<prompt> Periodicity is a characteritic featurw in which sinus infection:Maxillary sinus infectionFrontal sinus infectionSphenoid sinus infectionEthmoid sinus infection  <response>: Pain of frontal sinusitis shows characteristic periodicity,i.e comes upon walking,gradually increases and reaches its peak by midday and then stas subsiding. It is also called office headache as it is present only during office hours. Ref Dhingra 6e p 192 