Frontal sinus trephining
Definition: Trephination of frontal sinus is a surgical procedure where in a small opening is made in the floor of frontal sinus facilitating drainage of its contents.
History: Trephination of frontal sinus is nothing new. It dates back to prehistoric times. Two Peruvian skulls at the Museum of Man in San Diego show evidence of frontal trephination.
Indications of frontal sinus trephining:
1. Acute sinusitis not responding to medical management
2. Can be used to identigy frontal sinus opening inside the nasal cavity during endoscopic sinus surgery
3. To prevent stenosis of the frontal sinus infundibulum after endoscopic sinus surgery
Before the actual procedure the size of the frontal sinus must be assessed by taking a occipito frontal plain radiograph. This view will acutally demonstrate the size of frontal sinus. This procedure is a must as it will help in deciding where to place the opening.
This procedure can be carried out under both local or general anesthesia. Commonly local anesthesia is preferred as it provides a relatively blood less field.
2% xylocaine admixed with 1 in 10,0000 units adrenaline is used as infiltrating agent. This mixture has the advantage of providing anesthesia as well as local vasoconstriction of blood vessels. About 1/2 ml of this solution is infiltrated over the trochlear nerve area (skin over the antero inferior part of forehead). 10 minutes is given after the injection for the drug to take effect.
Image showing the site of trephintion
The point of trephenation is located as shown in the figure above. A horizontal line is drawn between the superior limit of each orbit. Another vertical line is drawn to intersect this horizontal line exactly in the midline. The point of perforation is located about 1 cm lateral to this midline. This depends on the size of the sinus and the location of the intersinus septum.
No incision is necessary. A small puncture is made at this site using a hand drill. After perforating the skin, the drill bit comes into contact with the bone. Bone in this area is drilled out. Hand drill is preferred since the power drills reduce the sensitivity of the surgeon who is drilling making him loose control. Once the bone is penetrated a needle made of teflon is put in place. A small catheter can be connected to this needle and wash can be given using a syringe. Before starting the irrigation procedure it must be ascertained whether the teflon needle is really inside the frontal sinus. This can be done by visualising air bubbles when the syringe filled with saline is connected to the catheter. Initially irrigation is done slowly under endoscopic control.
Complications can be avoided by following the guidelines given below:
Guidelines for safe frontal irrigation:
. Radiographic evaluation of the size of frontal sinus cavity
. Meticulous location of the site of trephination
. Control with aspiration of a good needle position before irrigation
. Slow irrigation of the cavity
Most of the complications following frontal trephination results from unfavourable anotomical conditions. To avoid serious complications trephination should not be performed if the pnuematization of the frontal sinus does not reach the superior limit of the orbit. In these condition trephination is not of much help since the frontal sinus itself is pretty rudimentary and can be accessed intranasally using an endoscope.
1. Brain injury
3. Orbital complications due to needle shift (common in home environment)