Motor axons supplying lumbrical muscles are less severely affected than axons 
supplying thenar muscles in the carpal tunnel syndrome; sometimes lumbrical 
motor fibers are less affected than digit 2 sensory fibers. This pattern is 
consistent with compression of both the anterior and posterior aspects of the 
median nerve in the carpal tunnel because nerve fibers responsible for thenar, 
lumbrical, and digit 2 functions lie in an anterior-posterior gradient within 
the distal median nerve. Recognition of lumbrical sparing supports the 
electrodiagnosis of carpal tunnel syndrome when the distal latency to thenar 
muscles or the palm-to-wrist mixed median nerve conduction velocity is normal.