Muscle Wasting
Look For
- Decreased mass of the thenar and/or hypothenar eminence.
Causes of Localised Wasting
- Forearm flexor wasting - median nerve lesion, e.g. entrapment at or above the cubital fossa
- Thenar wasting - median nerve lesion, e.g. entrapment at or above the carpal tunnel
- Hypothenar wasting (ulnar nerve) - ulnar nerve lesion e.g. entrapment at or above the cubital fossa
Causes of Generalised Wasting
- Normal aging
- Disuse
- Malnutrition - poor diet, malabsorption, cancer
- Denervation - trauma, ALS, Guillain-Barre Syndrome, neuropathy
- Muscular disorders - inflammatory myopathy, muscular dystrophies
- Chronic disease - cancer, heart failure, COPD, infection, cirrhosis, kidney disease
Tip
- Muscle wasting and shiny skin with reddish discolouration is a very specific for reflex sympathetic dystrophy.
Muscle Spasms
Look For
- Spontaneous, uncontrollable contraction(s) of muscle. Note whether the spasm affects a single region, is generalised or affects the ipsilateral arm and leg.
Causes of Muscle Spasms
- Exercise-induced spasm (cramping)
- Dehydration
- Electrolyte abnormalities - hyper/hyponatraemia
- Hereditary dystonia - idiopathic, Huntington's, Wilson's
- Acquired dystonia - brain damage, encephalitis, parkinsonism, brain tumour, stroke, drug-induced
- Factitious dystonia
Fasciculations
Look For
- Visible, spontaneous localised muscle contraction and relaxation.
Causes of Fasciculations
- Benign / normal
- Lower motor neuron disorders - ALS, radiculopathy, peripheral neuropathy, entrapment, syringomyelia, Creutzfeldt-Jakob disease
- Metabolic disorders - thyrotoxicosis, tetanus, anticholinesterase medications
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