Surgical Treatment of Myasthenia Gravis : open vs minimally-invasive appro

ach

Dong Kwan Kim, M.D.

Dept. of Thoracic & Cardiovascular Surgery

Asan Medical Center

College of Medicine, University of Ulsan

History

Sauerbruch (1910) : first transcevical thymectomy

Blalock (1936) : first transsternal thymectomy

Cooper (1988) : extended transcervical thymectomy

Jaretzki (1988) : maximal thymectomy (transcevical and transsternal thymecto

my) Massaoka (1996) : extended thymectomy

Surgical Approach for Thymectomy

Transcervical : simple

extended with Cooper thymectomy retractor transcervial + partial sternal splitting Transsternal

: standard extended maximal Video-assisted thoracic surgery

: unilateral bilateral extended

MG Task Force Thymectomy Classification (2000)

T-1 Transcervical thymectomy Basic ExtendedT-2 Videoscopic thymectomy Classic VATS VATETT-3 Transsternal thymectomy Standard ExtendedT-4 Transcervical and transsternal thymectomy

VATS, video-assited thoracic surgery ; VATET, video-assisted thoracoscopic extended thymectomy.

Transcervical Thymectomy (I)

Advantage: smaller incision

less postoperative pain

Disadvantage : possibility of incomplete excision disable resection of mediastinal fatty tissue → extended cervical thymectomy with cooper thymectomy retractor

Transcervical Thymectomy (II)

ReferenceSurgical

Technique

Follow-upDuration

(yrs)

Complete Remission Rate (%)

Bril et al (1998) Transcervical 8.4 44.2

DeFilippi et al (1994) Transcervical 5.0 43.0

Papatestas et al (1981) Transcervical 5.0 24.0

Shrager et al (2002) Transcervical 4.6 39.7

Cooper et al (1998)

Transcervical 3.4 52.3

Transcervical Thymectomy with Partial Sternal Splitting

Study DateInstitut

eCases, N RR PR

Maggi 1989

Torino 662 (nT+T) 37.9% (crude, nT)15.7% (crude, T)  

Levasseur 1989

Paris 720 (nT+T)   85% (crude, nT)70% (crude, T)

Venuta 1999

Rome 232 (nT+T) 29% (crude, nT)14.5% (crude, T)  

Residual Thymus after Transcervical Thymectomy

Massoka(1982)

: residual thymus in all 6 reoperation case

Henze (1984)

: 20 pts. in 95 transcervical thymectomies

who underwent reoperation

-> 18 residual thymus

Rosenberg(1983)

: 11 residual thymus in 13 reoperated pts.

Transsternal Thymectomy

Advantage : good exposure

easy to removal of mediastinal fatty tiss

ue

complete resection

Disadvantage : larger incision

more postoperative pain

longer recovery time

Extent of Resection in Extended Transsternal Thymectomy

Extended Transsternal Thymectomy (I)

* Masaoka et al. Ann Thorac Surg 1996;62:853

* Palliation curve after thymectomy

Extended Transsternal Thymectomy (II)

* Masaoka et al. Ann Thorac Surg 1996;62:853

Extended Transsternal Thymectomy (III)Study Date Institute

Cases

N RR PR Remark

Olanow et al 1987

Durham 55 (nT) 64%(crude)    

Evoli et al 1988

Rome 247     62%(crude,nT)  

Huang et al198

8Taipei 74 (nT) 46%(crude) 40%(crude,T)  

Hatton et al198

9Boston 52 (nT) 26.9%(2y)    

Mulder et al 1989

Los Angeles 333 (nT+T) 36%(crude,nT+T)    

Lindberg et al199

2Gothenberg 86 (nT+T) 53%(crude,nT)    

Frist et al 1994

Nashville 42 (nT) 33%(crude)    

Masaoka et al 1996

Osaka, Nagoya

286 (nT) 45.8%(5yr)    

Scott and Detterbeck

1999

North Carolina

100 (nT+T)   78%(crude,nT+T)  

Tsuchida et al 1999

Niigata 94 (nT+T) 30.8%(crude,nT+T)    

Nieto et al199

9Madrid 61 (nT+T) 49.5%(5yr,nT+T)    

Klein et al199

9Dusseldorf 51 (nT+T) 40%(5yr,nT+T)    

Stern et al200

1Cincinnati 56 (nT+T) 50%(crude,nT+T)    

Budde et al 2001

Atlanta 92 (nT+T) 21%(crude,nT+T)  Limited sternotomy (T-

shape)

Mussi et al 2001

Pisa 91 (nT+T) >70% ａ (3yr,NT+T)  Kaplan-Mier method

Pego-Fernandes et al

2002

Sao Paulo 478 (nT+T) 12.7%(crude,NT+T)  Limited ste

rnotomy

Maximal Thymectomy (I)

Transcervical and transsternal thymectomy Advantage : good exposure enbloc resection of all surgically available thymus

Disadvantage : largest incision more postoperative pain longer recovery time possible more complication ra

te

Composite Anatomy of the Thymus

* Jaretzki et al. Neurology 1997;48:s52

Estimated Extent of Six Thymectomy Resectional Techniques

* Jaretzki et al. Neurology 1997;48:s52

Estetimated Extent of Seven ThymectomyThymectomy Technique Maxima

l

Extended Sternal

Standard Sternal

Basic Cervical

Extended

Cervical

VATS VATET

Neck

En bloc resection + 0 0 0 0 0 0

Accessory lateral lobes + 0 0 0 0 0 ±

Pretracheal fat + 0 0 0 0 0 +

Retrothyroid exploration + 0 0 0 0 0 ±

Visualize recurrent nerves

+ 0 0 0 0 0 ±

Mediastinum

En bloc resection + + 0 0 0 0 0

Tissue beyond phrenic nerves

+ + 0 0 ± ± ±

Sharp dissection on pericardium

+ ± 0 0 0 0 0

Tissue in aortopulmonary window and retrocaval + + 0 0 0 ? ?

Visualize both phrenic nerves + + 0 0 ± ± +* Jaretzki et al. Neurology 1997;48:s52

Comparative Remission Rates (uncorrected data)

* Jaretzki et al. J Thorac Cardiovasc Surg 1988;95:747

Maximal Thymectomy (II)Author Date Institute Cases, N RR PR

Olanow 1982 Durham 47 (nT+T) 61% (crude) 83% 

Fischer 1987 Cincinnati 27 (nT+T) 63% (crude) 90%

Ashour 1995 Riyadh 48 (nT) 34.8% (crude)86.8

%

Bulkley 1997 Baltimore 127 (nT+T)  86% (5y)

Jaretzki 1997 New York72 (nT)15 (T)

46% (crude)13% (crude)

 

Problems in Comparison of Results Based on Type of Thymectomy

Data collection problems Virtual lack of uniformity in the reporting of result : disease severity, response to therapy, lack of objective assessment criteria, different pts. and

accompanying therapy

Data analysis problems Uncorrected crude data is used mostly to compare the result of various thymectomy instead of K-M life table analylsis

Remission Rates ( life table analysis)

* Jaretzki et al. J Thorac Cardiovasc Surg 1988;95:747

Extended vs Maximal Thymectomy

Crude remission rate is similar between two procedures (55.7% vs 46%)

Higher morbidity in maximal thymectomy : nerve injury, postoperative bleeding, chylothorax Thymic tissue in retrocarinal fatty tissue in 7.

4% of investigated autopsy cases

* Masaoka Chest Surg Clin North Am 2001:2:369-387

Video-Assisted Thymectomy (I) Advantage Minimally invasive Less pain Less morbidity Less pulmonary dysfunction Shorter hospitalization Better cosmesis Less exacerbation of myasthenia perioperativelyDisadvantages Requires significant endoscopic experience Clinical experience is still relatively limited Comparability to standard approaches not definitely

VATS Thymectomy(Right side vs Left side approach)

Right-sided approach by Mack (1996), Yim (1997)

• More space & better visualization

• Easy identification of innominate vein

Left-sided approach by Roviaro (1994), Mineo (1998)

• More complete dissection of left pericardiophrenic angle perithymic fatty tissue & A-P window

Bilateral approach by Novellino (1994), Chang(2005)

Video-Assisted Thymectomy (II)Study (Date) Operation Institute Cases, N RR PR

Mack (1996)   Dallas 33 (nT+T) 18.6%(crude)87.9%(crude)

Mineo (2000)   Rome 31(nT) 36.0%(4yr)96.0%(4

yr)

Yim (2002)   Hong Kong 36 (nT) 13.9%(crude)  

Mantegazza (2003) (VATET) Milan 159 (nT) 51.0%(5yr, K-

M) 

Lin (2005)   Taipei 51 (nT) 27.5%(crude)92.1%(crude)

Chang (2005) (BVTx) Kaoshiung 15 (nT) 33.3%(crude)  

Tomulescu (2006)   Bucharest 107 (nT) 42.9%(5yr, K-

M) 

Video-assisted Thoracoscopic Thymectomy vs Extended Transsternal Thymectomy in

MG Review of 31 cases : 15 bilateral VATS thymectomy(BVTx) 16 extended transsternal thymcetomy(ETTx) BVTx had longer operative time and less intraoperative blo

od loss. No significant difference in duration of chest tube drainage

and hospital stay. Mean F-up time : 33.0 Mo vs 29.4 Mo The remission rate and degree of postoperative activities

of daily life improvement were not significantly different.

* Chang et al. Eur Surg Res 2005;379:199-203

Video-assisted Thoracoscopic Thymectomy vs Extended Transsternal Thymectomy in

MG

Review of 82 cases : 51 VATS thymectomy(VATx) through right side approach 31 extended transsternal thymcetomy(ETTx) No significant difference in severity of MG between two gro

ups. VATx had less hospital stay, operative time, and ICU stay. Mean F-up time : 48.0 Mo No significant postoperative improvement classification be

tween two groups.

* Lin et al. Int Surg 2005;90:36-41

Video-assisted Thoracoscopic Extended Thymectomy vs Extended Transsternal Thym

ectomy in MG

* Mantegazza et al. Journal of Neurological Science 2003;212:31-36

Review of 206 cases : 159 Video-assisted Thoracoscopic Extended thymectomy (VATET) 47 extended transsternal thymcetomy(ETTx) Mean F-up time : 3.9 yrs Complete remission rate at 6 years F-up by life-t

able analysis was 50.6% in VATET and 48.7% in ETTx(P=0.153).

Other Less Invasive Thymectomy

Takeo(2001), Ohta(2003) : VATS thymectomy by lifting sternum Uchiyama(2001) : Infrasternal mediastinoscopic thymectomy Hsu(2004) : subxiphoid video-assisted thoracoscopic extended thymectomy Ashton(2003), Bodner(2004) : robot-assisted thymectomy

Conclusions

The most widespread method is extended thymectomy. The result of VATS thymectomy was impressive but long t

erm follow-up and more study were needed. Prospective randomized clinical trial is needed to evaluat

e various thymectomy technique. The use of clinical research standards is required. Quality-of-life evaluation should be employed. The method of thymectomy should be decided by the pati

ent clinical status and surgeon’s expertness.