Upper limb nerve palsies

57 Upper limb nerve palsies





Questions



image What are the causes of carpal tunnel syndrome?

image What is the sensory distribution of the hand?

image How would you test for an ulnar nerve palsy?

Nerve palsies are particularly common around the elbow and wrist. They often present with a functional deficit, and so knowledge of the underlying anatomy is important (Fig. 3.57.1). They occur as OSCE stations so it is important to know how to examine them.


image

Fig. 3.57.1 Cutaneous nerve innervation of the hand and dermatomes.




Carpal tunnel syndrome


There are 10 structures within the carpal tunnel: the median nerve and nine flexor tendons (four flexor digitorum profundus tendons, four flexor digitorum superficialis tendons and one flexor pollicis longus tendon; Fig. 3.57.2). Any process that narrows the width of the tunnel, either bony compression or fluid retention (below), will compress the median nerve as it passes through the tunnel. Causes of carpal tunnel syndrome include pregnancy (fluid retention is a common cause), repetitive strain injuries, Colles’ fracture, rheumatoid arthritis, myxoedema (hypothyroidism), diabetes mellitus, idiopathic and acromegaly (rare). The median nerve innervates four muscles in the hand (LOAF): lateral umbricals (two of these), opponens pollicis, abductor pollicis brevis, flexor pollicis brevis. The last three form the thenar eminence.


image

Fig. 3.57.2 Carpal tunnel syndrome.



Clinical features


The patient presents with numbness, tingling (‘pins and needles’), burning or pain, which is typically worse at night, in the median distribution (lateral 3.5 digits). The thenar eminence becomes wasted, and thumb abduction is weak. A nerve conduction test can be performed if there is doubt. The aims of an examination are to identify the symptoms of carpal tunnel syndrome, and to identify obvious causes.



Look


Wasting of the thenar eminence should be evident. The palmar side of the wrist might show scars from previous operations. The hands may have signs of rheumatoid arthritis, and there may be signs of systemic disease.

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Jul 3, 2016 | Posted by in MUSCULOSKELETAL MEDICINE | Comments Off on Upper limb nerve palsies

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