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Cases
found in certain professions where flexion-extension
wrist movements are repeated intensively and frequently
also suggest a micro- traumatic factor due to excessive
use.
This
is because the tendons which cross the carpal tunnel
beside the median nerve slide along a structure
know as the synovial sheath which allows them to
function smoothly. For mechanical, inflammatory
or hormonal reasons, the sheaths thicken and their
intra-tunnel volume increases, thus compressing
the nerve.
So-called secondary syndromes, i.e. linked to a
recognised illness, are caused by traumatism to
the wrist, inflammatory rheumatism (rheumatoid arthritis),
endocrinous diseases, the most frequent being diabetes,
hypothyroidism or renal failure requiring haemodyalisis,
and local causes represented by tumours or synovial
cysts, for example (the most obvious solution suggested
ever since the first scientific publication on the
subject by Dr Phalen being surgery).
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