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

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

1. Cappabianca P, Cavallo LM, de Divitiis E. Endoscopic endonasal transsphenoidal surgery. Neurosurgery. 2004;55(4):933-941.
2. Molitch ME. Diagnosis and treatment of pituitary adenomas: a review. JAMA. 2017;317(5):516-524.
3. 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.
4. 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.

For the intern

At 3 AM, your priority is identifying pituitary apoplexy—sudden severe headache, vision changes, and altered mental status require immediate imaging and urgent surgical decompression. Acute postoperative concerns include uncontrolled epistaxis (pack and monitor hemodynamics), new visual loss (emergent imaging for hematoma), and polyuria (check urine output, specific gravity, and serum sodium for diabetes insipidus (DI)). Clear rhinorrhea warrants beta-2 transferrin testing but is rarely acutely life-threatening. Routine postoperative headaches, nasal congestion, and stable visual fields can be addressed on morning rounds with the attending team.

Common pitfalls

• Missing medication-responsive prolactinomas: Always check prolactin levels preoperatively. Levels >200 ng/mL typically indicate prolactinoma, which should be treated with cabergoline first, not surgery. Operating without this workup wastes resources and risks unnecessary complications.

• Inadequate monitoring for SIADH (syndrome of inappropriate antidiuretic hormone): The triphasic response (early DI, then SIADH days 5-10, then possible permanent DI) catches inexperienced teams off-guard. Check sodium daily for two weeks postoperatively—hyponatremia from SIADH can cause seizures if missed.

• Confusing postoperative CSF (cerebrospinal fluid) leak with normal drainage: Some clear drainage is expected initially. True CSF leaks persist beyond 48-72 hours, are positional, and show glucose or beta-2 transferrin positivity. Premature reoperation causes unnecessary morbidity.

• Forgetting stress-dose steroids in Cushing patients: After removing an adrenocorticotropic hormone (ACTH)-secreting tumor, patients cannot mount a stress response. Perioperative hydrocortisone prevents potentially fatal adrenal crisis.

Make it stick

Imagine you're the intern on call overnight and a patient who just had a pituitary tumor removed via endoscopic transsphenoidal approach starts complaining of a severe headache and blurred vision. This could be pituitary apoplexy, a critical post-operative emergency. You order an urgent MRI or CT to rule out hemorrhage. Another common scenario: the patient is urinating excessively. You immediately check urine specific gravity and serum sodium to assess for diabetes insipidus (DI), a frequent and important complication. Remembering these critical postoperative assessments can make a huge difference in patient outcomes.

If you remember one thing

Always consider pituitary apoplexy in acute postoperative headache and visual changes, and meticulously monitor for diabetes insipidus (DI) with urine output and serum sodium checks.

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