{"id":1088,"date":"2020-04-26T00:47:19","date_gmt":"2020-04-26T00:47:19","guid":{"rendered":"http:\/\/caninemegaesophagusinfo.com\/staging\/?page_id=1088"},"modified":"2024-04-23T02:48:24","modified_gmt":"2024-04-23T02:48:24","slug":"myasthenia-gravis","status":"publish","type":"page","link":"https:\/\/caninemegaesophagusinfo.com\/index.php\/myasthenia-gravis\/","title":{"rendered":"Myasthenia Gravis"},"content":{"rendered":"

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My dog’s been diagnosed with a condition called Megaesophagus and is being treated for Aspiration Pneumonia. \u00a0I\u2019ve just learned that the cause is Myasthenia Gravis, a disease I\u2019ve never heard of that I can\u2019t even pronounce. \u00a0Now what?<\/p><\/blockquote>[vc_row_inner][vc_column_inner][vc_column_text]<\/p>\n

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Okay, let\u2019s start at the beginning. \u00a0Myasthenia Gravis (MG)<\/strong>, pronounced (My-as-theen-ee-a Grav-us), comes from Greek and Latin words meaning grave muscle weakness<\/strong>.<\/p>\n

It is a Neuromuscular Autoimmune<\/strong> disease. \u00a0Let\u2019s break that down:<\/p>\n<\/div>\n

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What is the neuromuscular system?<\/h3>\n

The nervous system is divided into the central nervous system (brain and spinal cord) and peripheral nervous system (also called neuromuscular system, composed of nerves and muscles). \u00a0The neuromuscular system consists of the nerves leaving the back of the brain to innervate muscles and glands of the head (cranial nerves), and peripheral nerves leaving the spinal cord to control in particular the muscles of the limbs. \u00a0The junction between the peripheral nerve and the muscles is called the neuromuscular junction.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

[\/vc_column_text][\/vc_column_inner][vc_column_inner width=”1\/2″][vc_empty_space][vc_single_image image=”1098″ img_size=”full” alignment=”center” style=”vc_box_border” border_color=”white” onclick=”zoom”][vc_empty_space height=”16px”][\/vc_column_inner][vc_column_inner][vc_column_text]A chemical messenger called acetylcholine (pronounced ah-See-tul-KO-leen) bridges this gap. This messenger is released from the end of the nerve, flows across the gap and fixes itself to a specific receptor (acetylcholine receptor) on the muscle. The acetylcholine attaches to the receptor (like a key fitting a lock) and triggers a signal, which causes the muscle to contract.[\/vc_column_text][\/vc_column_inner][\/vc_row_inner][vc_row_inner][vc_column_inner width=”1\/2″][vc_empty_space][vc_video link=”https:\/\/www.youtube.com\/watch?v=vyQWGclkGWQ” align=”center”][vc_empty_space height=”16px”][\/vc_column_inner][vc_column_inner width=”1\/2″][vc_column_text]<\/p>\n

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Autoimmune<\/strong><\/h3>\n

In Myasthenia Gravis, there is abnormal transmission of the message between the nerves and the muscles. \u00a0<\/strong>In the body of an MG dog there is a reduction of the number of receptor sites. \u00a0<\/em>The reduction in the number of receptor sites is caused by an antibody that destroys or blocks the receptor site. \u00a0Antibodies are proteins that play an important role in the immune system.<\/strong> \u00a0They are normally directed at foreign proteins called antigens<\/strong> that attack the body. \u00a0Such foreign proteins include bacteria and viruses. \u00a0 Antibodies help the body to protect itself from these foreign proteins.<\/strong> \u00a0For reasons not well understood, the immune system of a dog with MG makes antibodies against the receptor sites of the neuromuscular junction.<\/em> \u00a0Abnormal antibodies can be measured in the blood of many dogs with MG. \u00a0The antibodies destroy the receptor sites more rapidly than the body can replace them. \u00a0Muscle weakness occurs when acetylcholine cannot activate enough receptor sites.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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The Two Types of Canine Myasthenia Gravis<\/h3>\n

Congenital\u00a0Myasthenic Syndrome (CMS)<\/b><\/h6>\n

Congenital Myasthenic Syndrome is not a singular disease but a series of clinical heterogenous congenital syndromes affecting the NeuroMuscular\u00a0Junction (NMJ) resulting in skeletal muscle weakness and fatigability. These syndromes have a genetic basis and specific mutations. They have been identified for the Labrador Retriever, Golden Retriever, Jack Russell Terrier and the Smooth Fox Terrier. The onset of symptoms occurs at a few weeks to months of age.<\/p>\n

Acquired Myasthenia Gravis<\/h6>\n

This is a so-called 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. \u00a0Therapy centers on stopping this immune reaction and prolonging what acetylcholine activity is still present. \u00a0This is done with a combination ofimmunosuppressive agents <\/strong>and medication<\/strong> to inhibit acetylcholinesterase.<\/p>\n

Acquired Myasthenia Gravis can be further divided into three categories:<\/h6>\n

Group 1) \u00a0<\/strong>Mild or Focal MG<\/em> \u2013 only one body part, usually the esophagus, is involved.<\/p>\n

Group 2)<\/strong> \u00a0Moderate Generalized MG<\/em> \u2013 appendicular \u00a0(limb) weakness with or without Megaesophagus.<\/p>\n

Group 3)<\/strong> \u00a0Severe Generalized or Acute Fulminating<\/em> \u2013 rapidly progressive and usually fatal.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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Signs & Symptoms<\/h3>\n

MG affects the striated voluntary skeletal muscles of a dog.<\/h6>\n<\/div>\n<\/div>\n<\/div>\n

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Take a look at the illustration above; notice the heavy concentration of muscles in the neck area and hind quarters. \u00a0This is why 90% of dogs with MG also have Megaesophagus. \u00a0It is the reason why hind leg weakness is also a tell tale sign of MG.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

[\/vc_column_text][\/vc_column][vc_column width=”2\/3″][vc_column_text]\u2022 Megaesophagus
\n\u2022 Bark Change (usually high pitched)
\n\u2022 Hindquarter weakness or limb weakness \u2013 Sudden urge to \u201csit down\u201d. Weakness appears after exercise and condition improves after rest.
\n\u2022 Blink Reflex (Palpebral reflex) \u2013 A reflex elicited by touching the eyelid and observing for a blink. This response fatigues or is absent in animals with MG. \u00a0(watch how to test for Palpebral Reflex<\/a>)
\n\u2022 Walking with stilted rear legs, quivering or shaking rear legs, running sideways, unable to jump or climb stairs. (ex. of MG rear weakness<\/a>)
\n\u2022 Drooping lower lip \u2013 sudden increase in drool due to weakness in lower lip
\n\u2022 Drooping tail
\n\u2022 Trouble controlling urine stream or holding squat while defecating
\n\u2022 Lethargy
\n\u2022 Excessive Drool
\n\u2022 Moaning noise primarily when lying down<\/p>\n

Symptoms can vary from dog to dog. \u00a0A dog may have one symptom or many.<\/em><\/strong>[\/vc_column_text][vc_empty_space][\/vc_column][\/vc_row][\/vc_section][vc_row full_width=”stretch_row” css=”.vc_custom_1459246725272{background-color: #f6f5f2 !important;}”][vc_column][vc_column_text]<\/p>\n

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Diagnosis<\/h3>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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Congenital Myasthenic Syndrome (CMS)<\/b><\/h5>\n
Electrodiagnostic examination including repetitive stimulation testing or gene sequencing may be used to diagnose CMS. The AChR antibody blood test is not useful unless to rule out the immune-mediated MG. There is CMS genetic testing available for the Golden Retriever\u00a0and the Labrador Retriever through UC Davis Veterinary Genetics Laboratory\u00a0\u00a0https:\/\/vgl.ucdavis.edu\/<\/a><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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Tensilon Test<\/h5>\n

This test involves giving an injection of edrophonium chloride (brand name Tensilon) intravenously to a patient suspected of having myasthenia gravis. \u00a0Edrophonium chloride is a short-acting anticholinesterase. This allows acetylcholine to accumulate in the neuromuscular junction, strengthening the message from nerve to muscle. \u00a0A 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 titer test.<\/strong> \u00a0Treatment 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.<\/p>\n

*Tensilon is no longer available in the US. However, some neurologists are using injectable neostigmine in its place.\u00a0<\/em><\/p>\n

Watch Buddy\u2019s positive Tensilon test<\/a><\/h6>\n
Watch Lily\u2019s Positive Tensilon test<\/a><\/h6>\n
Focal MG Pre and Post Positive Tensilon Test<\/a><\/h6>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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Acquired Myasthenia Gravis<\/h5>\n

A blood test can be done to check for antibodies against acetylcholine receptors. \u00a0It is called an AChR test. \u00a0This blood test is able to detect 98% of pets with myasthenia gravis<\/strong>. \u00a0When antibodies drop to less than 0.6 nmol\/L, clinical signs generally resolve.<\/p>\n

Serum should be collected before corticosteroid therapy is initiated because immunosuppressive doses of corticosteroids for longer than 7-10 days lower antibody concentrations.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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Seronegative myasthenia<\/h5>\n

occurs in approximately 2% of dogs. The percentage of positive tests in the focal form of MG may be slightly less, but currently there is no other way to diagnose the form of MG. \u00a0If the vet strongly suspects MG and antibody test is negative, the positive clinical findings probably should take precedence over negative confirmatory test and a diagnosis of possible MG should be made and treatment should be started. \u00a0If clinical signs were recent in onset, retesting in 1-2 weeks may confirm the diagnosis.<\/p>\n

The test is available through one lab, Comparative Neuromuscular Lab at the University of California, San Diego, in LaJolla, CA. \u00a0The test takes between 5-7 business days to perform after it is received.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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Chest Radiographs (X-Rays)<\/h5>\n

A chest radiograph set should be taken to check for thymoma<\/strong>. A thymoma is a tumor on the thymus gland. Surgery to remove the tumor is sometimes recommended for patients who have thymic masses so it is important to identify these patients. Thymoma may be associated with an acute, fulminating MG. \u00a0Thymoma is much more prevalent in cats. In dogs, only around 3-4% of patients will fit this category.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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Another reason to take a chest radiograph is to look for megaesophagus and aspiration pneumonia.<\/p>\n

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Treatment<\/strong><\/h3>\n
Congenital Myasthenic Syndrome (CMS)<\/h6>\n
Jack Russell Terriers, Smooth Fox Terriers etc… that have mutations in the AChE gene may benefit from cholinesterase inhibitors such as pyridostigmine. Albuterol is used to treat a specific form of CMS where a mutation is identified in the COLQ gene. Labradors and Golden Retrievers may benefit from albuterol treatment. For further information contact Comparative Neuromuscular Lab\u00a0https:\/\/vetneuromuscular.ucsd.edu\/<\/a> or UC Davis Neurology Services\u00a0https:\/\/neurology.vetmed.ucdavis.edu\/<\/a><\/div>\n
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Acquired Myasthenia Gravis<\/h6>\n
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Anticholinesterases \u2013 first line of defense<\/strong><\/p>\n

Pyridostigmine <\/strong>\u00a0is the typical medication used to prolong the action of acetylcholine. \u00a0Neostigmine <\/strong>\u00a0is also sometimes used although Pyridostigmine\u00a0is preferred for fewer side effects. \u00a0By inactivating acetylcholinesterase, the receptors that have not been destroyed by the immune system can bind acetylcholine longer. \u00a0 It is typically given orally 2 to 3 times daily with food. \u00a0The syrup form should be diluted with equal parts water. \u00a0It comes in syrup, tablet and time span forms. \u00a0Close supervision with your veterinarian is advised in regards to dosing these drugs. \u00a0If patient exhibits signs of worsening weakness, vomiting, cramping, diarrhea, tearing or drooling the vet should be notified immediately. \u00a0Many canine patients will require no further treatment beyond this medication.<\/strong><\/p>\n

Sometimes corticosteroids, immune-suppression drugs, like prednisone, azathioprine,\u00a0mycophenolate\u00a0mofetil, and cyclosporine may be used if clinical signs of MG are not completely relieved with anticholinesterase drugs.<\/strong> Prednisone<\/strong> is a synthetic drug taken by mouth that resembles natural hormones produced by the cortex of adrenal glands. \u00a0The body depends on these hormones, called corticosteroids, during stress. Prednisone has a great many potential undesirable effects in dogs including suppression of adrenal gland functions, marked muscle weakness, and muscle atrophy.<\/p>\n

Unique to MG is the possibility of increasing weakness during the first two weeks of prednisone therapy. \u00a0This necessitates close medical supervision when prednisone is instituted, either on an outpatient or in-hospital basis. Azathioprine also may be of use 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.<\/p>\n

Medications can be complicated and must be monitored closely by you and your veterinary care professional.<\/strong><\/p>\n

Plasmapheresis or Plasma Exchange<\/strong> is a\u00a0treatment in which plasma (containing pathological\u00a0antibodies) is removed and exchanged with donor plasma. This is a treatment used often in human MG. Dogs may have 3-5 treatments and it requires hospital stay. It can be done in some university veterinary hospitals and larger vet specialty hospitals. It is quite costly if you do not have pet insurance that will cover it.The advantages are dogs can became ambulatory within 3 days of starting treatment with subsequent resolution of regurgitation and megaesophagus. Read Wasabi’s story<\/a><\/p>\n

Remission<\/h3>\n

Here\u2019s the really, really good news!<\/strong> Unlike humans, canines can actually go through spontaneous remission<\/strong> sometimes as early as four months after first clinical signs. The average time for remission is 6-8 months, with some dogs taking over a year to go into remission. \u00a0Many times the megaesophagus resolves as well.<\/p>\n

Prognosis<\/strong><\/p>\n

Prognosis is good! \u00a0As long as the symptoms of megaesophagus are well managed to lessen the danger of aspiration pneumonia, your pup has a good chance of kicking this thing!<\/strong><\/p>\n

Follow Up and Tips<\/h3>\n
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    Periodic chest x-rays and AChR antibody titer test<\/strong> are suggested to monitor the disease until remission is achieved. \u00a0Many Neurologist DVMs suggest every 3 months.<\/p>\n<\/li>\n

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    Wean off of meds slowly with your vets guidance<\/strong>. \u00a0Let your veterinarian be the toxicologist with the cocktail of drugs.<\/p>\n<\/li>\n

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    Avoid stress whenever possible.<\/strong>\u00a0 Excessive heat or cold, and overexertion can exacerbate symptoms.<\/p>\n<\/li>\n

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    Do not vaccinate<\/strong>. \u00a0Please discuss this with your veterinarian.<\/p>\n<\/li>\n

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    Trust your gut. \u00a0<\/strong>If you see something that doesn\u2019t look right, contact your vet and get in for an exam.<\/p>\n<\/li>\n

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    Stay vigil. \u00a0Relapses do occur.<\/strong> Sometimes the same muscle groups are affected, and sometimes it can look completely different.<\/p>\n<\/li>\n

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    Stay in close communication with your vet, <\/strong>especially in the early days. Daily check ins are really important, whether it be by phone or email with pictures and\/or videos.<\/p>\n<\/li>\n

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    If your vet is not knowledgeable about the disease, and does not want to consult with specialist to help your dog, find another. \u00a0Look for a Neurologist DVM.<\/p>\n<\/li>\n

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    Keep a daily log<\/strong> on what meds are administered and when. Record any reaction your pup may have; progress or set backs.<\/p>\n<\/li>\n

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    This site is for general information and support, and does not replace a visit with your vet. \u00a0Your vet will have the most accurate information and hands on knowledge about your pup.\u00a0<\/strong><\/p>\n<\/li>\n

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    Remember this\u2026as bad as it may look, MG is a painless disease<\/strong>. \u00a0There is not pain associated with the weakness they are experiencing.<\/p>\n<\/li>\n<\/ul>\n

    Take heart, you are not alone in this. We are here to help you through it!<\/strong>[\/vc_column_text][vc_empty_space height=”42px”][\/vc_column][\/vc_row][\/vc_section]<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

    [vc_row][vc_column][vc_empty_space][vc_row_inner][vc_column_inner][vc_column_text] Okay, let\u2019s start at the beginning. \u00a0Myasthenia Gravis (MG), pronounced (My-as-theen-ee-a Grav-us), comes from Greek and Latin words meaning grave muscle weakness. It is a Neuromuscular Autoimmune disease. \u00a0Let\u2019s break that down: [\/vc_column_text][\/vc_column_inner][\/vc_row_inner][vc_row_inner][vc_column_inner width=”1\/2″][vc_column_text] What is the neuromuscular system? The nervous system is divided into the central nervous system (brain and spinal cord) and […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"footnotes":""},"class_list":["post-1088","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/caninemegaesophagusinfo.com\/index.php\/wp-json\/wp\/v2\/pages\/1088","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/caninemegaesophagusinfo.com\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/caninemegaesophagusinfo.com\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/caninemegaesophagusinfo.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/caninemegaesophagusinfo.com\/index.php\/wp-json\/wp\/v2\/comments?post=1088"}],"version-history":[{"count":27,"href":"https:\/\/caninemegaesophagusinfo.com\/index.php\/wp-json\/wp\/v2\/pages\/1088\/revisions"}],"predecessor-version":[{"id":1888,"href":"https:\/\/caninemegaesophagusinfo.com\/index.php\/wp-json\/wp\/v2\/pages\/1088\/revisions\/1888"}],"wp:attachment":[{"href":"https:\/\/caninemegaesophagusinfo.com\/index.php\/wp-json\/wp\/v2\/media?parent=1088"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}