Myasthenia Gravis, Duchenne's, Degenerative MN Disease (4Q)

Question 0

Myasthenia gravis sx are exacerbated by:

Answer 0

activity

Question 1

Myasthenia Gravis: Most frequently involved muscle groups/sx

Answer 1

Extra ocular muscles (diplopia), ptosis, muscles of mastication, dysphagia, limbs. Respiratory muscles can be involved and represent a medical emergency.

Question 2

Common myasthenia gravis etiology for young women:

Answer 2

Women with HLA-DR3 mutation. Often occurs in women with SLE or RA. Can occur secondary to thymic tumor or hyperthyroidism.

Question 3

Myasthnia gravis: primary therapy

Answer 3

Reversible cholinesterase inhibitors: pyrodostigmine bromide

Question 4

Common myasthenia gravis etiology for older men:

Answer 4

Thymoma (benign tumor of thymus) or thymic tumor, thyrotoxicosis (hyperthyroidism).

Question 5

Are muscle paresthesias symmetric in myasthenia gravis?

Answer 5

No

Question 6

Is PERRLA intact in myasthenia gravis?

Answer 6

yes

Question 7

Describe the work-up for suspected myasthenia gravis:

Answer 7

1. Get a CT to r/o thymus cancer or thyroma.
2. Demonstrate decremating muscle response via electrophysiology with repetitive 2-3 Hz stimulation of motor neuron.
3. Immunoassay for circulating Ach receptor Abs (80-90% sens) or circulating antibody to muscle-specific tyrosine kinase receptors (MuSK).

Question 8

Myasthenia gravis: refractory treatments

Answer 8

1. Thymectomy

2. Corticosteroids

Question 9

What are are some signs of an upper motor neuron lesion?

Answer 9

Babinski, hyperactive DTRs, pronator drift.
LE: weakness in flexors>extensors
UE: weakness in extensors>flexors
weakness in supinators>pronators

Question 10

Degenerative MN disease: age/risk

Answer 10

30-60 yo, +FH, smoking.

Question 11

Progressive muscle weakness w/o sensory loss or sphincter disturbance with no identifiable cause except family history:

Answer 11

Degenerative motor neuron disease.

Question 12

Progressive bulbar palsy

Answer 12

DMND that affects primarily the motor nuclei of the cranial nerves.

Question 13

Pseudo Bulbar palsy

Answer 13

Same as progressive bulbar palsy and accompanied by “pseudo bulbar” sx: uncontrollable laughing/crying at inappropriate stimuli.

Question 14

Progressive spinal muscle atrophy

Answer 14

Lower motor neuron deficits in limbs due to degeneration of anterior horn cells

Question 15

Primary lateral sclerosis:

Answer 15

purely UPPER motor neuron deficits in limbs

Question 16

Amytrophic lateral sclerosis:

Answer 16

mixed upper and lower motor neuron deficits in limbs w/ cognitive decline, pseudobulbar sx, and/or parkinsonism. Most aggressive form (fatal in 3-5 yrs)

Question 17

Dysphagia, dysarthria, difficulty chewing/coughing, drooping palate, depressed gag reflex, wasted, fasciculating tongue are all….

Answer 17

Sx of bulbar DMND

Question 18

Which DMND patients have the worst prognosis?

Answer 18

Those with bulbar sx.

Question 19

Limb muscle weakness, stiffness, w/ wasting+fasciculations

Answer 19

Spinal muscle atrophy (SMA)

Question 20

Which muscles are spared in all types of DMND?

Answer 20

Sphincters

Question 21

DMND diagnosis:

Answer 21

1. R/o other causes
2. Electromyography w/ changes in 3 spinal regions or 2 spinal + bulbar
3. Cr Kinase will be elevated but less than in muscular dystrophy.

Question 23

Duchenne’s muscular dystrophy: patient

Answer 23

X-linked, recessive. Only males get it. Present between 3 and 5 yo. .

Question 24

Duchenne’s: Sx

Answer 24

Children fall frequently and have difficulty keeping up with friends. Complaints will be of progressive muscle weakness of the girdle muscles. Disease is progressive and by 8-10 the child will need braces. Sx are made worse by prolonged sitting. By age 12, many are wheelchair dependent. It is ultimately pulmonary dysfunction due to chest deformity and scoliosis that predisposes to infection and death. 
Intellectual impairment (about 1 sd below mean for age) is also common.

Question 25

Duchenne’s: Px

Answer 25

Gower’s sign (ask child to lie prone and stand up. The child will use their hands to “walk up” their legs). Contractures of achilles tendons and iliotibial bands (by age 6). Lordosis, toe-walking, and scoliosis.

Question 26

Duchenne’s: labs

Answer 26

Creatinine phosphokinase (CPK/CK) is elevated from birth, but declines in late disease. EMG demonstrates myopathy. 
Dx:
Biopsy shows muscle fibers of varying size w/ groups of necrotic fibers and regenerating connective tissue and fat, and sample will be deficient in dystrophin (western blot or immunocytochemical staining)

Question 27

Duchenne’s: tx

Answer 27

Prednisone 0.75 mg/kg/day can slow progression for up to 3 years.

Question 28

What are some symptoms of a LOWER motor neuron lesion?

Answer 28

Hypoactive DTRs, atrophy, fasciculations

Question 29

Duchenne’s clinical course

Answer 29

Progressive. By age 6- heel strictures, toe-walking, lordosis.
8-10 yo: joint contractures require use of braces
12+: wheelchair bound
Age 16: significant scoliosis causes chest deformation, loss of pulm function, recurring infections, death.