Myasthenia Gravis – Megaesophagus

Myasthenia Gravis MG

Myasthenia gravis (MG) is a disorder of neuromuscular transmission resulting from deficiency or dysfunction of the nicotinic acetylcholine receptor (AChR) on the postsynaptic membrane.

Acquired MG is an autoimmune disease in which antibodies directed against the AChR interfere with the interaction between acetylcholine and its receptor.

Case History

Belly is a 8y old German shepherd had represented with history of Intermittent vomiting, dysphagia, appendicular weakness, anorexia, weightloss, nausea, labored breathing.

Case Study

Physical ex

Revealed incomplete swallowing process and regurgitation of food bolus, auscultation lung fields expressed crackles respiratory noise, weakness of the hindlimbs musculature with weak proprioception.

Diagnostic Imaging

Radiography revealed ventral displacement of the trachea, aspiration pneumonia, tubular radiolucent structure above the trachea distended with gas, no affection neither in the axial nor appendicular skeleton and megaesophagus -which was confirmed with contrast radiography – contrast media fill the dilated esophagus.

Anticholinesterase test

Test used to diagnose Myasthenia gravis.

1. Place an intravenous catheter.

2. Mix together in one syringe: Neostigmine methylsulfate 0.01 mg/kg Atropine 0.02 mg/kg

3. Have equipment available for intubation and ventilation.

4. Exercise to the point of detectable weakness. 5. Administer the Neostigmine/Atropine combination

6. Monitor weakness.

Positive result: Myasthenia gravis (MG) exhibit obvious improvement in clinical signs resolution of weakness within 5 to 10 minutes after administration of intravenous Neostigmine.

Endoscopy:

Exploring the GIT in taking biopsies from the stomach and duodenum

Procedures:

Patient preparation:

withdrawal of food for at least 12 hours before the procedure so that the stomach is empty. Water does not need to be withheld before the procedure. Endoscopy too soon after a meal should be avoided because:

• Visualization is difficult; lesions and foreign bodies may be missed

• Pyloric intubation is difficult or impossible

• The endoscope may become clogged

• There is a danger of aspiration during recovery

It is preferable to hospitalize the patient overnight before gastroscopy; this allows time for preliminary investigations and ensures that the patient does not eat before the procedure.

Premedication: should be used to smooth induction and recovery Diazepam & ketamine.

Recent pilot study showed that the combination of butorphanol and dexmedetomidine made pyloric intubation faster than in patients premedicated with methadone and dexmedetomidine. Acepromazine maleate with buprenorphine is another suitable combination for dogs. In cats, ketamine or midazolam may be preferred

Antifoaming agents: A mixture of one part acetylcysteine to five parts simethicone is given orally at least 30 minutes before induction, Alternatively, simethicone can be added to the bottle supplying the water for irrigation during endoscopy.

Anesthesia: 

GA and intubation with an endotracheal tube tied securely in place is mandatory.

passage of the endoscope into the pharynx may be easier when the tube is tied to the mandible. Passing the tie around the back of the head is less secure, as the repeated movements of the endoscope tend to dislodge the endotracheal tube, but is a necessity in cats and brachycephalic dogs.

An elbow connector may be used to keep the anaesthetic circuit away from the insertion tube of the endoscope.

In dogs, a cuffed endotracheal tube is preferred, In cats, a non-cuffed endotracheal tube.

the assistant monitoring the anaesthetic should be alert to overinflation of the stomach, as it may cause cardiorespiratory compromise through compression of the diaphragm and caudal vena cava.

Patient positioning: left lateral recumbency, A mouth gag (speculum) must always be inserted to prevent damage to the endoscope, but this should be done with care in cats as excessive opening of the jaw can occlude blood flow to the brain, with deleterious neurological consequences.

Lumen examination, exploration and biopsy taking.

At least two biopsy samples should be collected from the fundus, four from the body (lesser and greater curvature) and two from the antral canal.

will be easier to biopsy if the stomach is deflated. Overinflation of the stomach stretches the mucosa, meaning that smaller amounts of tissue will be sampled

Recovery:

Recovery tends to be smoother if the stomach is deflated before the gastroscope is removed.

The esophagus lavaged., Leaving gastric acid, bile and digestive enzymes in the oesophagus of a patient recovering from anaesthesia (and therefore having a depressed swallowing reflex) can predispose to inhalation pneumonia, oesophagitis and even esophageal stricture formation.

Histopathology: Inflammatory cells infiltration and villous atrophy, Increased granularity, Increased friability.

Treatment plan:

Treatment of Myasthenia gravis undergo multiway treatment.

Megaesophagus secondary to Myasthenia gravis treated with sildenafil 500mg which discussed in recent researches that it could relax the smooth muscle of the lower esophagus, enabling it to open and let food pass to the stomach; it’s a selective phosphodiesterase-type 5 inhibitor that reduces the intracellular (cGMP) degradation and indirectly potentiates the action of nitric oxide (NO). NO is a neurotransmitter that plays an important role of smooth muscle relaxation at vessel and gastrointestinal (GI) tract. has inhibitory effects on lower esophageal sphincter and gastric slow wave amplitude, fundic tone and antral motility, thus facilitates the emptying of esophagus and reducing gastric contraction, resulting in reducing regurgitation and relieving megaesophagus.

-Animals with megaesophagus and regurgitation should be maintained in an upright position during feeding, drinking and for 10 to 15 minutes afterward to facilitate the movement of esophageal contents into the stomach, decreasing the chance of aspiration. Dogs can be trained to eat and drink while standing with their front feet on a raised platform, or a vertical feeding system (Bailey chair) can be used.

-Whenever aspiration pneumonia is present, a transtracheal wash should be performed for culture, and then aggressive treatment for the pneumonia should be initiated using antibiotics, fluids, nebulization.

-Administration of antibiotics that impair neuromuscular transmission (e.g., ampicillin, aminoglycosides) should be avoided.

-Anticholinesterase drugs are commonly administered in an attempt to improve muscular strength as neostigmine methylsulfate or Pyridostigmine bromide.

“Brief timeline of the case treatment”

Download Case Study

Thanks to the extraordinary teamwork, their efforts, dedication and consistency to do their best always and all the time gathered these end result.

Special Thanks to Dr. Ahmed Barakat for his dedication in this case dealing with Myasthenia gravis and helping us to provide more data about using sildenafil in the veterinary field with recorded results.