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

在严重的情况下，拇指底部的肌肉会发生萎缩。

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.

现在看看对手部的影响，正中神经支配大鱼际肌，控制大拇指运动，因此正中神经受损时，拇指运动受限。