⚠️ Teaching Case Note: This case has been de-identified and reconstructed for educational purposes. Clinical details reflect real surgical decision-making and outcomes. Patient identity is fully protected.
4.5 cm Skull Base Tumor, Basilar Artery Encased, Six Cranial Nerves at Risk — Resected, Function Preserved, Back at Work in Three Months
She was 48 years old, with two years of right facial numbness and pain, and six months of double vision and unsteady gait. MRI showed a 4.5 cm mass in the right petroclival region — the anatomical crossroads of the skull base, where the basilar artery, brainstem, and six cranial nerves converge in a space the size of a walnut. The tumor had wrapped around the upper basilar artery and superior cerebellar artery, compressed the brainstem, eroded the petrous apex, and extended into the posterior cavernous sinus.
Dr. Liangfu Zhou's team at Huashan Hospital, Fudan University, operated for six hours. Blood loss was 400 mL. The basilar artery was preserved. No new facial palsy. No hemiplegia. The patient was discharged on day twelve, returned to work at three months, and has been disease-free for five years.
The Anatomy: The Petroclival Region Is Neurosurgery's Highest-Risk Territory
The petroclival region sits at the junction of the middle and posterior cranial fossae, bounded medially by the clivus and laterally by the petrous bone. Within this confined space run the basilar artery and its perforating branches, the superior cerebellar artery, the posterior cerebral artery, the brainstem, and cranial nerves III through VIII. A tumor growing here does not displace these structures cleanly — it incorporates them.
Enhanced MRI with MRA and diffusion tensor imaging (DTI) defined the full extent of the problem. The tumor measured 4.5 cm at its maximum diameter, growing in a dumbbell configuration across the middle and posterior fossae. Four features determined the operative strategy.
First, vascular encasement: the tumor base had incorporated the upper basilar artery and the superior cerebellar artery. Both vessels remained patent on DSA — the tumor had narrowed but not occluded them — but the plane between tumor capsule and vessel wall was obliterated over a segment of approximately 2 cm.
Second, brainstem compression: the brainstem was displaced posteriorly and to the left, with visible edema on T2 imaging. Any additional retraction during surgery would risk ischemia to the corticospinal tracts.
Third, cranial nerve involvement: the trigeminal nerve (V) and the facial-vestibulocochlear complex (VII/VIII) were thinned and displaced by the tumor, with no clear arachnoidal plane visible on imaging. Intraoperative identification would depend on electrophysiological mapping rather than visual anatomy.
Fourth, bone erosion: the petrous apex was destroyed, and the tumor had extended into the posterior cavernous sinus — a region where bleeding is difficult to control and where the abducens nerve (VI) runs in a surgically inaccessible position.
DSA confirmed the tumor's blood supply arose primarily from the middle meningeal artery and basilar artery branches. Collateral circulation was assessed. KPS score: 80.
The MDT Decision: Function Over Total Resection
The multidisciplinary team discussion centered on a single principle that Dr. Zhou has articulated throughout his career: the goal of skull base surgery is not the maximum extent of resection — it is the maximum preservation of neurological function consistent with long-term tumor control.
For this tumor, that principle had a specific operative implication. The portion of the tumor encasing the basilar artery and adherent to the brainstem surface could not be removed without unacceptable risk of perforator injury, brainstem ischemia, or vascular rupture. The planned resection was therefore Simpson Grade II — macroscopic total resection with coagulation of the dural attachment — with deliberate residual tumor left at the basilar artery interface. The residual would be addressed with stereotactic radiosurgery (Gamma Knife) postoperatively.
The surgical approach selected was the retrosigmoid craniotomy combined with the Kawase medial petrosectomy — drilling the petrous apex to create a direct corridor to the petroclival region from the lateral skull base, without requiring significant cerebellar retraction. This approach, refined at Huashan Hospital over decades of skull base surgery, provides the widest exposure of the petroclival space while preserving the sigmoid sinus and minimizing the distance between the surgeon's instruments and the tumor's medial surface.
A staged approach — preoperative embolization followed by partial decompression, with second-stage resection — was held as a contingency if intraoperative bleeding proved uncontrollable.
The Operation: Six Hours at the Skull Base
Setup. General anesthesia. Left lateral decubitus position, Mayfield head clamp, head rotated and flexed to bring the right petroclival region to the highest point of the operative field. Neuronavigation registered to the preoperative MRI.
Approach. Retroauricular curved incision. Craniotomy extended to the sigmoid sinus margin. The Kawase petrosectomy was performed — the petrous apex drilled medially to the internal auditory canal, creating a triangular bony window that opened the corridor between the middle and posterior fossae without entering the labyrinth or sacrificing hearing.
Dural opening and CSF release. The dura was opened and suspended. The tentorium cerebelli edge was incised. CSF was released from the cisterns, allowing the cerebellum to fall away from the tumor surface under gravity — eliminating the need for retractor blades and the retraction injury they cause.
Tumor devascularization. The feeding vessels from the petrous surface were coagulated and divided along the petrous ridge before the tumor capsule was entered. Reducing blood supply before debulking is the critical first step — it converts a highly vascular resection into a controlled one.
Intracapsular debulking. CUSA (Cavitron Ultrasonic Surgical Aspirator) was used for intracapsular tumor removal, progressively collapsing the tumor from within. This technique — removing volume before attempting capsule dissection — is the foundation of safe skull base tumor surgery: it creates space, reduces tension on the surrounding neurovascular structures, and allows the capsule to fall away from the brainstem rather than being pulled from it.
Vascular dissection. Under the operating microscope, the tumor capsule was separated from the basilar artery and superior cerebellar artery using microsurgical dissectors. Dr. Zhou's technique at the vessel interface is to work in the plane immediately adjacent to the adventitia — not through the tumor, not away from the vessel, but along the vessel wall itself — preserving the perforating branches that supply the brainstem. At the segment where the plane was obliterated, dissection was stopped. The adherent capsule was left in situ.
Cranial nerve identification and preservation. Intraoperative neurophysiological monitoring (IONM) ran continuously throughout: somatosensory evoked potentials (SEP), motor evoked potentials (MEP), and free-running EMG for cranial nerves V, VII, and VIII. When EMG activity indicated proximity to the facial or trigeminal nerve, the surgical team paused, irrigated with warm saline, and repositioned before continuing. The trochlear nerve (IV) and oculomotor nerve (III) were identified at the tumor's superior pole and preserved under direct vision. The facial-vestibulocochlear complex was identified in the cerebellopontine angle and protected throughout the posterior fossa dissection.
Closure. Meticulous hemostasis. Dural repair with artificial dura. Petrous bone defect reconstructed with titanium mesh to prevent CSF egress through the Kawase corridor.
Operative data: Total time 360 minutes. Estimated blood loss 400 mL. Resection: Simpson Grade II. No intraoperative vascular injury. MEP and SEP stable throughout.
Pathology and Recovery
Final pathology: Transitional meningioma, WHO Grade I. Ki-67 proliferation index below 3% — consistent with slow growth and favorable long-term behavior.
The patient was awake and following commands in the recovery room. All four limbs moved to command — MEP had not declined intraoperatively, and the motor examination confirmed it. Facial numbness was unchanged from preoperative baseline. No new facial palsy. Abducens function showed marginal improvement compared to preoperative examination.
Two complications were managed without long-term consequence. Aseptic meningitis developed on postoperative day three — fever and CSF pleocytosis without bacterial growth, a recognized response to blood products and bone dust in the subarachnoid space after skull base surgery. It resolved with corticosteroids and empirical antibiotics. A small CSF rhinorrhea appeared through the Kawase corridor; lumbar drain placement for five days achieved complete resolution without reoperation.
Discharge on postoperative day twelve.
Follow-Up: Pain Gone, Gait Restored, Five Years Disease-Free
At three months: MRI showed the resection cavity without recurrence, brainstem decompressed and returned to midline. The facial pain that had been present for two years had resolved completely. Gait was stable. The patient had returned to full-time work. The small residual tumor at the basilar artery interface was treated with Gamma Knife stereotactic radiosurgery — a single-session, non-invasive treatment targeting the residual with millimeter precision while sparing the surrounding brainstem.
At one year: no recurrence on MRI. Mild residual facial numbness only — no functional limitation.
At five years: long-term follow-up confirmed no tumor progression at the surgical site or the radiosurgery-treated residual. Quality of life was self-reported as excellent.
Expert Commentary — Dr. Liangfu Zhou
"The petroclival region is where neurosurgery confronts its own limits. The structures that pass through it — the basilar artery, the brainstem, the cranial nerves — are not structures that can be sacrificed for the sake of a complete resection. A surgeon who removes every cell of a petroclival meningioma but leaves the patient hemiplegic or with a facial palsy has not succeeded. They have exchanged one disability for another.
The principle I have followed throughout my career is this: the goal is the patient's functional life, not the surgeon's operative report. For this tumor, that meant stopping at the basilar artery. The adherent capsule at the vessel wall was left deliberately. It was not a failure of technique — it was the correct decision, made in advance, confirmed intraoperatively, and completed with Gamma Knife. The combination of microsurgery and radiosurgery is not a compromise. It is the optimal treatment strategy for this anatomy.
The intraoperative monitoring data in this case directed the surgery in real time. When the EMG signaled proximity to the facial nerve, we stopped. We irrigated. We repositioned. That discipline — the willingness to pause, to reassess, to change the angle of approach rather than persist — is what separates skull base surgery that preserves function from skull base surgery that destroys it.
This patient is working. She has no facial palsy. She has been disease-free for five years. That is the outcome we planned for. It required six hours of surgery, five decades of anatomical study, and the judgment to know when to stop."
About Dr. Liangfu Zhou
Dr. Liangfu Zhou is a distinguished neurosurgeon and former director of the Neurosurgery Department at Huashan Hospital, Fudan University. He is internationally recognized for his expertise in skull base tumors, glioma surgery, and functional neurosurgery. Dr. Zhou has trained generations of neurosurgeons across China and remains a leading figure in Chinese academic neurosurgery, widely regarded as one of the founding authorities of modern Chinese neurosurgical practice.
How CMCS Supported This Patient
China Medical Concierge – Shanghai (CMCS) coordinated the full care pathway: specialist matching and priority access to Dr. Zhou's team at Huashan Hospital, multidisciplinary team coordination across neurosurgery, neuroradiology, and radiation oncology, Mandarin-English interpretation for all consultations — including the detailed informed consent process for a high-risk skull base procedure with explicit discussion of cranial nerve, vascular, and brainstem risks — family communication support throughout the twelve-day admission, and long-term follow-up coordination including serial MRI surveillance scheduling, Gamma Knife treatment planning, and neurological rehabilitation referral.
For international patients and expatriates in Shanghai facing complex skull base tumors — where the combination of surgical approach selection, intraoperative neurophysiological monitoring, and adjuvant radiosurgery planning determines both survival and the preservation of neurological function — CMCS provides end-to-end support from initial imaging review to five-year surveillance and beyond.
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