Skull Base Surgery: Endoscopic and Lateral Approaches
Scope
Skull base surgery tests anterior and lateral skull base anatomy, endoscopic endonasal approaches, cerebrospinal fluid leak, pituitary tumors, vestibular schwannoma, and complication management. The board expects safe corridor selection and recognition of endocrine and vascular emergencies.
Core rules
- Endoscopic endonasal corridors pass the cribriform plate, planum sphenoidale, sella, and clivus. Identify the optic nerve and internal carotid artery before drilling.
- Cerebrospinal fluid leak is confirmed with beta-2 transferrin. Repair may use a vascularized nasoseptal flap, fat, fascia, or synthetic graft depending on defect size.
- Pituitary macroadenoma can cause bitemporal hemianopia and hypopituitarism. Prolactinoma is treated medically with a dopamine agonist; pituitary apoplexy is an emergency requiring steroids and urgent decompression.
- Vestibular schwannoma management includes observation, stereotactic radiosurgery, and microsurgery. Translabyrinthine approach is used when hearing is not serviceable; retrosigmoid and middle fossa approaches may preserve hearing.
- Lateral skull base surgery requires facial nerve monitoring. Complications include cerebrospinal fluid leak, meningitis, diabetes insipidus, and carotid injury.
Worked example
A patient has bitemporal hemianopia and a pituitary macroadenoma with prolactin of 200 ng/mL. The diagnosis is prolactinoma. Dopamine agonist therapy is first-line and often shrinks the tumor; surgery is reserved for resistance, apoplexy, or persistent visual loss.
Traps
Ordering CT alone for skull base soft tissue; omitting prolactin and pituitary hormone testing; missing postoperative diabetes insipidus; failing to recognize a CSF leak; and drilling near the carotid without vascular imaging.