Transcranial and Endonasal Approaches to the Anterior Cranial Base

Introduction

Surgery of the anterior cranial base is often fraught with anxiety and concern because of the close proximity of major neurovascular structures. Often these tumors are extracranial; however, when tumors extend intracranially or invade into the brain parenchyma, a team effort of Neurosurgeons and Otolaryngologists is needed for surgical management. Most lesions of the anterior cranial base arise from the nasopharynx, nasal cavity, or paranasal sinuses, and a wide range of pathologic types are encountered ( Box 118.1 ).

Malignant tumors of the anterior cranial base are rare, accounting for only 3% of all tumors of the head and neck. A linkage between cigarette smoking and squamous cell carcinoma has been reported. Well-known risks of developing sinonasal malignancy include exposure to wood dust (adenocarcinoma), nickel-refining processes, leather tanning, mineral oils, chromium and chromium compounds, isopropyl oils, lacquer paint, soldering and welding, and radium dial painting.

Key Learning Points

• 1.

  Because of the location of tumors of the anterior cranial base, the initial clinical symptoms may be subtle and are often very similar to chronic inflammatory sinusitis.

• 2.

  Preoperative confirmation of histopathology is critical because of the wide variety of pathology of the anterior cranial base and the treatment options available.

• 3.

  Careful preoperative evaluation of imaging is important for planning the surgical approach (open, endoscopic, or combined).

• 4.

  Tumor invasion of the anterior table of the frontal sinus, orbital adipose tissue, floor of the nasal cavity, or carotid artery or gross parenchymal invasion precludes an endoscopic approach.

• 5.

  Care must be taken when elevating a bicoronal flap to preserve the blood supply from the supraorbital and supratrochlear vessels to the pericranial flap.

• 6.

  Elevation of the bicoronal flap must occur in a plane deep to the superficial layer of the deep temporal fascia in order to avoid injury to the temporal branches of the facial nerve.

• 7.

  Failure to preserve the superficial temporal vessels may forfeit the use of a temporoparietal flap for reconstruction.

• 8.

  A basal subfrontal approach is preferred to avoid excessive retraction of the frontal lobe.

• 9.

  If endoscopic resection of pathology of the anterior cranial base is being undertaken, oncologic principles should never be compromised, and the same resection must be achieved endoscopically as would be done through a traditional approach.

• 10.

  All frontal sinus mucosa should be drilled away to avoid late complications such as the formation of a mucocele.

• 11.

  Lack of a watertight barrier separating the intracranial contents from the paranasal sinuses may lead to cerebrospinal fluid (CSF) leakage or infection.

• 12.

  In the postoperative period, endoscopic manipulation can disrupt the reconstruction and cause an iatrogenic CSF leak.

Preoperative Period