Thymectomy for Juvenile Myasthenia
Abstract & Commentary
By Michael Rubin, MD
Professor of Clinical Neurology, Weill Cornell Medical College
Dr. Rubin reports no financial relationships relevant to this field of study.
Synopsis: Although never confirmed in a randomized clinical trial, thymectomy appears to be efficacious in children with antibody-positive myasthenia gravis.
Source: Heng HS, et al. Outcome of children with acetylcholine receptor (AChR) antibody positive juvenile myasthenia gravis following thymectomy. Neuromuscul Disord 2014:24:25-30.
Despite the lack of randomized, controlled trials, thymectomy is widely accepted as a treatment option for both seropositive and seronegative generalized myasthenia gravis (MG), even in the absence of thymoma. Thymectomy, however, remains controversial for the 10-16% of patients whose onset occurs before 15 years of age, and this retrospective review addresses the issue.
Medical record review was undertaken of patients with juvenile MG who underwent thymectomy between January 1996 and June 2010, at two London, UK, hospitals, Evelina Children's Hospital and Great Ormond Street Hospital for Children. Of 21 patients so identified, 20 had generalized MG, had undergone trans-sternal thymectomy, and are the subjects of this report. Disease severity was graded using the modified Osserman classification, grade 1 (focal disease) to grade 4 (life-threatening crisis), and patients were seen 1 month postoperatively, and every 3 months thereafter for a year. Response was rated using the Millichap and Dodge myasthenia scale, with A denoting complete remission, B good improvement needing medication, C slight improvement needing increased dosage of medication, D no change or worse, and E death.
Disease onset ranged from 13 months to 15.5 years of age. Median interval from disease onset to thymectomy was 9 months, with a median age at thymectomy of 11 years 1 month, ranging from 2 years 8 months to 16 years. Five children were younger than 10 years, of which two were younger than 3 years. All were acetylcholine receptor (AchR) antibody positive, with no correlation found between antibody level and disease severity. Prior to surgery, treatment included pyridostigmine (n = 20), oral prednisolone (n = 14), elective plasma exchange (n = 15), or intravenous immunoglobulin (n = 5). Thymic hyperplasia was found in nine patients, normal histology in six patients, thymoma in one patient, and no report was available for the remainder. At last follow-up, ranging from 10 months to almost 11 years (median 2.66 years), 19 of 20 were improved, with six in complete remission (A response), 12 showing good improvement but needing medication (B response), and one each showing C and D response, the non-responder being the patient with thymoma. Thymectomy is safe and efficacious for the treatment of AchR antibody positive juvenile myasthenia gravis.
Commentary
Thymic resection may be done by a conventional trans-sternal approach or via video-assisted thoracoscopic surgery (VATS). How do they compare? Among 120 patients with early-stage thymoma, who underwent thymectomy between 1991-2010 at the National Taiwan University Hospital, Taipei, Taiwan, 76 underwent VATS and 44 conventional sternotomy.1 Among the VATS group, 35 patients (46.1%) presented with myasthenia, compared to 14 (31.8%) in the sternotomy group. Neither group experienced significant complications or surgical-related mortality. Both groups had similar overall survival, recurrence-free survival, and time to tumor recurrence, but the VATS group experienced a significantly shorter time for both chest tube pleural drainage and hospital stay. Duration of surgery, visual analog pain score, and intraoperative blood loss were not significantly different between the groups, though all were lower in the VATS patients. VATS appears to be as good as, if not preferable to, sternotomy for early-stage thymoma removal, and, likely, for thymectomy in myasthenia as well.
Reference
- Liu TJ, et al. Video-assisted thoracoscopic surgical thymectomy to treat early thymoma: A comparison with the conventional transsternal approach. Ann Surg Oncol 2014;21:322-328.
