Myopathy Flashcards
Define myopathy
Neuromuscular disorders in which the primary symptom is muscle weakness due to dysfunction of muscle fiber
Gross and microscopic muscle anatomy
epimysium endomysium perimysium fassicle muscle fibre/cell-in fassicles blood vessels in perimysium tendon-attaches muscle to bone
Define motor unit
A motor unit is made up of a motor neuron and all the muscle cells it stimulates.
Motor units vary in size.
Small motor units are used for precise, small movements;
large motor units are are used for gross movements.
Cause of myopathy
- Endocrine: hyper/hypothyroidism,acromegaly
- Inflammatory eg polymyositis/dermatomyositis
- Neoplastic
- Infectious disease: toxoplasmosis
- Drugs/toxin induced: corticosteroid,statins,alcohol
- Critical illness: Duchenne
- Metabolic: glycogen myopathies,acid maltase deficiency
History a/w myopathy
Weakness Generally proximal but not invariable Difficulty getting out of a low chair Difficulty going up stairs Hanging out washing, brushing hair May be weakness of swallowing Respiratory compromise Pain/myalgia
What is seen on examination w/ myopathy
Proximal weakness
Gower sign
Rashes
Wasting-pattern
Hyporeflexia
Dark urine - myoglobulinuria(Due to destruction of muscle)
Other systems need to be examined for clues as to the causes
What are the investigations to be performed that are a/w myopathy
U&E with Mg, Ca Serum myoglobin CK FBC AI screen/ ESR AChR antibody test
Others: Genetic testing PFTs CXR EMG-electromyography Muscle MRI Muscle biopsy ECG,ECHO,Holte
Diagnostic studies a/w myopathy
normal nerve conduction studies
EMG can be normal
Differential diagnosis for myopathy
Motor neuron disease ALS Late onset spinal muscular atrophy Post-polio syndrome Neuromuscular junction disorders Myasthenia Gravis Lambert-Eaton myasthenic syndrome Motor neuropathy Myelopathy/ spinal stenosis Parkinson’s
Tx of myopathy
Cause
Physiotherapy
Occupational theapy
Define myasthenia gravis
~ Muscle weakness without wasting ~ Fatiguability ~ Ocular and bulbar muscles commonly involved: Ocular: Ptosis Diplopia Eye movements Cogans lid twitch
Bulbar (neck and palatal muscles) :
chewing difficulty
nasal voice/nasal regurgitation/
severe jaw weakness;jaw hangs open
swallowing difficult and aspiration may occur w fluids
neck flexors affected more than extensors
~ Responds well to treatment
Dx of myasthenia gravis
Anti Acetyl choline receptor antibodies
Anti MuSk
Neurophysiology
