68 THE NOSE AND PARANASAL SINUSES within the sinus. This may require to be got rid of by a proof puncture and lavage of the sinus (see Fig. 32, p. 73). The operation should be performed under general anaesthesia in acute cases. A trocar carrying a cannula is introduced into the antrum by piercing the bone of the lateral nasal wall near the roof of the inferior meatus where the wall is thinnest. The trocar is withdrawn and pus may be aspirated through the cannula and sent for bacteriological investigation and sensitivity tests. A Higginson's syringe is then attached to the cannula and sterile saline solution at blood heat is syringed into the antrum, the return flow passing through the ostium into the nasal cavity and collected in a receiver. In some cases a fine polythene tube is then passed into the sinus through the cannula which is withdrawn. The tube is attached to the cheek by strapping and the sinus may be washed out daily through it and a solution of the appropriate antibiotic instilled. Should there be a dental cause for the acute maxillary sinusitis the dentist may deal with the septic tooth under the antibiotic cover for the sinusitis. When the sinusitis has been precipitated by a rupture of the antral floor during a dental extraction the treatment is on conservative lines until the acute stage has settled. In many cases the sinus between the antrum and the alveolar margin will heal, but if not and if infection persists in the antrum corrective surgery will be required (p. 85). The ostium of the frontal sinus is favourably placed for drainage through the nasofrontal duct. Sometimes the duct remains occluded in spite of conservative therapy and in a few cases it may be necessary to open the frontal sinus externally through a small incision below the medial end of the eyebrow and to insert a drain into the sinus after making a small opening into its floor. Acute ethmoidal and acute sphenoidal sinusitis rarely require any form of surgical interference, but an orbital abscess following ethmoiditis will require incision and drainage. Short-wave diathermy should not be employed in the acute stage but is of value in the subacute phase to give relief from discomfort, and combined with decongestants to assist in drainage from the maxillary antrum.