Surgical Science, 2011, 2, 393-396
doi:10.4236/ss.2011.27086 Published Online September 2011 (
Copyright © 2011 SciRes. SS
Robotic–Assisted Thymectomy in Patients with
Nonthymomatous Myasthenia Gravis
Iskander Al-Githmi
Department of Surgery, Division of Cardiothoracic Surgery, King Abdulaziz University Ho spital, Jeddah,
Saudi Arabia
Received August 2, 2011; revised August 23, 2011; accepted September 1, 2011
Complete removal of the thymus and fatty tissue adherent to pericardium is crucial for treating myasthenia
gravis. Our aim was to analyze our surgical and clinical results and early experience of robot-assisted thy-
mectomy in patients with nonthymomatous myasthenia gravis. Between January 2008 and October 2010, 8
patients, all women, with nonthymomatous myasthenia gravis underwent robot-assisted thymectomy using a
3-port, left-sided approach. There were no operative mortality; 1 patient had left phrenic nerve injury. Com-
plete remission was achieved in 25% of the patients at 18 months’ follow-up. There was no significant
agreement between preoperative computed tomography and histopathology finding (kappa = 0.059; P = 0.85)
and no significant correlation between age and duration of symptoms (P = 0.51). Robotic-assisted thymec-
tomy is promising procedure. It can be performed safely and effectively. With follow-up greater than 12
months, 87.5% of the patients who underwent robot-assisted thymectomy demonstrated clinical improve-
Keywords: Myasthenia Gravis, Nonthymoma, Robot, Thymectomy
1. Introduction
Myasthenia gravis is an autoimmune disease affecting
postsynaptic nicotinic acetylcholine receptors at the neu-
romuscular junction block producing neuromuscular
transmission-producing muscular weakness of striated
Thymectomy is an established therapy in treating my-
asthenia gravis. Ferdinand Sauerbruch performed the
first successful thymectomy in a patient with myasthenia
gravis in 1911 in Zurich [1]. The efficacy of thymectomy
depends on complete removal of all thymic tissue. In
1941, Blalock said, “Complete removal of all thymus
tissue offers the best chance of altering the course of the
disease” [2].
Multiple described surgical approaches to thymectomy
include transcervical thymectomy [3], transsternal thy-
mectomy [4], infrasternal subxiphoid mediastinoscopic
thymectomy [5], and video-assisted thoracoscopic thy-
mectomy [6-8]. Introduction of robotic surgical-assisted
system contributed to the field of minimally invasive
surgery [9]. Yoshino described the first robotic thymec-
tomy in treating small thymoma [10]. However; ro-
bot-assisted thymectomy has been reported with good
short-term results. Only scant data are available on the
long-term results of robot-assisted thymectomy for my-
asthenia gravis. It is uncertain which patients may benefit
from robot-assisted thymectomy. This study sought to
analyze the surgical and clinical results of robot-assisted
thymectomy in patients with nonthymomatous myasthe-
nia gravis.
2. Materials and Methods
Between January 2008 and October 2010, 8 patients all
women (mean age, 28 y; range, 16 - 46 y) with nonthy-
momatous myasthenia gravis referred by neurologists
underwent robot-assisted thymectomy by 1 cardiotho-
racic surgeon at King Abdulaziz University Hospital,
Jeddah, Saudi Arabia. Preoperative patient clinical char-
acteristics, duration of symptoms, preoperative acetyl-
choline receptors antibody, preoperative Osserman clas-
sification, and computed tomogram of chest finding are
shown in (Table 1).
The diagnosis of myasthenia gravis was based on
clinical features, result of electromyography (decrement-
394 I. Al-GITHMI
Table 1. Preoperative demographic data.
Patient Characteristics Number
Mean age (y) 28 (16 - 46)
Mean symptoms duration (m) 7.75 (3-12)
CT scan chest
3 (37.5%)
5 (62.5%)
Acetylcholine receptor antibody
5 (62.5%)
3 (37.5%)
Osserman stage
Stage I
Stage IIa
Stage IIb
Stage III
Stage IV
0 (0.0%)
2 (25%)
5 (62.5%)
0 (0.0%)
1 (12.5%)
8 (100%)
5 (62.5%)
3 (37.5%)
tal response to repetitive nerve stimulation), and/or
demonstration of circulating antibodies against acetyl-
choline receptors.
Osserman classification was used for myasthenia gra-
vis staging: stage I, ocular myasthenia gravis; stage IIa,
mild generalized myasthenia gravis; stage IIb, moderate
myasthenia gravis with bulbar involvement; stage III,
acute fulminant myasthenia gravis; and stage IV, severe
late myasthenia gravis (Table 2).
Preoperative evaluation included thoracic computed
tomographic scan and pulmonary function test in all pa-
tients. Preoperative preparation included 3 sessions of
plasmapheresis in all patients. Informed consent was
obtained from all patients after explaining the procedure,
different approach of surgical technique, and potential
complications. The surgeries were performed using the
de Vinci system (Intuitive Surgical, Sunnyvale, CA,
USA) through a 3-port left-sided approach. The De
Table 2. Modified osserman classifications.
Stage Definition
I Ocular myasthenia gravis: involvement of extraocular
muscles with diplopia and ptosis.
Mild generalized myasthenia gravis: ocular symptoms are
associate to slow involvement of bulbar (dysphagia and
dysarthria) and skeletal muscles (generalized weakness).
Respiratory muscles are spared.
Moderately generalized myasthenia gravis: progressive
onset of symptoms with significant manifestation of
weakness. Respiratory muscles are spared.
Acute myasthenia gravis: rapid onset (within 6 months) of
severe bulbar and skeletal muscles involvement with
important weakness. Respiratory muscles are involved.
IV Severe late myasthenia gravis: progressive in severity for
2 or more years.
Filippi classification was used for postoperative outcome
clinical assessment (Table 3).
3. Surgical Technique
After general anesthesia induction avoiding the use of
nondepolarizing neuromuscular blocking agents, a dou-
ble-lumen endobronchial tube was placed for single lung
ventilation. The patient was placed in a supine position
with the left arm positioned as far back as possible to
gain enough space for robotic arms. Three skin incisions
were made along the left submammary fold; the camera
port (30-degree angled lens) was introduced through fifth
intercostal space along anterior axillary line. The right
and left robotic arms were introduced through fifth in-
tercostal space, midclavicular, and through third inter-
costal space, anterior to midaxillary line. The point of
reference to anterior mediastinum was the left phrenic
nerve. The left arm had an EndoWrist precise grasper;
the right arm has EndoWrist harmonic shear dissector.
After the robotic system was engaged, dissection started
inferiorly at the left pericardio-phrenic angle, and ex-
tended superiorly along the left phrenic nerve to the
jugular fold and continued inferiorly along retrosternal
area; the right pleural space was opened. The inferior
horn of thymus gland was isolated from the pericardium
and mobilized upwards. The dissection continued on the
right side with visualization of the right mediastinal
pleura and the right inferior horn. Isolation continued to
the neck until the superior horns were identified and iso-
lated. The innominate vein was identified, and dissection
continued along the border of the innominate vein to the
point where the thymic veins were identified, clipped,
and divided. The thymus gland and mediastinal fatty
tissue were removed en bloc, placed in endo-bag, and
retrieved through a trocar incision.
4. Results
The duration of symptoms ranged from 3 to 12 months
(mean, 7.75 months). The preoperative Osserman classi-
fication was stage IIa in 2 patients; stage IIb in 5 patients;
and stage IV in 1 patient. Anti-acetylcholine receptor
antibody was positive in 5 patients (62.5%) and negative
Table 3. De Filippi postoperative classification.
Class Description
1 Complete remission, no medication.
2 Asymptomatic, decreased medication.
3 Improved, decreased symptoms or decreased
4 No change.
5 Worsening symptoms.
Copyright © 2011 SciRes. SS
Copyright © 2011 SciRes. SS
Table 4. Selected preoperative variables and patient outcome.
Follow-up/De Filippi Classification
duration (month) Preop CT chest Histopathology 6 months 12 months 18 months
1 16 IIb 12 Hyperplasia Thymic involution Class 4 Class 3 Class 2
2 19 IIb 3 Normal Normal Class 4 Class 2 Class 3
3 23 IIa 12 Normal Normal Class 4 Class 3 Class 3
4 26 IIb 12 Hyperplasia Normal Class 4 Class 4 Class 3
5 28 IIb 5 Hyperplasia Hyperplasia Class 3 Class 3 Class 2
6 30 IV 3 Normal Hyperplasia Class 3 Class 2 Class 1
7 36 IIb 7 Normal Hyperplasia Class 3 Class 3 Class 2
8 46 IIb 8 Normal Thymic involution Class 3 Class 2 Class 1
in 3 patients (37.5%). The preoperative thoracic com-
puted tomogram showed normal anterior mediastinum in
5 patients (62.5%) and an enlarged thymic gland in 3
patients (37.5%). The operative time ranged from 88 to
300 minutes (mean, 260 min). All patients were extu-
bated in the operating suite. There was no operative
mortality. One patient developed postoperative myasthe-
nia crisis on day 3 and required endotracheal intubation
and mechanical ventilation and was successfully man-
aged with plasmapheresis and weaned of mechanical
ventilation on postoperative day 9. One patient had left
phrenic nerve injury. Histopathologic examination of the
specimens revealed normal thymus in 3 patients (37.5%),
thymic hyperplasia in 3 patients (37.5%), and thymic
involution in 2 patients (25%). Additionally, histopa-
thologic findings correlated with preoperative computed
tomogram of chest, revealing hyperplasia in 2 patients
(25%), which was reported normal on preoperative
computed tomogram that was not clinically significant
(kappa = 0.059; P = 0.85)
Six months’ follow-up showed improvement, decr-
eased symptoms (class 3) in 4 patients (50%), and no
change in symptoms or decreased medication in 4 pa-
tients (50%). Twelve months’ follow-up showed a
symptomatic, decreased medication (class 2) in 3 pa-
tients (37.5%) and improvement, decreased medication
(class 3) in 4 patients (50%). One patient (12.5%) ex-
perienced no change in symptoms or decreased medica-
tion (class 4). At 18 months, complete remission was
shown in 2 patients (25%), a symptomatic, decreased
medication (class 2) in 3 patients (37.5%), and im-
provement, decreased medication (class 3) in 3 patients
(37.5%) (Table 4).
5. Discussion
Thymectomy is an established therapy in treating myas-
thenia gravis combined with medical treatment [11].
Robot-assisted thymectomy is promising technique;
however, complete removal of the thymus gland is cru-
cial. Compared with video-assisted thoracoscopic thy-
mectomy, the robot-assisted technique provides several
advantages, particularly, in the corner of anterior medi-
astinum, which is difficult to reach with video-assisted
thoracoscopy. In addition, 3-dimensional visualization,
high-dexterity, and full range motion of EndoWrists,
make the robot system safe and efficient. We adopt the
left-sided approach and the use of pneumomediastinum
to facilitate dissection of thymus gland and perithymic
fatty tissue as proposed by Mineo and colleagues [6]. We
believe that left-sided approach offers excellent visuali-
zation of the left pericardiophrenic angle and aortopul-
monary window.
Our postoperative clinical results are good. Clinical
improvement is demonstrated in 87.5% of patients who
underwent robot thymectomy at follow-up greater than
12 months. These results are comparable to those re-
ported by others through a transsternal approach [4]. In
addition, clinical improvement continued over time, as
we have noted that complete remission is achieved in
25% of patients at 18 months’ follow-up. Regarding
preoperative computed tomogram of chest and histologic
findings, we observed no clinical significant correlation
in patients with nonthymomatous myasthenia gravis re-
ferred for thymectomy. This suggests that preoperative
computed tomogram has a limited role in differentiating
the nonthymomatous pathology in patients with myas-
thenia gravis. In addition, we observed no significant
correlation between symptom duration and age. We were
inclined to follow our patients using guidelines set by
Jaretski and colleagues [12].
Our study is limited, as the number of patients is small
and difficult to perform a multivariate analysis of inde-
pendent factors that affect the outcome. Long-term fol-
low-up is necessary for proper assessment of clinical
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