myotonic dystrophy type 1 and myotonic dystrophy type 2) as well as the nondystrophic myotonias, including the sodium and chloride channelopathies. Drs Jeffrey M. Statland and Rabi Tawil then provide us with a review of the clinical and pathophysiologic features of facioscapulohumeral muscular dystrophy, a disorder in which two unique genetic subtypes are now known to involve a shared downstream molecular pathophysiology resulting in expression of a toxic protein. Drs Jean K. Mah and Jeffrey T. Joseph next provide a detailed overview of the congenital myopathies, which are disorders that, despite being congenital, can sometimes progress or even present in adulthood and, therefore, need to be on the adult neurologist’s radar. In the final article in the issue related to muscle disease, Drs Stanley Jones P. Iyadurai and John T. Kissel extensively review the diagnosis and management considerations relating to the limb-girdle muscular dystrophies and the dystrophinopathies, including a discussion of the current role and possible pitfalls of modern genetic testing.
In the final review article of the issue, Dr Michael W. Nicolle discusses the pathophysiology, clinical features, neurophysiologic and laboratory diagnosis, and the most up-to-date management considerations for myasthenia gravis and Lambert-Eaton myasthenic syndrome. Some readers may note that the last time neuromuscular junction disorders were covered in the Continuum curriculum, we placed them in the peripheral nerve issue, but Dr Briemberg and I felt that disorders of the neuromuscular junction are more at home in an issue on muscle disease, where they now share equal billing in the issue’s name.
In the Ethical and Medicolegal Issues section, Dr Zachary Simmons discusses the ethical issues underlying genetic testing of presymptomatic individuals at risk for progressive myopathy. In the Practice Issues article, Dr Anant M. Shenoy updates us on the concept of participation in registries in a neurologic practice, using registry participation in neuromuscular disease as an example. In the Coding article (available as online-only content at www.ContinuumJournal.com and on the Continuum apps for iPad and Android), Drs Lyell K. Jones Jr and John P. Ney use illustrative case examples to discuss the many issues involved in the evaluation and management, procedural (including electrodiagnostic and ultrasound), and diagnosis coding in muscle disease.
As with every Continuum issue, several opportunities exist for CME. After reading the issue and taking the Postreading Self-Assessment and CME Test written by Drs Douglas J. Gelb and Ronnie Bergen, you may earn up to 12 AMA PRA Category 1 Credits™ toward self-assessment and CME. The Patient Management Problem, written by Dr Briemberg, describes the case of a 55-year-old man with a 6-month history of progressive muscle weakness and hyperCKemia. By following this patient’s case and answering multiple-choice questions corresponding to diagnostic and management decision points along his course, you will have the opportunity to earn up to 2 AMA PRA Category 1 CME Credits.
I would like to extend my sincere gratitude to Dr Briemberg for her remarkable devotion to all aspects of this issue from its conception to its publication, and I would also like to thank her and each of the expert contributors to this issue for providing us with the benefit of their tremendous experience and expertise, which we can all use as we diagnose, manage, and counsel our patients with disorders of muscle and the neuromuscular junction.
—Steven L. Lewis, MD, FAAN