International expert consensus statement about methods and indications for keyhole microneurosurgery from International Society on Minimally Invasive Neurosurgery

Cerebellar Cavernoma Resection: Case Report with Long-Term Follow-Up

Background: Cerebral cavernous malformations (CCMs), particularly when located in the cerebellum, pose unique clinical challenges due to the risk of hemorrhage and proximity to critical neurovascular structures. Surgical resection is often necessary to prevent further neurological deterioration. This case report describes the management of a symptomatic cerebellar cavernoma, emphasizing the use of microsurgical techniques and long-term follow-up. The objective of this study is to illustrate the surgical approach and outcomes of a patient with a hemorrhagic cerebellar cavernoma. Methods: A 63-year-old female presented with vertigo, and neuroimaging revealed a hemorrhagic cavernous malformation located in the right cerebellar hemisphere. Follow-up was conducted at two months and one year postoperatively, with serial imaging to assess lesion recurrence and neurological recovery. Results: Complete resection of the cavernoma was achieved without postoperative neurological deficits. Imaging at two months and one year post-surgery showed no signs of recurrence or new lesion formation. The patient remained asymptomatic, with no cranial nerve deficits or other long-term complications. Conclusions: This case demonstrates the effectiveness of microsurgical resection in treating symptomatic cerebellar cavernomas. The use of advanced intraoperative tools, such as neuronavigation and IONM, contributed to the successful outcome and prevention of postoperative complications. Long-term follow-up remains crucial to monitor for recurrence or the development of de novo lesions.

Validation of a dynamic 4D microsurgical bypass simulator for training and teaching microvascular anastomosis techniques with blood flow and fluorescence imaging

Objective

Microvascular anastomosis is challenging, and training surgeons to develop and maintain skills is imperative. Current training models either miss the simulation of the surgical workflow, lack 3D key-hole space, need ethical approval, require special preparation, or lack realism. To circumvent these issues, this study describes the use of a mixed reality 3D printed model with integrated blood flow for training cerebral anastomosis and assesses its validity.

Methods

Different-sized 3D-printed artificial micro artery models in a 3D brain space with a keyhole opening were used. The model was connected to a 4D simulator to induce pulsatile blood flow. Neurosurgical microscopes and exoscopes were used for visualization. Nine participants (n = 6 board-certified cerebrovascular neurosurgeons; n = 3 in-training) participated in the study and practiced anastomosis techniques with the simulator. Two senior, experienced vascular neurosurgeons mentored live teaching activity on the simulator. Participants completed a survey to score the face and content validity of the simulation on a 5-point Likert scale. Simulation time and anastomosis score differences between in-training and board-certified participants were compared for construct validity.

Results

Participants scored the simulation difficulty similar to actual surgery, proving face validity. All participants agreed that practice on the provided simulator models would improve bypass techniques (μ = 4.67/5 ± 0.47) and instrument handling (μ = 4.56/5 ± 0.68). Board-certified participants had better anastomosis scores than in-training participants (non-significant difference).

Conclusions

The 4D simulator and the high-fidelity artificial 3D printed model effectively simulated actual bypass surgery in a key-hole fashion with blood flow abilities. Limited resources and preparation time are needed for the training setup. The model provides benefits in learning and maintaining anastomosis skills and allows for easy adaptation to different microanatomical scenarios.

Burr Hole Endoscopic Mastoidectomy: A Morphometric Cadaveric Study

Introduction  Traditional open mastoidectomy is performed through a retro-auricular incision to expose the mastoid cortex. Few have addressed the possibility of performing an endoscopic minimally invasive mastoidectomy. Objective  Our objective was to test the feasibility of performing an endoscopic mastoidectomy through a 1 cm incision and burr hole. Methods  Ten cadaver heads (20 mastoids) were used for this morphometric study. We performed an endoscopic mastoidectomy through a 1 cm burr hole located over the antrum. The goals were to reach predetermined landmarks and maximize the drilling of cancellous mastoid bone. Computed tomography (CT) imaging was acquired at baseline, after endoscopic approach and after traditional open mastoidectomy. The scans were then analyzed with volumetric measurements of each mastoid. Results  Endoscopic mastoidectomy facilitated access to most anatomical landmarks. While open mastoidectomy enabled greater extents of mastoidectomy and tegmen exposure, the endoscopic approach exposed 76% of mastoid and 69.9% of the tegmen achievable by the open approach. Additionally, baseline mastoid volume and tegmen surface area positively correlated with the extent of mastoidectomy and tegmen exposure, respectively. Baseline mastoid volume negatively correlated with the percentage of mastoid drilled and tegmen exposed. Conclusion  We demonstrated the feasibility of an endoscopic mastoidectomy through a standardized postauricular burr hole. This approach reduces the incision size and the need for soft tissue dissection. Burr hole mastoidectomy is facilitated using angled scopes which are not reliant on 0-degree line-of-sight. Although the endoscopic approach afforded slightly less exposure, the location and burr hole size can be adjusted depending on the clinical indications.

Microsurgical Clipping of Multiple Intracranial Aneurysms via the Keyhole Approach

BACKGROUND

Keyhole surgery has been widely used to clip various intracranial aneurysms. Here, the feasibility of microsurgical clipping of multiple intracranial aneurysms via the keyhole approach was further investigated.

METHODS

The clinical data of 80 patients with multiple intracranial aneurysms treated with keyhole surgery were retrospectively analyzed. The patients included 25 males and 55 females, with an average age of 57.5 years. There were 13 patients with unruptured aneurysms, 67 patients with ruptured aneurysms (small aneurysms accounted for 52.2% of ruptured aneurysms), and a total of 198 aneurysms. A 4 cm incision and a bone hole of approximately 2.5 cm were used per craniotomy standards. Forty-eight cases were treated via the supraorbital keyhole approach, 45 cases via the pterional keyhole approach, and 3 cases via the interhemispheric keyhole approach.

RESULTS

A bilateral and unilateral keyhole approach was applied in 18 and 62 cases, respectively. A total of 170 ipsilateral and 7 contralateral aneurysms were clipped. The complete clipping rate was 98.9%. During the follow-up period of 6-12 months after surgery, the Glasgow outcome scale score was 5 points in 74 cases, 4 points in 5 cases, and 3 points in 1 case. The prognosis was associated with the preoperative Hunt-Hess classification but not with the number of operative sides, the operation opportunity, or the number of clipped aneurysms.

CONCLUSION

Early keyhole surgical clipping of multiple intracranial aneurysms is an effective treatment. Among ruptured aneurysms, small aneurysms are common and need attention and timely treatment.

'What's in a name', a systematic review of the pterional craniotomy for aneurysm surgery and its many modifications with a proposal for simplified nomenclature

BACKGROUND

The pterional or frontosphenotemporal craniotomy has stood the test of time and continues to be a commonly used method of managing a variety of neurosurgical pathology. Already described in the beginning of the twentieth century and perfected by Yasargil in the 1970s, it has seen many modifications. These modifications have been a normal evolution for most neurosurgeons, tailoring the craniotomy to the patients' specific anatomy and pathology. Nonetheless, an abundance of variations have appeared in the literature.

METHODS

A search strategy was devised according to the 2020 Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) statement. To identify articles investigating the variations in the pterional approach, the following search terms were applied: (pterional OR minipterional OR supraorbital) AND (approach OR craniotomy OR technique).

RESULTS

In total, 3552 articles were screened with 74 articles being read in full with 47 articles being included for review. Each article was examined according the name of the technique, temporalis dissection technique, craniotomy technique and approach.

CONCLUSION

This systematic review gives an overview of the different techniques and modifications to the pterional craniotomy since it was initially described. We advocate for the use of a more standardised nomenclature that focuses on the target zone to simplify the management approach to supratentorial aneurysms.

The Pterional Keyhole Craniotomy Approach: A Historical Perspective

The pterional craniotomy is a workhorse of cranial surgery that provides access to the anterior and middle fossae. However, newer "keyhole" approaches, such as the micropterional or pterional keyhole craniotomy (PKC) can offer similar exposure for many pathologies while reducing surgical morbidity. The PKC is associated with shorter hospitalizations, reduced operative time, and superior cosmetic outcomes. Furthermore, it represents an ongoing trend toward smaller craniotomy size for elective cranial procedures. In this historical vignette, we trace the history of the PKC from its origins to its current role in the neurosurgeon's armamentarium.

Robotic Arm-Protected Microsurgical Pericallosal and Middle Cerebral Artery Aneurysm Clipping: A Technical Note and Case Series

BACKGROUND

Managing intraoperative aneurysm rupture (IAR) during intracranial aneurysm clipping can be challenging given the excessive hemorrhage and limited field of view under the microscope for visualizing the proximal artery and safe temporary clipping.

OBJECTIVE

To describe the first known use of robotic arm for safeguarding IAR in microsurgical aneurysm clipping.

METHODS

A robotic arm was used to safeguard 3 microsurgical clipping cases (1 pericallosal and 2 middle cerebral artery) performed by a single surgeon. The device was installed onto the side rail of the operating table along with the clip applier attachment. After dissecting the cerebral artery segment proximal to the aneurysm, a temporary aneurysm clip was loaded and established at the appropriate segment before dissecting distally toward the aneurysm.

RESULTS

Setup for the robotic arm and temporary clip was simple, quick, precise, and without any unforeseen accommodations needed in all 3 instances. The temporary clip acted as an emergency gate and could be deployed either manually or remotely through a controller. IAR occurred in case 1, and the robotic-assisted temporary clip deployment achieved immediate hemostasis without complications. This method bypassed the need for significant suctioning, packing, and further exploration for safe temporary clipping. Case 2 and 3 demonstrated the feasibility for middle cerebral artery protection and ease of intraoperative readjustment.

CONCLUSION

This technical note highlights the feasibility and relative ease of using a robotic arm as a safeguard device, and it enables on-demand control of proximal blood flow and may enhance the safety of microsurgical aneurysm procedures.

Supraorbital eyebrow approach: A single-center experience

Background

Keyhole neurosurgery is the notion of safely removing brain and skull base lesions through smaller and more precise openings that lessen collateral damage to the surrounding scalp, brain, blood vessels, and nerves. The traditional frontal and pterional approaches require large craniotomies and this predisposes patients to significant and avoidable morbidity. With the growing expectation for minimally invasive surgery, we present our experience with the supraorbital keyhole craniotomy for surgical lesions in the anterior cranial fossa and parasellar regions.

Methods

We retrospectively analyzed and evaluated all cases of neoplastic, vascular, trauma, and infective pathologies of the anterior fossa and parasellar regions treated using a keyhole approach, the supraorbital eyebrow (SOE) approach from January 2018 to June 2022. Treatment outcomes were evaluated based on pathology.

Results

A total of 50 patients underwent a SOE craniotomy during the study period (28 females and 22 males). Their average age ranged from 12 to 86 years, with a mean age of 47.4 years. All patients had anterior skull base and/or anterior frontal lobe pathologies: (23 tumors, 17 ruptured aneurysms, five traumatic frontal hematomas, three extradural empyema, one cerebral cavernous malformation, and one traumatic frontal skull base fracture with dural tear and CSF leak). Gross total tumor resection was achieved in 87% of cases (13 meningiomas of which six were giant, three gliomas, two craniopharyngiomas, and two cerebral metastases). Clip ligation occlusion rate for our aneurysm cases was 100% and intraoperative rerupture was observed in three cases. Mean ICU stay was 2.2 days for the entire series. The overall 30-day mortality rate for our series was 16% (eight deaths). This was highest in the ruptured aneurysm subgroup, with all 5 mortality cases in the aneurysmal subgroup presenting as World Federation of Neurological Surgeons (WFNS) grades ≥ III. 4 of the deaths were in WFNS IV and V patients. The most frequent perioperative complication was transient periorbital swelling which resolved within 7 days. It was observed in 18 of the 50 patients. The next common complications in descending frequency were eyebrow alopecia (three cases), supraorbital hypoesthesia (two cases), CSF leak (two cases), and surgical site infection (one case). There was one approach-related intraoperative complication secondary to carotid injury in a giant meningioma redo case. Conversion to a larger craniotomy was never necessary. Clinical outcome for our cases was evaluated according to the Modified Rankin Scale (mRS) at 3-month postsurgery. A good clinical outcome (mRS ≤ 2) was achieved for 78% of our patients.

Conclusion

The SOE approach craniotomy is an effective minimally invasive approach for various pathologies of the anterior cranial base and parasellar regions. With experience, giant tumors and complex vascular pathology can be addressed with this keyhole approach.

Factors affecting global neurocognitive status and frontal executive functions in the early stage after surgical clipping of unruptured anterior circulation aneurysms with respect to keyhole clipping and conventional clipping

PURPOSE

This study investigated the most significant factor for the preservation of the global neurocognitive status and frontal executive functions in the surgical clipping of unruptured anterior circulation aneurysms, specifically in keyhole and conventional clipping procedures.

METHODS

The prospective study that was performed to examine the effects of aneurysm surgery on the patient's global neurocognitive status and frontal executive functions started on April 2016. After exclusion posterior circulation aneurysms, anterior communicating aneurysms treated by interhemispheric approach, giant aneurysms, and paraclinoid aneurysms, 23 patients who were enrolled before May 2017 were treated by conventional clipping, and 18 patients who were enrolled after June 2017 were treated by keyhole clipping. Two patients were excluded from each group due to missing data. Finally, 21 and 16 patients in each group were analyzed, respectively. Three-tesla magnetic resonance imaging was performed before and after surgery to detect the presence of perioperative cerebral infarctions and brain edema. The Mini-Mental State Examination, Frontal Assessment Battery, and Self-Rating Depression Scale scores were obtained before and 1 month after surgery.

RESULTS

Logistic regression analyses indicated that anterior communicating and internal carotid artery aneurysms were the most significant factors for poor outcomes and that keyhole clipping for these two types of aneurysm was the most significant factor for the preservation of patient global neurocognitive status. Keyhole clipping was also the most significant factor for the preservation of frontal executive functions in patients.

CONCLUSIONS

Keyhole clipping may be more favorable than conventional clipping for the preservation of the global neurocognitive status and frontal executive functions. Moreover, it may be the most effective factor for preservation of global neurocognitive status when it is indicated for anterior communicating or internal carotid artery aneurysms.

Mini-craniotomy for intra-axial brain tumors: a comparison with conventional craniotomy in 306 patients harboring non-dural based lesions

The use of a mini-craniotomy approach involving linear skin incision and a bone flap of about 3 cm has been reported for several neurosurgical diseases, such as aneurysms or cranial base tumors. More superficial lesions, including intra-axial tumors, may occasionally raise concerns due to insufficient control of the tumor boundaries. The convenience of a minimally invasive approach to intrinsic brain tumors was evaluated by comparing 161 patients who underwent mini-craniotomy (MC) for intra-axial brain tumors with a group of 145 patients operated on by the same surgical team through a conventional craniotomy (CC). Groups were propensity-matched for age, preoperative condition, size and location of the tumor, and pathological diagnosis. Results were analyzed focusing on operative time, the extent of resection, clinical outcome, hospitalization time, and time to start adjuvant therapy. Mini-craniotomy was equally effective in terms of extent of resection (GTR: 70.9% in the MC group vs 70.5% in the CC group) but had shorter operative time (average: 165 min in the MC group vs 205 min in the CC group p < 0.001) and lower rate of postoperative complications both superficial (1.03% vs 6.5% in the CC group p = 0.009) and deep (4% in the MC group vs 5.5% in the CC group p = 0,47). No relationship was found between the size or location of the tumor and resection rate. The MC group had reduced hospitalization time (average: 5.8 days vs 7.6 in CC group p < 0.001) and faster access to adjuvant therapies. 92.5% of the MC patients, which were scheduled for treatment, started radiotherapy within 8 weeks after surgery as opposed to 84.1% in the CC group (p = 0.04). These findings support the increasing use of mini-craniotomy for intra-axial brain tumors.

Supraorbital and mini-pterional keyhole craniotomies for brain tumors: a clinical and anatomical comparison of indications and outcomes in 204 cases

OBJECTIVE

The authors' objective was to compare the indications, outcomes, and anatomical limits of supraorbital (SO) and mini-pterional (MP) craniotomies in patients with intra- and extraaxial brain tumors, and to assess approach selection, utility of endoscopy, and surgical field overlap.

METHODS

A retrospective analysis was conducted of all brain tumor patients who underwent an SO or MP approach. The analyzed characteristics included pathology, endoscopy use, extent of resection, length of stay (LOS), and complications. On the basis of preoperative MRI data, tumor heatmaps were constructed to compare surgical access provided by both routes, including coronal projection heatmaps for parasellar tumors.

RESULTS

From 2007 to 2020, 158 patients underwent 173 (84.8%) SO craniotomies and 30 patients underwent 31 (15.2%) MP craniotomies; 71 (34.8%) procedures were reoperations. Of these 204 operations, 110 (63.6%) SO and 21 (67.7%) MP approaches were for extraaxial tumors (meningiomas in 65% and 76.2%, respectively). Gliomas and metastases together represented 84.1% and 70% of intraaxial tumors accessed with SO and MP approaches, respectively. Overall, 56.1% of tumors accessed with the SO approach and 41.9% of those accessed with the MP approach were in the parasellar region. Axial projection heatmaps showed that SO access extended along the entire ipsilateral and medial contralateral anterior cranial fossa, parasellar region, ipsilateral sylvian fissure, medial middle cranial fossa, and anterior midbrain, whereas MP access was limited to the ipsilateral middle cranial fossa, sylvian fissure, lateral parasellar region, and posterior aspect of anterior cranial fossa. Coronal projection heatmaps showed that parasellar access extended further superiorly with the SO approach compared with that of the MP approach. Endoscopy was utilized in 98 (56.6%) SO craniotomies and 7 (22.6%) MP craniotomies, with further tumor resection in 48 (49%) and 5 (71.4%) cases, respectively. Endoscope-assisted tumor removal was clustered in areas that were generally at farther distances from the craniotomy or in angled locations such as the cribriform plate region where microscopic visualization is limited. Gross-total or near-total resection was achieved in 120/173 (69%) SO approaches and 21/31 (68%) MP approaches. Major complications occurred in 11 (6.4%) SO approaches and 1 (3.2%) MP approach (p = 0.49). The median LOS decreased to 2 days in the last 2 years of the study.

CONCLUSIONS

This clinical experience suggests the SO and MP craniotomies are versatile, safe, and complementary approaches for tumors located in the anterior and middle cranial fossae and perisylvian and parasellar regions. The SO route, used in 85% of cases, achieved greater overall reach than the MP route. Both approaches may benefit from expanded visualization with endoscopy.

Eyebrow incision with a crescent-shaped orbital rim craniotomy for microscopic and endoscopic transorbital approach to the anterior and middle cranial fossa: A cadaveric study and case presentation

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The transorbital approach combining eyebrow incision and crescent-shaped craniotomy increases the surgical freedom to access the anterior and middle skull-base.

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The technic allows the use of both endoscope and microscope.

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The concept is at the crossroad between the supraorbital keyhole and endoscopic trans-orbital approach.

Streamlining brain tumor surgery care during the COVID-19 pandemic: A case-control study

BACKGROUND

The COVID-19 pandemic forced a reconsideration of surgical patient management in the setting of scarce resources and risk of viral transmission. Herein we assess the impact of implementing a protocol of more rigorous patient education, recovery room assessment for non-ICU admission, earlier mobilization and post-discharge communication for patients undergoing brain tumor surgery.

METHODS

A case-control retrospective review was undertaken at a community hospital with a dedicated neurosurgery and otolaryngology team using minimally invasive surgical techniques, total intravenous anesthesia (TIVA) and early post-operative imaging protocols. All patients undergoing craniotomy or endoscopic endonasal removal of a brain, skull base or pituitary tumor were included during two non-overlapping periods: March 2019-January 2020 (pre-pandemic epoch) versus March 2020-January 2021 (pandemic epoch with streamlined care protocol implemented). Data collection included demographics, preoperative American Society of Anesthesiologists (ASA) status, tumor pathology, and tumor resection and remission rates. Primary outcomes were ICU utilization and hospital length of stay (LOS). Secondary outcomes were complications, readmissions and reoperations.

FINDINGS

Of 295 patients, 163 patients were treated pre-pandemic (58% women, mean age 53.2±16 years) and 132 were treated during the pandemic (52% women, mean age 52.3±17 years). From pre-pandemic to pandemic, ICU utilization decreased from 92(54%) to 43(29%) of operations (p<0.001) and hospital LOS≤1 day increased from 21(12.2%) to 60(41.4%), p<0.001, respectively. For craniotomy cohort, median LOS was 2 days for both epochs; median ICU LOS decreased from 1 to 0 days (p<0.001), ICU use decreased from 73(80%) to 29(33%),(p<0.001). For endonasal cohort, median LOS decreased from 2 to 1 days; median ICU LOS was 0 days for both epochs; (p<0.001). There were no differences pre-pandemic versus pandemic in ASA scores, resection/remission rates, readmissions or reoperations.

CONCLUSION

This experience suggests the COVID-19 pandemic provided an opportunity for implementing a brain tumor care protocol to facilitate safely decreasing ICU utilization and accelerating discharge home without an increase in complications, readmission or reoperations. More rigorous patient education, recovery room assessment for non-ICU admission, earlier mobilization and post-discharge communication, layered upon a foundation of minimally invasive surgery, TIVA anesthesia and early post-operative imaging are possible contributors to these favorable trends.