How to: Pediatric Endoscopic Transsphenoidal Skull Base Approach and Closure: Technique and Technical Tips

INTRODUCTION

The transsphenoidal corridor is the most common endoscopic endonasal skull base approach, and it involves resection of portions of the anterior wall, posterior wall, and roof of the sphenoid sinus to access the sella, suprasellar, medial cavernous sinus, and clival recess regions. Endoscopic endonasal skull base surgery (EESS) is feasible, safe, and effective for pediatric skull base lesions. Long-term maxillofacial growth does not seem to be impacted by EESS at a young age, but there are some important anatomic considerations in this young population.

The first potential obstacle encountered during pediatric EESS is the relatively narrow nasal aperture in young children. Studies have shown bony piriform aperture width increases slowly in size over time; there is not a single growth spurt after which the aperture increases dramatically. Similarly, the cartilaginous nasal aperture grows slowly with age, with only an average of 2.54 mm diameter increase between the two- and four-year age groups and the 11-13 year age groups. Given these minute changes with age, the nasal aperture is unlikely to be prohibitive to EESS except in very young patients under two years of age or those with other anterior craniofacial dysmorphisms.

Sphenoid sinus pneumatization is also a consideration during pediatric EESS. The process of pneumatization of the sphenoid sinus is variable, but, generally, the sinus does not reach maturity until approximately 10-14 years of age. Pneumatization proceeds in an anterior-to-posterior and caudal-to-cranial direction. Though sphenoid sinuses with a conchal (non-pneumatized) configuration may increase drilling time, studies have shown that sphenoid pneumatization pattern does not affect outcomes in endoscopic skull base surgery in the pediatric population; specifically, it does not impede gross total resection or increase complications.

Perhaps the most important consideration for these cases is the cavernous intercarotid distance. In general, this distance should be at least 1 cm to allow sufficient access to the sella and/or suprasellar spaces. The clival portion of the internal carotid artery tends to have a stable intercarotid distance over time, and, therefore, this distance is generally not of concern in any age group. Patients younger than three or four years may have prohibitively narrow cavernous intercarotid distances; this is the primary reason why EESS is generally reserved for patients four years of age or older.

In this article, we review our pediatric EESS technique in patients with intra-operative high flow cerebrospinal fluid (CSF) leak, with a focus on details that differ from adult transsphenoidal surgery technique.

METHODS

Pre-Operative Evaluation

All patients are referred for CT scan, MRI, ophthalmology, and endocrinology consultations prior to surgery.

Surgical Technique

Following induction of general anesthesia, the endotracheal tube is secured to the left lower face, and the head of the bed is rotated 180 degrees. Cranial fixation pins are applied. The image guidance system is calibrated and accuracy confirmed using bony anatomic landmarks. The patient is then prepped and draped for EESS with the nose, philtrum, and possibly the eyes exposed in the operative field.

The entire approach is performed using a 0-degree endoscope with Endo-Scrub. A 2.7-mm scope may be considered in very young patients if a larger endoscope cannot be accommodated. Lidocaine 0.5%-1.0% with 1:200,000 epinephrine is injected into the head of the middle turbinate, the nasal septum, maxillary line, and into the head of the inferior turbinate bilaterally. A sphenoid injection of local anesthetic is not performed.

Next, a posterior inferior turbinate resection is performed to improve access to the choana bilaterally and provide a reservoir for blood accumulation during dissection. In patients younger than 12 years, there is often adenoid hypertrophy, but we elect not to resect the adenoid during these cases as the adenoid is known to harbor bacteria and biofilms, which could place patients at risk of post-operative infection. Posterior inferior turbinate resection is particularly important on the side where the nasoseptal flap harvest will take place. The inferior turbinates are laterally outfractured first. The microdebrider is used to resect the posterior third of the inferior turbinate. The decision to resect