Residency · Residency · Otolaryngology
Pituitary Tumors: Endoscopic Transsphenoidal Approach
Introduction
Pituitary adenomas account for approximately 15% of all intracranial neoplasms and are the most common sellar lesion. The endoscopic endonasal transsphenoidal approach has become the preferred surgical technique for most pituitary tumors, offering excellent visualization with lower morbidity compared to transcranial approaches. Otolaryngologists play a critical role in the nasal phase of this surgery as part of a multidisciplinary team with neurosurgery.
Anatomy of the Sella Turcica
Bony Landmarks
Sphenoid sinus: the surgical corridor; pneumatization pattern (conchal, presellar, sellar) determines feasibility. Sellar floor: thin bone overlying the pituitary gland. Tuberculum sellae: anterior boundary. Dorsum sellae and posterior clinoid processes: posterior boundary. Carotid prominences: lateral walls of the sphenoid sinus; bilateral internal carotid arteries (ICAs). Optic nerve and opticocarotid recess (OCR): critical landmarks for the lateral extent of dissection.
Pituitary Gland
Anterior lobe (adenohypophysis): source of adenomas. Posterior lobe (neurohypophysis): stores ADH and oxytocin. Pituitary stalk (infundibulum): connects to the hypothalamus. Cavernous sinuses: located laterally, containing CN III, IV, V1, V2, and VI along with the cavernous ICA.
Classification of Pituitary Adenomas
By Size
Microadenoma: <10 mm. Macroadenoma: >=10 mm. Giant adenoma: >=40 mm.
By Function
| Adenoma Type | Frequency | Hormone | Clinical Syndrome |
|---|---|---|---|
| Non-functioning | Most common (30-40%) | None | Mass effect (visual loss, hypopituitarism) |
| Prolactinoma | Most common functioning | Prolactin | Galactorrhea, amenorrhea, infertility |
| GH-secreting | 10-15% | Growth hormone | Acromegaly/gigantism |
| ACTH-secreting | 5-10% | ACTH | Cushing disease |
| TSH-secreting | Rare (<1%) | TSH | Secondary hyperthyroidism |
Non-functioning adenomas: most common (30-40%); present with mass effect. Prolactinoma: most common functioning adenoma; elevated prolactin. Growth hormone (GH)-secreting: acromegaly/gigantism. ACTH-secreting: Cushing disease. TSH-secreting: secondary hyperthyroidism (rare).
Knosp Classification (Cavernous Sinus Invasion)
Grade 0-2: medial to the intercarotid line; surgically resectable. Grade 3-4: lateral to or encasing the ICA; unlikely complete resection.
Clinical Presentation
Visual field defects: bitemporal hemianopsia from chiasmal compression. Headache: dural stretch. Hypopituitarism: from compression of normal gland. Hormonal hypersecretion syndromes: galactorrhea, acromegaly, Cushing features. Apoplexy: acute hemorrhage into a tumor causing sudden headache, visual loss, and ophthalmoplegia — a surgical emergency.
Preoperative Workup
Complete endocrine panel: prolactin, GH/IGF-1, ACTH/cortisol, TSH/free T4, LH/FSH, testosterone/estradiol. MRI with gadolinium: dedicated pituitary protocol with thin coronal and sagittal cuts. Formal visual field testing (Humphrey or Goldmann perimetry). CT sinuses: assess sphenoid sinus pneumatization and septal anatomy. Nasal endoscopy: evaluate for septal deviation, spurs, or prior surgery.
Endoscopic Transsphenoidal Technique
Nasal Phase (Otolaryngology)
Lateralization of middle turbinates or partial turbinectomy for access. Identification of the sphenoid ostium medial to the superior turbinate. Posterior septectomy to create binostril corridor. Wide sphenoidotomy with removal of the anterior sphenoid wall. Identification of key landmarks: sellar floor, carotid prominences, OCR, planum sphenoidale.
Sellar Phase (Neurosurgery)
Opening of the sellar floor with drill or Kerrison rongeurs. Dural incision in cruciate fashion. Tumor removal with ring curettes and angled instruments. Assessment for residual tumor with angled endoscopes (30-degree, 45-degree).
Reconstruction
Small defects: absorbable hemostatic agents and tissue sealant. Large defects or CSF leak: nasoseptal flap, fat graft, fascial graft, multilayer closure.
Complications
CSF leak: 1-5% with modern reconstruction techniques. Diabetes insipidus (DI): transient in 10-20%, permanent in 1-2%. Hypopituitarism: new deficits in 5-10%. Carotid artery injury: rare (<1%) but catastrophic. Epistaxis and septal perforation. Visual worsening: rare, typically from hematoma or vascular injury. SIADH: typically occurs days 5-10 postoperatively; monitor sodium closely.
Key Clinical Pearls
Prolactinomas are managed medically with dopamine agonists (cabergoline) first; surgery is reserved for medication failure or intolerance. Always check a prolactin level before surgery — a level >200 ng/mL strongly suggests prolactinoma. The triphasic response of DI (polyuria, then SIADH, then permanent DI) should be anticipated postoperatively. Conchal-type sphenoid sinuses lack pneumatization and require neuronavigation for safe drilling. Cortisol replacement must be given perioperatively for Cushing disease patients to prevent adrenal crisis.
References
- Cappabianca P, Cavallo LM, de Divitiis E. Endoscopic endonasal transsphenoidal surgery. Neurosurgery. 2004;55(4):933-941.
- Molitch ME. Diagnosis and treatment of pituitary adenomas: a review. JAMA. 2017;317(5):516-524.
- Kassam AB, Prevedello DM, Carrau RL, et al. Endoscopic endonasal skull base surgery: analysis of complications in the authors' initial 800 patients. J Neurosurg. 2011;114(6):1544-1568.
- Jane JA Jr, Laws ER Jr. The surgical management of pituitary adenomas in a series of 3093 patients. J Am Coll Surg. 2001;193(6):651-659.