Neuromuscular disorders Flashcards
(28 cards)
What are non-specific signs of generalised neuromuscular disease?
- Tetraparesis and exercise intolerance/collapse
- Stiff-stilted gait with reduced stride length, bunny hopping, may fatigue
- Narrow based-stance
- Tremors/fasciculations
- Regurgitation or altered oesophageal motility
- Myalgia
- Dysphonia
- Reduced reflexes and tone
- Muscle atrophy
- Ventroflexion of head + neck = cats
What are Ddx for acute onset neuropathy problem?
- Polyradiculoneuritis
- Distal denervating disease
What are Ddx for acute onset Junctionopathy problem?
- Myaesthenia gravis
- Botulism
- Organophosphate toxicity
- Tick paralysis
- Snake bite
What are Ddx for acute onset myopathy problems?
- Polymyositis (severe) immune mediate / infectious
- Electrolyte abnormalities - addison’s / hypokalaemia / hypothyroidism
What are Ddx for chronic progressive neuropathies?
- Inflammatory / infectious =
-chronic relapsing polyradiculoneuritis
-chronic inflammatory demyelinating polyneuropathy
-protozoal - (neospora/toxo), viral - FeLV / FIV - Toxic neuropathy = lead, vincristine OP
- Metabolic / endocrine =
-diabetes mellitus, cushings, hypothyroidism, hypoglycaemia (insulinoma)
-cats = hyperchylomicronaemia, hyperoxaluria - Idiopathic, degenerative / inherited neuropathies
What can cause localised neuromuscular disorders?
- Focal neuropathy = bilateral/unilateral
-infectious, inflammatory, vascular, traumatic, metabolic, neoplastic - Focal myopathy = traumatic, infectious, inflammatory, neoplastic
What is diagnostic approach to neuromuscular disorders?
- Haematology
- Biochemistry - electrolyes (K+, Ca2+, Na+), glucose, cholestrol, CK
- Urinalysis - myoglobinuria
- Chest radiographs - megaoesophagus, aspiration pneumonia
(Also consider abdominal imaging, endocrine tests, serology, genetic tests, CSF)
What are benefits of electrodiagnostic testing?
- Definitive evidence of dysfunction
- Localisation
- Extent + severity
- Prognosis / treatment monitoring
What muscles would you biopsy where?
- Thoracic limb = lateral head of the triceps
- Pelvic limb =
-Biceps femoris
-Vastus lateralis
-cranial tibial
How would you perform a muscle biopsy?
- Incise skin + fascia
- Isolate sample for biopsy 0.5-1cm wide 1-2cm long
- Grab + incise at one end, lift, incise other end
What is the most common nerve to biopsy?
Common peroneal nerve on lateral hindleg
What is polyradiculoneuritis? (PRN)
- Relatively common (dogs>cats) (bengal cats)
- Inflammation of nerves + roots + demyelination
- Affects ventral spinal roots = pure motor deficits
- Acute onset + rapidly progressive
-tetraparesis
-flaccid paralysis
-can affect respiratory muscles
Dx of PRN? Tx?
- Dx = clinical signs + history, electrophysiology + CSF analysis
- Tx =
-supportive = recumbency care, physio, ventilatory support
-specific = human IV Ig, (plasmapharesis)
What is acquired immune mediated myasthenia gravis?
- Antibodies target nACh receptors on post-synaptic membrane = receptor blockade + endplate destruction
- Megaoesophagus in 90% of dogs (15% cats)
- Abyssinian cats predisposed
- Can arise in cats on thiourylene med for hyperthyroid
How is M. gravis diagnosed?
- CS
- nAChR test = gold standard
- Elecrodiagnostic tests
- Response to cholinesterase inhibitor (edrphonium / neostigmine)
What is treatment of M. gravis?
- Anti-cholinesterase = pyridostigmine / neostigmine
- Supportive = postural feeding for megaoesophagus
What causes botulism? CS?
- C. botulinum from contaminated food
-blocks ACh release - CS =
-Nicotinic ACh synapses (junctionopathy) = acute onset, rapidly progressive tetraparesis
-Muscarinic ACh synapses (dysautonomia) = urinary dysfunction, mydriasis, reduced tear production
Dx, Tx + prognosis of Botulism?
- Dx = CS, electrophysiology
- Tx = supportive = bladder management, recumbency care, megaoesophagus management, physio
-anti-toxin - Prognosis = poor if impaired ventilation / aspiration pneumonia
What are different types of myositis?
- Inflammatory (generalised / focal)
- Cancer-associated - pre-neoplastic / paraneoplastic (thymoma / lymphoma)
- Infectious = protozoal, tick borne
What are clinical signs of immune-mediated polymyositis?
– Pyrexia, stiffness, non-ambulatory tetraparesis, reluctance to move, lowered head carriage, myalgia, muscle swelling
– Generalised weakness, muscle atrophy, exercise intolerance, fatigue
– +/- oesophageal involvement – regurgitation
– “Overlap syndrome” – IM polymyositis and MMM
Dx + Tx of immune mediated polymyositis?
- Dx = H+B (elevated CK/AST)
-Muscle biopsy - Tx = Prednisolone
What are CS of neosporosis in puppies?
– Radiculoneuritis and polymyositis
– pelvic limb hyperextension (usually starts in one limb and progresses to other)
– ascending paralysis of pelvic limbs with muscle contracture and arthrogryposis
Dx + Tx of infectious myositis?
- Dx = CS, CK, AST, EMG, biopsy, serology
- Tx = clindamycin / TMPS + pyrimethamine
CS, Dx + Tx of masticatory myositis?
- Causes by antibodies to 2M myosin isoform
- CS = swollen painful MM, exopthalmos, MM atrophy
- Dx = imaging, 2M antibodies, EMG, biopsy
- Tx = prednisolone + physio
