Nmj And Myopathies

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Clinical Rules for Myopathies

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-weakness is more proximal and symetrical(will have trouble getting our of chair)
-muscle bulk is normal until late in the process (atrophy will not appear until very late in the disease)
-are not focal; more generalized
-reflexes are preserved until muscle is too weak to contract
**NO SENSORY SYMPTOMS!!!

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Causes of myopathies

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*the majority are inherited!
-can be acquired through endocrine probs, toxins or an inflammatory processes(most common)

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Muscular Dystrophy (MD)

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-Duchenne & Becker, Limb Girdle MD and Myotonic Dystrophy
-all of these have an abnormality in the dystrophin associated glycoprotein complex which is a transmembrane protein that stabilizes the sarcolemma when the muscle contracts

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Duchenne MD

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-X-linked recessive disease
-muscle completely lacks dystrophin protein
-lethal...typically fatal in late 20"s

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Symptoms of Duchenne MD

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-delay in motor development around 2-5 yrs old
-mild decrease in IQ; scoliosis in preteen yrs
-a gower's maneuver is present(using arms and hands to assist getting up)
-muscle hypertrophy(muscle is replaced with fibrous and fatty tissue)
-death usually results from cardiac involvemet

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Myotonic Dystrophy

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-most common inherited myopathy in adults
-autosomal dominant
-defect in protein kinase myotonin gene on chromosome 19; many systems are affected
-onset is early childhood to late teens
-no treatments

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Symptoms of Myotonic Dystrophy

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-early cataracts*, endocrine abnormalities, cardiac involvement, peripheral neuropathy(weakness is profound and proximal)
-bilateral ptosis, long face, facial muscle weakness

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Limb-Girdle MD

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-second most common myopathy/muscular dystrophy in adults
-major form is autosomal recessive
-onset is late teens to middle adult years
-presents with proximal weakness that is progressive and insidious; difficulty walking due to affected hip girdle muscles
-by the time you are in your 40's-50's, you may be completely wheel chair bound

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Diagnosing and Treating Limb-Girdle MD

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-creatine kinase(CK) is usually elevated**
-EMG studies; muscle biopsy
-treat with aggressive steroid and immunosuppressant drugs to stop muscle destruction

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Neuromuscular Transmission Disorders

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-Can have a post-synaptic defect(most common), which is Myasthenia Gravis
-Can alternatively have a pre-synaptic defect

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Myasthenia Gravis

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-autoimmune disorder with anti-bodies to the ACh receptor; when this receptor is blocked, fewer AP's can be generated, thus weakness occurs
-can occur at any age, in any sex
-

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Presentation of Myasthenia Gravis

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-often presents with ocular findings: ptosis & diplopia
-ability to chew, swallow and speak affected as disease progresses-> breathing problems*
-symptoms improve upon resting(naps help)
-worse at the end of the day

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Clinical Work up for Myasthenia Gravis

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-check antibodies to ACh
-Tensilon Test-endrophonium(short lived cholinesterase inhibitor)
-nerve conduction studies with 3 Hz stimulation
-CT of the chest and screen for associated disorders (tumor of the thymus gland)
-test CSF for antibodies
-ice bag test

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Treatment for Myasthenia Gravis

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-anticholinesterase inhibitors(pyridostigmine)
-immunosuppression(steroids)
-Thymectomy(isnt a cure, but makes pt.'s more responsive to treatment

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Botulism

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-rare but serious condition from the bacteria Clostridium botulinum
-postsynaptic disorder; rapid progression; early death rates due to poor ventilation
-three types: infantile, wound and food-borne
-there seems to be a face/orbital/mouth to GI involvement in all 3 types, along with some form of paralysis
-infant botulism: constipation, floppy movements, irritable, no sucking, not eating well
-treat with an antitoxin

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Diagnosis of Botulism

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-clinical evaluations
-nerve conduction
-analysis of blood, stool or vomit for evidence of the toxin(may take weeks to come back, so have to start treatment early)