NEUROMUSCULAR DISORDERNEUROMUSCULAR DISORDERIN ANIMALSIN ANIMALS

Naveen KumarPhD Scholar

Department of Veterinary Pharmacology and ToxicologyCVSc, GBPUAT, Pantnagar, Uttarakhand

E_mail: knaveen7v@gmail.com

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Most commonly encounter diseases in veterinary clinical practices

Diseases affecting the peripheral nerves: hypothyroid neuropathy, diabetic neuropathy, and immune mediated neuropathy

Diseases affecting the neuromuscular junction: botulism, tick paralysis, and myasthenia gravis

Diseases affecting the muscles: myositis, myotonia, muscular dystrophy, and metabolic myopathies

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Out of these the most commonly reported diseases in our clinic are:

MYASTHENIA GRAVIS (MG)

Disease of the neuromuscular junction characterized by fluctuating weakness of certain skeletal muscle groups.

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MG is an autoimmune disease in which antibodies are formed against ACh and a reduction in ACh receptor sites at the neuromuscular junction

Acetycholine (ACh) is an important neurotransmitter that stimulates muscle tissue to contract

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Clinical manifestations

Easy fatigability of skeletal muscle during activity

Muscles involved: eyes and eyelids, chewing, swallowing, speaking, and breathing

Fluctuating weakness: usually strong in the morning and progressively weaker with activity

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Clinical manife…

~ 90% of patients have eye involvement Facial mobility may be impaired Muscles of limb and trunk are less often

affected No sensory or reflex loss Muscle atrophy is rare

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Therapeutic management

Anticholinesterase- prevents anticholinestersase from breaking down ACh; helps neurotransmission

i.e., Prostigmine, Mestinon Corticosteroids- decrease immune response i.e., Prednisone Plasmapheresis- removes ACh antibodies;

for short-term improvement

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LARYNGEAL PARALYSIS (LP)

Fig. 3

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LP also known as Laryngeal Hemiplegia, Recurrent Laryngeal Neuropathy and in horses may be called Roaring or Roarer’s Syndrome

Generally, large or giant breeds are most affected, especially as they get to middle age or older

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In this condition the nerves and muscles supplying the larynx, cease to function properly, causing the cartilages at the front of the larynx to remain stationary during breathing and swallowing

In a normally functioning larynx these cartilages i.e., arytenoid cartilages, open wide during inspiration, and close during swallowing, thus preventing food or water from entering the wind pipe

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Causes of LP are mostly idiopathic and Congenital

Commonly affected breeds for idiopathic LP are Irish setters and Labrador retrievers

Congenital form is seen in Bouvier de Flandres, Siberian huskies, Bull terriers and Dalmatians

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Clinical signs

The signs of LP typically develop gradually and can often be misinterpreted as ageing

Coughing (especially after exercise or exertion is probably the most frequently reported symptom), noisy breathing, exercise intolerance and a change in the sound of the bark (dysphonia)

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Clinical signs…

In sudden severe cases the dog may develop respiratory distress with bluish mucous membranes (cyanosis) in the mouth and dog may collapse

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Diagnosis

Diagnosis is based mostly on symptoms but can only be confirmed by examining the larynx under sedation or light general anaesthesia and watching for normal movement of the arytenoids

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Treatment Mild cases can usually be managed medically, using

mild sedatives and anti-inflammatory drugs to limit the swelling around the larynx that often accompanies this condition

In more severe cases may require surgery Surgery alleviates the respiratory symptoms but may

increase the risk of aspiration pneumonia

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INFLAMMATORY MYOPATHIES (IM)

A heterogeneous group of disorder characterized by nonsuppurative cellular infiltration of skeletal muscle

It is primarily an immune mediated polymyositis, not associated with any other systemic or infectious causes

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Commonly observed clinical signs include weakness, exercise intolerance and a stiff gait

Two forms of IM have been reported in dog-i. Generalized inflammatory myopathy (gIM) &ii. Focal inflammatory myopathy (fIM)

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gIM used for diffuse inflammatory myopathies, including infectious and preneoplastic syndromes

gIM include polymyositis (PM), an immune-mediated disorder

fIM is used for the localized syndromes Both forms (gIM & fIM) of inflammatory

myopathies have been reported in the dog

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Clinical signs

Clinical signs include muscle weakness, stiffed gait, and muscle atrophy

Abnormally high serum creatine kinase (CK) concentrations, abnormal electromyography (EMG), histologic confirmation of lymphocytic infiltrates in skeletal muscle

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Clinical signs …..

fIM include masticatory muscle myositis (MMM) and extraocular myositis (EOM), with cellular infiltrates restricted to these particular muscle groups

The most common clinical signs of fIM associated with MMM are inability to open the jaw, jaw pain, and masticatory muscle atrophy

Cellular infiltrates in MMM selectively affect the muscles innervated by the mandibular branch of the trigeminal nerve, including masseter, temporalis, pterygoids, tensor tympani, and tensor veli palatini muscles

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Diagnosis

A definitive diagnosis of immune mediated polymyositis is poorly defined in veterinary medicine

Although most authors agree that the disease can be diagnosed if the following features are present Clinical signs of muscle weakness Elevated serum creatinine kinase concentrations Abnormal electromyography examination with normal

motor nerve conduction velocities and Muscle biopsy shows an inflammatory infiltrate

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Treatment Treatment of immune mediated polymyositis is

based on immunosuppression, initial pain relief and supportive care

Prednisolone is the most commonly used immunosuppressive drug although other drugs such as aziathioprine may also be helpful, particularly if long term therapy is required to control the clinical signs

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CANINE NEOSPOROSIS

Causative organism Neospora caninumProtozoal parasite, closely related to

Toxoplasma gondii Most commonly reported in puppies but may

present in dogs of all ages

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In addition to canine infections, N. caninum occurs naturally in cattle, sheep, goats, deer, and horses

Neosporosis occurs worldwide, and there are no breed or sex predilections

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Although breeds like Yorkshire terrier, Cavalier King Charles spaniel, West Highland White terrier, Border collie, Springer spaniel, Husky, Great Dane, Bernese mountain dog, Irish wolfhound, Labrador retrievers and Boxers have been well represented

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Clinical signs

The course of the disease is variable Neosporosis is a neuromuscular disease usually

characterized by ascending paralysis The most commonly syndrome involves- hindlimb

paresis (which progresses to paralysis), forelimb weakness and difficulty in swallowing and breathing resulting in death of animal

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Clinical signs....

Death results from the progressive paralysis and meningoencephalomyelitis, heart failure, pneumonia

In peracute cases, animals dying within 1 week of the first signs being noticed

It is an important cause of stillbirth and abortion in cattle but no natural cases have yet been reported in cats or humans

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Clinical signs....

In chronic cases (in which signs gradually progress over several weeks). Initially owners often notice a bunny-hopping type of gait, a reluctance to jump up or a splaying out of legs when squatting

Other signs: Paresis/Paralysis of forelimb(s) only, ataxia, gait abnormalities, altered behaviour, blindness, head tilt, tremors, seizures, pneumonia, myocarditis (may cause sudden death) and/or nodular/ulcerative dermatitis may present in dog

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ThanksFor your kind attention

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