Bottom screen flashes white

Hi,

My son said he dropped his dsi xl and now it won't switch on. The power light comes on and the bottom screen flashes white quickly then goes off, as does the power light.

I understand this means there's a problem with the top screen?

I can't see that the top screen is cracked, could it be a loose connector? If so do I need to take apart the top section only, or does the bottom half need taking apart too?

Many thanks!