Lecture 7: Myesthenia Gravis, GBS, Myopathic disorders Flashcards Preview

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Flashcards in Lecture 7: Myesthenia Gravis, GBS, Myopathic disorders Deck (23):

Myesthenia Gravis: essentials of Dx

-fluctuating weakness of commonly used voluntary muscles, producing ax's such as diplopia, ptosis, and difficulty swallowing
-activity increases weakness
-short acting anticholinesterases transiently improve the weakness


Myesthenia Gravis: general considerations

-occurs in all ages, sometimes in association with thymic tumor, thyrotoxicosis, RA or SLE
-most common in young women with HLA-DR3
-sx's are due to ABs binding to Ach receptors so that Ach action is blocked


MG: signs/sx's

-present with ptosis, diplopia ,difficulty chewing, swallowing, resp difficulties, limb weakness or combo of these
-weakness: localized or generalized
-most likely to be affected: ocular, masticatory, facial or pharyngeal muscles


MG: Phys exam

-sustained activity of muscles increases weakness, which improves after brief rest
-NO reflex changes


MG: Dx

-Tensilon test: administer tensilon ( which prevents breakdown of Ach), if ptosis gets better than is MG
-single fiber EMG
-Antibody measurement: AchR, MUSL


MG: Tx

Neostigmine and pyridostigmine = anti cholinesterase drugs
-immunosuppressant drugs
-immunomodulation: PE or IVIg


Drugs that can worsen MG

-Ca channel blockers
-curariform drugs


Guillain-Barre Syndrome (GBS): essentials of dx

-acute or subacute progressive polyradiculoneuropathy
-weakness is more severe than sensory disturbances
-acute dystautonomia may be life threatening


GBS: General considerations

-acute or subacute polyradiculoneuropathy sometimes follows infective illness, inoculations, or surgical procedures
-associated with preceding Campylobacteri jejuni enteritis
-probably has immunologic basis but mechanism is unclear


GBS: Epidemiology

-incidence: 1-4/100,000
-any age, peak in 4th decade; males > females
-60-70% with antecedent infxn: C. Jejuni
- other causes: surgery, lymphos, lupus,


GBS: Signs/sx (AIDP)

AIDP= acute idiopathic demyelinating polyneuropathy
-paresthesias in feet then ascending
-weakness beginning distally then ascending
-can have other patterns: like onset in eye, face with descending pattern; or onset in hands and arms with descending and ascending pattern
-autonomic disturbances are common: tachycardia, cardiac irregularities, hypo/hyper-tension, facial flushing, sweating, pulm dysfxn, impaired sphincter control


GBS: Lab findings

-CSF: high protein
-nerve conduction studies: abnormal sensory condution (arm > leg); abnormal motor nerve conduction


GBS therapies

-IV Ig, PE
-supportive: PT, OT, swallow, dysautonomnia, skin, nutrition, vent. monitoring, support


GBS: prognosis

-50% left with residual near signs: loss of reflexes, mild sensory loss, abnormal nerve conduction
-10% have significant neuro deficit
-5% mortality rate



AMSAN= acute motor and sensory axonal neuropathy
AMAN = acute motor axonal neuropathy
-caused by ABs to gangliosides on axon membrane
-similar to AIDP (clinical picture similar)
-pathophys: axon loss


GBS variant: Miller fisher syndrome

-this has ataxia, areflexia and opthalmoplegia
-also associated with anti-GQ1b ABs


Lambert-Eaton Syndrome : essentials of dx

-variable weakness, typically improving with activity
-a hx of malignant dz may be present
-dysautonomic sx's may also be present


Lambert-Eaton: gen considerations

-may be associated with small cell carcinoma and occasionally with certain autoimmune dz.'s
-defective release of Ach caused by voltage gated Ca channel ABs--> leads to weakness, especially of PROXIMAL muscles of limbs
-unlike MG: power increases with sustained contraction


Lambert Eaton dx

-confirmed with electrophysiogically: muscle response to stimulation of its motor nerves increases if the nerve is stimulated repetitively at high rates


Lambert Eaton tx

-Plasma exchange and immunosuppressive therapy
-symptomatic therapy: K channel antagonists


Duschend Type MD

-X linked recessive
-onset = 1-5 y/o
-Distribution= pelvic, then shoulder girdle; later is reap muscles and limbs
-rapid progression, mortality within 15 yrs of onset
-intellectual retardation is common
-increase in serum creatinine kinase


Becker type MD

-X linked recessive
-onset = 5-25 yrs old
-pelvic then shoulder girdle weakness
-slow progression, may have normal life span
-dystrophin levels normal with increased serum CrK


Myotonic type MD

-autosomal dominant
-any age, usually 20-40 y/o
-face, neck and limb weakness
-slow progression
-other features: cataracts, frontal baldness, testicular atrophy, DM, cardiac abnormalities, intellectual changes