RecruitingPhase 1Drug trialGreater Occipital Nerve Blockade in Veterans With Post-concussion Headache: Sub-study 1The acute and subacute sensations that occur on the scalp with injection of different concentrations of bupivacaine for grater occipital nerve blockade will be compared. Each Veteran participant will be randomized to receive three different concentrations, which will be injected one week apart each.