What are the steps for transsphenoidal pituitary adenoma excision surgery?

Transsphenoidal Pituitary Adenoma Excision: Surgical Steps

Transsphenoidal surgery for pituitary adenomas consists of three distinct operative phases—nasal/sphenoid exposure, tumor resection, and sellar reconstruction—with endoscopic approaches preferred over microscopic techniques for superior visualization and preservation of pituitary function. 1, 2

Phase 1: Nasal and Sphenoid Exposure

• Achieve optimal bony exposure of the sphenoid and sellar regions, as adequate exposure directly improves the extent of tumor resection 2
• Perform endoscopic endonasal approach through the nostril, advancing through the nasal cavity to the sphenoid sinus 3
• Remove the anterior wall of the sphenoid sinus to expose the sella turcica 2
• For patients with incompletely pneumatized sphenoid sinuses (common in children), drilling of the sphenoid bone may be required, though this does not limit surgical outcomes 1
• Computer-assisted navigation may be used during this phase, though evidence is insufficient to recommend its routine use 2
• Create adequate sellar opening by removing the sellar floor to expose the dura 2

Phase 2: Tumor Resection

• Open the dura carefully to access the adenoma 2
• Resect tumor using endoscopic visualization, which provides superior visualization of residual tumor, particularly in suprasellar and parasellar extensions 2, 3
• Remove tumor systematically, starting with debulking the central portion, then addressing lateral and superior extensions 4
• For large tumors with significant suprasellar, frontal, or temporal extension, consider a combined transsphenoidal and transcranial approach rather than attempting complete resection through the transsphenoidal route alone 2
• Inspect the surgical cavity thoroughly with the endoscope to identify residual tumor, as endoscopic visualization after initial resection frequently reveals residual tissue 2
• Identify and preserve the normal pituitary gland, pituitary stalk, and surrounding neurovascular structures 4

Phase 3: Sellar Reconstruction and Closure

• Recognize any intraoperative CSF leak immediately, as failure to do so leads to postoperative CSF fistula with associated risks of meningitis and brain abscess 2
• If CSF leak is identified, perform multilayer closure using fat graft, fascia lata, or synthetic dural substitute 5
• Reconstruct the sellar floor using bone, cartilage, or synthetic materials 2
• Close the sphenoid sinus and nasal mucosa 5

Critical Perioperative Management

• Implement strict fluid and electrolyte balance monitoring peri-operatively and post-operatively, as changes in water metabolism are common complications 1
• Monitor for transient diabetes insipidus (occurs in 4.6% of cases), permanent diabetes insipidus (0.4%), and SIADH (1.1%) 5
• Watch for biphasic or triphasic patterns of AVP deficiency, which may develop over several days postoperatively 1
• Risk factors for postoperative diabetes insipidus or SIADH include female sex, cerebrospinal fluid leak, drain placement after surgery, invasion of the posterior pituitary by tumor, or manipulation of the posterior pituitary during surgery 1
• Avoid "overshoot" iatrogenic SIADH and hyponatremia when treating diabetes insipidus with desmopressin 6

Surgical Considerations by Tumor Characteristics

• Surgery should be performed by experienced pituitary surgeons in centers with extensive experience (at least 50 pituitary operations per year per unit) 1, 7
• Gross-total resection rates for large and giant adenomas (≥3 cm) average 24%, with mean resection rates of 82.9% 8
• Predictors of lower extent of resection include higher Knosp grade, larger preoperative tumor volume and diameter, hemorrhagic components, posterior extension, and sphenoid sinus invasion 8
• For tumors with these unfavorable characteristics, consider staged operations to maximize extent of resection 8

Common Pitfalls to Avoid

• Inadequate bony exposure in Phase 1 limits tumor resection and increases residual tumor rates 2
• Over-reliance on intraoperative MRI can lead to unnecessary additional resection attempts due to false-positive findings 2
• Failure to use endoscopic visualization after initial resection misses residual tumor 2
• Inadequate postoperative monitoring for diabetes insipidus and SIADH leads to preventable complications 1, 5

Expected Outcomes

• Improvement in hypopituitarism occurs in 35% to 50% of surgically treated patients 7
• Visual acuity improves in 73% and visual fields improve in 61.8% of patients 8
• Overall complication rates are approximately 7-12%, with CSF leak (1.3-4.7%), meningitis (0.8-2.0%), and transient diabetes insipidus (4.6%) being most common 7, 5
• Mortality directly related to the surgical procedure is extremely rare 5