Paroxysmal hypertension

If your patient has episodic (as opposed to persistent) spells of hypertension, which diagnostic avenues should you pursue? The list is actually quite small, and the one I was taught is as follows:

• Anxiety disorders, including panic attacks (usually only a mild increase in BP)
• Drug abuse (only some types, like cocaine)
• Phaeochromocytoma

Most of the other causes of hypertension lead to a persistent elevation of the blood pressure.