Shorter case, but interesting.

Pt tried to to pull the blankets back to his side of the bed in the middle of the night, felt a pop in his elbow/proximal forearm, about a month ago. Now he has difficulty bending the thumb IP joint. He can flex about 40 - 50 degrees, but with 3/5 strength. No numbness/tingling/paresthesias. Exam show just the thumb problem, normal strength, sensation and reflexes otherwise.

Median and ulnar motor and sensories were completely normal.

I tested the median nerve to the FPL, it had a distal latency of 5.1 (nl <3.6) and amplitude of 2.4 (nl > 3.8).

Needle exam normal for Delt, Bic, Tric, PT, FDIM and APB, but incresed insertional activity and 2+ fibs and PSW's in the FPL and PQ with decreased recruitment in those two, more so in the FPL. Motor unit morphology normal.

Dx - Anterior interosseous syndrome.

Could have needled the median-innervated FDP, but with ulnar-innervation of the other two and some variation, I don't rely on it.

If the EMG was negative, what would have been the most likely diagnosis?

You get some nice cases.



If the EMG was negative, what would have been the most likely diagnosis?

Come on guys/gals. Play the game. DDx of isolated thumb flexor weakness. Start with a broad differential. Think neurologic (peripheral and central) and non-neurologic. With a normal EMG - the differential shrinks.

C8 radic, FPL strain/tear, median nerve injury (some wacky deep thenar branch?)

C8 radic, FPL strain/tear, median nerve injury (some wacky deep thenar branch?)

I wouldn't think C8 radic would be enough to give thumb weakness without needle findings.

FPL injury would be the more common injury, and should be #1 on the diff Dx.

I didn't make it to the board soon enough to answer this one, but I wanted to thank PMR 4 MSK for posting such interesting cases. I love EMGs. :)