Neuromuscular Junction Disorders Flashcards
What are the three major neuromucular disorders?
Myasthenia Gravis
Lambert-Eaton Myasthenia
Botulism
Myasthenia Gravis is an ________ [type] disease, that affects the ________ [where] neuromuscular junction
What are common first presenting signs (4):
Smptoms are usually _____ [timing] to when they come
Types of MG (4):
Myasthenia Gravis is an AUTOIMMUNE disease, that affects the POST-SYNAPTIC neuromuscular junction
What are common first presenting signs:
ptosis, diplopia, dysarthia, dysphagia
Smptoms are usually VARIABLE to when/severity/extent
Types of MG (4):
Ocular myasthenia, generalized myasthenia, neonatal mysathenia, myasthenic crisis
Occular myathenia are patients with only visual symptoms such as:
____ % of MG patients
many MG patients begin with visual symptoms yet _____ develop further symptoms
Occular myathenia are patients with only visual symptoms such as: ptosis, diplopia after 2-3 years
10-20% of MG patients
many MG patients begin with visual symptoms yet MOST develop further symptoms
Generalized myasthenia are patients that:
_____ % of MG patients
Generalized myasthenia are patients that have MORE THAN just visual/ocular disturbances
80-90 % of MG patients
Neonatal mysathenia occurs when …..
Will the neonate always have MG?
Neonatal mysathenia occurs when newborn is born from mother with MG, but otherwise health
Will the neonate always have MG? newborn will have MG symptoms until maternal antibodies wash out
Myasthenic crisis is due to
*neurological emergency that requires…..
Differential diagnosis…
In MG sensation and reflexes are _____ [intact/diminished/gone]
Myasthenic crisis is due to severe illness/infection of MG patient OR progression of illness of MG patient
*neurological emergency that requires intubation, mxn ventilation, ICU, RX for concurrentillness and RX for MG
Differential diagnosis…extensive infarction of brainstem (w/hyper-reflexia), guillian-bare (over some days, other specific features), acute paralysis of spinal cord (spares CN, localized loss)
In MG sensation and reflexes are REMAIN NORMAL
MG pathogenesis:
Normal immune system abnormally reacts to a specific, normal self antigen. ____ - cells stimulate _____ cells to _____ against _____ receptors
_____ R are destroyed faster than made –> decreased receptors, thus the normal architecture of post-synaptic NMJ is lost when observed under electron microscopy
_____ glands seem to pay a role, since they are important for _____ cell development; in MG patients there is ____ of the gland or thyroid tumor (thyoma) less commonly seen
What are some triggers to the development of MG?
MG pathogenesis:
Normal immune system abnormally reacts to a specific, normal self antigen. T - cells stimulate B cells to make antibodies against ACh receptors
ACh R are destroyed faster than made –> decreased receptors, thus the normal architecture of post-synaptic NMJ is lost when observed under electron microscopy
THYMUS glands seem to pay a role, since they are important for T-cell development; in MG patients there is hyperplasia/glandular enlargement of the gland or thyroid tumor (thyoma) less commonly seen
What are some triggers to the development of MG?
no known triggers of MG
Diagnosis of MG:
Clinical history is important. Neuro exam in a rested patient should be _____; if symptoms are present, injection of ______ should improve - suggestive of MG
serum ____ antibodies are most specific
some patients also have serum antibodies to ______
Diagnosis of MG:
Clinical history is important. Neuro exam in a rested patient should be NEARLY NORMAL; if symptoms are present, injection of acetylcholinesterase inhibitory drugs (edrophonium/tensilon), should improve - suggestive of MG
serum AChR antibodies are most specific
some patients also have serum antibodies to muscle specific R tyrosine kinase (MuSK) - essential protein for clustering of AChRs
RX for MG:
oral _____ drugs; these are require close monitoring due to the chance of _____ crisis.
________ durgs
surgery for _______
In a Myasthenic crisis…. (2)
RX for MG:
oral anticholinesterase drugs; these are require close monitoring due to the chance of cholinergic crisis: weakness, sweating, diarrhea, salivation, excessive urination
immunosuppresant durgs - corticosteriods (prednisone), azathioprine, mycophenoate, cyclosporine
thyectomy - surgery for thymus gland removal
In a Myasthenic crisis: IVIG (IV immunoglobins), plasmapheresis (selectively remove anit-ACHR anitbodies - TEMP sx relief, moa unknow)
Lambert-Eaton Myasthenic Syndrome (LEMS):
______ targets ____ channels at _____ membrane. Usually associated with _____ (such as ..) or else, etiology unknown
Lambert-Eaton Myasthenic Syndrome (LEMS):
Auntoimmune that targets voltage-gated calcium channels at pre-synaptic membrane. Usually associated with cancer, small cell carcinoma of the lung or else, etiology unknown
LEMS:
Clinical sx ….. preodminately where?
Do you see similar symptoms as MG?
What specific symtoms can be seen in relation with a nervous system?
Symptoms could mimick what other pathology?
LEMS CLINICAL:
muscle fatigue and weakness predominately at proximal muslces of the shoulder, hips, trunk
usually no eye, swallowing or speech involvement and muscle reflexes are decreased (unlike MG)
sensory, cognitive and pain is NOT seen in LEMS
Autonomic SX can occur - dry mouth, orthostatic hypotension, erectile dysfunction
Mimicking weakness of myopathy
Diagnosis of LEMS:
Exams-
Labs-
Associated dz states-
Diagnosis of LEMS:
Exams- repetitive nerve stimulation, electromyography labs usually show presynaptic abnormalities
Labs- serum antibodies to presynaptic VG- Ca2+ channels
Associated dz states- small cell carcinoma of the lung
Treatment of LEMS:
(4)
If related to cancer, Rx to target cancer
Drugs that enhance ACh release –> guanidine, 3,4-diaminopyridine (can improve strength or fatigue)
immunosuppresants
plasmapheresis
