Endoscopic Middle Cranial Fossa Reconstruction with a Subtemporal Keyhole

Background Skull base reconstruction is an essential technique for repairing cerebrospinal fluid (CSF) leakage. A reliable method for middle cranial fossa (MCF) reconstruction with minimal invasiveness has not been reported. An initial case of endoscopic MCF reconstruction with a subtemporal keyhole is described. Case Description A 57-year-old man developed severe meningitis and was diagnosed with spontaneous CSF leakage from bone defects on the tegmen tympani. Endoscopic MCF reconstruction with a subtemporal keyhole was carried out. Three skin incisions, including 1 subtemporal incision for a subtemporal keyhole and 2 temporal line incisions on the superior temporal line, were made, and a 0-degree endoscope was introduced into the subcutaneous space. The deep temporal fascia (DTF) was bluntly dissected and separated from the superficial temporal fascia and the temporal muscle, and the DTF was incised to shape a pedicled flap under endoscopic view. Blood supply to the pedicled DTF flap was confirmed with indocyanine green angiography. A subtemporal keyhole was then made, and a 30-degree endoscope was used to explore the extradural space of the MCF floor, visualizing the bone defects on the tegmen tympani. The vascularized DTF flap passed easily through the subtemporal keyhole and adequately overlaid the bone defects. The patient's postoperative course was uneventful, and the CSF leakage disappeared without mastication problems. Conclusions This purely endoscopic technique using a vascularized DTF flap provided reliable MCF reconstruction through a subtemporal keyhole. This technique is also expected to be applicable for MCF reconstruction after subtemporal keyhole surgery for skull base tumors.