Myasthenia gravis is a relatively rare autoimmune condition that affects neuromuscular junctions, causing weakness and fatigue. The reported rates of incidence (number of new cases) and prevalence (number of all cases) have increased over the last 60 years, according to Dr. Aisling S. Carr and collaborators in Northern Ireland. These authors identified 55 population-based epidemiological studies for review. Overall, an average of 77.7 cases per million persons has been reported. There are wide variations in reports from different studies, so the authors suggested that variations in diagnosis rates are important, as well as environmental factors.
About half of the studies show a bimodal age distribution of myasthenia gravis new cases in women. The first peak is in the age group 20-29, and the second peak is in the age group 70-79. Other studies show a steady increase in incidence with age for women up to age 79. Diagnosis after age 80 is less common. Men have approximately the same overall risk as women, but without the peak at younger ages.
Treatment options include corticosteroids, immunosuppressive agents, and anticholinesterase drugs, as well as surgery to remove the thymus gland. Dr. Iwao Takanami and coworkers in Japan reported that standard thymectomy is safe and effective, based on their study of 54 patients. Those with severe symptoms and shorter duration of illness experienced more benefits from surgery.
“The value of thymectomy in improving the symptoms of patients with MG is well established, Takanami noted. “Controversy, however, remains in regard to the extent of surgery and the indications for it.” Surgical options include transsternal, transcervical, and video assisted.
Dr. Imran Zahid and coauthors in London, UK, reported that video-assisted surgery is preferable because patients need less postoperative medication and have better cosmetic results with this approach. Video-assisted surgery requires a longer operating time, but this disadvantage is offset by less time spent in intensive care units. The treatment outcomes are equivalent for video-assisted and transsternal surgeries.
Carr AS et al, “A systematic review of population based epidemiological
studies in myasthenia gravis”, BMC Neurology 2010; 10: 46-54.
Takanami I et al, “Therapeutic outcomes in thymectomied patients with
myasthenia gravis”, Ann Thorac Cardiovasc Surg 2009; 15: 373-77.
Zahid I et al, “Video-assisted thoracoscopic surgery or transsternal
thymectomy in the treatment of myasthenia gravis?” Interact CardioVasc
Thorac Surg 2011; 12: 40-46. http://www.ncbi.nlm.nih.gov/pubmed/20943831
Reviewed May 26, 2011
Edited by Alison Stanton
Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D.
in Physics and an M.S. in Macromolecular Science and Engineering. Her
background includes academic and industrial research in materials
science. She currently writes song lyrics and health articles.