Compressive Neuropathies
NERVE INJURY
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Pathological processes
Usually neuropraxia +/- axonotmesis with different fibres damaged by varying degrees
Neuropraxia
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Seddon 1942
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Reversible physiological nerve conduction block
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Segmental
demyelination
due to compression
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causes loss of some types of sensation and muscle power
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recovers within days or weeks
Axonotmesis
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Axonal disruption but endoneurium and nerve in continuity.
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Wallerian degeneration
of axons occurs
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Axonal regeneration within hrs, 1-3mm/day
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Target organs atrophy, if not reinnervated within 2 yrs, don't recover
Double Crush Syndrome
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Proximal entrapment makes nerve susceptible to effects of more distal entrapment
MEDIAN NERVE
Median nerve Anatomy
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From C5,C6,C7,C8,T1
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Condensation of lateral & medial cords of
brachial plexus
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Travels lateral to brachial artery in arm, but crosses medial to artery in antecubital fossa
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No branches before elbow
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Between 2 heads of pronator teres at the elbow
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5-6cm distal to elbow gives off anterior interosseous branch (motor to FPL, FDP index finger & pronator quadratus)
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Proceeds betw. FDS & FDP
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Palmar cutaneous branch (sensory to thenar skin) arises 5cm proximal to wrist joint & overlies flexor retinaculum
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Enters carpal tunnel betw. PL & FCR
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Recurrent motor branch to thenar muscles arises at distal end of carpal tunnel
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