Clinical Study
Endoscopic transnasal intradural repair of anterior skull base cerebrospinal fluid fistulae

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Abstract

This study presents the techniques and results of endoscopic diagnosis and repair of cerebrospinal fluid (CSF) fistulae involving the anterior skull base and paranasal sinuses.

Design. A retrospective cohort study of all consecutive patients undergoing endoscopic repair of anterior skull base CSF fistulae.

Setting. Tertiary referral institutions.

Materials and methods. Fifty-two patients underwent endoscopic repair of CSF fistula. Thirteen cases were traumatic in origin, 11 spontaneous not associated with meningoencephalocele and 12 with meningoencephalocele. Eleven were iatrogenic and five associated with transphenoidal pituitary surgery, two acute and three delayed following radiotherapy. The average age of patients was 43 and the male to female ratio was 2:1. A variety of techniques were used to repair the dural defect. In the majority of cases placement of a fat plug on the intracranial surface of the dura was performed.

Results. Forty-seven of the 52 patients had successful primary endoscopic repair of the CSF fistula and skull base defect. Five patients required a repeat procedure due to early failure of the repair. After an average follow-up of 27 months no patient has had any recurrence of leak giving a primary closure success rate of 90% and secondary closure rate of 100%.

Conclusions. The endoscopic transnasal approach for repair of anterior skull base CSF fistula is a reliable technique and is now the procedure of choice for patients presenting with this problem.

Introduction

The transnasal endoscopic approach is now recognised as the preferred method for the diagnosis and repair of anterior skull base cerebrospinal fluid leaks.[1], [2], [3], [4] The endoscopic transnasal approach carries minimal morbidity, has been demonstrated to be effective and has replaced transcranial techniques of repair as the first line procedure for these problems. Anterior skull base cerebrospinal fluid fistula may occur following anterior skull base fractures, surgery on the paranasal sinuses or be spontaneous. Spontaneous cerebrospinal fluid (CSF) leaks may occur in the cribriform plate region or in the sphenoid. They may also be associated with a congenital meningoencephalocele which occur typically in the frontoethmoid or sphenoid sinus. Usually, the cause is uncertain but there has recently been an association between middle aged overweight female patients and spontaneous CSF leaks.5 The cause of this is thought to be a malabsorption of CSF from dilated arachnoid granulations. Usually, these granulations are associated with large intracranial venous sinuses and the CSF drains from them into the venous system. However, in the very pneumatized sphenoid these granulations may not be associated with a venous sinus. Chronic coughing and CSF pulsation is thought to erode the thin bone of the skull base in this region with a meningocoele and finally a CSF leak developing. There may also be an association with benign intracranial hypertension increasing CSF pressure. However, in most cases the reason for patients developing a spontaneous CSF leak is uncertain. In some patients, the CSF leak may be intermittent and this creates a problem both with confirming that the fluid is CSF and also with localisation of the site of leak. The use of Beta-2-asialotransferrin testing of the fluid is very specific for CSF and the most effective test for CSF. Previously used investigations such as nuclear medicine studies using intrathecal isotope have a very poor anatomic specificity and high false positive rate and should no longer be used in the investigation of these patients.

Although there have been a large number of techniques described for the transnasal endoscopic closure of CSF leaks, there are few large series where predominantly one technique has been used. The authors have a large experience with the fat plug technique where a fat plug is placed through the defect onto the intracranial surface of the dura and reinforced with a mucoperiosteal graft on the nasal surface.6 This technique has been termed the “bath plug” technique as it uses the CSF water pressure to help maintain the seal of the fat on the intracranial surface of the defect much in the same way that intracranial techniques lay dura or fascia lata over the defect on the intracranial surface of the anterior skull base. In addition a free mucosal graft reinforces the closure on the nasal surface of the graft. We present the results of endoscopic management of a large series of patients with CSF fistula using both this and other techniques.

Section snippets

Materials and methods

All consecutive patients with anterior skull base cerebrospinal fluid fistulae managed by the authors between 1995 and 2002 were included in this study. In a number of cases cerebrospinal fluid rhinorrhoea was due to a CSF fistula into the temporal bone with leakage down the Eustachian tube and these patients were not included. There were 52 patients with 35 males and 17 females and a male to female ratio of 2:1. The average age was 43 years (standard deviation=20.4 years). Eleven patients had

Surgical technique

In all cases intrathecal Fluorescein is used to stain the CSF. This is placed via a lumbar drain before or after induction of general anaesthesia and is used to identify the site of the fistula. The fistula cannot be closed if the site cannot be identified. In most cases a fine slice high definition CT scan and T2-weighted MRI scan will be sufficient to identify the site of the leak but in some patients, specifically patients with small intermittent leaks, identification can be difficult. The

Results

Of the 52 patients who underwent endoscopic repair of their CSF fistula and skull base defect, 47 have had successful primary closure with no recurrence of the CSF leak. Five patients required a repeat procedure due to early failure of the repair. After an average follow-up of 27 months no patient has had any recurrence of leak giving a primary closure success rate of 90% and secondary closure success rate of 100%. Of the five patients requiring a second procedure, two were due to early

Discussion

It is clear that endoscopic repair of CSF fistula is effective in the hands of experienced surgeons. A number of authors report high success rates with successful primary repair in 90% or more of cases.[7], [8], [9] Potential benefits of an endoscopic transnasal approach rather than a transcranial approach is the minimally invasive procedure and a high success rate compared to the average success rate of 70% achieved with transcranial approach.10 Achieving an effective repair of CSF fistula via

Conclusion

The endoscopic transnasal technique for repair of anterior skull base CSF fistula is safe and effective and is now the procedure of choice for patients presenting with CSF rhinorrhoea due to anterior skull base defects. This series confirms that the “bath plug” technique of endoscopic repair is effective and reliable and may be used for a variety of types of defects.

References (13)

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