What are the differential and workup for a patient with findings suggestive of idiopathic intracranial hypertension without papilledema on examination?  

I agree with Dr. @Goldberg, and find it less difficult to "justify" a lumbar puncture than Dr. @Subei, although admittedly very sympathetic to his approach. I would perform an LP. Lumbar puncture is a very low-risk procedure and in this setting, it isn't all about visual loss, although that is clear...

I look at it from a different approach. There is no immediate threat to visual function if there is no disc edema. How would the LP be helpful? It will tell you whether the opening pressure is high or not. In either case, a patient with increased ICP (holocephalic headache, pulse synchronous tinnitu...

If the patient has the endocrinological picture associated with IIH, the headaches typical of IIH I would do an LP and measure the pressure.

I would do a spinal tap. I would want to know if indeed the opening pressure is increased, what could possibly be causing it to be increased, and see if there is anything treatable so I may potentially prevent intracranial hypertension from eventually causing papilledema, while I still can. Besides,...