What is Myasthenia Gravis: Is fatigue were muscles become progressively weaker during periods of activity, and improve after periods of rest. Muscles that control eye and eyelid movement, facial muscles (the dogs jowls hang lower), chewing, and swallowing/oesophagus are especially susceptible. The muscles that control breathing, neck and limb movements can also be affected. The onset of this disorder can be sudden. In most cases, the first noticeable symptom is weakness of the eye muscles (no blinking reaction when you touch the eye) and difficulty in swallowing. The degree of muscle weakness involved in MG varies greatly among dogs, ranging from a localized form to a severe and generalized form in which many muscles—sometimes including those that control breathing—are affected.
Congenital Myasthenia Gravis: The dog is born without normal neuromuscular junctions to striated muscles. There is no effective treatment. Myasthenia Gravis has been described as a recessive genetic disease.
Acquired Myasthenia Gravis: This is an autoimmune disease, meaning that the immune system is destroying neuromuscular junctions as if they were foreign invaders. What muscles are affected depend on which junctions have been destroyed. Therapy centres on stopping this immune reaction and prolonging what acetylcholine activity is still present. This is done with a combination of immunosuppressive agents and medication to inhibit acetyl cholinesterase. There are generally 3 different levels of acquired MG:
- Mild or Focal MG – only one body part, usually the esophagus, is involved.
- Moderate Generalized MG – appendicular (limb) weakness with or without Mega oesophagus.
- Severe Generalized or Acute Fulminating – rapidly progressive and usually fatal.
Symptoms & Diagnosis of Myasthenia Gravis: Vary in type and severity, with dogs having few or many symptoms which may include:
- Weakness of the muscles that control eye movements
- An unstable or waddling gait
- Weakness in legs with urges for them to sit down, quivering or shaking
- Running sideways and unable to jump
- Weakness in neck
- Lethargy
- A change in facial expression with drooping lower eye lids and lower lip
- Difficulty in swallowing
- Shortness of breath.
- Bark change – usually to a high pitched bark
- Blink reflex absent
- Some dogs can have trouble controlling when they urinate or deficate
Myasthenia Gravis does not directly affect the heart muscle. For a diagnosis initial observations are done and a Mestinon/Pyridostigmine Bromide injection can be administered which can immediately reversed the symptoms of muscle weakness for a very short time. A dog is in no pain from having Myasthenia Gravis.
Tensilon Test: This test involves giving an injection of edrophonium chloride (brand name Tensilon) intravenously to a patient suspected of having myasthenia gravis. Edrophonium chloride is a short-acting anticholinesterase. This allows acetylcholine to accumulate in the neuromuscular junction, strengthening the message from nerve to muscle. A dramatic increase in muscle strength following the IV injection should give a presumptive diagnosis of acquired MG while waiting for the results of the AChR antibody titter test. Treatment could be initiated based on the results of the dramatic positive test. Unfortunately, not all dogs are responsive to Tensilon, and dogs with other neuromuscular diseases may show a subjective positive response.
Treatment: Mestinon/Pyridostigmine Bromide liquid or tablets are given regularly through the day. They act by slowing the normal degradation of acetylcholine at nerve endings, thereby overcoming the inhibition of the receptors. The difficult thing with the treatment is that the symptoms of Myasthenia Gravis – Diarrhoea, vomiting, salivating and teary eyes – are the same as an overdosing of the drug. Look out for overdoes signs:
- Coughing / Gagging
- Regurgitation of food
- Lethargy
- Breathing difficulties
- Diarrhoea
- Small pupils
- Vomiting
- Lots of saliva
- Lots of tears from eyesAzathioprine can also be used in canine MG but side-effects require frequent monitoring of blood counts to detect rapid drops in the number of white and red cells in the blood, and periodic liver function tests to detect potential toxicity to the liver.
Drug Frequency: The drug needs to be administered as evenly as possible throughout the day with multiple doses. This even distribution helps to even out the level in the dogs system. As one dose wears off just before the next dose you may see a slight deterioration in the dog. Also if administering higher doses of the drug you may see slight overdose symptoms 1.5 – 2hrs after administration.
Causes of Myasthenia Gravis: One of the causes is an autoimmune response which features antibodies directed against proteins that are naturally present in the body its cause could be anything that the dog has come into contact with or has been given.
Dog Upright Feeding Bin: Dogs with a mega-oesophagus need to be fed in an upright position. Small dogs can be fed on your lap and held in an upright position for 20-30 mins to enable the food to drop into the stomach. For larger dogs a bin or box can be used. We used a waste paper bin which was clipped to the wall for stability and put a harness on the dog which was clipped to the inside of the bin to stop the dog standing up.
Drug Cost: Mestonin syrup/Pyridostigmine Bromide – Depending on the quantity supplied costs between 0.55p and 0.72p per 1mg. Prednisone has a great many potential undesirable effects in dogs including suppression of adrenal gland functions, marked muscle weakness, and muscle atrophy.
Remission: Some dogs can go through spontaneous remission sometimes as early as four months after the first clinical signs. The average time for remission is 6-8 months, and some dogs take over a year to go into remission. And many times the mega oesophagus resolves as well.
Prognosis: As long as the symptoms of mega esophagus are well managed to lessen the danger of aspiration pneumonia, you and you dogs have a good chance of working through it.
- Your normal vet will probably not have enough, if any experience, with this disease, so it is wise to request to be referred to a Neurologist.
- Keep a written and video diary as this can help you learn to know what is normal and abnormal for your dog with MG and if it has any reactions to drugs.
- X-rays and the antibody titer test are suggested to monitor the disease until possible remission is achieved. Many Neurologist/Vets suggest every 3 months, but it is an expensive test with samples having to be sent to Germany or the USA.
- When weaning off of the medication do it very slowly.
- Avoid stressful situations, excess heat or cold, and overexertion which can exacerbate symptoms.
- Some people say to not vaccinate. Please discuss this with your veterinarian as if your dog has already been regularly vaccinated then it will carry the vaccine antibodies.
- If you see any small changes to that you expect contact your vet and get your dog checked as relapses can occur which may mean a variation in drug dosing.
Case History of Lula:
One evening in September 2012 one of our cocker spaniels ‘Lula’ started vomiting for seemingly no apparent reason.
We gave it 24 hours thinking is was an upset tummy or something she ate that would ‘pass’ through her.
However every time we fed her she brought the food back up within initially 20 minutes which gradually decreased to 5 minutes and she wasn’t able to hold down water either.
We had given it 24 hours but booked her into the vets the next day as by now she was getting a bit dehydrated.
We explained to them that the food she was eating was coming back up complete with no bile or stomach fluids and did not smell or look like vomit as nothing was digested. They kept her in to X-ray her and later on operated on her as they said they had seen something in her stomach.
When we collected her they showed us what they had removed from her stomach. It was a very small clump of grass with a small head of grass. We were very surprised that something so small would cause her to vomit.
We were told that the problem was sorted as the vets had kept her in for 4 days, fed her and she had kept the food down. We took her home with Rymadil tablets and a course of antibiotics.
We started feeding Lula small meals so her stomach could heal, however every time we fed her the food was coming straight out again. We phoned the vets in worry explain that we felt the food was not getting to her stomach before it was expelled and were told that she was still getting over the operation and to take her back for an anti-sickness injection which we did.
Lula had a blockage in her Oesophagus in the February of 2012 and was very successfully operated on by Queens Veterinary Collage. As she was still vomiting and unable to hold down water the vets spoke to Queens Veterinary College who said that the previous operation she had would not have anything to do with her current condition.
3 days later we had collected her from the vets Lula was not doing well and we took her back to the vets at 10am in the morning. She was lethargic and dehydrated. We explained to them that she was regurgitating with foam in it now. They checked her over and manually looked down her throat and told us that she did not have pneumonia. We asked that they checked her throat with an endoscope, but they did not have one so said they would ask a neighbouring vets if that vet could check Lula’s throat for them. They could not do this till the following day as the other vets with the facilities was closed.
That evening of 23rd Sept 2012 at 9.30pm she started vomiting very badly, coughing and straining. All that was coming up was foam. It was awful to see how much she was struggling. By now she had lost so much weight her ribs and hips were protruding and now she was severely dehydrated.
We contacted the vets and were told to wait till the morning until we had had the endoscopy. We were not happy at all and demanded that the vets immediately referred us to Queens Veterinary School Hospital. They did so and at 12.30am she was booked into QVSH under Edward Ives MRCVS. QVSH said that she had Pneumonia and started re-hydrating her, stabilised her, did x-rays, blood tests and performed an endoscopy. They phoned us at 02.45am with an update on her condition and treatment.
At 07.30am QVSH phoned us with a full diagnosis. She had Myasthenia Gravis which had caused a mega-Oesophagus which in-turn caused her to get aspiration Pneumonia due to the constant re-gurgitation.
QVSH had done a drug trial on Lula to confirm their diagnosis. They done initial observations then gave her the Mestinon/Pyridostigmine Bromide injection which immediately reversed her symptoms of muscle weakness but only lasted 10 minutes. She could only do exercise for 5 mins before she collapsed shaking and weak.
After 5 days we collected Lula from QVSH with an intense regime of treatment:
- She needed to be fed 4 times a day with her front legs raised during her feeding and kept raised for 15-20 minutes afterwards.
- She could not drink freely (which was very difficult for us as we have 7 other dogs and had to remove her access to water). There is a company that specialises in neck rings to stop dogs from bending down to drink http://www.wagtailfarms.com/.
- The food had to be fed in small sticky balls a couple of centimetres diameter with the Mestinon Syrup and her other tablet drugs inside.
- She also needed coup age performed regularly on her chest to bring up the mucus and help with the Pneumonia.
We started sitting her on our laps to feed her but sitting there 4 time a day without her fidgeting was difficult. So we made a feeding bin using a waste paper bin with a thick towel inside and with a harness clipped to it which stopped her standing up to get out of the bin. The bin was also clipped to a hook in the wall to stabilise the bin. We have seen a web page which manufacturers some great feed chairs http://www.baileychairs4dogs.com/, however if your dog is a fidget there doesn’t seem to be a clip mechanism to keep them in the chair for the required length of time, but I sure one could be fitted.
We regularly went back to QVSH for chest x-rays to see if, after the drug treatment, she still had a mega-Oesophagus and blood tests were done to see if she was producing the acetylcholine antibody receptors. (This showed as positive each time).
The drug needed to be administered as evenly as possible throughout the day. Lula had 0.35ml 3 times a day, so she was given the syrup at 7.30am, 3.30pm and at 11.30pm. This even distribution helps to even out the level in her system. As one dose wears off just before the next dose you may see a slight deterioration in the dog. Also if administering high doses of the drug you may see slight overdose symptoms 1.5 – 2hrs after administration.
After over a year in February 2013 we took her to QVSH for chest x-rays and another blood test for acetylcholine antibody receptors (which showed negative this time). We had not seen any regurgitation from her for at least a month and she was not gurgling or salivating. So QVSH instructed us to start reducing the quantity of Mestonin syrup/Pyridostigmine Bromide weekly by 0.05ml.
In April 2013 we had just got her down to a 0.05ml dose when Lula started showing symptoms again. So QVSH who instructed us to the increase the drug dose back up to 0.35ml 3 times a day for 5 days then 0.4ml for 5 days and so on increasing by 0.05ml every 5 days until we reached 0.7ml. We also had to start feeding her back in the bin in an upright position again due to the regurgitation. We took her to QVSH for chest x-rays and another blood test for antibodies against acetylcholine receptors (which showed positive this time). We were a little worried about her having Pneumonia so an antibiotic course was started.
Since then we have continued the drug treatment 3 times a day and her oesophagus has returned to normal so she is eating in a normal position now.
We are unsure as to when or if we will reduce the drug treatment but are happy to continue it as she is doing so well.
She is a spaniel and they are renowned for having a high autoimmune response, and in some cases an over reactive response. And although the cause of the condition is unknown, one month before her symptoms started we used a well-known prescription flea treatment which I had not used on any of the dogs before leading me to wonder whether this was the cause of her autoimmune reaction.
During all if this she has regularly been with us on shoots. However, due to the potential muscle weakness her job has changed from being in the beating line and with retraining she is now used for picking up and a peg dog.
Myasthenia Gravis doesn’t necessarily mean a death sentence for a dog if it is managed and you are able to fit the necessary routines into your day.
There are many web pages out there with lots of help and tips and tricks. Chat to others of their forums as they have experienced what you are currently experiencing and their knowledge is valuable.