Comprehensive Anatomic Assessment of Ipsilateral Pterional Versus Contralateral Subfrontal Approaches to the Internal Carotid Ophthalmic Segment: A Cadaveric Study and Three-Dimensional Simulation

OBJECTIVE: Medially pointing aneurysms of the ophthalmic segment of the internal carotid artery (oICA) represent a neurosurgical challenge. Conventional ipsilateral approaches require internal carotid artery and optic nerve (ON) mobilization as well as anterior clinoidectomy (AC), all associated with increased surgical risk. Contralateral approaches could provide a better exposure of the superomedial aspect of the oICA, ophthalmic artery, and superior hypophyseal artery, sparing AC and internal carotid artery or ON mobilization. However, the microsurgical anatomy of this approach has not been systematically studied. In the present work, we exhaustibly analyzed the anatomic and morphometric characteristics of contralateral approaches to the oICA and compared them with those from ipsilateral approaches. METHODS: We assessed 36 ipsilateral and contralateral approaches to the oICAs in cadaveric specimens and live patients, using for the latter a three-dimensional virtual reality (VR) system. RESULTS: Contralateral approaches spared sylvian fissure dissection and required only minimal frontal lobe retraction. The ipsilateral and contralateral oICA were found at a depth of 49.21 +/- 1.8 mm (VR, 50.1 +/- 2.92 mm) and 65.1 +/- 1.5 mm (VR, 66.05 +/- 3.364 mm) respectively. The exposure of the superomedial aspect of oICA was 7.25 +/- 0.86 mm (VR: 6 +/- 1 mm) contralaterally without ON mobilization and 2.44 +/- 0.51 mm (VR, 2 +/- 1 mm) ipsilaterally even after AC. Statistical analysis showed that, for nonprefixed chiasm, contralateral approaches achieved a significantly higher exposure of the ophthalmic artery, superior hypophyseal artery, and the superomedial aspect of the oICA with its perforating branches (all P< 0.01). CONCLUSIONS: Contralateral approaches may enable successful exposure of the oICA and related vascular structures, reducing the need for AC or ON mobilization. Systematic clinical/surgical studies are needed to further determine the effectiveness and safety of the approach.