A Novel Method for Multilayer Autograft Placement during Middle Cranial Fossa Encephalocele and CSF Leak Repair: The Suture Pull-Through Technique
Background: The combined mastoid-middle cranial fossa approach for CSF fistula and encephalocele repair is commonly employed for large or medial tegmen defects, particularly those that involve the epitympanum and an intact ossicular chain. Optimal multilayer graft placement is tedious given the narrow corridor afforded by the subtemporal middle fossa approach, especially when a limited craniotomy is combined with dynamic (non-fixed) temporal lobe retraction. We present our preliminary results using a novel modification to the standard middle fossa floor reconstruction technique, utilizing a composite autologous graft with suture pull-through. This technique has improved ease of graft placement, ensuring accurate substrate layering and graft position while decreasing the risk of graft migration.
Surgical Technique: A postauricular “lazy S” incision is fashioned, extending from the mastoid tip to the mid-temple. A bone graft is harvested from the mastoid cortex followed by a mastoidectomy to confirm and localize the tegmen defect. Herniating tissue is carefully dissected free from the ossicular chain and reduced with bipolar coagulation. If it is determined that the tegmen repair would significantly benefit from a combined approach, a limited craniotomy (2 × 3cm) is centered over the defect and subtemporal extradural dissection is performed until the entire tegmen dehiscence is clearly visualized from above. While the defect is being exposed, an autologous composite graft is constructed ex-situ, layering fascia, bone or cartilage, and dural substitute. The medial, leading edge of the composite graft is then sutured in several places to ensure the fascia does not fold on itself during placement. Finally, a single horizontal suture is placed in the center of the assembly to ensure the layers stay intact upon placement. The suture tails are left long and the free ends are passed from the middle cranial fossa, through the tegmen defect, and delivered into the mastoid. Then, with minimal temporal lobe retraction, the composite graft is advanced over the tegmen defect from above while being guided from below by careful traction on the free suture tails in the mastoid. Once it is over the defect, the graft is held in place by the suture ends, and temporal lobe retraction is released. The sutures are then cut, and any additional reinforcement can be performed from below. This technique ensures that the graft is centered on the defect and reduces the risks of poor layering and graft migration.
Results: We have now used this method in 3 patients, all of whom have had satisfactory clinical outcomes. To date, there have been no recurrences or episodes of meningitis.
Conclusions: The middle cranial fossa suture pull-through technique is a safe and effective method for temporal bone CSF fistula and encephalocele repair. Theoretical advantages include decreased operative time since the composite graft is assembled ex-situ while the defect is being exposed, improved confidence in graft placement, minimal temporal lobe retraction, and a reduced learning curve for multilayered closure.