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CSF Rhinorrhea: Operative Technique

The intranasal or transnasal (meaning surgery is performed through the nose) repair of CSF rhinorrhea may be performed using either an endoscope or surgical microscope depending on the location of the fistula site. Although we have used both the endoscope and microscope for this purpose for many years, the endoscope is our instrument of choice. 

The etiology, size and location of the cranial base defect and duration of the CSF rhinorrhea each may influence the use of ancillary procedures and the appropriateness of an intranasal approach

A brief summary of these considerations appears in the following table.

Etiology of Rhinorrhea

Finding

Outcome

a. Spontaneous rhinnorrhea.

a. CSF rhinorrhea of unknown etiology, or spontaneous, raises the possibility of increased intracranial pressure or hydrocephalus. Imaging and measurement of CSF pressure should be performed to rule out hydrocephalus. Temporary lumbar drainage should be considered.

b. Head trauma.

b. CSF rhinorrhea can be associated with facial fractures. The repair of the fracture may provide exposure to the site of the fistula and permit closure at the time of reduction of the fracture.

Duration of Rhinorrhea

Finding

Outcome

a. Several weeks or less.

a. The more recent the rhinorrhea, the more likely the fistula will close with grafting without the use of lumbar drainage.

b. Many months or years.

b. Long duration fistulas require the choroid plexus to produce large amounts of CSF to replace the rhinorrhea. The repair of fistula eliminates the diversion of CSF, and the excess fluid may place undue pressure on the graft site. In such cases, several days of lumbar drainage should be considered. 

Size of skull base defect

Finding

Outcome

a. Defects > 2.5 cm.

a. The ability to repair large skull base defects may be limited by pressure on the graft by the brain. As such opening to the subarachnoid space exceeds 2.5 cm, intranasal repair becomes more difficult.

Location of skull base defect

Finding

Outcome

a. Anterior cranial fossa floor and sphenoid sinus.

a. The roof of the ethmoid sinus and sphenoid sinus are both very accessible through the nose.

b. Posterior wall of the frontal sinus.

b. The lateral, superior, and posterior wall of the frontal sinus are difficult to reach through an intranasal approach. An external procedure may be required to repair these sites.

Anesthesia

Endoscopic repair of CSF rhinorrhea may be performed under local or general anesthesia depending on the patient's preference, the surge on's experience, the health and age of the patient, and the complexity of the proposed procedure.

Operative Technique

As outlined in the prior table, lumbar drainage may or may not be performed depending on the site and size of the CSF fistula, the amount of CSF drainage, the etiology of the rhinorrhea and the duration of the leakage. If lumbar drainage is employed, a lumbar drain is place immediately after induction under general anesthesia. If the fistula may be difficult to localize, hypodense fluorescein (2.5 -10 mgm) may be introduced into the subarachnoid space at this time (Guimaraes, 2001; Keerl, 2004). 

Surgery then begins with a careful examination of the nose. Total ethmoidectomy is first performed to expose the roof of the ethmoid sinus. In patients with CSF drainage through the sphenoid sinus, sphenoidotomy is also performed to visualize this sinus. The nose and sinuses are carefully examined to locate the path of drainage of CSF into the nose. In some cases, such as those patients with prior multiple surgeries or large lateral recesses of the sphenoid sinus, the fistula site can be difficult to identify and the use of hypodense fluorescein has proven very valuable (Keerl, 2004). 

After localizing the site of CSF drainage, all mucous membrane, scar and arachnoid villi are debrided to expose the bony skull base and dura. Each of these steps is important. The mucous membrane and scar must be removed to permit the tissue graft to adhere to the bony skull base. In the acute phase of CSF rhinorrhea, the arachnoid reacts to the breach in the subarachnoid space and attempts to maintain the integrity of this space by growing into the fistula site. 

In chronic CSF rhinorrhea, the same process in which the arachnoidal membranes attempt to close the fistula site may prevent the overgrowth of mucous membrane and scar, preventing normal closure of the defect after surgery. 

 Coronal Section Repair - Skull Base Defects

Coronal cadaver section illustrating various forms of repair of skull base defects. The three forms of grafting are the underlay, overlay and combined. In the underlay technique a graft (5) is placed on the under surface of the bony skull base (3). To improve adhesion of the graft to bone, the mucous membrane (4) is removed around the fistula site. In the overlay technique, the graft (2) is ideally placed between the dura (1) and the skull base (3). The third approach is to place two separate grafts, one as an overlay and the other as an underlay.

After debridment of the fistula site, several options for tissue grafting to repair the skull base defect are available. The tissue graft can consist of allografts or homografts (tissue of the same species, but in the former cases not of genetically the same individual), or xenografts (tissue of an entirely different species) or synthetic grafts. 

Various grafting sources within the human body are available as donor sites, such as the mucous membrane within the nose, fat and the fascial membranes covering muscles. The latter has excellent qualities as a grafting material, but requires a separate surgical incision to harvest the fascia. Whatever tissue is utilized, the graft may be placed using an overlay, underlay or combined technique (see illustration for further explanation of grafting). 

 Intraoperative Photograph - Skull Base Defect

Intraoperative photograph of skull base defect through the brain (1) can be seen with the dura (2) and mucous membrane (3) of the ethmoid sinus in the foreground.

With the current choice of grafting materials and techniques, we have achieved our best results using combined overlay and underlay grafts. In smaller defects, a combination of fat for the intracranial portion of the repair, and a commercially available xenograft or mucous membrane may be used for the nasal grafting. In larger defects, mucous membrane or xenografts are utilized.

 CSF Rhinorrhea (small) - Surgical Treatment

Abdominal fat graft (1) is shown being placed within the intracranial defect (2). When this step is completed, >80% of the fat graft is intracranial with only a small portion projecting through the dura into the nose. Fat works particularly well for such repairs because it "plugs" or fills the opening well and minimally shrinks over time.

Tissue glue is utilized to adhere both the intranasal and intracranial grafts to their respective sites. However, in our opinion the placement of the intracranial should be so mechanically optimal to immediately stop the CSF rhinorrhea rather than depend on tissue glue or packing to maintain a seal. 

Intranasal / Intracranial Grafts - Tissue Glue Stage

The next stage of the repair is placement of tissue glue (1) as defect site, and then adheres the second graft (2) to roof of the nose. The procedure is completed with the placement of absorbable packing against the intranasal graft. 

The last step in the repair is the placement of absorbable packing against the intranasal graft and within the adjacent ethmoid sinus. Although some surgeons use non-absorbable packing which is removed several days later, we prefer to not place anything near the graft which has to be later removed.

We base this opinion on our concern for dislodging the graft during removal of the packing, the discomfort to the patient caused by the packing, and our feeling that the quality of the grafting is the most important factor in successful closure.

Coronal CT Sacm of CSF Pooling in Right Sphenoid Sinus

Coronal CT scan showing CSF pooling in the right sphenoid sinus secondary to a defect in the wall of this sinus. CSF fistulas into the sphenoid sinus are repaired using similar techniques and tissue grafting as described for the ethmoid sinus.

Postoperatively patients should avoid for four weeks straining and any activity that increases their blood pressure. Such activities also increase the pressure within the subarachnoid space, and can compromise the integrity of the repair. Thereafter, normal exercise and other activities should be resumed over the next two months. We usually recommend avoiding flying for three months due to changes in the cabin pressure. However, the surgical wound continues to heal for up to six months and we are unaware of animal or human studies that would give firm scientific evidence to better refine our recommendations.

References

Bachert, C., Verhaeghe, B., van Cauwenberge, P. and Daele, J. 2000 Endoscopic endonasal surgery (EES) in skull base repairs and CSF leakage. Acta Otorhinolaryngol. Belg. 54:179-189.

Guimaraes, R., and Becker, H. 2001 A new technique for the use of intrathecal fluorescein in the repair of cerebrospinal fluid rhinorrhea using a hypodense diluent. Rev Laryngol Rhinol (Bord) 122:191-193.

Keerl, R., Weber R.K., Draf W. and Schaefer S.D. 2004 Use of sodium fluorescein solution for detection of cerebrospinal fluid fistulas-An analysis of 420 administrations and reported complications in Europe and the United States. Laryngoscope. (in press)

Mattox, D. E., and Kennedy, D. W. 1990 Endoscopic management of cerebrospinal fluid leaks and cephaloceles. Laryngoscope, 100:857-862.

Senior, B.A., Jafri, K. and Benninger, M. 2001 Safety and efficacy of endoscopic repair of CSF leaks and encephaloceles: A survey of the members of the American Rhinologic Society. Am. J. Rhinol. 15:21-25.

Sillers, M.J., Morgan, C.E. and el Gammal, T. 1997 Magnetic resonance cisternography and thin coronal computerized tomography in the evaluation of cerebrospinal fluid rhinorrhea. Am. J. Rhinol., 11:387-392.

Stammberger, H., Greistorfer, K., Wolf, G. and Luxenberger, W. 1997 Surgical occlusion of cerebrospinal fistulas of the anterior skull base using intrathecal sodium fluorescein. Laryngorhinootologie, 76:595-607.

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