Reconstructive Techniques in Endoscopic Skull Base and Orbital Surgery

Pre-Reconstruction Considerations

Given the multitude of options available for reconstruction, an effort has been made to define the indications and utility for each type of repair. Likely the most important factor guiding the selection of a repair method is classifying the volume and flow of CSF leak (if any) as well as the size and complexity of the anticipated defect. The CSF flow rate can be classified as no leak (no intracranial opening, or appreciable leak into the nose), a low-flow (intracranial opening but minimal flow observed or no direct communication with a cistern or ventricle), and a high-flow leak (intracranial opening, direct communication into a ventricle or cistern). Preoperative imaging can be used to predict the type of CSF leak likely to be encountered after resection of a given lesion.

When there is no CSF leak, the repair is at the surgeon’s discretion and can range from simple onlay or epidural/subdural underlay placement of a synthetic graft or repair with packing and/or dural sealant at the level of the sella. Skull base defects that are small with a low-flow CSF leak can be reconstructed with a wide variety of multilayered (or even monolayered) avascular free grafts or biosynthetic materials with high success rates and limited morbidity. Larger and more complex skull base defects (> 2–3 cm) and those that are associated with high-flow CSF leaks are best repaired with a multilayered technique using a vascularized flap of tissue ( Table 37.1 ).

In addition to leak type, other independent factors must be considered to help guide the reconstructive decision-making process. The extent of the skull base defect should be assessed because resections involving extended approaches often result in large and more complex defects with high-flow CSF leaks that are best managed with vascularized flaps. Specific disorders also carry an increased potential for postoperative CSF leak, and as such, the use of a vascularized pedicled flap should be strongly considered in these unique instances. Among these are meningiomas (extensive bony and dural resection with intracranial disruption of the arachnoid plane), craniopharyngiomas (often requiring expanded approaches and involving arachnoid dissection), Cushing disease (reduced healing from hypercortisolemia), and morbid obesity (possible increased intracranial pressure, also potentially present with Cushing disease). Furthermore, in patients who have had or will potentially need radiation therapy, vascularized flaps should be strongly considered, as they are more likely to withstand the effects of radiation therapy in providing a durable repair. Lastly, independent of CSF leak and radiation status, vascularized reconstructions may provide adequate coverage of exposed neurovital structures (e.g., internal carotid artery) that may be uncovered and mobilized during tumor resection.

The use of a lumbar drain as part of the reconstructive strategy deserves consideration as preoperative planning takes place. The placement of a perioperative lumbar drain has not been shown to positively affect postoperative leak rates when vascularized flaps are used. However, the use of a lumbar drain in the setting of a postoperative CSF leak has been shown to be effective as first-line therapy. In our experience, lumbar drains can provide advantages in some high-risk clinical situations. In addition to potentially enhancing the success rate in some complex, high-flow CSF leak cases, the use of drains also provides the opportunity to (1) measure opening pressures before and after repair and (2) permit the intrathecal injection of fluorescein, which may be of value in some cases. The use of lumbar drains is associated with certain attendant risks that must be balanced in any given case.

The Reconstructive Ladder

A thoughtful and systematic way to organize available options is to use the idea of a “reconstructive ladder” when considering skull base reconstruction.