Pterion Prep CraniPro VUMC Case Prep
2026-06-27

Case Prep: Basilar Apex (Tip) Aneurysm

Case / Approach Snapshot

One-Liner

[Age]yo [M/F] with [ruptured/unruptured] basilar apex aneurysm presenting with [SAH / incidental] planned for [orbitozygomatic / pterional-transsylvian / subtemporal] craniotomy for clipping — OR endovascular coiling (often first-line).

Figures, Imaging & Video

🎥 Operative video — search operative video on YouTube ▸ · The Neurosurgical Atlas ▸

🧭 Operative approach: Orbitozygomatic craniotomy — detailed corridor setup, step-by-step technique & figures

External sources — operative figures/atlases are copyrighted (linked, not copied). See media-sources.md.

Operative technique & approach

Imaging

Open-access figures

Basilar-apex aneurysm via orbitozygomatic approach — posterior perforators visualized (A), dissected off the dome and excluded from the clip construct (B), with post-clip ICG confirming perforator preservation (C)

Basilar-tip clipping: P1/basilar-apex perforators dissected off the dome; post-clip ICG videoangiography confirms perforator preservation. Source: Norat et al., Front Surg 2019;6:34, Fig 3. CC BY 4.0.

High-Yield Literature

Curated Image Set

Open-access figures are embedded from PubMed Central articles and kept unique to this guide.

Basilar Apex Aneurysm — Figure 1 Figure 1. A: Head CT scan shows that the hemorrhage was localized on the pontine cistern and interpeduncular cistern, extending to the right of the ambient cistern, into the posterior horn of the… Source: Endovascular Treatment of Bilateral Carotid Artery Occlusion with Concurrent Basilar Apex Aneurysm: A Case Report and Literature Review — International Journal of Medical Sciences 2011; CC BY-NC-ND.

Basilar Apex Aneurysm — Figure 2 Figure 2. Common carotid artery DS angiographs: occlusion at the beginning of internal carotid artery, with the remaining external carotid artery. No formation of anatomosis between the external… Source: Endovascular Treatment of Bilateral Carotid Artery Occlusion with Concurrent Basilar Apex Aneurysm: A Case Report and Literature Review — International Journal of Medical Sciences 2011; CC BY-NC-ND.

Basilar Apex Aneurysm — Figure 3 Figure 3. A,B: Angiograph of the vertebral artery showing developed posterior circulation with blood supply through the bilateral posterior communicating artery. No delay was observed in the… Source: Endovascular Treatment of Bilateral Carotid Artery Occlusion with Concurrent Basilar Apex Aneurysm: A Case Report and Literature Review — International Journal of Medical Sciences 2011; CC BY-NC-ND.

Basilar Apex Aneurysm — Figure 4 Figure 4. A, B: DS angiographs taken after the aneurysm coil embolization. The aneurysm with dense embolization is not seen. Source: Endovascular Treatment of Bilateral Carotid Artery Occlusion with Concurrent Basilar Apex Aneurysm: A Case Report and Literature Review — International Journal of Medical Sciences 2011; CC BY-NC-ND.

Basilar Apex Aneurysm — Figure 5 Figure 5. A,B: One year after embolizing the aneurysm with the endovascular approach, embolization was still in good condition, without recanalization. Source: Endovascular Treatment of Bilateral Carotid Artery Occlusion with Concurrent Basilar Apex Aneurysm: A Case Report and Literature Review — International Journal of Medical Sciences 2011; CC BY-NC-ND.

Basilar Apex Aneurysm — Figure 1 Figure 1. Preoperative cerebral angiography, (a) anterior-posterior and (b) lateral views of a left vertebral artery injection, shows a large, 11-mm wide-necked basilar bifurcation aneurysm with a… Source: Double-barrel Y-configuration Stenting for Flow Diversion of a Giant Recurrent Basilar Apex Aneurysm with the Pipeline Flex Embolization Device — Journal of Neurosciences in Rural Practice 2016; CC BY-NC-SA.

Basilar Apex Aneurysm — Figure 2 Figure 2. Cerebral angiography, (a) anterior-posterior and (b) lateral views of a left vertebral artery injection, shows significant recurrence of the previously stent-coiled and twice recoiled… Source: Double-barrel Y-configuration Stenting for Flow Diversion of a Giant Recurrent Basilar Apex Aneurysm with the Pipeline Flex Embolization Device — Journal of Neurosciences in Rural Practice 2016; CC BY-NC-SA.

Basilar Apex Aneurysm — Figure 3 Figure 3. Follow-up magnetic resonance angiography 10 months after the flow diversion procedure, (a) axial time-of-flight and three-dimensional reconstruction, (b) anterior-posterior and (c)… Source: Double-barrel Y-configuration Stenting for Flow Diversion of a Giant Recurrent Basilar Apex Aneurysm with the Pipeline Flex Embolization Device — Journal of Neurosciences in Rural Practice 2016; CC BY-NC-SA.

Basilar Apex Aneurysm — Fig. 1. Fig. 1.. (A) Axial unenhanced CT demonstrates basilar apex aneurysm measuring 20 mm in width in the interpeduncular fossa. (B) Axial CTA shows aneurysmal lumen measuring 12 mm in width at its… Source: Intrasaccular flow disruption (WEB) of a large wide-necked basilar apex aneurysm using PulseRider-assistance — Interdisciplinary neurosurgery : Advanced techniques and case management 2020; CC BY.

Basilar Apex Aneurysm — Fig. 2. Fig. 2.. (A) Right vertebral arteriogram in frontal projection shows wide-necked, large basilar apex aneurysm incorporating both PCA origins. (B) Lateral projection of right vertebral arteriogram… Source: Intrasaccular flow disruption (WEB) of a large wide-necked basilar apex aneurysm using PulseRider-assistance — Interdisciplinary neurosurgery : Advanced techniques and case management 2020; CC BY.

History of Present Illness

Imaging Review

CTA / DSA

Labs

Neurological Examination

Surgical Planning

Case Logistics, OR Needs & Orders

Approach Selection

Position

Approach: Orbitozygomatic Craniotomy (most common)

Microsurgical Steps

  1. OZ craniotomy with orbital osteotomy
  2. Wide sylvian fissure split — expose ICA, optic nerve, posterior carotid space
  3. Open the membrane of Liliequist → access interpeduncular cistern
  4. Identify ICA, PComA — work in the opticocarotid or carotid-oculomotor triangle
  5. Identify basilar trunk below the bifurcation for proximal control
  6. Identify bilateral P1s, SCAs, and thalamoperforators (posterior to the basilar apex)
  7. Posterior clinoidectomy if needed for proximal control/visualization
  8. Temporary clip on basilar trunk (below SCA origins) for dome dissection
  9. Dissect neck, separate perforators from the aneurysm (most critical and dangerous step)
  10. Clip placement (often fenestrated to spare P1/perforators)
  11. Confirm: ICG, micro-Doppler — both P1s, SCAs, perforators patent

Critical Anatomy & Structures at Risk

  1. Thalamoperforating arteries — from P1/basilar apex; injury → devastating midbrain/thalamic infarct (decreased consciousness, oculomotor dysfunction, hemiparesis)
  2. Bilateral P1 / PCA — must preserve
  3. Superior cerebellar arteries — just below P1
  4. CN III (oculomotor) — runs between PCA and SCA in interpeduncular cistern
  5. Brainstem (midbrain) — directly posterior
  6. Vein of Labbé (subtemporal approach) — sacrifice → temporal venous infarct

Equipment

Monitoring

Anesthesia

Potential Complications

  1. Perforator infarction — leading cause of morbidity; meticulous perforator preservation
  2. Brainstem injury
  3. CN III palsy
  4. Intraoperative rupture (deep, hard to control)
  5. Temporal lobe retraction injury (subtemporal)

Operative Note Template

Preoperative Diagnosis: [Ruptured (Hunt-Hess __, Fisher __) / Unruptured] basilar apex aneurysm

Postoperative Diagnosis: Same

Procedure: [Right] orbitozygomatic craniotomy for microsurgical clipping of basilar apex aneurysm [with posterior clinoidectomy]

Surgeon / Assistant: Anesthesia: General endotracheal EBL / Fluids / Blood products: [2 units crossmatched available] Adjuncts: Neuronavigation, micro-Doppler, ICG videoangiography, [adenosine for flow arrest], burst suppression, lumbar drain Implants: Aneurysm clip(s) [type/size — fenestrated as needed] Monitoring: SSEP / MEP / EEG / BAER — stable [note changes] Complications: None

Indications: [Age]yo [M/F] with a [ruptured/unruptured] basilar apex aneurysm ([size], [projection]). Given [wide neck / branch incorporation / young patient / failed coiling], microsurgical clipping was chosen over endovascular treatment. Risks/benefits/alternatives discussed.

Description of Procedure: After consent and time-out, general anesthesia was induced, arterial/central access and neuromonitoring established, and a lumbar drain placed. The head was fixed in Mayfield, rotated ~30° contralateral and extended. A [right] orbitozygomatic craniotomy was performed with orbital osteotomy, and the dura opened.

Under the microscope, the sylvian fissure was widely split and the carotid, optic, and interpeduncular cisterns were opened with CSF egress for relaxation (aided by the lumbar drain). The ICA, optic nerve, and PComA were identified and the membrane of Liliequist opened to access the interpeduncular cistern. [A posterior clinoidectomy was performed to expose the basilar trunk for proximal control.] The basilar trunk below the SCA origins, both P1 segments, the superior cerebellar arteries, and the thalamoperforating arteries posterior to the apex were identified.

With burst suppression [and adenosine/temporary clip on the basilar trunk] for proximal control, the aneurysm neck was dissected and the perforators were meticulously separated from the dome. A [fenestrated] clip was applied across the neck, sparing both P1s and all perforators. ICG videoangiography and micro-Doppler confirmed obliteration of the aneurysm with patency of both P1s, the SCAs, and the perforators.

Hemostasis was confirmed, the orbitozygomatic segment reconstructed, the bone flap replaced, and the wound closed in layers. The patient was transferred to the NSICU in stable condition.

Postoperative Plan

Chief-Level Case Review

Use these as the senior-level mental model for Basilar Apex (Tip) Aneurysm:

Common Pimp Questions

Use these to pressure-test preparation for Basilar Apex (Tip) Aneurysm:

  1. What is the proximal-control plan before the lesion is manipulated?
  2. Which branch, perforator, or venous structure is most likely to be injured in this exposure?
  3. What are the intraoperative rupture steps, including temporary clip, suction, BP, and backup clip strategy?
  4. What confirms treatment success: ICG, Doppler, puncture/deflation, DSA, or postoperative CTA?
  5. What postoperative BP, vasospasm, antiplatelet, or anticoagulation issue changes the orders tonight?

Attending Preference Variables

Items that commonly vary by surgeon or institution: