Benign Tumors of the Skull Base Treatment & Management

Medical therapy is used in a few very selective cases. Inflammatory lesions of an infectious etiology, such as osteomyelitis or fungal infection, require appropriate antibiotic treatment (with or without surgical drainage) depending on response.

Hormonal antiandrogenic therapy has been advocated as a method to slow the growth of juvenile angiofibromas. Sclerotherapy using intralesional sclerosing agents has been used in low-flow vascular lesions.

Radiation therapy is generally considered as an adjuvant treatment in combination with surgical resection; however, in nonsurgical candidates' cases, it can be used as first-line therapy. Various forms of radiation delivery, including external beam, brachytherapy, and stereotactic radiation, have been described.^[7] External beam delivery carries a significant risk of damage to adjacent vital structures such as the eye, brain, and brainstem. For this reason, dosing is generally limited to 4500 rads. Brachytherapy often is difficult to administer because of the complex anatomy, which precludes safe insertion of delivery rods. Stereotactic radiation has been a major advance in recent years and allows for safe delivery of a relatively high dose of radiation into a focused area. Adjacent structures are at a much-reduced risk of radiation damage; however, the technique cannot be used as sole treatment for large tumors.

The treatment of choice for the vast majority of benign skull base tumors is surgical excision. In contrast to malignant neoplasms, a wide surgical margin is unnecessary with benign tumors. To reduce the risk of local recurrence, however, perform a complete resection unless this carries an unacceptable risk of morbidity. In such cases, a subtotal debulking procedure can be attempted. This is particularly true of lesions with extensive intracranial extension or those involving the petrous carotid, cavernous sinus, and sellar and parasellar regions. Postoperative radiation therapy can then be used as adjuvant therapy to further limit or arrest continued growth. The advances in stereotactic radiation therapy have greatly facilitated this approach in recent years.

In selected cases, observation can be used. Factors that favor observation (with periodic imaging to monitor tumor growth) include slow-growing nondestructive masses, the absence of significant symptoms or deficits, tumors located deep in the central skull base (where attempts to remove them carry a significant risk of serious complications), and increasing age.

Various surgical approaches have evolved to access the various parts of the skull base and are outlined as follows.

• Anterior skull base

  • Frontocranial
  • Subfrontal-subcranial
  • Transmaxillary - Midface degloving, nasomaxillotomy, LeFort I, midfacial split, maxillary removal-reinsertion
  • Transfacial - Lateral rhinotomy, Weber-Fergusson
  • Craniofacial - Combination of an intracranial approach from above and a transfacial or transmaxillary approach from below
• Middle cranial base

  • Subtemporal - Infratemporal fossa (preauricular and postauricular)
  • Pterional - Frontotemporal zygomatic
  • Mandibular swing
• Posterior cranial base

  • Translabyrinthine
  • Retrosigmoid
  • Suboccipital
• Central skull base

  • Transoropalatal
  • Maxillotomy - LeFort I, Maxillary swing
  • Maxillofacial swing
  • Mandibular swing, labiomandibuloglossotomy
  • Transseptal - Transsphenoidal

The majority of patients with skull base growths typically require postoperative monitoring and management in an intensive care setting. This period may last anywhere from 1-2 days up to several days, depending on the degree of surgery and any complications that may develop. Most patients have tracheotomies, which are generally removed after 1 postoperative week. CN deficits, particularly VII, IX, and X, are not uncommon. Supportive care (eg, eye protection, enteral or parenteral nutritional support, speech and swallowing physiotherapy) is an important postoperative consideration.^[8] Typically, patients require 1-2 weeks of hospital care following major cranial base resections, if no complications are encountered.

Once the patient is beyond the acute postoperative phase (ie, 4-6 wk), routine periodic monitoring is necessary every 4-6 months to assess for recurrence of the primary pathology. This involves careful clinical evaluation and diagnostic imaging.

Skull base surgery is very complex, and the risk of complications is relatively high. The most significant life-threatening event is massive internal carotid intracranial hemorrhage that occurs because of intraoperative misfortune or early in the postoperative period. Other vascular complications include delayed carotid artery rupture, air embolus, stroke, and hematoma formation.

CSF leaks occur in approximately 20% of major cranial base procedures. Manage high-flow leaks from the outset with surgical re-exploration to identify and repair the site of leakage. Low-flow leaks can be treated conservatively with bed rest and a lumbar drain to divert the CSF; however, surgical intervention is indicated if the leak persists after 3-5 days.

Brain edema is a common finding after significant manipulation and retraction. Treatment includes mannitol, diuretics, and barbiturate coma.

Pneumocephalus can result from a variety of causes. In virtually all cases in which a craniotomy is performed, some degree of passive air exists in the cranial cavity because the brain does not fully reexpand immediately after surgery. With time, this tends to resolve without further problems. Large amounts of air that persist, however, are worrisome dead spaces that predispose the patient to intracranial infection. Tension pneumocephalus is a serious complication and can be life threatening if brain compression occurs. Tension pneumocephalus arises from air being forced under pressure from the aerodigestive tract (during coughing, straining, and nose-blowing) through the surgical skull base into the cranial cavity, where it becomes trapped via a ball valve phenomenon. Tracheotomy is routinely recommended concurrent with skull base surgery to divert air away from the skull base wound and to help prevent the occurrence of pneumocephalus.

Meningitis is relatively uncommon and is bacterial in origin. Treat with appropriate antibiotics.

Wound infection is not uncommon following extensive procedures, particularly when the surgical wound is exposed to the aerodigestive tract for extended periods during surgery. Antibiotic therapy and drainage as necessary usually resolve the infection.

CN deficits result if resection or significant manipulation and injury have occurred during surgery. Postoperative treatment includes a variety of compensatory surgical and rehabilitative procedures depending on the nerves involved and the degree of deficit.

Pituitary gland dysfunction can occur following sellar and parasellar tumor removal and requires careful hormonal and metabolic monitoring afterward. Use replacement hormonal therapy and fluid-electrolyte management, when indicated.

Seizures can occur in the early postoperative period or can onset in delayed fashion. They are most common when temporal lobe manipulation has taken place. Treatment involves anticonvulsant therapy.