200 THE HEAD AND NECK 



maxillary sinus is opened into, and there is danger of surgical 

 emphysema occurring, unless the patient is warned not to blow 

 his nose. 



The Frontal Air Sinus arises soon after birth as an out- 

 growth of the mucous membrane lining the middle meatus of 

 the nose, but it does not begin to enlarge until the seventh year. 

 It grows upwards and backwards, and penetrates into the antero- 

 medial portion of the orbital part of the frontal bone. The 

 two sinuses are separated from one another by a thin septum, 

 which, although median below, is usually deflected to one or 

 other side above. According to Logan Turner the average 

 dimensions of the frontal sinus are : Height, from the fronto- 

 maxillary suture upwards, i J inches ; width, from the septum 

 laterally, i inch ; depth, from the surface backwards, between 

 the orbit below and the anterior cranial fossa above, f inch. 

 As the cavity is lined with muco-periosteum, which is continuous 

 with the nasal mucosa, the sinus may be infected secondarily to 

 nasal mischief. On the other hand the anterior and middle 

 ethmoidal cells are frequently infected by direct spread from a 

 diseased frontal sinus. The infundibulum, or duct of the sinus, 

 is not disadvantageously situated for drainage, but, owing to 

 small bony septa which may be present, loculi are sometimes 

 formed, and they prevent pus from draining away into the 

 nose. 



Empysema of the Frontal Sinus can be recognised by trans- 

 illumination or radiograms (Fig. 59), and, by these means, the 

 position of the septum between the two sinuses can be ascertained. 

 This detail is of extreme importance, as the surgeon must be 

 certain of opening the infected sinus only. Retained pus in 

 the frontal sinus may find its way through the floor into the orbit, 

 and point at or near the medial palpebral commissure (inner 

 canthus). 



The sinus is approached from in front by an incision which 

 follows the eyebrow, and may be extended medially and down- 

 wards on to the nose. After it has been opened up, the infun- 

 dibulum is enlarged so as to permit the passage of a drainage 

 tube down into the nose. In this process the anterior ethmoidal 

 cells, which are usually affected, are broken down, and the an- 

 terior extremity of the inferior concha (turbinated bone) will 

 probably require to be removed. 



Fractures of the frontal bone may open into the frontal sinus 

 without involving the cranial cavity. In these cases, as in 



