Myasthenia Gravis : en retrospektiv journalstudie ved Ullevål universitetssykehus i 2005

Abstract

Myasthenia Gravis: a retrospective study of case records at Ullevål University Hospital in 2005

Medical student Hilde Teigen Andås Medical student Tahira R. Ahmad Guidance by Chantal ME Tallaksen Department of Neurology, UUH

Background Myasthenia gravis (MG) is an autoimmune neurological disease caused by a disturbance in the neuromuscular transmission. The most frequent type is associated with the presence of antibodies to the acetylcholine receptor (AChR) in the neuromuscular junction (80-85% of the cases). The world prevalence of MG is estimated to be between 8-15/100 000.

Objectives and hypothesis Our main objectives were to establish the prevalence of myasthenia gravis at Ullevål University Hospital in August 2005, and to examine how various factors influence the course of the disease; > age at onset > severity at onset > antibodies > treatment

We also wanted to confirm in our hospital population that 1. MG most frequently affects fertile women 2. The older group of patients have a more severe illness 3. Elders have better effect of treatment

Design A study of case records.

Data and methodology Myasthenia gravis is diagnosed in the hospital at the department of neurology. This implies that all patients with MG at some time have been examined at a hospital. We searched the hospital’s archives for MG patients the last 15 years using the ICD-10 and ICD-9 criteria’s. We found a total of 150 patients. After examining the case records we could include 80 patients who were still alive and had a verified MG in our study. We divided our patient material in two groups, group I with disease onset under 50 years, group II with disease onset after 50 years. It is important to be aware that our data might be insufficient because of faulty case records. The data was registered in Microsoft Excel and made anonymous. The statistical analysis was preformed using SSPS.

Results There are twice as many women than men in our material. In group I (56% of the patients) 32% were men and 67% were women. Men had a milder condition, but there wasn’t a clear difference between the women. 81% of the patients had documented elevated AChR antibodies. There was no significant difference in respect of antibodies between group 1 and 2. 60% of the patients were thymectomized, with no difference between men and women. All men and 80% of the women in group 1 were thymectomized, compared to 20% and 31% in group 2.

Discussion The prevalence of MG in our population at August 1st 2005 was 10.5/100 000. All our hypotheses were verified in our material. 81% of the patients had positive AChR antibodies, which concurs with literature. 20 % (6) of the women diagnosed before 50 years of age were not thymectomized. Eight patients diagnosed after the age of fifty were thymectomized. This is higher than expected, but six of these had a thymoma. Our study confirms current literature reports about MG patients, particularly the differences between the patients with early and late onset. The hospital reports were unfortunately often insufficient to study these differences in details, and more detailed studies (without anonymity) would be necessary to further examine these differences.