Flashcards in neuromuscular Dz Deck (30):
What potential stages of the neuromuscular system may be affecte?
> many different diseases give very similary presentations
Cardinal signs of neurouscular dz
> weakness (generalised or focal) and excercise intolerance
> change in morphology
- muscle atrophy (generalised or focal)
- muscle hypertrophy (generalised or focal)
- limb/skeletal deformities
- gait abnormalities annd/or lameness (palmigrade/plantigrade stance esp neuropathies)
> change in function
- dysphagia (weak gag?)
- laryngeal paralysis
- dysphonia (esp. neuropathies)
- weak palpebral
How does the proportion of striated muscle differ between species?
100% dog and human
How may weakness manifest?
- plantigrade/palmigrade stance
- limbs under centre of gravity, very straight
Defining the system.. Ddx of weakness?
- thymoma -> myasthenia gravis
How can cv/resp casues be ruled out?
- PE (auscultation, pulse rate/quality)
- |Blood pressure
- thoracic rads
How can metabolic/systemic causes be ruled out?
- serum biochem
- electrolyte analysis
- blood gas analysis
Which electrolytes may be imbalanced -> weakness?
- hypokalamia (low head carriage and stiff limbs characteristic)
How can neuro causes be refined?
> 1* neuro dz
> dysfunction 2* to
= investigations (Hx, PE, Neuro exam)
How may neuromuscular dz present other than weakness/loss of function/change in morphology?
- self mutilation if sensory only affected (some dz)
How can localision within the neuromuscular region be defined?
VERY DIFFICULT!!! - broad generalisations...
- v/absent spinal reflexes and postural reactions
- platigrade/palmigrade stance
- reduced/absent muscle tone
+- neurogenic atrophy
- normal/reduced spinal reflexes and postural reactions
+- exercise intolerance
- spinal reflexes and postural reactions normal
- generalised weakness
- +- myalgia
Generalised neuromuscular disease indicates what localisation..
Either multiple focal lesions SC (C6-T2 and L4-S3) - RARE!
or generalised neuromuscular (most ilekly)
Something about bear skin with 4 limbs generalised. focal neuromuscular UMN/LMN?? EMAIL!!
How can the lesion be localised neuron/NMJ/muscle?
> muscle enzymes
= all these would suggest myopathy
What are EMGs?
- needle inserted into muscle belly, measures difference between mid and outside needle
- small waveform seen on insertion of needle
- then should be very little activity
> will not determine aetiology but will be abnormal (see waveforms) if disease affects muscle or LMN
- can help differentiate disuse and denervation atrophy
- map distribution of lesions
What are the 2 main types of electrodiagnostics?
> nerve conduction studies
- measure velocity of impulse through neuron (may indicate myelination defect)
- measure time taken for conduction through wole neuro/NMJ/muscle (by subtracting time between waveforms to pass 2 needles)
- assess axon function (amplitude of wave)
> EMG electromyography (mentioned prev)
How are diagnostic tests chosen?
prioritise based on Ddx (6 finger rule)
Which are the most important attributes of the disease process to limit Ddx with neuromuscular dz?
- onset and localisation
> acute generalised
> acute focal
> chronic generalised
> chronic focal
Look up all highlighted ddx as suggested further reading
Most common cause of acute focal NMD?
Most common cause of chronic generalised NMD?
3 pathologies that serology can be carried out for?
> myasthenia gravis
- nicotinic acetylcholine R Ab titre
> masticatory myositis
- 2M myofibre Ab titre
> infectious agents
- toxoplasma [cats], neospora [dogs]
What is extraocular/masticatory myositis and how can it be diagnosed?
- consistent clinical signs and imagine, NOT Dx on imaging alone
- immune mediated attack of the "M myofibres (masticatory) not sure about extraocular
What further diagnostic tests can be used to define the lesion?
- muscle biopsy
- CSF analysis (can SOMETIMEs change wih nerve root disease) usually shows central disease
- nerve biopsy
If generalised decreased reflexes seen, How can neuro and muscle athologies be differenttied?
CK to r/o muscle
- if reflexes lacking most likely neuro
How are purebred animals workedup slightly differently?
- look for predisposiions if small genetic pool!
eg. of a breed speicifc predispose disease?
> Bengal polyneuropathy
- recurrent relapsing/remitting de-re-myelination
- resolves spontaneously
Most common cause of polyneuropathy in cats?
- diabetic polyneuropathy
How do reflexes of cats compare to dogs?