Surgical Anatomy - exam-focused guide
Surgical Anatomy tests the skull base, circle of Willis, cranial nerves, ventricles and spine as they appear in operative approaches. The exam favours three-dimensional relationships and safe corridors.
Core rules
- The circle of Willis connects anterior and posterior circulations; common variants include a hypoplastic A1 or P1, anterior communicating artery aneurysms and posterior communicating artery aneurysms.
- Cavernous sinus contains the internal carotid artery and CN III, IV, V1, V2 and VI. CN VI is lateral to the ICA and vulnerable in cavernous sinus surgery.
- The pterional approach exposes the sylvian fissure, ICA, MCA, anterior communicating complex and basal cisterns. The subtemporal approach reaches the tentorial edge and posterior circulation.
- The cerebellopontine angle contains CN V–XI, the cerebellum and brainstem; vestibular schwannoma arises at the internal acoustic meatus.
- Ventricular landmarks: frontal horn, foramen of Monro, thalamus and choroid plexus. Safe entry avoids eloquent cortex and deep veins.
- Spinal anatomy: pedicle, pars interarticularis, facet joint, intervertebral foramen and ligamentum flavum define decompression and fusion corridors.
Worked example: A patient has a posterior communicating artery aneurysm causing CN III palsy. The aneurysm arises at the ICA–PCom junction and compresses the oculomotor nerve. The pterional approach provides access to the ICA and the aneurysm neck; the surgeon identifies the PCom and preserves perforators before clipping.
Traps: confusing CN VI with the ophthalmic division in the cavernous sinus; injuring perforators while exposing an aneurysm; entering the ventricle through eloquent cortex; mistaking the facet joint for the pedicle; ignoring anatomic variants on angiography.