All of a sudden, I'm finding I can't pick up a penny or hold a piece of paper between my right thumb and index finger. I don't have any pain or other symptoms. What could be causing this to happen?
You may be observing the first signs of a nerve entrapment. The anterior interosseous branch of the median nerve in the forearm is responsible for that movement. Pressure on that portion of the nerve could be affecting the nerve impulses to the muscles that make it possible to form a pinch grip.
The median nerve starts up in the upper arm when it is formed by the brachial plexus (a group of nerves leaving the neck and traveling down the arm). Midway down the forearm, the median nerve divides to form a branch called the anterior interosseous nerve (AIN).
The anterior interosseous nerve has no sensory branch. That's probably why you don't have any pain or numbness. It only controls movement of the flexor muscles on the inside of the forearm. It's this nerve that makes it possible for you to hold a piece of paper or make the OK sign with your thumb and index finger.
There's no way to know for sure what's happening without some diagnostic work. An orthopedic surgeon or a hand specialist will be able to perform the necessary clinical and imaging tests to figure out what's going on and what to do about it. Early, accurate diagnosis can make the difference between full recovery and permanent palsy. Make an appointment as soon as possible in order to get to the bottom of the problem.
Alan C. Dang, MD, and Craig M. Rodner, MD. Unusual Compression Neuropathies of the Forearm, Part II: Median Nerve. In Journal of Hand Surgery. December 2009. Vol. 34A. No. 10. Pp. 1915-1920.
*Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.