Kind of amazing that this needs to be said really isn't it?
But have a look on the special needs board and you'll see regular threads popping up from parents whose children are routinely the only one - or the only girl/boy - excluded from invitations.
It doesn't matter if you think the child wouldn't enjoy it or couldn't access it - let the parent judge that - send the invitation anyway. If the child has behavioural problems and the invitation is accepted, I think you should ask the parent to stay at the party.