Y4 Myopathy Flashcards
what are features of myopathy?
Gradual onset
Symmetrical, proximal weakness: difficulty combing
hair, climbing stairs, getting up from chairs
what are the reflexes of myopathy?
preserved - normal
what is the difference in locations affected between myopathy and neuropathy ?
neuropathy - distal
myopathy - proximal
what two conditions have fatiguablity ?
MG, LEMS
what type of myopathy would be indicated by pain on exercise ?
ischaemia or metabolic myopathy
what type of myopathy would be indicated by pain at rest ?
inflammyopathy
what investigations should be done for myopathies?
ESR, CK, AST, LDH
EMG
state two inflammatory myopathies ?
Polymyositis
Dermatomyositis
what metabolic conditions can cause myopathies ?
Hyperthyroidism, Cushing’s, ↑/↓Ca2+
what medication can cause myopathies ?
steroids, statins, EtOH
state the two common types of muscular dystrophies ?
Duchennes
Beckers
what is the genetic inheritance of muscular dystrophies ?
X linked
what age does duchennes present ?
4years
what are the features of duchennes?
Difficulty standing
Calf pseudohypertrophy
Respiratory failure
what one investigation apart from genetics can confirm duchennes?
↑↑CK
is duchennes or beckers more severe?
duchennes
what muscular dystrophies has Difficulty puffing cheeks and raising arms above head?
Facioscapulohumeral MD
what is the genetic inheritance of Facioscapulohumeral MD ?
Autosomal dominant
what are three signs of Facioscapulohumeral MD ?
Weakness of face, shoulders and upper arms
(often asymmetric ̄c deltoids spared)
Winging of scapula
Foot drop.
what is the cause of Myotonic Dystrophy?
Cl- channelopathy
what does the face look like with myotonic dystrophy ?
Myopathic facies: long, thin, expressionless
Wasting of facial muscles and SCM
Bilateral ptosis
Dysarthria: myotonia of tongue and pharynx
what is myotonia ?
Myotonia: slow relaxation
what do the hands look like in myotonic dystrophy?
Myotonia: slow relaxation
E.g. inability to release hand after shake
Wasting and weakness of distal muscles + areflexia → wrist drop
Percussion myotonia: percuss thenar eminence → involuntary thumb flexion
state some other features of myotonic dystrophy?
Frontal balding Cataracts DM Cardiomyopathy, tachy- / brad-arrhythmias Dysphagia Testicular atrophy
what medication can improve myotonia during myotonic dystrophy?
phenytoin
what is the pathophysiology of myasthenia gravis ?
Autoimmune disease mediated by Abs vs. nicotinic Ach receptors.
what are the reflexes like with myasthenia gravis?
normal
state the presenattion of myasthenia gravis ?
- extra ocular
- bulbar
- face
- neck
- limb
Extra-ocular: bilateral ptosis, diplopia
Bulbar: voice deteriorates on counting to 50
Face: myasthenic snarl on attempting to smile
Neck: head droop
Limb: asymmetric, prox. weakness
what two abs are present in myasthenia gravis ?
Anti-AChR Abs
MuSK abs
what investigations should be done for myasthenia gravis ?
Tensilon Test Give edrophonium IV +ve if power improves w/i 1min Anti-AChR Abs EMG
what gender is myasthenia gravis associated with <50 and >50yrs ?
<50 = women >50 = males
what condition is myasthenia gravis associated with <50yrs ?
thymic hyperplasia.
what condition is myasthenia gravis associated with >50yrs ?
thyme tumour/atrophy
what medication can be given for myasthenia gravis?
Anticholinesterase: e.g. pyridostigmine.
what is the management of myasthenia gravis ?
steroids anti cholinesterase immunosuppression (methotrexate) IV Ig plasma exchange (plasmapheresis) thymectomy
what is a Myasthenic Crisis?
Weakness of respiratory muscles during relapse may be lethal.
how is a myasthenic crisis monitored ?
Monitor FVC: vent support if <20ml/kg
what does LEMS stand for
Lambert-Eaton Myasthenic Syndrome
what is the pathophysiology of LEMS ?
Abs to VGCC ↓ influx of Ca2+ during presynaptic excitation → ↓ presynaptic ACh-vesicle fusion.
therefore less ACh being released and binding to receptors
what does VGCC stand for in LEMS ?
voltage-gated calcium channels
what are two common causes of LEMS ?
Paraneoplastic: e.g SCLC
Autoimmune
what abs are present in LEMS ?
anti VGCC abs
what is the presentation of LEMS ?
same as myasthenia gravis + Leg weakness early (before eyes) Extra: Autonomic and areflexia Movement improves symptoms Small response to edrophonium
what treatment is available for LEMS?
3,4-diaminopyridine or IVIg
how does botulism toxin work?
prevents ACh vesicle release
what is the presentation of botulism ?
Descending flaccid paralysis ̄c no sensory signs
what is the treatment for botulism ?
benpen + antiserum
