In severe situations, the thenar muscles at the base of the thumb can start to waste away.

在严重情况下，拇指底会发生萎缩。

Now moving on to the hand, the median nerve innervates the thenar muscles which control the movements of the thumb, so thumb movements are limited.

现在看看手影响，正中经支配大鱼际，控制大拇指运动，因此正中经受损时，拇指运动受限。