There is no difference in the functional outcome of patients with a myasthenic exacerbation treated with either IVIg or plasma exhange

 

Clinical Problem: Mr. NMJ is a 65 yo man with known myasthenia gravis (MG). He presents to the ER with an acute myasthenic episode of difficulty breathing which requires intubation/ventilation and ICU admission.

 

Clinical Question: In patients with MG crisis, does IVIg or plasma exchange (PE) treatment result in a better functional outcome?

 

Clinical Bottom Lines

1. No difference was observed in the functional outcome of patients with a MG exacerbation treated with IVIg or PE at 2 weeks follow-up.

2. There was a trend towards a more rapid treatment response with PE (9d) vs. IVIg (>15d, p=0.14).

3. More adverse events occurred with PE (8/41) vs. IVIg treatment (1/48, p=0.01). 2 of the 8 events in the PE group were clinically significant (femoral vein thrombosis, retroperitoneal hemorrhage). NNH = 5.8 (3.3, 22.3)

 

Evidence

Randomized, prospective, non-blinded, multicenter trial (7 centers) assessing the efficacy of IVIg vs. PE in MG exacerbation. 87 patients included in the study, 41 received PE (3 cycles of 1.5 volumes) and 46 IVIg (0.4g/kg for 3 or 5 days). Endpoints: absolute variation in myasthenic muscular score (MMS) in 15 days. Secondary endpoints included time to treatment response (20 point increase in MMS) within 2 weeks and AchR status at 15 days.

 

Data

 

PE
(95% CI)

IVIg
(95% CI)

 

Mean variation in MMS at day 15

16.6
(11.6, 21.6)

15.6
(10.9, 20.3)

p=0.65

# of Rx responses within 2 weeks

26/41

22/48

 

Median time to Rx response

9d

15d

p=0.14

Mean variation in AchR status

-13.8%
(-40.8, 13.2)

-16.8%
(-24.9, 58.5)

p=0.36

Adverse events

19.5%
(7.4, 31.6)

2.2%
(0, 6.4)

p=0.01

NOTE: "Rx response" = 20 point increase in MMS.

 

Comments

1. Although the MMS is a valid and reliable scale (J. Neurol. 247:286-290, 2000), it's responsiveness (ability to detect a change) has not yet been demonstrated. The clinical significance of a 20 point change in MMS is uncertain.

 

2. The effect of PE and IVIg have both been shown to be transient, lasting several months. It would have been useful to determine if one treatment provided a more prolonged effect/benefit.

 

3. The trial was not designed to demonstrate equivalence of IVIg and PE for MG exacerbation.

 

4. One potential confounding factor in this study is that anticholinesterase medications were used as needed. The details of dosage and frequency received by each treatment group was not described.

 

Reference:

Gajdos et al. (1997) Clinical trial of PE and high dose IVIg in myasthenia gravis. Ann. Neurol. 41:789-796.

 

Key Words:  myasthenia gravis, ivig, plasma exchange

 

Appraiser: Miguel Bussiere and the UWO Evidence Based Neurology Group

 

Date appraised: December 2001

                                                           

Copyright 2002-2003

Evidence Based Neurology Group

University of Western Ontario