Myasthenia Gravis Flashcards
Myasthenia Gravis: Definition, general presentation
Progressive muscular weakness and fatigue with repetitive activity (if under control, progression is very slow)
Pt becomes progressively weakened with more and more repititions
Pathology
Autoimmune disoder of the neuromuscular junction
Body attacks the Ach receptors on muscles- antibodies attach to receptors and prevent Ach from binding
4 Characteristics of MG
- Cranial muscles affected as well as limb muscles (myopathic weakness, prox > distal)
- Severity of weakness varies within the day, from day to day, or over longer periods (remission and relaxation)
- EMG: no evidence of denervation or loss of motor units, no DTR’s or atrophy
- reversal of weakness via acetylcholinesterase inhibitors
Epidemiology: peaks of incidence
- women in teens and 20s
2. Men in 70s and 80s
Epidemiology: Thymoma
15% of pts with tumor in the thymus
may trigger or maintian production of antibodies that cause the weakness
Risk Factors of MG
- hyperactivity or persistent activity of thymus gland (tumor)
- pt or family hx of autoimmune disorder (hashimotos, MS, lupus, RA, GBS)
- Specific human leukocyte antigen genotypes
Types of MG
- Acquired autoimmune form: more in women (teens and 20s)
2. nonimmune heritable congenital MG: more in children
Eaton-Lambert Syndrome
presents like MG, but is a paraneoplastic syndrome (secondary to CA)
When they tag for the MG antibody, will not be present
Classic Eval Test
Repeated EMG stimulation of Levator Palpabrae- results in weaker/no contraction –> eye droop (ptosis)
Administration of Achesterase inhibitor - repeated EMG –> ptosis does not occur
Medication for MG (first line of treatment)
- Anticholinesterases –> FIRST LINE
- Manipulation of immune system
- Thymectomy (sternal precautions)
Anticholinesterases
- Mestinon
- Phystigmine
- Edrophonium
Methods of Manipulation for the immune system
- Plasmaphoresis (acute crisis)
- steroids
- thymectomy (best outcome in young: 20-30)
Clinical Stages of MG: Stage 1
“Ocular Myasthenia”
these pts won’t be coming into the hospital, likely will not see them
Clinical Stages of MG: Stage 2a
“mild generalized myasthenia”
good drug response
can return to all activities
Clinical Stages of MG: Stage 2b
“moderate generalized myasthenia”
drug response is less than satisfactory
Clinical Stages of MG: Stage 3
“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)
Clinical Stages of MG: Stage 4
“late severe myasthenia”
same as 3, but you had to have had the disease for at least 2 yrs –> never really leave crisis stage
Problem List (how you should address it in PT)
- Respiratory function (MUST evaluate; incentive spirometry, PFTs)
- Vision secondary to ptosis (use steri-strips to keep eye open in therapy)
- Fatigue (scares them! may not trust you)
- Endurance (use intermittent, small bursts- repitition is an issue)
- Proximal > Distal Weakness
Monitoring a pt with MG (outcome measures, guarding)
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
