Myasthenia Gravis

Question 1

What are common neuromuscular defects?

Answer 1

myasthenia gravis
lambert-eaton syndrome
congenital mysathenia

Question 2

Pathophysiology of MG:

Answer 2

antibodies are directed towards the AChR at the neuromuscular junction of skeletal muscles resulting in a decreased number of nicotinic AChR at the motor endplate.

Autoimmune disease- do not have enough AChR protein.

Question 3

What is found in patients with MG?

Answer 3

anti-AChR antibody in 80-90%

Question 4

What is MG considered, disease wise?

Answer 4

slow progressive B cell mediated

Question 5

What are the risk factors for MG?

Answer 5

age > 40
short hx of disease
thymoma
female preponderance (mean age of onset M: 42, F: 28)

Question 6

What is the first thing effected in MG?

Answer 6

occular muscles

Question 7

What is the clinical presentation of MG?

Answer 7

visual symptoms w/ limb weakness and fatigue
weakness of the bulbar muscles with speech and swallowing difficulty
evolves over a few weeks to months and then stabilizes

Resp muscles involved in MG- 20%

Question 8

T/F: activity decreases weakness of affected muscles in MG

Answer 8

false it increases it

Question 9

PE of MG:

Answer 9

variable ptosis
eye muscle weakness with diploplia (bi)
facial weakness (bi)
fatigue, poor sleep
dyspnea and orthopnea

Question 10

DX of MG:

Answer 10

tension test
repetitive nerve stimulation test
single fiber EMG
antibody measurements (AChR and MUSK)

Question 11

TX of MG:

Answer 11

beef up neurotransmission: AChE inhibitors (neostigmine and pyridostigmine)
Immunosuppresant drugs: prednisone
thymectomy
immunomodulation: PE, IV-Ig

Question 12

Drugs that can worsen MG:

Answer 12

corticosteroids
BB
Ca+ blockers
aminoglycosides
curariform drugs
Mg+

Question 13

Prognosis of MG:

Answer 13

remissions and relapses; remissions variable (40-60%)

Question 14

Guillian Barre Syndrome:

Answer 14

acute poly neuropathy, usually motor dominant

Question 15

What are the types of GBS?

Answer 15

acute inflammatory demyelinating polyneuropathy (AIDP)
acute motor sensory axonal neuropathy (AMSAN)
acute motor axonal neuropathy (AMAN)
Miller-Fisher syndrome

Question 16

What are the risk factors of GBS?

Answer 16

any age
M>F
60-70% w/ antecedant infection
surgery

Question 17

AIDP:

Answer 17

parasthesia in feet and ascending

progression of the weakness in 3 weeks = 80%

Question 18

PE of GBS:

Answer 18

symmetric weakness in limbs, usually dital and proximal
loss of DTR
mild but definite sensory loss (vibration and proprioception)
facial weakness in 50%
resp weakness in 20%
NO FEVER
bladder and bowel are spared

Question 19

Labs of GBS:

Answer 19

LP:

high protein, normal cell count

Question 20

Miller fisher syndrome:

Answer 20

ataxia
areflexia
opthalmoplegia

Question 21

Therapy for GBS:

Answer 21

IV- Ig
PE
Supportive (PT, OT…)

Question 22

Prognosis of GBS:

Answer 22

some residual neurological signs in >50%
lost reflexes
mild sensory loss
MORTALITY RATE : 5%

Question 23

T/F: activity decreases weakness of affected muscles in LES.

Answer 23

True

Question 24

Myasthenic syndrome (lambert-eaton):

Answer 24

variable weakness, improving with activity
dysautonomic symptoms may also be present
history of malignant disease (small cell carcinoma)
defective release of ACh

Question 25

Tx of LES:

Answer 25

plasmapharesis and immunosupressive thrapy (prednisone and azathioprine)

Question 26

Duchenne muscular dystrophy:

Answer 26

pseudohypertrophy of muscles
intellectual retardation
serum creatinine kinase is increased
X- linked recessive

age of onset 1-5

Distribution: Pelvic, then shoulder girdle; later, limb and respiratory muscles.

Question 27

Prognosis of Duchenne:

Answer 27

Rapid progression. Death within about 15 years after onset.

Question 28

Genetic component of Duchenne:

Answer 28

Xp21

Dystrophin (loss of functional expression)

Question 29

Becker

Answer 29

X-linked recessive
serum creatinine kinase is increased
dystrophin levels are normal but the gene is altered
Age of onset: 5-25
Distribution: Pelvic, then shoulder girdle.

Question 30

Prognosis of Becker:

Answer 30

Slow progression. May have normal life span.

Question 31

Tx for Duchenne and Becker:

Answer 31

none, prednisone to increase muscle strength and function

Question 32

Types of Myotonic dystrophy:

Answer 32

two types:
1- results from expanded CTG repeat in a protein kinase in chromosome 19
2- defect is a CCTG repeat expansion in a gene for zinc finger protein-9 on chromosome 3

Question 33

Characteristics of Myotonic dystorphy:

Answer 33

slowly progressive dominant inherited disorder
manifests in the 3-4 decade
Muscle stiffness
Marked delay before the muscles can relax after contraction
weakness and wasting of facial, SCM, and distal limb muscles

Question 34

Tx for myotonic dystrophy:

Answer 34

none