Endonasal Approach to the Sella and Parasellar Areas

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Surgery of the central cranial base has evolved over the past several decades from open transcranial or transfacial approaches that require significant retraction or disruption of normal anatomy, to endoscopically assisted approaches that maintain surgical principles, improve visualization, and preserve normal function. Surgical approaches to the sella and parasellar areas exemplify this principle and are the keystone to other endoscopic approaches to the anterior skull base. The sella was traditionally approached via a microscopic sublabial or transnasal, transseptal approach. The problem with this approach included limited visualization and freedom of movement of instruments, incomplete tumor resection and limited ability to deal with severe complications, such as carotid artery injury. The advent of endoscopic approaches to the paranasal sinuses in the 1980s, followed by widespread adoption in otolaryngology, gradually led to the expansion of endonasal techniques beyond inflammatory sinus disease. After neurosurgeons experimented with endoscopic assistance for microscopic pituitary surgery for several years, a solely endoscopic approach to the sella was described in the mid-1990s.

Subsequent improvements in technology have included improved optics, high-definition displays, navigation systems, and better instrumentation for endoscopic cranial base surgery. The next step using techniques devised for endoscopic pituitary surgery was the resection of suprasellar pathologies, cavernous sinus dissection, and more advanced procedures in the sagittal and coronal planes. The team approach, involving neurosurgeons and otolaryngologists, has led to excellent patient outcomes with a midline transnasal approach. For the purposes of this chapter, discussion will be limited to the sellar and parasellar regions.

Key Operative Learning Points

1.
The sella lies in the midline of the posterior wall of the sphenoid sinuses, bounded laterally by the cavernous internal carotid artery (ICA) siphon and superiorly by the superior intercavernous sinus and optic nerves. Recognition of the medial and lateral opticocarotid recesses is important to prevent injury to these structures.
2.
The need for a vascularized nasoseptal flap reconstruction should be considered prior to sphenoidotomy in order to preserve the vascular pedicle.
3.
Exposure of the cavernous sinuses lateral to the sella is a safe way to identify the course of the parasellar ICA.

Preoperative Period

History

1.
History of present illness
- a.
  A thorough history should be taken to elicit visual changes, including decreased visual fields or diplopia, endocrine symptoms, headaches, clear rhinorrhea, and frequent urination.
- b.
  Specifically, symptoms of Cushing’s syndrome and acromegaly should be elicited.
- c.
  A rapid onset of headache and visual symptoms may represent pituitary apoplexy, which is a surgical emergency.
2.
Past medical history
- a.
  Prior treatment:
  - 1)
    Medical treatment for pituitary tumor (dopamine antagonists)
  - 2)
    Prior radiation therapy (stereotactic or intensity-modulated)
- b.
  Medical illnesses:
  - 1)
    Heart disease
  - 2)
    Intracranial hypertension (may be undiagnosed in obese patients)
  - 3)
    Diabetes mellitus
  - 4)
    Diabetes insipidus
  - 5)
    Recurrent acute or chronic rhinosinusitis, particularly nasal polyposis with pulmonary symptoms
    - a.
      Cystic fibrosis
    - b.
      Allergic fungal rhinosinusitis
    - c.
      Samter’s triad
- c.
  Surgery:
  - 1)
    Prior endoscopic, transseptal, sublabial, or transcranial approach to the sella
  - 2)
    Nasal surgery including septoplasty or functional endoscopic sinus surgery
- d.
  Family history:
  - 1)
    Bleeding disorders
  - 2)
    Pituitary tumors (multiple endocrine neoplasia Type 1)
- e.
  Medications:
  - 1)
    Anticoagulants or antiplatelet drugs
  - 2)
    Dopamine antagonists
  - 3)
    Insulin or oral hypoglycemic agents
  - 4)
    Steroids
  - 5)
    Nasal steroids
  - 6)
    Topical nasal decongestants (intraoperative topical decongestant is less effective)
- f.
  Social history: alcohol, tobacco, or illegal drugs
  - 1)
    A history of or active cocaine abuse may result in perforation, submucosal cartilage loss, and/or submucosal scarring of the septum; topical decongestants are less effective.

Physical Examination

1.
General
- a.
  Features of Cushing’s syndrome: abnormal distribution of adipose tissue, “buffalo hump” or “moon facies”
- b.
  Features of acromegaly: frontal bossing, macroglossia, prognathism, enlarged hands and feet
2.
Eyes
- Assessment of visual fields, visual acuity, and proptosis or abnormal position of the globe. Full examination by an ophthalmologist is warranted if there is any involvement of the optic nerve, chiasm, or orbit on imaging.
3.
Neurologic
- A thorough cranial nerve examination should be performed with particular attention to nerves III, IV, V, and VI.
4.
Skin
- Note the presence of striae, abnormal pigmentation, or ecchymoses suggesting Cushing’s syndrome.
5.
Nasal endoscopy
- Assess for intranasal pathology, including septal deviations or perforations, polyps, purulence, or intranasal masses. If prior surgery has been performed, assess for adequacy of nasoseptal flap pedicles.

Imaging

1.
Maxillofacial computed tomography (CT) with contrast
- a.
  Allows for delineation of bony anatomy of paranasal sinuses, orbits, and skull base
- b.
  Coronal and sagittal reconstructions are helpful to evaluate the slope of the skull base, the position of the anterior ethmoid arteries, and the presence of posterior ethmoid cells associated with the optic nerve (Onodi cells).
- c.
  Contrast angiography allows for delineation of the interface with intracranial vessels and improved visualization of the ICA.
2.
Magnetic resonance imaging of skull base with gadolinium
- a.
  Extent of tumor
- b.
  Location of residual pituitary gland and stalk
- c.
  Cavernous sinus invasion
- d.
  ICA anatomy
- e.
  Relation to optic chiasm

Indications

Infectious/inflammatory sphenoid sinus disease
Sinonasal tumors involving the sphenoid sinus
Fibro-osseous lesions
Pituitary adenoma
- Functional tumors uncontrolled with medical therapy
- Macroadenomas with visual compromise
- Interval growth of macroadenoma
Craniopharyngioma
Rathke’s cleft cyst or pituitary cysts with headaches or visual compromise
Meningoceles/meingoencephaloceles
Planum sphenoidale or tuberculum meningioma
Select lesions extending into the medial or anterior compartments of the cavernous sinus
Medial optic nerve and orbital apex decompression

Absolute Contraindications

Cardiopulmonary disease that prohibits surgery
Pathology that is on the deep side of a nerve or vessel

Relative Contraindications

Significant lateral extent
Bleeding disorder
Prolactinoma that has not been trialed on medical therapy
Vascular encasement

Preoperative Preparation

Evaluation by otolaryngology and neurosurgical teams
Endocrine consultation for pituitary tumors
Ophthalmologic consultation for visual disturbances
Discontinue aspirin and anticoagulants prior to surgery.
It is important to manage acute bacterial rhinosinusitis before endoscopic endonasal skull base surgery.

Operative Period

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