Frontal sinusotomy is a broad term which encompasses both external and intranasal approaches to open and/or create a permanent communication from the sinus to the nose.
Endoscopic frontal sinusotomy is defined as creating a permanent opening from the frontal sinus into the nose. This simple definition includes a range from relatively simple to highly complex procedures (Weber, 2001). The complexity of endoscopic frontal sinusotomy is determined by the site of obstruction to the outflow tract or disease within the sinus, and variations in frontal and ethmoid sinus anatomy.
The frontal sinus (FS) drains into the nose through the frontal recess (fr) which is partially bordered by the middle turbinate (mt) and the cells of the ethmoid sinus (ES). MS = maxillary sinus, up = uncinate process, if = inferior turbinate.
Variations in the uncinate process (up) can approximate the outflow tract of the frontal sinus (black arrow). As the uncinate process extends towards the floor of the frontal sinus, or towards the lateral boundary of the ethmoid sinus (i.e., lamina papyracea) as is illustrated, the frontal is prevented from draining into the nose (red).
Another anatomic variant which potentially impairs the drainage of the frontal sinus into the nose are frontal cells (Schaeffer, 1916). Frontal cells collectively include ethmoid cells extending into the ethmoid infundibulum (the funnel-like cleft which drains the anterior ethmoid sinus, yellow ellipse), or from the ethmoid into the frontal sinus (green ellipse). Frontal cells can also arise within the frontal sinus (blue ellipse).
Coronal CT scan showing frontal sinusitis (1) secondary to frontal cells blocking the sinus from draining into the nose. Although the left frontal sinus is nearly completely filled with mucous, the patient primarily complained of right frontal pain. This reflects the intermittent aeration (2) of the right sinus and its inability to equilibrate to changes in atmospheric pressure. The patient was most symptomatic during descending in an airplane. In contrast, the left frontal sinus was only symptomatic when the mucous within the sinus was infected.
Frontal sinusitis is most is frequently due to obstruction of the outflow tract or frontal recess, rather than disease within the frontal sinus (Schaefer, 1990). Therefore, most endoscopic frontal sinus surgery focuses on removing obstructing disease within the frontal recess and restoring drainage of the sinus. Such surgery is described by Draf as a type I frontal sinusotomy (Draf, 1992;1995).
Coronal illustration of right type I endoscopic frontal sinusotomy. In this procedure, surgery is confined to removal of polyps, obstructing ethmoid cells or uncinate process. vision) and progress to total blindness (modified from Rice DH, Schaefer SD. Endoscopic Paranasal Sinus Surgery, 3rd Ed. Lippincott; Philadelphia. 2003).
Draf, W. 1992 Endonasal micro-endoscopic frontal sinus surgery, the Fulda concept. Op Tech Otolaryngol Head Neck Surg;2:234-240.
Draf, W., Weber, R., Keerl, R., and Constantinidis, J. 1995 Aspects of frontal sinus surgery. Part I Endonasal frontal sinus drainage for inflammatory sinus disease. HNO 43: 352-7.
Schaefer, S.D. 1990 Endoscopic management of frontal sinus disease. Laryngoscope 100: 155-60.
Schaeffer JP 1916 The genesis, development, and adult anatomy of the nasofrontal region in man. Am. J. Anat. 20:125-143.
Weber, R., Draf, W., Kratzsch, B., Hoseman, W., and Schaefer, S.D. 2001 Modern concepts of frontal sinus surgery. Laryngoscope 111: 137-146.