Flashcards in Neurology: Weakness and Muscle Disease Deck (42):
Describe the pathogenesis of Myasthenia Gravis.
A trigger causes antibodies to be directed against ACh receptors which block and prevent activation. Complement may also activate and cause damage to muscle membranes.
What feature on CT scan of the thorax may indicate MG?
Enlarged thymus or thymoma due to increased Ab production.
What two muscular regions are the biggest worry if they are affected by MG?
Pharyngeal muscles and respiratory muscles.
Describe the test that can be used for MG diagnosis.
-use edrophonium (AChase inhhibitor) and if symptoms improve it is a (+) test
Other tests include:
-Ab testing for anti-AChR, anti-MUSK, anti-striated muscle antibodies
How can MG be differentiated from:
2. Muscular Dystorphies
1. No diplopia or eye symptoms
2. No diplopia or eye symptoms
3. Symptoms gets worse with exercise (LE it gets better)
4. Botulism can be diagnosed with micro tests and generalized descending paralysis
Name two medications that can treat MG.
Name 3 procedures that can treat MG.
2. IV IgG
-both clear immune attack on host
3. Surgical removal of thymoma
Name some immunosuppressive drugs that can be used to treat MG.
Steroids, azathioprine, cyclophosphamide, cyclosporin, mycophenolate mofetil
What is Myasthenic Crisis?
Progression of myasthenia gravis that is defined as a need for ventilator support.
Can occur after major surgery, infection, or steroids.
How is MG different from Cholinergic crisis?
CC won't get better with a tensilon test because no ACh is being made.
What causes neonatal mysathenia?
Maternal antibodies cross the placenta and affect the fetus.
What is the cause of congenital myasthenia?
Autosomal recessive inheritance leading to a synaptic dysfunction from faulty protein production. Patients usually present with ophthalmoplegia.
What are some drugs that can cause Drug-Induced Myasthenia?
Neuromuscular blockers and "-mycin" antibiotics.
D-penicillamine, phenytoin, trimethodone, colistin
What is the pathogenesis of Lambert Eaton syndrome?
Ab attack of presynaptic calcium channels to prevent NT release.
What condition is associated with LE syndrome?
Small cell lung carcinoma (also breast and lymphomas)
-considered a paraneoplastic syndrome
What are 5 clinical features of LE syndrome?
3. Dry mouth
4. Metallic Taste
5. Autonomic Signs
Ideal treatment for LE syndrome.
Treat the tumor causing the Ab response.
Name the protein that is attacked by the botulinum toxin.
(a snare protein)
Best treatment for botulism toxin.
(anti-toxins usually take too long and the damage is already done)
How do you diagnose a Potassium Associated Paralysis?
Check the electrolyte balance in the blood.
What kind of weakness presents in myopathies?
Proximal, usually shoulder or hip joints
Protein missing in Duchenne Muscular Dystrophy (DMD).
What are the clinical features of DMD?
Symptoms before Age 3
No more walking by age 11
Pseudoypertrophy of calves
What is the genetic therapy for DMD?
Inserting a truncated dystrophin gene into DMD patients to improve the condition to Becker.
How can females be tested to see if they are carriers for DMD?
Check CPK (creatine phosphokinase) levels
-will be elevated in carriers
-same as creatine kinase
What is the Beevor Sign?
Test for Facioscapulohumeral Muscular Dystrophy.
-have a patient sit up from supine position, if the belly button moves it indicates FMD.
What is clinically significant on H&P for FMD?
Patients cannot whistle
Weakness is asymmetric and in the face and shoulder.
What is myotonic dystrophy (Steinert disease) and what is unique about its clinical presentation?
Autosomal dominant (chromo 19) defect in muscle membrane function.
-tight hand shake, they cannot let go due to myotonia
-weakness and wasting in DISTAL limbs
What is unique about the EMG test for Myotonic dystophy?
It makes a funny noise? He imitated it in class.
How do we treat myotonic dystrophy?
Pacemaker if they have cardiac arrhythmias
Eye surgery for any caratacts
Phenytoin, quinidine, procainamide for the myotonia
What is unique about the presentation of myotonia congenita?
Very young kids present with a very muscular appearance.
What is one unique symptoms of tetany?
What glycogen storage disorder can lead to cramps?
Treatment for cramps.
Stretching, phenytoin, diazepam, procainamide, carbamazepine
Where does the rash present in patients with Dermatomyositis?
Face, eyelids, extensor surfaces of knuckles, elbow, knees
What kinds of cancers are associated with Dermatomyositis?
Lung, breast, GI
(basically the most common cancers)
What are the clinical features with polymyositis?
-Proximal muscle weakness
-middle age onset
-EOM are always intact
-no improvement with medication
How is polymyositis diagnosed and treated?
Diagnose with H&P, biopsy, Labs (CPK, Sed rate), EMG
Treat with steroids and supportive treatments
What drug class is associated with causing myopathies?
Cholesterol drugs (statins)
How is zidovudine associated with causing myopathies?
Interferes with mitochondrial function.
What are the features of myopathies caused by:
Hyper: mild to moderate, tremor, twitching, fasciculations
Hypo: stiffness, myoedema, "hung-up" reflexes, increased CPK.