Neurology: Neuromuscular Disorders Flashcards
How are neuromuscular diseases located?
- Cranial nerve reflexes
- Gait and postural reactions
- Muscle bulk and tone
Spinal reflexes
* Peripheral sensory
* Central
* peripheral motor
What are pitfalls of neuromuscular lesion location?
multiple lesions
spinal shock
What are non-specific signs of generalised neuromuscular disease?
- Tetraparesis and excercise intolerance/collapse
- Stiff-stilted gait with reduced stride length, bunny hopping, fatigue
- Narrow based-stance
- Tremors/fasiculations
- Regurgitation/altered oesophageal motility
- Myalgia
- Dysphonia
- Reduced reflexes and tone
- Muscle atrophy
What clinical signs are specific to neuropathy?
- Cranial/spinal nerves
- Mono/multiple/generalised
- Motor ± sensory defecits
- Severe flaccid paresis
What are clinical signs implying junctionopathy?
- Generalised
- Classically excercise intolerance with fatigue
- Normal sensory function
- Often intact tendon refelxes
What are clinical signs of myopathy?
- Generalised or focal
- Atrophy or hypertrophy
- Specific: dimple contractions, myalgia, restricted joint movement
- Normal sensory function
- Often normal tendon reflex
What are the DDXs for acute onset generalised neuromuscular:
neuropathy, junctionopathy and myopathy?
Neuropathy
* Polyradiculoneuritis
Junctionopathy
* Myaesthenia gravis
* Botulism
* Organophosphate toxicity
Myopathy
* Polymyositis
* Immune mediated or infectious
* Electrolyte abnormalities
* Addisons
* Hypokalaemia
What are causes of chronic neuromuscular neuropathy, junctionopathy, and myopathy?
Neuropathy
* Infectious- polyradiculoneuritis, protozoal
* Toxic- lead
* Metabolic, diabetes mellitus, cushings, hypothyroidism
* Idiopathic- distal denervating disease
* Degen/inherited
Junctionopathy- congenital/acquired myasthenia gravis
Myopathy
* Inflammatory polymyostitis
* Infectious polymyositis
* Metabolic/Endocinre- hypothyroid, cushings
* Paraneoplastic
* Degen/inherited
What can cause bilateral and unilateral focal neuropathy?
What can cause a focal myopathy?
Bilateral- multiple
* infectious- neospora
* inflammatory- trigeminal
* vascular
Unilateral
* trauma
* inflammatory/infectious
* metabolic
* neoplastic
Focal myopathy
* Traumatic contractures
* Infectious/inflammatory/neoplastic
What are the initial tests for neuromuscular disease
- Haematology
- Biochem- electtrolytes, glucose, cholesterol, CK
- Urinalysis- myoglobinuria
- Chest rads- megaoesophagus, aspiration pneumonia
What further tests can be used for neuromuscular disease?
- Abdominal imaging
- Endocrine- T4, TSH, ACTH stim
- Serology
- Disease specific auto abs
- Lactate and pyruvate- mitochondrial dysfunction
- CSF- nerve roots, central involvment
What is the purpose of electrodiagnostic testing?
- Definitive evidence of dysfunction
- Localisation
- Extent and severity
- Prognosis/monitor
Electromyography- extracelluar recordings from myofibres, normal muscle silent
Nerve conduction studies- evaluate amplitude, latency and velocity of waveforms
- How are muscle/nerve biopsies processed?
- What muscle and where?
- Formalin-fixed
- Affected- lateral tricep, biceps femoris, vstus lateralis, cranial tibial
Area where muscle fibres in single orientation, distant from tendons
Describe a masticatory muscle biopsy?
- Identify temporalis dorsal to zyomatic arch
- Clip and prep
- Incise skin and frontal muscle
- Tempral has white, shiny aponeurosis
How can nerve biopsy be done?
Muscle biopsy
* denervation changes
* intrafasicular nerve branches
Fasicular nerve biopsy
* Axon strucutre and density
* Myelin sheath thickness integrity
* Schwann cells, support tissues
Common- cranial tibial muscle
- What is can cause polyradiculoneuritis?
- Where is most affected usually?
- How does it present?
- Inflammation of nerve and roots
* idiopathic/vaccine (rabies)
* Campylobacter and raw feeding
* Breed- bengal cats
* Demyelination- in severe forms
2) Ventral spinal roots- usually pure motor defeicits
3) Acute, rapid progression
* Tetra/paraparesis to non ambulatory paresis/plegia
* Flaccid
* can affect respiratory muscles
How is polyradiculoneuritis diagnosed?
How is it treated?
Diagnosis- clinical signs, history, electrophysiology and CSF analysis
Inflammation is of short progression, recovery depends on severity of damage
Treatment- supportive, physio
What causes myasthenia gravis?
- Congenital- genetic defect
- Acquired- immune- mediated (ab target nACH receptors)
How does myasthenia gravis present in cats and dogs?
Dogs- usualy generalised, can be focal (facial, pharyngeal), megaoesophagus in nearly all
Cats- usually generalised, megaoesophagus less likely, cranial mediastinal mass (thymoma)
How is myasthenia gravis diagnosed?
Clinical signs
* nAchR Ab test gold standard
* Electroiagnostic tests
* Response to cholinesterase
How is myasthenia gravis treated?
- Anti-cholinesterase
- Immunosuppresison
- Thymectomy
- Suppotive- postural feeding
Prognosis- guarded to poor, appears to be self-limiting
What causes botulism?
What are the clinical signs?
- Exotoxin produced by clostridium botulinum
- Acts to block vesicle fusion with the presynaptic membrane and ACh release
Clinical signs
* Nicotinic Ach synapses (junctionopathy)- acute onset, rapidly progressive tetraparesis
* Muscarinic ACh synapses- dysautonomia- urinary dysfunction, GI dismotility, mydriasis, reduced tear production
How is botulism diagnosed and treated?
Diagnosis
* clinical signs
* demonstrate- toxin, serology
Treatment
* supportive- bladder managment, recumbency care, megaoesopgagus managment
* physio
Prognosis- depends on severity of clinical signs
What is immune mediated polymyositis?
- Autoimmune condition usually idiopathic- can be immune diseae or neoplasia
- More common in dogs
CS- acute or chonic
* Pyrexia, stiffness, non-ambulatory, tetraparesis, reluctance to move
* Generalise weakness- atrophy
How is immune mediated polymyositis diagnosed and treated?
- Haem and biochem- inflammatory leucogram, CK
- Electro- EMG abnormalities
- Muscle biopsy
Tx- prednisolone
- What cause infectious myostitis?
- What are the clinical signs of neosporsosis in puppies?
- How is it diagnosed?
- How is it treated?
- Protozoal-neospora/toxoplasma
- Radiculoneuritis, polymyositis, pelvic limb hyperextension, ascending limb paralysis
- Clinical signs- CK/AST, EMG, biopsy, serology, PCR
- Clincamycin/trimethroptim
Poor prognosis with contractures
- What causes masticatory myositis?
- How does it present?
- How is it diagnosed and treated?
- Dogs- antibodies to 2M myosin isoform, juvenile form in CKCS
- Acute/chronic- swollen/painful MM, exophthalmos, trismus, MM atrophy
- Imaging, CK, 2M antibodies
TX- prednisiolone
- What causes trigeminal neuritis?
- What are the clinical signs?
- How is it diagnosed and treated?
- Inflammation throughout trigeminal nerves, demyelination
- Acute onset paresis/plegia of masticatory muslces- dropped jaw, normal gag anf tongue tone, sensory defecits, masticatory muscle atrophy
- DX- MRI-swollen, inflammed nerves, CSF
TX- resolves in 3 weeks
What can cause unilateral temporal muscle atrophy?
How is it treated?
Trigeminal sheath tumour or other neoplasia- MRI diagnosis
TNST treatment- radiotherapy, prednisolone
What are the different types of traumatic neuropathies?
Neuropraxia- temporary nerve damage- no disruption of the nerve or myelin sheath
Axonotmesis- disruption of the axon but intact basal lamina and myelin sheath
Neurotmesis- partial or complete transection of the nerve, partial recovery possible but inlikely
How does brachial plexus avulsion present?
C6-T2
* Monoparesis, cutaneous trunci absent ipsilaterally
* Cranial/caudal/complete
* Radial function necessary for gait
* Poor prognosis
What are the signs of a tail pull injury?
- Urinary function affected
- Perineal sensation and anal tone
- Tail base sensation
What are neurological defecits of neurological defects?
- Partial/complete plexus involvment
- Monoparesis-plegia
- Progression to myelopathy
- Palpable mass
Chronic progressive thoracic limb, pain, muscle atrophy
