L05: Neuromuscular Syndromes (Carrera)

Question 1

Motor Unit

Answer 1

LMN
Neuromuscular jx
Muscle

Question 2

muscle mass and tone are maintained by:

Answer 2

tonic inputs from the LMN

Question 3

how quickly does denervation atrophy happen?

Answer 3

rapidly (5-7days)

Question 4

Common LMN signs

Answer 4

paresis, plegia
m. atrophy
poor/loss of m. tone
weakness to loss of reflexes
exercise intolerance
paretic, stiff gait
ataxia UNLIKELY

Question 5

Disease that affects nerve root of LMN

Answer 5

Polyradiculoneuritis

Question 6

Disease process that affects nerve of LMN

Answer 6

polyneuropathies (axon and myelin)

Question 7

disease processes that affects neuromuscular junction of LMN

Answer 7

tick paralysis
botulism
myasthenia gravis
snakebite

Question 8

dz proccesses that affects m.

Answer 8

inflammatory
infectious
neoplastic
snakes

Question 9

chars. of polyradiculoneuritis

Answer 9

• nerve root disorder
• demyelinating
• may require ventilation, supportive care
• mildly delayed nerve conduction velocity
• albuminocytologic dissociation on CSF

Question 10

CS of polyradiculoneuritis

Answer 10

• acute, ascending flaccid paralysis (MOTOR only)
• loss of reflexes and tone
• cn deficit (cn 7)
• weak gag reflex
• rapid recovery

Question 11

types of Polyneuropathy

Answer 11

degenerative
paraneoplastic
endocrine
genetic/heritable
infectious
toxic: vincristine (a microtubule modulator)

Question 12

CS of degenerative polyneuropathy

Answer 12

• laryngeal paresis/paralysis
• dysphonia
• esophageal dysfx
• esophageal dysfx
• paresis (esp. in PL)
• abn. gait
• common in labs; affects myelin and axons*

Question 13

Name 3 endocrine neuropathies

Answer 13

Paraneoplastic (ie. insulinoma)
Hypothyroidism
Diabetic neuropathy (cats)

Question 14

Etiology of Tick Paralysis

Answer 14

-effects NEUROMUSCULAR JX
-presynaptic neuromuscular blockade
-Dermacentor & Amblyomma most common
-Dogs flaccid 5-9d after attachment
+/- megaesophagus

Question 15

chars. of Tetanus

Answer 15

• effects NEUROMUSCULAR JX
• toxin produced by Clostridium tetani absorbed at the NMJ and travels to spinal cord
• inhibits glycine/GABA release at spinal cord –> constant m. contraction
• cats resistant

Question 16

CS of Tetanus

Answer 16

stiffness, lockjaw (trismus), sawhorse stance, elevated nictitans, risus sardonicus (grin) 5-10d post infection

Question 17

Tx of tetanus

Answer 17

• vax only in horses
• tetanus antitoxin
• abx, wound debridement
• sedatives
• supportive care

Question 18

what is tetany?

Answer 18

hyperexcitability of the membrane due to electrolyte imbalance (is not same as tetanus)

Question 19

causes of tetany

Answer 19

Na,K,Ca, or Cl- imbalance
hypocalcemia
hypoMg (cows)
strychnine

Question 20

mech. of botulism

Answer 20

botulinum toxin blocks presynaptic ACh release from the nerve terminal at the NMJ

Question 21

CS of botulism

Answer 21

-progressive, symmetric ascending paresis/paralysis
-loss of reflexes and tone
-cn 7, megaesophagus, decreased gag and jaw tone
+/- mydriasis, constipation, urinary retention

Question 22

Dx of Botulism

Answer 22

• detect organism in ingesta, serum, vomit
• neutralization in small rodents
• in vitro test measuring toxin antigenicity

Question 23

Prognosis of Botulism

Answer 23

-improves in 1-3 wks after motor endplates have regenerated (2-4mo.)

Question 24

chars. of CONGENITAL Myasthenia gravis

Answer 24

• rare
• generalized weakness since birth
• Jack Russels
• INSUFFICIENT RECEPTORS
• tx ineffective

Question 25

chars. of ACQUIRED myasthenia gravis

Answer 25

Autoantibodies against nicotinic acetylcholine receptors on the post-synaptic membrane -receptor blocked --> m. weakness -3 forms: Focal (esophageal weakness) Generalized (exercise intolerance) Fulminant (25% of generalized patients; grave) -usually immune mediated in younger dogs and neoplastic in older dogs

Question 26

CS of myasthenia gravis

Answer 26

- exercise intolerance - postural rxns INTACT - reflexes present but withdrawal may be slow - NO cn deficits - megaesophagus

Question 27

Dx of myasthenia gravis

Answer 27

- Tensilong test using ultra-short acting AChE inhibitor (think video) - ACh receptor Ab titer - Electrodiagnositcs: repetitive nerve stimulation

Question 28

Tx of myasthenia gravis

Answer 28

AChE inhibitor (increases ACh at the NMJ) Immunosuppression (stops Ab production) Tx underlying dz

Question 29

Causes of generalized myopathy

Answer 29

``` immune-mediated infectious (neospora caninum) pre/para-neoplastic (lymphoma) dermatomyositis congenital (m. dystrophies ```

Question 30

Chars. of generalized Polymyositis

Answer 30

- generalized weakness, stilted gait, dysphagia, m. atrophy - Do NOT lose reflexes - Boxers, Newfies

Question 31

Chars. of Masticatory myositis

Answer 31

-AutoAb to Type 2M variant muscle fibers, but only expressed in masticatory muscles -Acute and chronic forms: acute: pain on opening mouth, mild exophthalmia chronic: masticatory m. atrophy and fibrosis, can't open mouth

Question 32

Dx of masticatory myositis

Answer 32

serum 2M antibody titer (Gold Standard!)

Question 33

Tx of masticatory myositis

Answer 33

immunosuppression | consider m. biopsy for prognosis

Question 34

extraocular myositis

Answer 34

- can't move eyes - bilateral ventromedial strabismus - tx same as masticatory myositis

Question 35

CS of Neospora caninum

Answer 35

- polyradiculoneuritis and polymyositis - m. atrophy - contracture of PLs

Question 36

which myofibers more affected by endocrine myopathies?

Answer 36

Type 2

Question 37

Endocrine myopathy causes

Answer 37

``` Hypo (dogs) or Hyperthyroidism (cats) Glucocorticoid excess (dogs) Electrolyte derangements ```

Question 38

CS of Hyperthyroidism-induced myopathy in cats

Answer 38

- paresis - cervical ventroflexion - tremors - abnormal gait

Question 39

Toxoplasma gondii can also cause feline myopathy

Answer 39

:)

Question 40

CS of snake envenomation

Answer 40

mentation, paresis/plegia, rigidity, CP defitis

Question 41

Diamondbacks venom mech.

Answer 41

Myokymia - Ca interference on nerve membrane

Question 42

Mojave rattlesnake venom mech.

Answer 42

toxin inhibits Ach release at the presynaptic terminal of the NMJ leading to complete neuromuscular blockade

Question 43

Mech. of coral snake venom

Answer 43

- postsynaptic alpha-neurotoxins - neuromuscular blockade - generalized LMN weakness --> resp. paralysis

Question 44

name 3 congenital myopathies

Answer 44

muscular dystrophy (Goldens) myotonia congenita hyperkalemic periodic paralysis (horses)

Question 45

Exercise Induced Collapse

Answer 45

- labs - collapse, marker hyperthermia during episode but otherwise normal - dx of exclusion - cause: DNM1 mutation (gene involved in neurotransmission,etc.)

Question 46

myoclonus

Answer 46

sudden contraction-relaxation of muscles | -assoc. with distemper