After a lumbar puncture for iih my pulsatile tinnitus disappeared for 1 week. then gradually returned. why is this?

Depending on: how much CSF was removed, the opening pressure and closing pressure difference might be sufficient to lower pressure up stream. Typically the return of symptoms would be minutes to hours unless there is a bit of a CSF leak at the site of tap. Carbonic anhydrase inhibitors like Diamox, (acetazolamide) Topirimate and Zonisamide can keep the CSF pressure below 20 CM H20 in many cases. Diuretics and surgery can too