Vol 8 | Issue 3 | September-December 2022 | Page: 15-18 | Chetan Pataki, Daniel Shuttleworth, Gamunu Ratnayake
Author: Chetan Pataki , Daniel Shuttleworth , Gamunu Ratnayake 
 Department of Anaesthesia and Intensive Care, Musgrove Park Hospital, Taunton, UK.
Address of Correspondence
Dr. Chetan Pataki,
Specialty Doctor, Department of Anaesthesia and Intensive Care, Musgrove Park Hospital, Taunton, UK.
A 69-year-old male patient was admitted to the hospital with history of generalised weakness and significant weight loss in the preceding months. This was investigated by general practitioner (GP) and was recently diagnosed with Myasthenia Gravis. He was referred to our hospital for further investigations and management.
The patient had a respiratory arrest secondary to aspiration pneumonia in the ward. He was resuscitated and was treated in critical care unit. The myasthenic crisis was treated with medical management and Plasma exchange therapy.
On CT Chest and Barium Swallow, the patient was incidentally diagnosed with a big pharyngeal pouch with some collection. The pharyngeal pouch was stapled by ENT surgeon with endoscopic approach.
The patient was successfully treated for the aspiration pneumonia, Myasthenic Crisis and Pharyngeal pouch. He was discharged from hospital on day 24 of admission.
Keywords: Myasthenia Gravis, Myasthenic Crisis, Pharyngeal Pouch, Zenker’s Diverticulum, Aspiration Pneumonia
Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction due to formation of autoantibodies to the neuromuscular junction receptors. These antibodies block neuromuscular transmission resulting in skeletal muscle weakness. The disease often causes ptosis and diplopia initially and ultimately the disease generalises in two-thirds of patients leading to weakness of the bulbar, neck, limb, and respiratory muscles . Respiratory muscle involvement including the diaphragm can result in respiratory failure requiring ventilatory support.The pharyngeal pouch is a uncommon anatomical abnormality which mostly occur in elderly patients leading to dysphagia, aspiration, and weight loss. The diagnosis of pharyngeal pouch is easily established with barium studies. Treatment is surgical via an endoscopic or external cervical approach.We present a rare case of Myasthenia Crisis with an incidental finding of a pharyngeal pouch.A literature search of Medline found no case reports of a similar presentation published before.
A 69-year-old male gentleman presented to the hospital with a history of ptosis, diplopia, slurred speech, difficulty in swallowing solid food and generalised weakness for 3 months. He also had on-going significant weight loss of almost 48 kilograms over period of 18 months. He was investigated by the GP and diagnosed him of Myasthenia Gravis (MG) with anti-acetylcholine antibodies (AChR). The patient was referred to our hospital for further investigations and management. He was admitted under medical team and was referred to neurology team for management of MG. The treatment was initiated as per the neurology advice and is discussed in management section of this article. In the ward, lung functions of the patient were assessed twice daily as per the protocol by neurology team. His vital capacity was in range of 1.8 to 2.5 litres which was reassuring. The safety to feed the patient orally was assessed by the speech and language therapy (SALT) team and was fed orally in the ward.On day 7 of admission to hospital, the patient suddenly became unresponsive in the ward. The crash call was activated to summon the resuscitation team. He was resuscitated and ROSC (return of spontaneous circulation) was achieved in just one cycle of Advanced cardiac life support. The downtime was less than 2 minutes. He was intubated by the resuscitation team and then transferred to critical care unit for mechanical ventilation and further management. His neurological status was assessed on next day of admission to critical care unit after overnight mechanical ventilation under sedation. The patient was opening eyes spontaneously, following commands and was neurologically appropriate without any residual neurological deficits.Patient’s blood investigations were unremarkable. We continued the management of Myasthenia Gravis as advised by the Neurology team.To optimise his calorie intake, we decided to feed the patient through Naso-Gastric tube (NG tube) while he was intubated. The insertion of the NG tube was challenging. Even after multiple attempts by senior clinicians with use of direct laryngoscope and Magill’s forceps, it was evident on chest X-ray that NG tube was coiled in the pharynx. Inability to insert NG tube raised a suspicion of lymphoma or malignancy either in neck or the mediastinum. We decided to perform CT scan of his neck and thorax to rule out such pathology. In the interim, we initiated the parenteral feeding as per the dietician advice to avoid refeeding syndrome. On the CT scan of thorax, there was an incidental finding of the pharyngeal pouch. The opinion of ENT Surgeons was sought for further management.During his stay in the intensive care unit, we attempted to wean his mechanical ventilation support. We also attempted to extubate his endotracheal tube, however, due to generalised weakness and oropharyngeal secretions, he failed the extubating criteria. A decision was made to perform tracheostomy on day 10 of admission to hospital to wean from invasive mechanical ventilation and also to help in clearance of oropharyngeal secretions which were in copious amount.The ENT Surgeons reviewed the images and decided to staple the pharyngeal pouch through rigid oesophagoscope. The patient was transferred to operating room for endoscopic stapling of pharyngeal pouch on day 13 of admission to hospital. After successfully clipping the pouch, NG tube was inserted by the ENT surgeon with help of rigid oesophagoscope. The patient was fed enterally as per the dietitian advice after confirmation of NG placement on Chest X-ray.
The patient had multiple Chest X-ray to confirm position of Nasogastric (NG) tube as well as to assess pulmonary changes after aspiration. Apart from a coiled NG tube in a peculiar circular fashion in pharyngeal space, lung fields were clear as demonstrated in figure 1. A Volume CT with HR Reconstruction scan was performed to investigate the cause for obstruction in placement of NG tube as well as the cause for his weight loss. The CT demonstrated an incidental finding of filling defect in the laryngo-pharyngeal area as shown in figure 2.This was reported as a pharyngeal pouch which was a new diagnosis. We also performed a Barium swallow study to confirm the diagnosis of the Pharyngeal pouch and it demonstrated a big pharyngeal pouch as demonstrated in figure 3.
The current case report demonstrates the unusual presentation of a patient with MG and pharyngeal pouch, both of which could potentially cause aspiration pneumonia. Considering the patient’s presentation to the hospital, our initial working diagnosis was respiratory failure due to bulbar dysfunction caused by MG causing aspiration pneumonia. As patient had significant weight loss in short duration and we struggled to insert NG Tube, we suspected a mass like thymoma, lymphoma or some other malignancy as the cause of this.On initiating treatment for MG, there was some improvement in patient’s strength, however, our attempts to wean the patient from mechanical ventilator failed due to weakness as well as copious secretions caused by Cholinesterase inhibitors. A Volume CT and Barium swallow instead had shown the incidental finding of pharyngeal pouch. A pharyngeal pouch along with the skeletal muscle weakness caused by MG led to the complication of aspiration pneumonia leading to respiratory arrest.
• The patient was treated with antibiotics for aspiration pneumonia as per the hospital antimicrobial policy.
• The management of MG was initiated by the neurology team and supported us with input for the ongoing management of the Myasthenic Crisis. The patient received following regimen for MG –
A. In the ward-
• Subcutaneous Neostigmine.
• Injection Pyridostigmine 30 mg three times a day for 2 days followed by 60 mg afterwards.
• Tab Prednisolone 20 mg once a day per NG/oral and was weaned as per the protocol.
B. In the Critical Care unit-
• Continued the medications from ward.
• Enteral pyridostigmine after successful placement of the NG tube.
• Plasmapheresis/plasma exchange therapy (PLEX)- Due to failure to wean patient from mechanical ventilation, it was decided to perform three cycles of PLEX. This intervention helped to improve muscular weakness and aided weaning from invasive ventilation.
• Aggressive chest physiotherapy
• Carbocisteine- to loosen thick secretions and tracheostomy to clear the copious secretions.
• The pharyngeal pouch was treated by the ENT surgeon by stapling it with rigid oesophagoscopy.
• Patient was haemodynamically stable and required minimal vasopressor support during his stay in critical care unit and was weaned off.
• After a significant improvement in muscular function, the patient was weaned from mechanical ventilation as per the weaning protocol. The tracheostomy was de-cannulated on day 20 after admission to hospital.
• After the SALT assessment, oral feeding was reinitiated.
• The patient was discharged from critical care unit on day 21.
• He was discharged from the hospital on day 24.
The myasthenia gravis is not very common disease and it has prevalence of about 15 per 1,00,000 in the UK population, although this figure has increased over time . The diagnosis of MG is based on thorough history and clinical examination of the patient. The diagnosis can be supported with various pharmacological, serological and electrodiagnostic tests. With advances in serological testing, multiple relevant antibodies can be identified which play a role in the pathophysiology of MG. These include-
• antibodies directed towards the skeletal muscle acetylcholine receptor called as Anticholinergic receptor antibodies or AChR.
• antibodies directed towards Muscle specific receptor Tyrosine Kinase called as MuSK antibodies.
As per the literature, AChR antibodies are present in up to 85% of the patients in serological tests .The common symptoms which raise the suspicion of MG are ocular with either ptosis, diplopia or both together. These symptoms are found in 85% of patients with generalized MG (most AChR). In the patients with MuSK antibodies , the presenting symptoms may be ptosis and or diplopia as in AChR positive patients, but MuSK positive patients characteristically show progressive weakness of the bulbar muscles leading to dysarthria and swallowing difficulty .Myasthenic Crisis (MC) is an important and common complication in the natural history of MG. The MC is often evident with symptoms and signs of weakness of the upper airway muscles leading to obstruction and aspiration, weakness of respiratory muscles leading to reduced tidal volumes or from weakness of both muscle groups. A patient could present to hospital with MC as a first clue of diagnosis of MG in first two years following the onset of the disease . Lung volumes are helpful to quantify and depict the course of MG disease. It is also helpful to guide the medical management of MG. A Vital Capacity less than 1 L (or <20-25 mL/kg) or an Negative Inspiratory Force <20 cm H O indicates significant respiratory 2weakness; both measurements are commonly used to define myasthenic crisis .In patients with progressed MG or a patient with MC, the management often includes not only early intubation and positive end-expiratory pressure but also aggressive chest physiotherapy and frequent suctioning .It remains unclear when first to attempt extubation after myasthenic crisis. Fluctuating weakness and pulmonary complications often confound the decision to extubate . Whether patient is in MC or not, the treatment of MG involves the use of Cholinesterase inhibitors and Immunomodulation therapies which include systemic steroids. Differences in response rates in the various subtypes of MG to cholinesterase inhibitors have been reported in several studies. In MuSK MG, non-responsiveness to cholinesterase inhibitors seems to be much more common when compared to seronegative or AChR MG . Intravenous Immunoglobulin therapy and PLEX are used for patients in respiratory failure or in MC. A rapid clinical response in patients with a respiratory crisis or during severe exacerbations can be achieved with these interventions .The prevalence of Pharyngeal pouch is very low with annual incidence of pharyngeal pouch to two per 100,000 people per year . A patient with a pharyngeal pouch could present with variety of symptoms like
• typical symptoms of dysphagia,
• regurgitation, choking, borborygmi in the cervical region,
• chronic cough, chronic aspiration, halitosis and weight loss.
As the pouch enlarges, symptoms generally become more severe and can result in malnutrition . In our patient, weaning from mechanical ventilator was challenging in presence of copious amount of oropharyngeal secretions which could be also due to use of cholinesterase inhibitors. The secretions were regurgitating from the collection in pharyngeal pouch and leading to aspiration.There are various surgical options discussed in literature for excision of a pharyngeal pouch. These include an internal or external approach. Pharyngeal pouch surgery is associated with a risk of significant complications, mostly after open surgery. Recently endoscopic stapling devices have become increasingly popular. The reported complication rates are very low with endoscopic stapling of pharyngeal pouch but long term outcomes are yet to be ascertained .In our case, the patient underwent endoscopic stapling of the pharyngeal pouch which, in our opinion, lead to better control of secretions and aided the weaning from mechanical ventilation. In our case, all the suggested therapies for MG/MC were attempted, however, it is likely that the long-standing pharyngeal pouch could also have contributed to poor nutrition and weakness in this patient. In summary, the patient was treated successfully for MC as well as pharyngeal pouch with a multidisciplinary team approach.
Learning Points/Take-home Messages
• Multidisciplinary team management is crucial for better and timely management of patients.
• Patients with Myasthenia Gravis can present with acute respiratory failure early in disease progression.
• If hypercapnic respiratory failure occurs in patients with no underlying pulmonary disease and the patient does not improve despite appropriate management for MG, physicians should suspect alternative pathology
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|How to Cite this Article: Pataki C, Shuttleworth D, Ratnayake G | Aspiration Pneumonia from a Large Pharyngeal Pouch Masquerading as Myasthenia Gravis Related Bulbar Dysfunction | Journal of Anaesthesia and Critical Care Case Reports | September-December 2022; 8(3): 15-18.