What Causes Occipital Headaches With Loss Of Balance?

ok, well my husband is in the army and he informed me that he has been having severe headaches in the back of his head, i would like to know what can it be, also when resting his head with a headache he lost balance and was unable to stay sitting and fell over but could not help himself. can this be any sign of brain tumors or is it just migraines?