LOL
Trust me, If anything is strong enough to break through the shell you're dead anyway, All any helmet is packed with is just hard foam, It is scary to think about stuff like that happening but if it does you're done, Anything with enough force to break through your shell is gonna break your neck most likely in the event the extra density of the foam saved it from going through.
Leather doesn't protect against spikes either, You would pretty much need military spec armor in that situation.
Sent from my toaster