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|Year : 2015 | Volume
| Issue : 4 | Page : 561-563
Rare case of myasthenia gravis associated with situs inversus totalis: Implications in management
Sagar Badachi, G. R. K. Sarma, Thomas Mathew, Raghunandan Nadig
Department of Neurology, St. John's Medical College, Bengaluru, Karnataka, India
|Date of Web Publication||4-Aug-2015|
Department of Neurology, St. John's Medical College Hospital, Sarjapur Road, Bengaluru - 560 034, Karnataka
Source of Support: None, Conflict of Interest: None
A rare case of simultaneous occurrence of myasthenia gravis and situs inversus totalis is reported. The implications of the presence of these two entities on management are discussed
Keywords: Myasthenia gravis, situs inversus totalis, thymectomy
|How to cite this article:|
Badachi S, Sarma G, Mathew T, Nadig R. Rare case of myasthenia gravis associated with situs inversus totalis: Implications in management. Neurol India 2015;63:561-3
|How to cite this URL:|
Badachi S, Sarma G, Mathew T, Nadig R. Rare case of myasthenia gravis associated with situs inversus totalis: Implications in management. Neurol India [serial online] 2015 [cited 2020 Jun 1];63:561-3. Available from: http://www.neurologyindia.com/text.asp?2015/63/4/561/162050
| » Introduction|| |
Acquired myasthenia gravis (MG) is the most common primary disorder of neuromuscular transmission. Recent estimates indicate that the U.S. prevalence is approximately 20/100,000.  Situs inversus totalis (SIT) is a rare condition with a predicted incidence of one in 10,000 among the general population.  Here we report a rare occurrence of MG in SIT (which is not described in literature till date) and highlight the importance of this association in management.
| » Case Report|| |
A 26-year old female patient presented with decreased exercise tolerance and easy fatigability for one year. She had drooping of eyelids and diplopia that worsened as the day progressed. There was no history of recurrent respiratory infections. Her general physical examination was normal. Her heart sounds were present on the right side, which were normal in quality and intensity and no murmurs were audible. Fatigable ptosis, motor fatigability, and a single breath count of 20 were noted. The diagnosis of myasthenia gravis (MG) was confirmed by a significant decremental response on repetitive nerve stimulation from bilateral orbicularis oculi, nasalis, right deltoid, and trapezius. Acetylcholine receptor antibody titers yielded a positive result (16.7 nmol/L, normal levels < 0.25 nmol/L). Her hemogram, renal function parameters, liver function parameters, and thyroid function tests were normal. Her antinuclear antibody test and ELISA for HIV were negative. The chest X-ray showed dextrocardia [Figure 1] and computed tomogram (CT) of the chest revealed situs inversus totalis (SIT) [Figure 2], which was confirmed by an abdominal ultrasound. The thymus visualized on CT chest was normal for her age and located normally in the anterior mediastinum. No obvious ectopic thymic tissue was noted. Pulmonary function tests were normal. Treatment was started with pyridostigmine and prednisolone. After MG was stabilized, the patient was planned for a transsternal thymectomy. Close monitoring was done in the pre-, intra- and post-operative period. Stress doses of hydrocortisone (100 mg IV 8 hourly) were given perioperatively. A mixture of isoflurane, propofol, and oxygen was used for induction of anesthesia. The induction, maintenance, and reversal of anesthesia were uneventful and the patient tolerated surgery without any complications. Intra-operatively, no obvious ectopic thymic tissue was identified. Intramuscular neostigmine injections preceded by glycopyrrolate were given six hourly for 4 days following surgery. She had a smooth recovery and was reverted back to oral steroids and pyridostigmine. Histopathology of thymus revealed mild germinal center hyperplasia.
|Figure 2: Computed tomogram chest showing situs inversus totalis. Liver (wide, long arrow), stomach (wide, short arrow), and spleen (long thin arrow)|
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| » Discussion|| |
Myasthenia gravis is the most common primary disorder of neuromuscular transmission. SIT is a rare condition with a predicted incidence of one in 10,000 among the general population. Its etiological factors are still not completely understood. During the embryological development, a 270° clockwise rotation instead of the normal 270° anti-clockwise rotation of the developing thoraco-abdominal organs results in mirror image positioning of the abdominal and thoracic viscera.  There is no established gender or racial difference in its incidence, but its genetic predisposition and familial occurrence suggest multiple inheritance patterns. 
Myasthenia gravis may be associated with thyrotoxicosis, seizures, rheumatoid arthritis, diabetes mellitus, and HIV infection. Neurological conditions associated with SIT include spinal deformities like split cord malformations, spina bifida, meningomyelocele, scoliosis, etc.  The association of SIT with MG has not been described in the literature till date. However, the causal link between the two entities cannot be ascertained.
Management of MG associated with SIT poses a significant challenge as the association of situs inversus with other syndromes and diseases such as Kartagener's syndrome, mucociliary dysfunction, airway anomalies, etc., may predispose the patient to numerous varieties of airway difficulties and pulmonary infections that can have considerable consequences during the administration of anesthesia  and also has the potential to cause a myasthenic crisis.
Our patient did not have any anesthetic complications. However, it is interesting to note that masseter spasm was encountered during induction with isoflurane, propofol and succinylcholine in a patient of SIT posted for open cholecystectomy.  The perioperative period in that patient was characterized by frequent copious secretions from the respiratory tract that had to be cleared regularly for smooth ventilation. Injection of hydrocortisone (100 mg) had to be given prophylactically to prevent any bronchospasm. Extubation was delayed as the patient developed prolonged postoperative apnea.  A case of prolonged paralysis after administration of succinylcholine has been reported earlier in a patient with SIT. 
Primary ciliary dyskinesia is present in 25% of the patients with SIT with an increased probability of developing respiratory complications. Therefore, moist and filtered mixture of gases should be administered during mechanical ventilation.  It is pertinent to note that SIT may be associated with numerous cardiac anomalies such as atrial septal defects, ventricular septal defects, transposition of great vessels, absent coronary sinus, double-outlet right ventricle, total pulmonary anomalous venous defect, and pulmonary valve stenosis either singly or in combination.  The electrocardiography electrodes have to be applied in the opposite direction as the changed surface electric polarity may give a false picture of perioperative ischemia. The transposition of the thoracic viscera alters the various anatomical landmarks, which one should be aware of, in case the need for an invasive central venous cannulation arises. In case of cardiac arrhythmias and cardiac arrest, great care has to be taken while applying direct current with the defibrillator pads positioned on the right side.
There are important surgical implications for a thymectomy as well in patients with the simultaneous presence of SIT and MG, owing to the possibility of the presence of ectopic thymic tissue. Ectopic thymic tissue was found in 39.5% patients of MG.  The presence of active ectopic thymus was the most significant predictor of a poor outcome in MG after a thymectomy.  It is unknown if the location of ectopic thymic tissue is different in SIT when compared to its location in situs solitus. Hence, it is important to systematically study the location of ectopic thymus tissue in SIT to improve the surgical outcomes of MG in this group.
| » Conclusion|| |
A thorough preoperative evaluation, anticipation of anesthetic and surgical complications and knowledge of anatomical variations in patients of SIT associated with MG can minimize the difficulties encountered during treatment and is of paramount importance in achieving a successful outcome.
| » References|| |
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[Figure 1], [Figure 2]