. A manual of diseases of the nervous system. Fig. 53.—Paralysis of the musculo-spiral nerve; maximum extension ofwrist and fingers. The extension of the fingers progressively diminishesfrom the first to the fourth. (From a photograph.) the humerus. The pronators may ultimately become shortened. Theover-flexion of the carpus, and its deficient support by the extensor tendons, leads to a pro-minence of synovial sacs,and perhaps of the bones,at the back of the carpus(Fig. 55). In severe casesthe muscles waste, and themaximum circumference ofthe limb below the elbowmay be a quarter or half aninch
. A manual of diseases of the nervous system. Fig. 53.—Paralysis of the musculo-spiral nerve; maximum extension ofwrist and fingers. The extension of the fingers progressively diminishesfrom the first to the fourth. (From a photograph.) the humerus. The pronators may ultimately become shortened. Theover-flexion of the carpus, and its deficient support by the extensor tendons, leads to a pro-minence of synovial sacs,and perhaps of the bones,at the back of the carpus(Fig. 55). In severe casesthe muscles waste, and themaximum circumference ofthe limb below the elbowmay be a quarter or half aninch less than on the otherside. The electrical reac-tions depend on the seve-rity of the lesion of the nerve; commonly there is well-marked degene-. Fig. 54.—Prominence at back of hand from para-lysis of the extensors. The patient was sufferingfrom wrist-drop due to silver-poisoning (see , Argyria.) NEEVES OF THE ARM. 87 rative reaction. The affection of sensibility in the area supplied bythe nerve is very variable. The skin of the upper arm rarely losesfeeling; in the hand sensation may be normal, although the muscularparalysis is complete. There may be subjective tingling in the partalthough there is no loss of sensibility. The diagnosis is easy in most cases. The affection is distinguishedfrom lead palsy by its common limitation to one arm, by the affec-tion of the supinator, and often by the sudden onset; that from leadis gradual. These characters, and the commonly obtrusive cause,always suffice for the diagnosis. It must be remembered, however,that this nerve is one most frequently affected in many other forms ofmultiple neuritis {q. v.). The prognosis in disease of the mnsculo-spiral nerve depends on the severity of
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