neuromuscular Dz

Question 1

What potential stages of the neuromuscular system may be affecte?

Answer 1

• neuropathy
• junctionopathy
• myopathy
  > many different diseases give very similary presentations

Question 2

Cardinal signs of neurouscular dz

Answer 2

>  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?)
- regurgitation 
- megaoesophagus
- laryngeal paralysis
- dyspnoea
- dysphonia (esp. neuropathies)
- myalgia 
- weak palpebral

Question 3

How does the proportion of striated muscle differ between species?

Answer 3

100% dog and human
80% cat
65% horse
30% pig

Question 4

How may weakness manifest?

Answer 4

• tremors
• plantigrade/palmigrade stance
• limbs under centre of gravity, very straight
• knuckling

Question 5

Defining the system.. Ddx of weakness?

Answer 5

> CV/resp? 
- hypotension 
- arrhythmias
- hypoxaemia
> metabolic/systemic
- hypoglycaemia
- anaemia
- sepsis
> paraneoplastic 
- thymoma -> myasthenia gravis 
> neuro

Question 6

How can cv/resp casues be ruled out?

Answer 6

• hx
• PE (auscultation, pulse rate/quality)
• |Blood pressure
• ECG
• thoracic rads
• echo

Question 7

How can metabolic/systemic causes be ruled out?

Answer 7

• hx
• PE
• haematology
• serum biochem
• electrolyte analysis
• blood gas analysis

Question 8

Which electrolytes may be imbalanced -> weakness?

Answer 8

• hypokalamia (low head carriage and stiff limbs characteristic)
• hypocalcaemia (tremors)
• hypERmagnesaemia

Question 9

How can neuro causes be refined?

Answer 9

> 1* neuro dz
- neuromuscular
> dysfunction 2* to
- CV/resp
- metabolic/systemic
= investigations (Hx, PE, Neuro exam)

Question 10

How may neuromuscular dz present other than weakness/loss of function/change in morphology?

Answer 10

• self mutilation if sensory only affected (some dz)

Question 11

How can localision within the neuromuscular region be defined?

Answer 11

VERY DIFFICULT!!! - broad generalisations…
> neuropathy
- v/absent spinal reflexes and postural reactions
- platigrade/palmigrade stance
- reduced/absent muscle tone
+- neurogenic atrophy
> junctionopathy
- normal/reduced spinal reflexes and postural reactions
+- exercise intolerance
> myopathy
- spinal reflexes and postural reactions normal
- generalised weakness
- +- myalgia

Question 12

Generalised neuromuscular disease indicates what localisation..

Answer 12

Either multiple focal lesions SC (C6-T2 and L4-S3) - RARE!

or generalised neuromuscular (most ilekly)

Question 13

Something about bear skin with 4 limbs generalised. focal neuromuscular UMN/LMN?? EMAIL!!

Answer 13

-

Question 14

How can the lesion be localised neuron/NMJ/muscle?

Answer 14

> muscle enzymes
- CK
- AST
- ALT 
> urinalysis
- myoglobinuria
= all these would suggest myopathy

Question 15

What are EMGs?

Answer 15

• electromyography
• 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

Question 16

What are the 2 main types of electrodiagnostics?

Answer 16

> 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)

Question 17

How are diagnostic tests chosen?

Answer 17

prioritise based on Ddx (6 finger rule)

• localisation
• signalment
• onset
• progression
• symmetry
• pain

Question 18

Which are the most important attributes of the disease process to limit Ddx with neuromuscular dz?

Answer 18

- onset and localisation
> acute generalised
> acute focal
> chronic generalised
> chronic focal

Question 19

Look up all highlighted ddx as suggested further reading

Answer 19

-

Question 20

Most common cause of acute focal NMD?

Answer 20

trauma

Question 21

Most common cause of chronic generalised NMD?

Answer 21

breed related

Question 22

3 pathologies that serology can be carried out for?

Answer 22

> myasthenia gravis 
- nicotinic acetylcholine R Ab titre
> masticatory myositis 
- 2M myofibre Ab titre
> infectious agents 
- toxoplasma [cats], neospora [dogs]

Question 23

What is extraocular/masticatory myositis and how can it be diagnosed?

Answer 23

• consistent clinical signs and imagine, NOT Dx on imaging alone
• immune mediated attack of the “M myofibres (masticatory) not sure about extraocular

Question 24

What further diagnostic tests can be used to define the lesion?

Answer 24

• muscle biopsy
• CSF analysis (can SOMETIMEs change wih nerve root disease) usually shows central disease
• nerve biopsy

Question 25

If generalised decreased reflexes seen, How can neuro and muscle athologies be differenttied?

Answer 25

CK to r/o muscle

- if reflexes lacking most likely neuro

Question 26

How are purebred animals workedup slightly differently?

Answer 26

• look for predisposiions if small genetic pool!

Question 27

eg. of a breed speicifc predispose disease?

Answer 27

> Bengal polyneuropathy

• recurrent relapsing/remitting de-re-myelination
• non-painul
• resolves spontaneously

Question 28

Most common cause of polyneuropathy in cats?

Answer 28

• diabetic polyneuropathy

Question 29

How do reflexes of cats compare to dogs?

Answer 29

More brisk

Question 30

What type of tumour do peripheral nerve sheath tumours behave like?

Answer 30

Soft tissue sarcoma