You may be asked to examine a patient who has weakness, falls, difficulty climbing stairs etc.
Routine for examination of lower limbs:
Inspect (walking aids, wasting)
Power (MRC grade) and palpate muscles for bulk and tenderness. Ask patient to rise from sitting with arms crossed. Ask them to raise arms above head. Is the weakness proximal or distal or both?
Sensation (normal unless peripheral neuropathy too)
Coordination (normal or in proportion to weakness)
Gait and Rhombergs
If time allows:
- Examine the upper limbs as well as neck flexion/extension, cranial nerves (especially CNs 3,4,6,7) and fatiguability check NB: don’t miss ptosis! (myaesthenia gravis). Make sure to look for fasciculations (seen in motor neuron disease)
- Look for a cause of proximal myopathy:
- Look closely at the skin of the face, trunk, hands and nails, limbs (dermatomyositis) NB: see “Station 5 Dermatomyositis”
- Does the patient appear Cushingoid from steroid use?
- Is there evidence of diabetic fingerprick marks? Renal replacement therapy? Goitre/thyroid eye disease? Cancer? Chronic liver disease? Acromegaly?
Present to the examiner:
This patient has proximal wasting and weakness (mention MRC grade) of the lower (and upper) limb muscles. Tone, reflexes, coordination and sensation were normal. There was no fatiguability/ptosis/opthalmoplegia to suggest myaesthenia gravis. I looked for evidence of a cause… there were (no) features of dermatomyositis, Cushing’s syndrome, acromegaly, thyroid disease, diabetes, CKD, CLD etc.
Causes of proximal myopathy:
- Inflammatory: polymyositis/dermatomyositis. NB: can overlap with other connective tissue disease eg. mixed connective tissue disease
- Other connective tissue disease eg. SLE, vasculitis, RA, systemic sclerosis.
- Cancer (paraneoplastic: carcinomatous neuromyopathy)
- Drugs (statins, steroids)
- Infections (bacterial infections, HIV, CMV, EBV, Hepatitis)
- Endocrine (thyroid, addisons, osteomalacia, cushings, acromegaly, diabetic amyotrophy)
- Toxins (alcohol)
- Metabolic (renal/liver failure, electrolyte disturbance)
- Miscellaneous (inclusion body myositis, rhabdomyolysis, sarcoidosis, mitochondrial myopathy, muscular dystrophy)
Differential Diagnosis is a neurological cause rather than muscular: cord/plexus/root/nerve/NMJ (eg. motor neuron disease, Guillain Barre syndrome, motor neuropathy, myasthenia gravis)
Other differentials include conditions not associated with true weakness:
- Polymyalgia rheumatica (pain and stiffness cause apparent weakness) +/- giant cell arteritis
- Fibromyalgia (pain, fatigue, stiffness, sleep disturbance)
- OA/rotator cuff problem (muscular atrophy and weakness secondary to joint pain)
Investigations of proximal weakness:
- Routine (FBC, U+E, LFT, Ca, P, Mg)
- CK, AST, ALT, LDH
- TFTs, vitamin D and bone profile, HBa1C, fasting glucose, cortisol, HIV, Hepatitis screen, CMV/EBV/adenovirus, serum ACE
- Rheumatological screen: ESR (normal/increased), CRP (normal usually), ANA (50-80%), ANCA, RF, anti-CCP, ‘myositis blot’ (myositis associated antibodies eg. anti-RNP, Anti-Pm-Scl, Anti-Ku, anti-Ro) and myositis specific antibodies eg. antisynthetase/anti-jo-1, anti-SRP, anti Mi2), immunoglobulins, complement
- Urine dip and urine PCR
- Nerve conduction studies and EMG (myopathic changes)
- MRI muscle eg. thigh (inflamed muscle)
- Muscle biopsy eg. thigh (inflammation) +/- skin biopsy
- Systemic assessment: ECG, CXR, Echo, lung function tests, HRCT, OGD/colonoscopy/barium swallow
- Cancer screen if dermato/polymyositis: FOB, CXR, mammogram, CT, tumour markers (PSA, CEA, CA125, CA19-9, CA15-3)
Management: treat the cause!
Written by Dr Sarah Kennedy
Resources used to write this document include those listed in the references section of this webpage and also:
Rheumatology Secrets by Sterling West