My husband has hydrocephalus with shunt. placed 21 years ago. he is having headaches, some pretty severe. should we be concerned?

Shunt problem: Yes. Shunts can fail over time, and do sometimes require revision. You should see either his original surgeon (if they are still in practice) or someone who specializes in shunts (many pediatric neurosurgeons do see adult patients with hydrocephalus and shunts).There are other things this could be, so let the neurosurgeon figure that out. Let us know how it turns out.

See a neurosurgeon: There are many causes of headache. With a history of a vp shunt, i would suggest having the shunt evaluated by a neurosurgeon in their office and go from there.