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Brief Report
13 (
2
); 321-325
doi:
10.1055/s-0042-1743444

Outcomes after Thymectomy in Patients with Thymomatous Myasthenia Gravis

Department of Thoracic Surgery, General Referral Hospital of Niamey, Niamey, Niger
Faculty of Medicine and Pharmacy, Abdou Moumouni University of Niamey, Niamey, Niger
Department of Thoracic Surgery, Hassan II University Teaching Hospital of Fez, Fez, Morocco
Department of Neurology, National Hospital of Niamey, Niamey, Niger
Department of Neurology, Hassan II University Teaching Hospital of Fez, Fez, Morocco
Faculty of Medicine and Pharmacy, Sidi Mohammed Ben Abdallah University of Fez, Fez, Morocco

Toudou-Daouda Moussa, MD Department of Neurology, National Hospital of Niamey P.O. Box 238, Niamey Niger moussatoudou@gmail.com

Licence
This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)
Disclaimer:
This article was originally published by Thieme Medical and Scientific Publishers Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.

Abstract

Abstract

Objectives This article describes the clinical outcomes after thymectomy in patients with thymomatous myasthenia gravis (T-MG) managed in the department of thoracic surgery of Hassan II University Hospital of Fez, Fez, Morocco.

Materials and Methods We performed a retrospective analysis of medical records of 16 patients with T-MG between January 2009 and January 2017.

Results There were 11 women and 5 men with a median age of 40 years at the thymectomy time and a median time of onset of symptoms to thymectomy of 12 months. At the preoperative evaluation (Myasthenia Gravis Foundation of America [MGFA] clinical classification), 7 patients were class II, 7 class III, and 2 class IV. Nine patients were in Masaoka stage I, and the remaining 7 patients stage II. We recorded one case of postoperative myasthenic crisis. At 3 years of follow-up after thymectomy, 6 patients had complete stable remission and the other 10 patients improved. Of these patients with clinical improvement, 6 patients were in MGFA class I and the remaining 4 patients class II.

Conclusion The present study shows the beneficial effect of thymectomy in patients with T-MG. Postoperative clinical outcomes seem to be better when the preoperative severity of myasthenic symptoms is mild (MGFA class II).

Keywords

myasthenia gravis
thymoma
thymectomy
clinical improvement
complete stable remission rate

Introduction

The beneficial effect of thymectomy in myasthenia gravis (MG) management was first reported in 1941 by Blalock et al.1 Thymectomy increases the rates of complete stable remission (CSR) in the patients with MG who underwent thymectomy compared with those managed medically alone.2 3 In Morocco, few studies have been reported on thymectomy in MG management.4 5 The present study aimed to describe the clinical outcomes after thymectomy in patients with thymomatous MG (T-MG) managed in the department of thoracic surgery of Hassan II University Hospital of Fez, Fez, Morocco.

Materials and Methods

Study Design and Patients

We performed a retrospective analysis of the medical records of 16 patients with T-MG who underwent thymectomy in the department of thoracic surgery of the Hassan II University Hospital of Fez between January 2009 and January 2017. The diagnosis of MG was made by the neurologists of the department of neurology of the Hassan II University Hospital of Fez. All patients were diagnosed with seropositive generalized MG and referred to the department of thoracic surgery for thymectomy. For each patient, a preoperative clinical evaluation was performed by a neurologist, and the Myasthenia Gravis Foundation of America (MGFA) clinical classification6 was used for clinical staging. For each patient, the postoperative clinical evaluation data using quantitative myasthenia gravis score were collected up to 3 years after surgery, as well as the modification of medical treatment. MGFA postintervention status was used to assess the clinical status of patients after thymectomy.

Ethical Approval

Ethics approval for this study was not required because it was a retrospective study, and the patient management was not affected. The written informed consent has been waived by the Institutional Review Board of Hassan II University Teaching Hospital of Fez.

Results

There were 11 women and 5 men (sex ratio females to males at 2.2). Table 1 details the baseline characteristics of the 16 patients. The median age of the patients was 40 years at the thymectomy time and the median time of onset of symptoms to thymectomy was 12 months. Before thymectomy, 7 patients were in MGFA class II, 7 patients class III, and 2 patients class IV. In 3 patients (patients 4, 6, and 9), a cure of intravenous immunoglobulins (2 g/kg administered over 5 days) was performed to improve myasthenic symptoms before thymectomy. Before surgery, 6 patients were under azathioprine (AZT) and pyridostigmine bromide (PB); 3 patients under AZT, PB, and prednisone (PN); and 3 patients under PB and PN. Four patients were under PB alone.

Table 1
Baseline characteristics of the 16 patients with seropositive generalized myasthenia gravis

Patient no.

Sex

Age at surgery (y)

Onset to surgery (mo)

MGFA classa

Acetylcholinesterase inhibitor

Corticosteroid or immunosuppression therapy

Chest CT

1

M

46

5

IIa

PB, 180 mg

PN, 50 mg

Thymoma

2

F

25

120

IIb

PB, 240 mg

AZT, 100 mg

No thymoma

3

M

35

48

IIb

PB, 240 mg

AZT, 150 mg

Thymoma

4

F

45

48

IIIb

PB, 300 mg

AZT, 150 mg

Thymoma

5

M

48

108

IIa

PB, 240 mg

AZT, 100 mg

Thymoma

6

M

48

12

IVa

PB, 240 mg

PN, 20 mg + AZT, 150 mg

Thymoma

7

M

40

3

IIIa

PB, 300 mg

Thymoma

8

F

36

12

IIIa

PB, 300 mg

PN, 20 mg + AZT, 150 mg

No thymoma

9

F

53

24

IVb

PB, 240 mg

AZT, 150 mg

Thymoma

10

F

52

6

IIIa

AMBC, 50 mg

PN, 40 mg

Thymoma

11

F

17

15

IIIa

PB, 240 mg

PN, 10 mg + AZT, 150 mg

Thymoma

12

F

29

36

IIa

PB, 240 mg

AZT, 100 mg

Thymoma

13

F

62

6

IIIa

PB, 300 mg

PN, 50 mg

Thymoma

14

F

35

2

IIa

PB, 240 mg

Thymoma

15

F

39

1

IIa

PB, 240 mg

Thymoma

16

F

40

3

IIIa

PB, 240 mg

Thymoma

Patient no.

Preoperative preparation

Surgical approach

Surgical gesture

Postoperative course

WHO histologic classification

Masaoka clinical stage

Adjuvant therapy

1

No

VTS

TEAFT

Simple

B1 thymoma

I

No

2

No

TS

TEAFT

Hemothorax

B1 thymoma

I

No

3

No

VTS

TEAFT

Simple

TC

II

CT

4

IVIG

VTS

TEAFT

Simple

TC

II

RT

5

No

VTS

TEAFT

Simple

B3 thymoma

I

RT

6

IVIG

VTS

TEAFT

Simple

B2 thymoma

II

RT

7

No

VTS

TEAFT

Simple

B1 thymoma

I

No

8

No

VTS

TEAFT

Simple

B1 thymoma

I

No

9

IVIG

VTS

TEAFT

Simple

AB thymoma

II

CT

10

No

VTS

TEAFT

MC

B2 thymoma

I

No

11

No

VTS

TEAFT

Simple

B1 thymoma

I

No

12

No

VTS

TEAFT

Simple

B1 thymoma

I

No

13

No

VTS

TEAFT

Simple

AB thymoma

II

No

14

No

VTS

TEAFT

Simple

B1 thymoma

II

No

15

No

VTS

TEAFT

Simple

B2 thymoma

II

RT

16

No

VTS

TEAFT

Simple

B1 thymoma

I

No

Abbreviations: AMBC, ambenonium chloride; AZT, azathioprine; CT, chemotherapy; CT, computed tomography; F, female; IVIG, intravenous immunoglobulins; M, male; MC, myasthenic crisis; MGFA, Myasthenia Gravis Foundation of America; PB, pyridostigmine bromide; PN, prednisone; RT, radiotherapy; TC, thymic carcinoma; TEAFT, thymectomy enlarged to the adjacent fatty tissues; TS, thoracoscopy; VTS, vertical total sternotomy; WHO, World Health Organization.

Note: Stage I corresponds to macroscopically completely encapsulated and microscopically no capsular invasion; Stage II, macroscopic invasion into surrounding fatty tissue or mediastinal pleura.

Class II corresponds to mild weakness; class III, moderate weakness; class IV, severe weakness; a indicates predominantly limb and axial presentation; b, predominantly bulbar presentation.

The surgical approach was a vertical total sternotomy in 15 patients and thoracoscopy in the other patient (patient 2). All patients had undergone a thymectomy enlarged to the adjacent fatty tissues. According to Masaoka's clinical staging,7 9 patients were classified as stage I and stage II for the other 7. The postoperative course was simple in 14 patients, while one patient (patient 10) had presented a postoperative myasthenic crisis and the other patient (patient 2) hemothorax.

According to the World Health Organization histologic classification,8 the histologic analysis showed AB thymoma in 2 patients, B1 in 8 patients, B2 in 3 patients, B3 in 1 patient, and thymic carcinoma in 2 patients. Adjuvant therapy (chemotherapy or radiotherapy) was performed in the 2 patients with thymic carcinoma (patients 3 and 4), the patient with B3 thymoma (patient 5), and in the 3 patients with B2 thymoma (patients 6, 9, and 15).

At 3 years of follow-up after thymectomy (Table 2), 6 patients had CSR and the other 10 patients improved with reduced doses of PB and/or AZT. Of these 10 patients who improved, 6 patients were in MGFA class I and the remaining 4 patients class II. There were no cases of disease exacerbation or myasthenic crisis during the 3 years of follow-up in the 10 patients who improved. Among the 6 patients with CSR, 4 patients (patients 2, 12, 14, and 15) were in MGFA class II and the other 2 patients (patients 7 and 11) class III at the preoperative evaluation. Five patients (patients 2, 7, 11, 12, and 14) among the 6 patients with CSR had the histologic type B1 thymoma while the other patient (patient 15) had a B2 thymoma. We recorded no cases of recurrence of MG in the 6 patients with CSR. We also did not record any deaths during the follow-up period in the 16 patients.

Table 2
Outcomes at 3 years after surgery

Patient no.

MGFA classa

Acetylcholinesterase inhibitor

Immunosuppression therapy

MGFA postintervention status

1

I

PB, 120 mg

AZT, 100 mg

Improved

2

CSR

3

I

PB, 120 mg

AZT, 75 mg

Improved

4

IIa

PB, 180 mg

AZT, 100 mg

Improved

5

I

PB, 120 mg

AZT, 50 mg

Improved

6

IIa

PB, 120 mg

AZT, 100 mg

Improved

7

CSR

8

I

PB, 120 mg

AZT, 75 mg

Improved

9

I

PB, 120 mg

AZT, 100 mg

Improved

10

I

AMBC, 20 mg

AZT, 100 mg

Improved

11

CSR

12

CSR

13

IIa

PB, 120 mg

AZT, 100 mg

Improved

14

CSR

15

CSR

16

IIa

PB, 120 mg

AZT, 100 mg

Improved

Abbreviations: AMBC, ambenonium chloride; CSR, complete stable remission; MGFA, Myasthenia Gravis Foundation of America; PB, pyridostigmine bromide.

Class I corresponds to ocular muscle weakness with or no weakness of eye closure; Class IIa, mild weakness predominantly affecting limb and axial muscles.

Discussion

The present study shows a rate of CSR of 37.5% and an improvement rate of 62.5% at 3 years of follow-up after thymectomy in patients with T-MG, aged 17 to 62 years (median age 40 years).

The T-MG forms are more severe, characterized not only by the predominance of bulbar and respiratory signs but also by the high frequency of postoperative myasthenic crises varying from 17 to 35.2%.4 9 The frequency of postoperative myasthenic crisis was 6.3% in the present study. Findings inferior to ours have also been reported in patients with T-MG, ranging from 3 to 3.4%.10 11 The rates of CSR after thymectomy in patients with T-MG are variable. Nguyen et al12 reported a rate of CSR of 22.6% at 12 months of follow-up, whereas Bouchikh et al4 and Agasthian and Lin10 reported at 5 years of follow-up a rate of CSR of 7 and 28%, respectively. A study with a follow-up of 24 to 56 months after thymectomy (a follow-up period similar to ours which is 36 months) reports a rate of CSR of 14.9%,9 a result lower than ours which is 37.5%. Studies have reported mild preoperative severity of myasthenic symptoms (MGFA class I–II) as an independent factor of postoperative CSR in patients with T-MG.11 13 In the present study, 7 patients (43.8%) were in MGFA class II on the whole sample, and among the 6 patients with CSR, 5 patients (5/6 = 83.3%) were in MGFA class II. The variability of the CSR rates between studies in patients with T-MG could be explained both by the degree of the preoperative severity of myasthenic symptoms and the duration of postoperative follow-up period, as demonstrated in the study by Nguyen et al.12

A study has shown that patients with thymoma had a higher rate of recurrence of MG than those without thymoma.9 The rate of recurrence of MG ranges from 3 to 7.5% in patients with thymoma.9 12 Agasthian and Lin10 do not report a recurrence of MG in their patients. In the present study, we recorded no cases of disease exacerbation or myasthenic crisis in the patients who improved or of recurrence of MG in the patients with CSR during the 3-year follow-up period after thymectomy. In addition, we did not record any deaths during the follow-up period in the present study.

The main limitations of the present study were its retrospective nature, the small sample size, and the postoperative follow-up period relatively short (36 months).

Conclusion

The present study shows the beneficial effect of thymectomy in patients with T-MG. Postoperative clinical outcomes seem to be better when the preoperative severity of myasthenic symptoms is mild (MGFA class II). Although so modest due to the small sample size, the results of this study could help the neurologists of our institution choose the alright patients with T-MG to suggest for thymectomy.

Conflict of Interest

None declared.

Funding None.

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