Klumpke's palsy

[spezimdoc]

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What causes the PIP and DIP flexion in Klumpke's? From what I understand (and from Moore's), all the finger flexors are innervated by C8 and T1, but FA on pg 354 says it's the "forearm finger flexors (fed by part of median nerve with C5-C7). I can't find any forearm finger flexors that are not C8 or T1.

 

[McGillGrad]

I have never seen this level of detail on questions, if that makes you feel any better.

 

[Finelines]

http://www.wheelessonline.com/ortho/intrinsic_weakness_and_claw_hand

I agree with McGillGrad though, I never saw an anatomy question that detailed. I had a few anatomy questions on my exam and they were all very straight forward, a couple on the common peroneal, 3 on the nerves of the hand (numbness of 3 1/2 digits, what nerve is involved), 3 on the blood supply to the gut and a few on the pelvis and perineum.

 

[IonClaws]

What causes the PIP and DIP flexion in Klumpke's? From what I understand (and from Moore's), all the finger flexors are innervated by C8 and T1, but FA on pg 354 says it's the "forearm finger flexors (fed by part of median nerve with C5-C7). I can't find any forearm finger flexors that are not C8 or T1.

I know it's a necrobump but I was wondering this myself and just figured it out. I want others searching the forum with the same question to have some kind of answer. There are 2 points:

1. The interossei are paralyzed in Klumpke's palsy because they are innervated only by the ulnar nerve, whose fibers arise from C8-T1. Since the interossei are the main extensors of the IP joints, flexion is unopposed. This may sound confusing because it seems like the flexors would be paralyzed by C8-T1 damage too. However this is not the case;

2. Due to innervation of the flexor digitorum superficialis (FDS) solely by the median nerve, which innervates this muscle with fibers from C7-T1, the PIP joints remain flexed. This innervation is in contrast to the flexor digitorum profundus (FDP) and the lumbricals, which receive fibers only from the C8 and T1 spinal nerves. Thus, the injury affecting C8-T1 spares flexion through the C7 fibers of the median nerve supplying the FDS. The MP joints remain extended and the DIP and PIP joints flexed because the lumbricals power the flexion of the MP joints and extension of the DIP and PIP joints.

P.S. Although the DIP joint is not controlled by the FDS, I suppose that the tendency is for the DIP joints to flex given the extension of MP and the flexion of PIP joints.