What are the usual causes and treatment for headache at the base of the skull?

Several but commonly: Commonly a headache starting at the base of the skull or neck is a tension-type headache. They're often throbbing in character & range in severity from mild to severe. Typical otc meds can help(i.e. Tylenol, (acetaminophen) aleve, etc), but appropriate dosing & precautions should be followed. Prevention/treatment approaches include stretching, exercise, massage, stress-reduction, stress-management. See doc 4 more.

Occipital neuralgia: Sounds like occipital neuralgia which is caused by an irritation of the occipital nerve as is comes through the muscles in the back of the neck. It is commonly seen in patients with other headaches or pain syndromes. It may not respond well to usual headache medications. It can be treated with an occipital nerve block.