Motor Disorders and Demyelinating Diseases

Question 1

what’s the Neuro exam for the motor system?

Answer 1

Muscle appearance (watch pt walk into the room)

Muscle tone

Muscle power

Tendon reflexes (Key)

Superficial reflexes, Coordination, Gait

Question 2

what is key to document on the neuro exam?

Answer 2

Tendon reflexes

-need to write down which muscle groups have weakness and to what extent AND to document there reflexes

Question 3

what is myasthenia gravis?

Answer 3

neuromuscular disorder characterized by weakness and fatigability of skeletal muscles

Question 4

what is the underlying defect in myasthenia gravis (what’s it due to?)

Answer 4

decrease in the number of available acetylcholine receptors (AChRs) at neuromuscular junctions (post-synaptic muscle membrane) due to an antibody-mediated autoimmune attack

Question 5

is ACh released normally in myasthenia gravis?

Answer 5

YES!!! there is just a decrease in the number of ACh receptors

Question 6

the decrease in the ACh receptors in myasthenia gravis fails to trigger what? results in what?

Answer 6

fails to trigger muscle action potentials (muscles can’t receive the message from the brain) -> results in weakness of muscle contraction

Question 7

Myasthenia gravis pts do worse as ____ and improve with ___

Answer 7

Myasthenia gravis pts do worse as day goes on/repeated use and improve with rest/sleep

Question 8

what organ plays a role in the autoimmune response of MG? what’s one of the tx’s?

Answer 8

the thymus - it is abnormal in 75% of pts with AChR antibody-positive MG

***one of the tx’s is to take out the thymus

Question 9

when is the peak incidence of MG in females and males?

Answer 9

females - 20’s and 30’s (W>M)

males - 50’s and 60’s

Question 10

what are the cardinal features of MG?

Answer 10

weakness and fatiguability of muscles

Question 11

what can unmask MG, exacerbating its sx’s?

Answer 11

Menses, pregnancy, antibiotics, CCB, phenytoin, lithium

Question 12

what occurs in MG during the first few years after the onset of the disease?

Answer 12

exacerbations and remissions (remission are not complete or permanent)

Question 13

what can lead to increase MG weakness and precipitate an MG “crisis”?

Answer 13

infections or systemic disorders

-e.g. the flu -> MG gets exacerbated

Question 14

what is the characteristic distribution pattern of muscle weakness in MG? what are common initial complaints in MG?

Answer 14

The cranial muscles, particularly the lids and extraocular muscles, are typically involved early in the course of MG

diplopia and ptosis are common initial complaints

Question 15

what facial expression does the facial weakness in MG produce the pt attempts to smile?

Answer 15

a “snarling” expression

Question 16

what may MG pts speech be like? what is it d/t?

Answer 16

have a nasal timber caused by weakness of the palate or a dysarthria “mushy” quality d/t tongue weakness

Question 17

why does difficulty in swallowing occur in MG? what does it give rise to?

Answer 17

as a result of weakness of the palate, tongue, or pharynx, giving rise to nasal regurgitation or aspiration

Question 18

what is especially prominent in MuSK antibody-positive MG?

Answer 18

bulbar weakness

Question 19

in 85% of pts with MG, what happens to the weakness?

Answer 19

it becomes generalized, affecting the limb muscles as well

Question 20

when is it likely that the weakness in MG will NOT become generalized? what do these pts have?

Answer 20

If weakness remains restricted to the extraocular muscles for 3 years

Pts said to have ocular MG

Question 21

what’s the limb weakness like in MG?

Answer 21

proximal and asymmetric

Question 22

what is preserved in MG that is KEY?

Answer 22

deep tendon reflexes are preserved

Question 23

what is one thing you ALWAYS worry about with muscle disorders?

Answer 23

respiratory weakness

Question 24

sx’s of MG?

Answer 24

Diplopia, Ptosis, Dysarthria, LE weakness, general weakness, dysphagia, masticatory weakness, UE weakness