SURGICAL MANAGEMENT OF PITUITARY & PARASELLAR DISEASES

Chen & Wormald - Exam Notes

1. INTRODUCTION & HISTORY

Key Historical Milestones (High-Yield for MCQs)

2. SURGICAL APPROACHES - COMPARISON

A. Microscopic Sublabial-Transseptal Approach

• Sublabial incision → elevation of septal mucosa → fracture of quadrangular cartilage → removal of bony septum → access to sella
• Limitation (HIGH YIELD): Microscopic view is limited by the speculum - cannot visualize lateral extension of tumour
• Variation: Transseptal approach with hemitransfixion incision using self-retaining retractor

B. Endoscopic Transsphenoidal Approach - Advantages over Microscope

• No brain retraction
• Decreased wound breakdown
• Shorter hospitalization
• No external scar
• Wide-angle panoramic view - critical landmarks and tumour seen in same field
• Allows visualization of tumour extensions beyond sella turcica
• Angled views with instrument mobility
• No external incision or numbness (as occurs with sublabial approach)
• Endoscope allows bimanual dissection by second surgeon
• 30° angled endoscope used for parasellar and suprasellar extensions

C. Extended Approaches (for large tumours)

• Transplanum
• Transclival / Transodontoid
• Transpterygoid
• Dictated by size, type, and extent of tumour

3. PATHOLOGIES ADDRESSED

• Most common: Pituitary adenomas
• Others: Meningiomas, Chordomas, Germ cell tumours, Epidermoid cysts, Rathke cleft cysts, Craniopharyngiomas, Fibrous dysplasia, Chondrosarcomas, Epidermoid cysts

4. PRE-OPERATIVE ASSESSMENT

History & Physical Exam

• Full neurological assessment
• Cranial nerves through cavernous sinus - special attention
• Visual assessment (acuity, visual fields, gaze restrictions) - best performed by ophthalmologist
• Rigid nasal endoscopy - assess for sinonasal disease or anatomic obstructions
• Endocrinologist involvement for pituitary tumours - hormonal status and pituitary function must be determined prior to surgery

Snyderman Difficulty Levels (5 Levels)

• Level II: Pathology confined to sella
• Level III: Extrasellar extension but remains extradural
• Level IV: Intra-dural dissection
• Level V: Most complex

Imaging (HIGH YIELD)

• Bone windows: tumour invasion or bony remodelling
• Sinonasal disease, septal deviation (for nasoseptal flap planning)
• Sphenoid sinus aeration
• Anatomical variants: Onodi cells, sphenoid intersinus septa
• Course of carotid artery and optic nerve
• Potential dehiscence areas
• If carotid artery concern → CT angiogram

• Differentiates tumour from obstructed mucus/fluid
• Dural enhancement or invasion
• Superior to CT for tumour morphology
• Image Guidance Navigation (IGN): used routinely for all skull base cases
  • IGN is NOT a substitute for anatomical knowledge
  • Especially helpful for: revision cases, challenging anatomy, expanded approaches, extrasellar extension
  • Associated with: improved accuracy, reduced morbidity, shorter ICU stays
  • Limitation: systems require practice; not always accurate

5. ENDOSCOPIC TRANSSPHENOIDAL APPROACH - STEP BY STEP

Pre-operative Setup

• Abdomen or thigh prepared as graft donor site (fat + fascia for closure)
  • Abdomen: rectus abdominis fascia (most pituitary tumours)
  • Thigh: fascia lata (larger defects - craniopharyngiomas, meningiomas, chordomas)
• Head of bed: Reverse Trendelenburg - decreases venous congestion and bleeding
• Lumbar drains: NOT routinely required even if CSF leak created
• Two-surgeon approach - table turned so anaesthetist is at foot
• Patient catheterized for fluid balance (risk of diabetes insipidus)
• Broad spectrum prophylactic antibiotics
• Nose decongested with topical and local vasoconstrictive agents
• Scuba head strap for electromagnetic IGN; patient is registered

Surgical Technique - Step by Step

• Septoplasty + removal of concha bullosa if present
• Lateral wall of middle turbinate assessed on CT

• Lateralize middle turbinate → expose sphenoethmoid recess and superior turbinate
• Remove inferior half of superior turbinate to expose sphenoid sinus

• Located medial to superior turbinate junction of lower 1/3 and upper 2/3
• If not visible: 4mm microdebrider blade can measure 12mm from posterior choana
• Blunt Freer elevator to palpate sphenoid face and confirm entry
• Entry with Freer has low risk of injury to critical structures

• Widen ostium → open posterior ethmoids → widen to lamina papyracea
• Final size: septum to lamina (lateral), roof to floor of sphenoid (vertical)
• Hajek-Koffler and Kerrison punches used (biting mechanism minimizes risk of inadvertent injury to optic nerve and carotid)
• Mucosa elevated medial to lateral (lateral mucosa stays on bone) - creates two mucosal flaps to reconstitute anterior pituitary fossa

• Raised as nasoseptal (pedicled septal) flap for extended approaches or anticipated large CSF leak
• Incision: from lower edge of natural sphenoid ostium → horizontal → 3-4cm anteriorly
• Suction Freer mobilizes flap to posterior bony choana
• Posterior septectomy: 1-1.5cm of posterior septum removed (above previously mobilized pedicle)
• Intersinus septations removed with rongeur or diamond drill - septations frequently veer toward carotid artery/optic nerve (Figure 115.3)

• Medial and lateral opticocarotid recesses
• Anterior genu of carotid arteries
• Both optic nerves
• Confirmed with image guidance suction probe

• Soft bone (macroadenoma): Freer elevator gently fractures → 2mm Kerrison punch
• Hard bone (microadenoma): diamond burr to "eggshell" the bone → fracture
• Kerrison punch: bone off dura from one cavernous sinus to the other, pituitary fossa floor to just below tuberculum sella (HIGH YIELD landmark)
• U-shaped dural incision: flap based superiorly, 2mm medial to each cavernous sinus → joined at floor
• Cruciate incisions no longer used

• Extracapsular resection attempted for complete removal
• Consistency: soft to firm → instruments vary (suction, scalpel, large backbiting forceps)
• 30° angled endoscope for parasellar/suprasellar extension
• Macroadenoma: tissue immediately apparent → histology sent
• Microadenoma: MRI + image guidance helpful

6. CLOSURE

1. Haemostasis with Gelfoam paste (Gelfoam powder + saline) + pressure
2. Pituitary fossa: gently filled with Gelfoam paste
3. Dura placed over paste
4. Sphenoid mucosal flaps placed over dura → secured with Surgicel + fibrin glue
5. No packing in sphenoid sinus

1. Identify diaphragma sellae defect
2. Fat plug placed into defect
3. Additional fat in sella + fascia over fat
4. Dura and sphenoid mucosa draped over fascia
5. Surgicel + fibrin glue → Gelfoam → BIPP soaked ribbon gauze (removed day 3)
6. Large CSF leak / extended approach with arachnoid defect → raise pedicled septal flap
7. Fascia (or DuraGen) as underlay intracranial graft + pedicled septal flap over this graft

7. PARASELLAR (CAVERNOUS SINUS) EXTENSION

• Initially dealt with same as above
• Tumour may extend anteriorly into cavernous sinus (Figure 115.7a)
• Philosophy: Only address cavernous sinus extensions in secreting tumours (risks outweigh benefits in benign non-secreting tumours)
• Bone anterior to anterior genu of cavernous carotid artery gently removed
• 2mm diamond burr → blunt hook dissects carotid from bone → osteotomies fracture and remove bone → expose carotid artery
• Cavernous sinus can be approached from anterior and lateral to carotid
• Exposed carotid covered by pedicled septal flap post-tumour removal

8. COMPLICATIONS

Delayed Complications

• Most common: CSF leak
  • Philosophy: Do NOT limit tumour resection due to fear of CSF leak
  • Post-operative CSF leak is a complication but acceptable
  • Accepted rate of post-operative CSF leak: <5%
  • Management: bedrest + lumbar drain; if no cessation in 24 hours → formal closure in theatre
  • Multilayer closure (fibrin glue + sphenoid sinus pack) bolsters repair
• Mucosal scarring
• Hyposmia or anosmia
• Nasal crusting
• Sinusitis

Immediate Complications

• Vision damage
• Venous and arterial bleeding
• Carotid artery injury - most feared
  • Up to 30% neurological sequelae
  • ~20% mortality rate (HIGH YIELD)
  • Most challenging endonasal situation
  • Management: crushed muscle as patch on bleeding vessel (quickest, safest, most effective)
  • Pre-operative imaging identifies risk: Onodi cell pneumatization lateral/superior to sphenoid (optic nerve runs through it), medial carotid location, intersinus septum attaching to carotid

Key Risk Factors to Identify Pre-operatively

1. Onodi cell - optic nerve runs within it; failure to identify = optic nerve at risk
2. Medial location of carotid artery (Figure 115.1a)
3. Intersinus septum attaching to carotid artery (Figures 115.3a, 115.3b)

9. KEY EXAM POINTS - QUICK RECALL

10. CONCLUSION