Pituitary Surgery

Pituitary Anatomy & Physiology - Gland Central

• Location: Sella turcica (sphenoid bone), covered by diaphragma sellae.
• Lobes & Origin:
  • Adenohypophysis (Anterior Lobe): From Rathke's pouch (oral ectoderm).
    • Hormones: GH, PRL, ACTH, TSH, FSH, LH. (📌 FLAT PiG)
    • Blood: Superior hypophyseal artery (hypophyseal portal system).
  • Neurohypophysis (Posterior Lobe): From neuroectoderm (diencephalon downgrowth).
    • Stores: ADH (vasopressin), Oxytocin (produced in hypothalamus: Supraoptic & Paraventricular nuclei).
    • Blood: Inferior hypophyseal artery.
• Key Relations:
  • Superior: Optic chiasm (compression → bitemporal hemianopia).
  • Lateral: Cavernous sinuses (contains CN III, IV, V1, V2, VI; Internal Carotid Artery).
  • Inferior: Sphenoid sinus (transsphenoidal surgical approach).

⭐ The cavernous sinus, lateral to the pituitary, contains CN III, IV, V1, V2, VI and the ICA. Lateral pituitary expansion can cause ophthalmoplegia and sensory loss in V1/V2 distributions.

Indications & Pre-op Eval - Surgical Summons

• Indications:
  • Pituitary Adenomas:
    • Functioning: Cushing's, Acromegaly, Prolactinoma (med-refractory)
    • Non-Functioning: Mass effect (visual loss, hypopituitarism), apoplexy
  • Other lesions: Craniopharyngioma, Rathke's Cleft Cyst (symptomatic), Sellar/Parasellar tumors.
• Pre-op Evaluation (📌 Mnemonic: HOME):
  • Hormonal: Full pituitary panel; dynamic tests prn.
  • Ophthalmological: Visual acuity, fields (perimetry).
  • MRI: Sellar region (gold standard); CT for bony detail.
  • Endoscopy (Nasal): For transsphenoidal approach.
  • General fitness (ASA) & detailed counselling.

⭐ Bitemporal hemianopia is a classic visual field defect in pituitary adenomas due to optic chiasm compression.

Surgical Approaches - The Sellar Gateway

• Transsphenoidal Approach (TSA): Primary route for >95% of pituitary tumors.
  • Types:
    • Endoscopic Endonasal (EEA): Gold standard. Superior visualization, wider surgical corridor.
    • Microscopic: Traditional, still used.
  • Corridors: Transnasal (most common), sublabial (historical), transseptal.
  • Advantages: Minimally invasive, direct midline access, no external scar, ↓ hospital stay, ↓ morbidity.
  • Key Complications: CSF leak (most common, ~5-15%), meningitis, diabetes insipidus (DI), sinusitis, vascular injury (ICA).

  ⭐ The most feared complication of TSA is injury to the internal carotid artery (ICA).

• Transcranial Approach (TCA): Reserved for select cases.
  • Indications: Large/giant adenomas with significant lateral (cavernous sinus) or anterior/posterior fossa extension, non-adenomatous sellar pathology, failed TSA.
  • Routes: Pterional, subfrontal, orbitozygomatic.
  • Disadvantages: More invasive, brain retraction, higher risk of neurological deficits, longer recovery.

Complications & Post-op Care - Pituitary Pitfalls

• Immediate/Early:
  • CSF Leak: Most common. β2-transferrin test. Manage: bed rest, drain, repair if >5-7 days.
  • Hemorrhage: Sellar hematoma. Risk of vision loss.
  • Visual loss: Optic nerve/chiasm injury.
  • CN Palsy: III, IV, VI; often transient.
• Endocrine:
  • DI: ↓ADH. Polyuria (>250ml/hr), ↑Na+ (>145 mEq/L), ↓Urine Osm (<300 mOsm/kg). Rx: DDAVP.
  • SIADH: ↑ADH. Oliguria, ↓Na+ (<135 mEq/L), ↑Urine Osm. Rx: Fluid restriction.
  • Hypopituitarism: ACTH/TSH deficiency common. Lifelong replacement.
• Other: Meningitis, nasal septal issues.
• Post-op Care:
  • Monitor: UO, Serum Na+, vision.
  • Nasal pack (2-5 days). Avoid straining/nose blowing.
  • Stress-dose steroids (Hydrocortisone).

⭐ CSF rhinorrhea is the most common complication. Beta-2 transferrin is pathognomonic for CSF.

High‑Yield Points - ⚡ Biggest Takeaways

• Transsphenoidal approach: gold standard for most pituitary adenomas.
• Endoscopic endonasal approach: improved visualization, wider access, reduced morbidity.
• Key complications: CSF leak, diabetes insipidus (DI), SIADH, meningitis, visual loss, hypopituitarism.
• Prolactinomas: most common, often medically managed (dopamine agonists: cabergoline/bromocriptine).
• GH-adenomas cause acromegaly/gigantism; ACTH-adenomas cause Cushing's disease.
• Non-functioning adenomas: present with visual defects (bitemporal hemianopia) or hypopituitarism.
• Post-op MRI: assesses resection completeness, sellar integrity.