Pterion Prep CraniPro VUMC Case Prep
2026-06-27

Case Prep: MCA Aneurysm Clipping

Case / Approach Snapshot

One-Liner

[Age]yo [M/F] with [ruptured/unruptured] middle cerebral artery bifurcation aneurysm presenting with [worst headache of life / incidental finding] planned for left/right pterional craniotomy for microsurgical clipping.

Figures, Imaging & Video

🎥 Operative video — Microsurgical Clipping of MCA & ICA-Terminus Aneurysms · Barrow Neurological Institute

More operative video: YouTube ▸ · Neurosurgical Atlas ▸

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

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

Operative technique & approach

Imaging

Open-access figures

MCA aneurysm — dissected neck with parent vessel and two branches (A), clipped neck (B), and intraoperative ICG videoangiography confirming aneurysm exclusion with branch patency (C)

Intraoperative clipping with ICG videoangiography confirming complete aneurysm exclusion and preserved MCA branch flow. Source: Norat et al., Front Surg 2019;6:34, Fig 2. 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.

MCA Aneurysm Clipping — Fig. 1 Fig. 1. Contrast Pterional approach, LSO approach and modified LSO approach bone window shape in craniotomy. a represents a conventional Pterional approach, b represents a classical LSO… Source: Comparison between modified lateral supraorbital approach and pterional approach in the surgical treatment of middle cerebral artery aneurysms — Chinese Neurosurgical Journal 2018; CC BY.

MCA Aneurysm Clipping — Fig. 2 Fig. 2. Contrast modified LSO approach and Pterional approach bone window shape in middle aneurysm clipping surgery. a and b represent the shape of the bone flap of the modified LSO approach and… Source: Comparison between modified lateral supraorbital approach and pterional approach in the surgical treatment of middle cerebral artery aneurysms — Chinese Neurosurgical Journal 2018; CC BY.

MCA Aneurysm Clipping — Figure 2 Figure 2. A CT scan taken at admission showed SAH (Fisher group 3) (Fig. 2a,b), and 3DCTA showed an intracranial aneurysm in the left MCA bifurcation (Fig. 2c). Intraoperative monitoring results… Source: Precise MEP monitoring with a reduced interval is safe and useful for detecting permissive duration for temporary clipping — Scientific Reports 2020; CC BY.

MCA Aneurysm Clipping — Figure 10 Figure 10. Source: Safe time duration for temporary middle cerebral artery occlusion in aneurysm surgery based on motor-evoked potential monitoring — Surg Neurol Int. 2017 May 10;8:79. doi: 10.4103/sni.sni_410_16; CC BY-NC-SA.

History of Present Illness

Past Medical History

Imaging Review

CT Head (non-contrast)

CTA Head

MRI/MRA (if applicable)

DSA (Digital Subtraction Angiography)

Labs

Neurological Examination

Mental Status

Cranial Nerves

Motor

Speech/Language (dominant hemisphere)

Surgical Planning

Case Logistics, OR Needs & Orders

Diagnosis & Indication

Position

Incision

Approach: Pterional Craniotomy

Microsurgical Steps

  1. Craniotomy and sphenoid wing drilling — flat to anterior skull base
  2. Dural opening — curvilinear based on sphenoid ridge/middle fossa
  3. Sylvian fissure split — inside-out technique preferred
    • Identify sylvian veins — preserve superficial middle cerebral vein
    • Open arachnoid sharply along the fissure
    • Wide split to expose M1, bifurcation, and proximal M2s
  4. CSF drainage — open carotid and chiasmatic cisterns for brain relaxation (or use lumbar drain)
  5. Identify M1 (proximal control) — follow M1 distally toward bifurcation
  6. Identify lenticulostriate perforators — arising from superior surface of M1; must be preserved
  7. Identify M2 branches — superior and inferior trunks; identify early temporal branches
  8. Expose aneurysm neck — circumferential dissection of neck
  9. Assess dome projection and adhesions — if ruptured, dissect dome last
  10. Temporary clip application — on M1 if needed for final dissection or in case of intraoperative rupture
  11. Permanent clip application:
    • Select clip (straight, curved, fenestrated, or combination)
    • Clip blades parallel to M1/M2 axis to avoid branch compromise
    • Confirm: no branch vessel stenosis, complete neck obliteration
  12. Confirmation:
    • Micro-Doppler of M1 and M2 branches
    • ICG videoangiography — aneurysm filling, branch patency
    • Papaverine if vasospasm
  13. Inspection of clip and surrounding anatomy
  14. Hemostasis and closure

Critical Anatomy & Structures at Risk

  1. M2 superior and inferior trunks — can be kinked or stenosed by clip
  2. Lenticulostriate arteries — arise from M1, supply internal capsule and basal ganglia; devastating if injured
  3. Anterior temporal artery — early M1 branch, supplies temporal lobe
  4. Superficial middle cerebral vein — preserve during sylvian fissure split
  5. Frontotemporal branch of CN VII — protect during scalp dissection (interfascial technique)
  6. Dominant hemisphere language areas — Broca (posterior frontal), Wernicke (posterior temporal)
  7. M1 perforators to corona radiata/internal capsule

Equipment & Instrumentation

Monitoring

Anesthesia Considerations

Potential Complications & Contingencies

  1. Intraoperative rupture — temporary clip on M1, suction, complete neck dissection under proximal control, definitive clipping
  2. Branch vessel occlusion by clip — ICG/micro-Doppler check, reposition clip, consider fenestrated clip
  3. Vasospasm (ruptured) — papaverine irrigation, induced hypertension, consider nimodipine
  4. Retraction injury — minimize retraction, use CSF drainage for relaxation
  5. Incomplete clipping — intraoperative angiography or ICG confirmation; consider clip revision
  6. Perforator injury — meticulous dissection; if compromised, may cause contralateral hemiparesis

Operative Note Template

Preoperative Diagnosis: [Ruptured/Unruptured] left/right MCA bifurcation aneurysm

Postoperative Diagnosis: Same

Procedure: Left/Right pterional craniotomy for microsurgical clipping of MCA bifurcation aneurysm

Surgeon: Assistant: Anesthesia: General endotracheal anesthesia

EBL: Fluids: Specimens: None Drains: [Subgaleal drain / None] Complications: None Implants: [Aneurysm clip type/size], [titanium plates and screws for bone flap fixation]

Indications: The patient is a [age]yo [M/F] who presented with [thunderclap headache and was found to have SAH (Hunt-Hess grade __, Fisher grade __) with a __ mm left/right MCA bifurcation aneurysm on CTA/DSA / an incidentally discovered __ mm left/right MCA bifurcation aneurysm]. After multidisciplinary discussion and counseling regarding risks, benefits, and alternatives including endovascular treatment and observation, the patient elected to proceed with microsurgical clipping.

Description of Procedure: After informed consent was verified and the surgical site was marked, the patient was brought to the operating room and placed supine on the operating table. General endotracheal anesthesia was induced. Neurophysiological monitoring was established with SSEPs, MEPs, and EEG, and stable baseline signals were obtained. An arterial line, Foley catheter, and [lumbar drain] were placed.

The patient was positioned supine with the head rotated [30-45] degrees to the [contralateral] side, slightly extended, and the vertex tilted toward the floor. The head was secured in a Mayfield skull clamp with the single pin placed in the [contralateral] frontal region and the double pins placed in the [ipsilateral] mastoid/retroauricular region. All pressure points were padded. [Stereotactic navigation was registered with CTA dataset, and accuracy was confirmed to be within ___ mm.] A time-out was performed.

The [left/right] frontotemporal region was prepped and draped in the standard sterile fashion. Preoperative cefazolin [2g] and dexamethasone [10mg] were administered. [Mannitol ___ g was infused.]

Incision: A curvilinear skin incision was made beginning 1 cm anterior to the tragus at the zygomatic root, curving posterosuperiorly behind the hairline. The scalp flap was reflected anteroinferiorly. An interfascial dissection was performed to protect the frontotemporal branch of the facial nerve. The temporalis muscle was incised along its superior temporal line insertion and reflected anteroinferiorly, exposing the pterion and surrounding calvarium.

Craniotomy: A [keyhole] burr hole was made at the pterion (McCarty point). A [second burr hole] was placed [posteriorly along the superior temporal line]. A craniotomy was performed with the craniotome, and the bone flap was elevated. The sphenoid wing was drilled flush with the anterior skull base floor using a high-speed drill to maximize exposure of the proximal sylvian fissure. Epidural hemostasis was achieved with bipolar cautery and bone wax.

Dural opening: The dura was opened in a curvilinear fashion based on the sphenoid ridge and reflected anteriorly. Dural tacking sutures were placed.

Microsurgical procedure: Under the operating microscope, the sylvian fissure was identified and split using an inside-out technique. The superficial middle cerebral veins were identified and preserved. The arachnoid was opened sharply, progressively exposing the M1 segment of the MCA. The [carotid and chiasmatic cisterns / opticocarotid cistern] were opened to drain CSF and relax the brain.

The M1 segment was followed distally toward the bifurcation. The lenticulostriate arteries were identified arising from the superior surface of M1 and carefully preserved. The M2 superior and inferior trunks were identified and dissected free. The aneurysm neck was then identified at the MCA bifurcation. [The dome was adherent to ___ and was carefully dissected free.]

Proximal control was established on M1. [A temporary clip was placed on M1 for __ minutes to facilitate final dissection of the aneurysm neck.] The aneurysm neck was circumferentially dissected. A [straight/curved/fenestrated] __ mm clip was applied across the aneurysm neck, with the blades oriented parallel to the axis of the M2 branches.

Confirmation: Micro-Doppler confirmed flow in both M2 branches and the M1 segment. ICG videoangiography demonstrated complete obliteration of the aneurysm dome with patent flow through all branch vessels including the lenticulostriate arteries. [Papaverine was applied to the vessels to relieve mild vasospasm.]

Hemostasis: Meticulous hemostasis was achieved with bipolar cautery and Surgicel. The surgical field was copiously irrigated with warm saline and inspected under the microscope.

Closure: The dura was closed in a watertight fashion with 4-0 Nurolon running suture. [A dural sealant (DuraSeal) was applied.] The bone flap was replaced and secured with [titanium plates and screws / cranial fixation system]. The temporalis muscle was reapproximated with 2-0 Vicryl sutures. The galea was closed with 3-0 Vicryl interrupted sutures. The skin was closed with staples. A sterile dressing was applied. [A subgaleal drain was placed prior to closure.]

Postoperative: The patient was awakened from anesthesia, extubated, and found to be following commands with [intact motor function / baseline neurological status]. Neuromonitoring signals remained stable throughout the case. The patient was transferred to the neurosurgical ICU in stable condition.

Postoperative Plan

Chief-Level Case Review

Use these as the senior-level mental model for MCA Aneurysm Clipping:

Common Pimp Questions

Use these to pressure-test preparation for MCA Aneurysm Clipping:

  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: