Microvascular reconstruction of the skull base: a clinical approach to surgical defect classification and flap selection

Abstract

Skull-base tumor resection and reconstruction produce a major physiologic and anatomic impact on the patient. At our institution, the use of vascularized, free-tissue transfer has replaced pedicled flaps as the preferred modality for reconstructing complex cranial base defects involving resection of dura, brain, or multiple major structures adjacent to skull base, including the orbit, palate, mandible, skin, and other structures. The goals of reconstruction are to: (1) support the brain and orbit; (2) separate the CNS from the aerodigestive tract; (3) provide lining for the nasal cavity; (4) re-establish the nasal and oropharyngeal cavities; (5) provide volume to decrease dead space; and (6) restore the three-dimensional appearance of the face and head with bone and soft tissues. Surgical management requires a multidisciplinary effort with collaborating neurosurgical, head and neck, and plastic surgical teams. Successful reconstruction of skull base defects is predicated upon a careful appreciation of the specific region. Defects may be classified based on their anatomic location and loss of volume, support, and skin cover. Free flaps provide reliable, well-vascularized soft tissue to seal the dura, obliterate dead space, cover exposed cranial bone, and provide cutaneous coverage for skin or mucosa.

Figure 1

A skull should be available in the operating room.

Figure 2

Defect classification.

Figure 3

The use of the galeal-pericranial flap is well established for simple central defects of the anterior cranial fossa.

Figure 4

(A) Patient with squamous cell carcinoma of the ethmoid perforating through the nasal bone and involving the overlying skin. (B) Through-and-through surgical defect with resection of the skin of the nose, nasal bones, ethmoid complex, and cribriform plate. (C) Reconstruction completed with a folded radial forearm free flap and a free bone graft. Photos reproduced with permission.

Figure 5

(A) Patient with extensive basal cell carcinoma involving the scalp, calvarium, and right orbit. (B) MRI scan in coronal plane shows extensive infiltration of the tumor through the calvarium into the extradural space of the anterior cranial fossa. (C) Surgical defect shows repair of the dural defect accomplished using a bovine pericardial graft. (D) Reconstruction of the defect of the calvarium and the scalp, accomplished with a rectus abdominis free flap. Photos reproduced with permission.

Figure 6

(A) Patient with a locally advanced carcinoma of the maxillary antrum involving the orbit, nasal cavity, ethmoid complex, and the overlying skin. (B) Surgical defect showing through-and-through resection of the tumor with skin of the face, nose, contents of the orbit, maxilla, nasal cavity, and ethmoids. (C) Surgical specimen showing three-dimensional resection of the entire tumor in a monoblock fashion. (D) Rectus abdominis free flap seen in the oral cavity replacing the resected part of the hard palate, providing a water-tight closure in the oral cavity. (E) Second island of skin on the rectus abdominis free flap used to cover the skin defect with the underlying muscle, providing coverage for the dead space. Photos reproduced with permission.