Myasthenia Gravis

Question 1

Myasthenia Gravis: Definition, general presentation

Answer 1

Progressive muscular weakness and fatigue with repetitive activity (if under control, progression is very slow)
Pt becomes progressively weakened with more and more repititions

Question 2

Pathology

Answer 2

Autoimmune disoder of the neuromuscular junction

Body attacks the Ach receptors on muscles- antibodies attach to receptors and prevent Ach from binding

Question 3

4 Characteristics of MG

Answer 3

1. Cranial muscles affected as well as limb muscles (myopathic weakness, prox > distal)
2. Severity of weakness varies within the day, from day to day, or over longer periods (remission and relaxation)
3. EMG: no evidence of denervation or loss of motor units, no DTR’s or atrophy
4. reversal of weakness via acetylcholinesterase inhibitors

Question 4

Epidemiology: peaks of incidence

Answer 4

1. women in teens and 20s

2. Men in 70s and 80s

Question 5

Epidemiology: Thymoma

Answer 5

15% of pts with tumor in the thymus

may trigger or maintian production of antibodies that cause the weakness

Question 6

Risk Factors of MG

Answer 6

1. hyperactivity or persistent activity of thymus gland (tumor)
2. pt or family hx of autoimmune disorder (hashimotos, MS, lupus, RA, GBS)
3. Specific human leukocyte antigen genotypes

Question 7

Types of MG

Answer 7

1. Acquired autoimmune form: more in women (teens and 20s)

2. nonimmune heritable congenital MG: more in children

Question 8

Eaton-Lambert Syndrome

Answer 8

presents like MG, but is a paraneoplastic syndrome (secondary to CA)
When they tag for the MG antibody, will not be present

Question 9

Classic Eval Test

Answer 9

Repeated EMG stimulation of Levator Palpabrae- results in weaker/no contraction –> eye droop (ptosis)
Administration of Achesterase inhibitor - repeated EMG –> ptosis does not occur

Question 10

Medication for MG (first line of treatment)

Answer 10

1. Anticholinesterases –> FIRST LINE
2. Manipulation of immune system
3. Thymectomy (sternal precautions)

Question 11

Anticholinesterases

Answer 11

1. Mestinon
2. Phystigmine
3. Edrophonium

Question 12

Methods of Manipulation for the immune system

Answer 12

1. Plasmaphoresis (acute crisis)
2. steroids
3. thymectomy (best outcome in young: 20-30)

Question 13

Clinical Stages of MG: Stage 1

Answer 13

“Ocular Myasthenia”

these pts won’t be coming into the hospital, likely will not see them

Question 14

Clinical Stages of MG: Stage 2a

Answer 14

“mild generalized myasthenia”
good drug response
can return to all activities

Question 15

Clinical Stages of MG: Stage 2b

Answer 15

“moderate generalized myasthenia”

drug response is less than satisfactory

Question 16

Clinical Stages of MG: Stage 3

Answer 16

“Acute fulminating myastenia with respiratory crisis”
poor drug response
Acute crisis- involves respiratory system; brought to ER
medications no longer working
Goal: get out of acute crisis and return to stage 2b (possible 2a)

Question 17

Clinical Stages of MG: Stage 4

Answer 17

“late severe myasthenia”

same as 3, but you had to have had the disease for at least 2 yrs –> never really leave crisis stage

Question 18

Problem List (how you should address it in PT)

Answer 18

1. Respiratory function (MUST evaluate; incentive spirometry, PFTs)
2. Vision secondary to ptosis (use steri-strips to keep eye open in therapy)
3. Fatigue (scares them! may not trust you)
4. Endurance (use intermittent, small bursts- repitition is an issue)
5. Proximal > Distal Weakness

Question 19

Monitoring a pt with MG (outcome measures, guarding)

Answer 19

Use a clear outcome measure based on repititions that can be performed before poor form appears (STS, incentive spirometry)
If you notice a decline in function, the pt may be entering into acute crisis phase

Guarding: ALWAYS right next to them- no indication they may buckle