Neuromuscular disorders Flashcards
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
What is trigeminal neuritis? CS? Dx? Tx?
- Inflammation throughout trigeminal nerves including ganglia bilaterally
- Demyelination>axon degeneration
- CS =
–Acute onset paresis/plegia of masticatory muscles = dropped jaw
–Normal gag and tongue tone and movements
–Sensory deficits in ~30% of cases
–Masticatory muscle atrophy - Diagnosis =
–MRI: swollen, inflamed nerves
–CSF - Treatment = Resolves usually within 3 weeks, Supportive care
What are Cs, DX + Tx of unilateral temporal muscle atrophy?
- Clinical signs =
–Neurogenic atrophy of masticatory muscles, otherwise may be normal at onset
–May be abnormal sensation (face rubbing, absent palpebral and corneal reflexes)
–Progression to involve other cranial nerve and brainstem functions if neoplastic - Diagnosis = MRI
- Treatment = TNST – RT, prednisolone (palliative)
If a cat has a tail problem what should be checked?
- always check bladder - tail pull = urinary retention = full bladder
How are brachial plexus tumours diagnosed? Treated?
- Elecrodiagnostics
- Imaging - MRI
- Treatment + definitve diagnosis = surgery = poor prognosis if spinal involvement
