<prompt> Periodicity is a characteristic feature in which sinus infection?Maxillary sinus infectionFrontal sinus infectionSphenoid sinus infectionEthmoid sinus infection  <response>: A frontal headache is usually severe and localized over affected sinus. It shows characteristic periodicity, ie. comes upon waking, gradually increases and reaches its peak by about midday and then stas subsiding. It is also called an office headache because of its presence during the office hours. Ref: Textbook of Diseases of ENT, PL Dhingra, 7th edition, pg no. 214 