Myopathy Flashcards
what is the most common neuropathic complication of DM?
distal symmetric polyneuropathy
what characterizes symmetric PROXIMAL neuropathy?
insidious, progressive (weeks-months) weakness affecting hip and thigh muscles
what are the findings in asymmetric proximal motor neuropathy?
- prominent anterior thigh pain with weakness of quadriceps / iliopsoas with loss of patellar reflex
- initial recovery may be rapid but incomplete
which is more common in diabetic peripheral neuropathy:
- pain and paresthesias, or
- sensory weakness and sensory loss?
pain and paresthesias
what is the polyol pathway theory with respect to diabetic peripheral neuropathy?
- elevated blood glucose levels lead to high nerve glucose concentration
- glucose gets converted to sorbitol via polyol pathway catalyzed by aldose reductase which leads to decreased myoinosotol
- decreased myoinosotol interferes with Na pump
- decreased aldose reductase leads to decreased levels of NO and glutathione buffer against oxidative injury
what are the clinical features of diabetic peripheral neuropathy?
- insidious combination of sensory, motor, and autonomic features
- length-related or stocking glove pattern
- usually worse at night
what are the treatment options for peripheral neuropathy that target underlying conditions and palliative options?
- treat underlying condition: blood sugar, offending toxin, B12 / thyroid deficiency
- IVIG, plasmapheresis
- palliative / preventative: foot care, weight reduction. orthotics
what are the treatment options for peripheral neuropathy that target symptoms?
- antidepressants
- antiepileptic
- analgesics
- topical agents
what are the age of onset characteristics in myasthenia gravis?
bimodal: 15-30 (women) and 60-75 (men)
what is the clinical history for myasthenia gravis?
- hallmark: fluctuating weakness, increased with exertion and improved with rest
- ptosis, diplopia on presentation
- bulbar symptoms: facial weakness, dysarthria, dysphagia, neck flexor more than neck extensor
what is the provocative test for myasthenia gravis?
upgaze for 30’-60’
what are the muscular manifestations of myasthenia gravis?
- ocular: failure of upgaze, asymmetric ptosis
- facial muscle: unable to bury lashes, horizontal smile
- oropharyngeal: flaccid dysarthria with nasal regurgitation, jaw weakness
- limbs: upper extremities more common than lower
which upper limb muscles are primarily affected in myasthenia gravis?
deltoid and wrist
what is the pathophysiology of myasthenia gravis?
- structure and function of NMJ is altered
- anti-Ach Abs block post synaptic receptors
- blockade starts an immunological cascade damaging postsynaptic membrane
- leads to decreased ability of muscle to depolarize, and therefore, weakness
what are the diagnostic tests for myasthenia gravis?
- edrophonium
- electrodiagnostic testing, single fiber EMG
- imaging: CT
- labs: Ach receptor antibodies, anti-striated muscle Ab
what is the MOA of edrophonium?
AchE inhibitor - increases Ach at NMJ
what is the symptomatic treatment for myasthenia gravis? what are the side effects?
- cholinesterase inhibitors - inhibit breakdown of Ach at NMJ
- Gi hyperactivity, increased secretions
what is the disease modifying therapy for myasthenia gravis? who is it for and what does it do?
- thymectomy - for generalized disease under age 60
- reduces immune response
what are the immunosuppressive drugs for myasthenia gravis?
- corticosteroids
- azathioprine
- mycophenolate mofetil
- cyclosporin
what therapies are used for myasthenic crisis?
- plasmapheresis
- IVIG
what are the features of myopathies?
- weakness: symmetric, proximal, neck flexor, waddling gait
- preserved sensation / reflexes
- creatine kinase
what marker is elevated in the majority of myopathies?
CK
what are the broad categories of myopathies?
- inflammatory
- endocrine
- toxic
- muscular dystrophies
- metabolic
what are the clinical features of polymyositis?
- subacute proximal weakness
- painless
- spares eyes, face
- neck weakness, dysphagia
