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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.