Subtemporal Keyhole Research Articles

The endaural subtemporal keyhole: a novel minimally invasive approach to the middle cranial fossa.

The goal of this study was to evaluate the feasibility of a minimally invasive approach to the middle cranial fossa using a novel endaural keyhole. The charts of all patients who underwent this novel minimally invasive approach to the middle cranial fossa were retrospectively reviewed. In addition, cadaveric dissection was performed to demonstrate the feasibility of the endaural keyhole to the middle cranial fossa. Six patients (5 female and 1 male; age range 47-77 years) who underwent craniotomy for CSF leak (n = 3), intracerebral hematoma evacuation (n = 2), and tumor resection (n = 1) via the endaural subtemporal approach were identified. There were no approach-related complications noted. Representative imaging from cadaveric dissection is provided with a stepwise discussion of the procedure. The endaural subtemporal keyhole craniotomy provides a novel approach to middle fossa skull base pathology, as well as a minimally invasive approach to intra-axial pathology of the temporal lobe and basal ganglia. Further research is needed to establish the limitations and potential complications of this novel approach.

Purely endoscopic subtemporal keyhole anterior transpetrosal approach to access the petrous apex region: surgical techniques and early results.

The anterior transpetrosal approach using a microscope to provide wider access to the petrous apex region has been described for radical resection of lesions of the middle and posterior skull base. The microscopic anterior transpetrosal approach (mATPA) requires a wide craniotomy and meticulous epidural procedures to minimize temporal lobe retraction. Recently, the clinical application of transcranial endoscopic keyhole approaches for minimally invasive surgery has been steadily expanding. In this study, the details of the purely endoscopic subtemporal keyhole ATPA (eATPA) for petrous apex lesions are described and its initial results are reported. Between May 2022 and May 2023, the authors performed eATPA in 10 patients with petrous apex lesions, of which 6 were meningiomas, 3 were trigeminal schwannomas, and 1 was epidermoid cyst. The surgical procedure of the purely eATPA is as follows. After a small temporal craniotomy, the endoscopic procedure is started. The anterior rim of the petrous bone and Meckel's cave are exposed via an intradural subtemporal approach. The lesion is removed with additional drilling of Kawase's triangle, cutting the superior petrosal sinus, opening Meckel's cave, and cutting the tentorium. The authors also compared the outcomes of mATPA versus eATPA for consecutive cases of petrous apex lesions. Gross-total resection was achieved in 8 of the 10 patients. The average operative time was 4 hours 13 minutes. There were 3 cases of transient abducens nerve palsy and 1 case of trochlear nerve palsy in the postoperative period. No new-onset motor deficits or CSF leakage was noted in any of these patients. Only 1 patient exhibited postoperative asymptomatic temporal lobe edema. The Karnofsky Performance Scale (KPS) scores remained unchanged or improved for all patients postoperatively. Compared with mATPA, eATPA achieved a similar extent of resection and comparable postoperative KPS scores with a significantly shorter mean operative time, much smaller temporal craniotomy, and thus less mean blood loss during surgery with lower rates of new-onset temporal lobe edema in the postoperative period. An eATPA allows a direct route to access Meckel's cave and posterior cranial fossa lesions similar to conventional mATPA, with shortening the operative time and reducing the risk of postoperative temporal lobe edema. This eATPA is considered one of the new surgical techniques that can be expected to develop in the future.

Minimally Invasive Approaches to the Lateral Cavernous Sinus and Meckel's Cave: Comparison of Transorbital and Subtemporal Endoscopic Techniques

Transorbital and subtemporal keyhole approaches have recently been proposed to approach lesions in the lateral wall of the cavernous sinus (CS) and Meckel's cave (MC). Our goal was to compare these approaches and suggest indications for each of them. Five cadaver heads (10 sides, 40 procedures) were used. The lateral transorbital approaches were carried out without and with the removal of the lateral orbital rim, herein referred to as the lateral transorbital approach (LTOA) and the lateral orbital wall approach (LOWA). The subtemporal approaches were performed without and with the removal of the zygomatic arch, referred to as the subtemporal approach (STA) and the subtemporozygomatic approach (STZA). Five targets were chosen and 2 triangles were created representing thelateral wall of the CS and MC. Stereotactic measurements were quantified to calculate angles of attack, surgical freedom, and temporal lobe retraction for each approach. LTOA presented the smaller horizontal angles of attack. LOWA increased the angles to the same level of STA and STZA. STA and STZA presented larger vertical angles of attack. The surgical freedom presented gradual increase from LTOA to LOWA, STA, and STZA. STA and STZA needed greater temporal lobe retraction for most targets. LTOA is a good option to biopsy a lesion in the lateral wall of the CS and LOWA increased the surgical corridor to work with microsurgical techniques. STA and STZA could be better options when wide exposure is necessary, but temporal lobe retraction should be taken into consideration.

Pure Endoscopic Surgery via Subtemporal Extradural Keyhole Approach for Middle Cranial Fossa Tumors

Extradural subtemporal keyhole approach could provide adequate removal for some specific middle skull base tumors. The combination of endoscopy and keyhole technique might further help to minimize the complications and provide optimal surgical visualization. Here, a series of attempts with endoscopy by mini-invasive subtemporal extradural approach for 5 middle skull base tumors were successfully achieved. From November 2015 to November 2018, resections of 5 cases of middle cranial fossa tumors were performed with pure endoscopy via subtemporal extradural keyhole approach. Patient medical records, imaging data, surgical procedures, pathology results, and follow-up outcomes were collected and analyzed. Adequate extradural subtemporal space was successfully established for endoscopy, and tumor resection was performed. Postoperative pathology confirmed cholesteatoma, cholesterol granuloma, schwannoma, granuloma, and osteoblastoma, respectively. Two patients with osteoblastoma and granuloma received subtotal resection, and the other 3 achieved total resection. One patient suffered from brain edema and was relieved after systematic mannitol treatment. No other complications were observed, and no progression was found during follow-up. This exploratory series demonstrated the safety and effectiveness of pure endoscopic surgery via subtemporal extradural route for satisfactory middle cranial base tumor resection.

Intradural Subtemporal Keyhole Approach with Neuronavigational Assistance to the Petroclival and Ventrolateral Brainstem Regions: Quantitative Analysis of Anatomic Exposure and Surgical Freedom

The purpose of this study was to evaluate the advantages of endoscopy and navigational assistance in the intradural subtemporal keyhole approach and the intradural Kawase approach by studying anatomic exposure and surgical freedom in the posterior cranial fossa. Twenty endoscopic intradural subtemporal keyhole approaches (EISKA) were performed on 10 cadaveric heads. An intradural Kawase approach and a navigation-assisted intradural Kawase approach were then carried out on a random side of each specimen. Related anatomic structures were observed through a 0° endoscope and a microscope. Anatomic exposure and surgical freedom were measured by transparent graph paper and analyzed. Compared with the microsurgical technique, the superior, inferior, and medial limits of the endoscopic anatomic exposure increased by 2.9, 15.65, and 10.2 mm, whereas the surgical freedom increased by 2.9, 7.55, and 6 mm (P < 0.05) in the intradural subtemporal keyhole approach. In the intradural Kawase approach and the navigation-assisted intradural Kawase approach, the endoscopic anatomic exposure and surgical freedom also increased (P < 0.05). Using a frameless navigational device, the inferior limit of the anatomic exposure increased 3.8 mm by endoscopy and 3.5 mm by microscopy, whereas the surgical freedom increased by 2.7 and 2.2 mm, respectively (P < 0.05). The EISKA provides greater anatomic exposure and surgical freedom primarily in the superior, inferior, and medial directions of the brainstem region. Maximum anatomic exposure and surgical freedom of the posterior cranial fossa was obtained by navigational assistance with fewer complications.

Endoscopic intradural subtemporal keyhole approach with neuronavigational assistance: An anatomic study

Objective To evaluate the feasibility of a purely endoscopic intradural approach to the suprasellar, petroclival and ventrolateral brainstem regions through a subtemporal keyhole and to assess the value of neuronavigational assistance in the Kawase approach. Methods Twenty operations through endoscopic intradural subtemporal keyhole approach were performed on 10 cadaveric heads. An intradural Kawase approach and a navigation-assisted intradural Kawase approach were then carried out on a random side of each specimen. Related anatomic structures were observed through endoscopes. Two types of the milled Kawase rhombus ranges and the thicknesses of residual bones were compared. Results Through the keyhole endoscopic technique, anatomic structures in the suprasellar, petroclival and ventrolateral brainstem regions were clearly visualized via an intradural subtemporal route. Most structures in the suprasellar region could be observed in the oculomotor nerve-posterior communicating artery space. Using a frameless navigational device, the mean area of milled Kawase rhombus was larger than that in the intradural Kawase approach (276.8±14.6 mm2vs. 244.8±12.6 mm2,P<0.05), and the thicknesses of residual bones including the superior wall of internal acoustic meatus (1.0±0.2 mm vs. 2.5±0.4 mm), the medial superior wall of cochlear (1.0±0.2 mm vs. 3.0±0.4 mm) and the superior wall of petrous segment of internal carotid artery (1.2±0.2 mm vs. 3.4±0.4 mm) were all thinner than those in the intradural Kawase approach (all P<0.05). Conclusions The endoscopic intradural subtemporal keyhole approach could facilitate excellent observation of the suprasellar, petroclival and ventrolateral brainstem regions with less invasiveness. More anatomic exposure and surgical freedom could be achieved via neuronavigational assistance. Key words: Neuroanatomy; Neuronavigation; Neuroendoscopy; Subtemporal approach; Keyhole; Kawase approach

Endoscope-Assisted Microsurgical Subtemporal Keyhole Approach to the Posterolateral Suprasellar Region and Basal Cisterns.

Refinements in optics and instrumentation have enabled surgeons to approach deep-seated intracranial diseases with reduced exposure and brain retraction. The anterior subtemporal keyhole approach is a minimally invasive route to the posterolateral aspect of the suprasellar area and petroclival region. In this cadaveric study, we show the benefits of endoscope-assisted microsurgical techniques in the anterior subtemporal keyhole approach. The anterior subtemporal keyhole approach was performed bilaterally on 5 formalin-fixed human specimens using standard microneurosurgical methods. Dissections compared the exposure afforded by the microsurgical route with the endoscope-assisted technique, using 0° and30° angled rod-lenses. Anatomic relationships among the surgical target and the surrounding neurovascular structures were described. Endoscope-assisted maneuvers enhanced the operative view afforded by the microscope and helped to minimize parenchymal retraction and neurovascular injury. Endoscope-assisted microsurgery provides a panoramic picture of the surgical target and its surroundings. It enables the operator to see into hidden corners beyond the microsurgical view. The endoscope provides enhanced visualization of the neurovascular structures located in the posterolateral suprasellar region, basal cisterns, upper clivus and midclivus, and interpeduncular region. Endoscope-assisted microsurgery provides a means to approach selected lesions located in the posterolateral suprasellar region, perimesencephalic cisterns, and upper clivus and midclivus. The operative view can be maximized by introducing the 0° and 30° angled endoscopes. Minimally invasive techniques help to optimize surgical exposure and lessen parenchymal retraction, thus improving control of the surrounding neurovascular structures.

Endoscopic Intradural Subtemporal Keyhole Approach with Neuronavigational Assistance to the Suprasellar, Petroclival, and Ventrolateral Brainstem Regions: An Anatomic Study

The purposes of this study were to evaluate the feasibility of a purely endoscopic intradural approach to the suprasellar, petroclival, and ventrolateral brainstem regions through a subtemporal keyhole and to assess the value of neuronavigational assistance in the Kawase approach. Twenty endoscopic intradural subtemporal keyhole approaches were performed on 10 cadaveric heads. An intradural Kawase approach and a navigation-assisted intradural Kawase approach were then carried out on a random side of each specimen. Related anatomic structures were observed through 4-mm 0° and 30° endoscopes; data were measured by a frameless navigational device. In addition, 2 types of the milled Kawase rhombus ranges and the thicknesses of the residual bones were compared. This keyhole endoscopic technique clearly visualized the anatomic structures in the suprasellar, petroclival, and ventrolateral brainstem regions via an intradural subtemporal route. Most of the structures in the suprasellar region were observed by the oculomotor nerve-posterior communicating artery space. Using a frameless navigational device, the mean area of the milled Kawase rhombus increased by 32.04 mm2 (P < 0.05), and the thicknesses of the residual bones including the superior wall of the internal acoustic meatus, the medial superior wall of the cochlea, and the superior wall of the petrous segment of the internal carotid artery reduced by 1.55, 2.03, and 2.19 mm on average, respectively (P < 0.05). The endoscopic intradural subtemporal keyhole approach could facilitate excellent observation of the suprasellar, petroclival, and ventrolateral brainstem regions with less invasiveness. More anatomic exposure and surgical freedom could be achieved via neuronavigational assistance with fewer complications.

Subtemporal keyhole approach to Meckel’s cave epidermoid cyst: Case report and review of literature

We report the first case of subtemporal keyhole surgery approach with neuronavigation and endoscopy, for total resection of an uncommon case of epidermoid cyst of the Meckel’s cave in a 43‑year‑old woman who presented with paroxysmal headache and diplopia. Magnetic resonance imagines revealed the tumor location on the right area of the cavernous sinus. Postoperative examinations showed complete recovery of symptoms.

Endoscopic Intradural Subtemporal Keyhole Kawase Approach to the Petroclival and Ventrolateral Brainstem Regions.

To study the endoscope anatomy of the petroclival and ventrolateral brainstem regions via the intradural subtemporal keyhole Kawase approach and discuss the feasibility and indications of this approach to the regions. Craniotomy procedures performed via the intradural subtemporal keyhole Kawase approach were simulated on 16 sides of 8 adult cadaveric heads fixed by formalin, and the related anatomical structures were observed through the 0-degree endoscope or alternatively 30-degree one. Measurements of the shortest distances from the highest point of arcuate eminence to the 4 anatomic marks and the lengths of the Kawase rhombus were recorded, and the 2 kinds of milled ranges of petrous apex were compared. Most of the related anatomical structures could be clearly observed under the endoscope. The shortest distances from the highest point of arcuate eminence to the foramen spinosum, the greater superficial petrosal nerve hiatus, the intersection of the greater superficial petrosal nerve and mandibular nerve, and the outside edge of the trigeminal impression are 22.90 ± 2.34, 14.05 ± 2.09, 24.94 ± 1.98, 23.49 ± 2.38 mm. The area of routine milled Kawase rhombus is 3.04 ± 0.47 cm, which would increase 0.66 cm on average after the maximum drilling of the petrous apex. The intradural subtemporal keyhole Kawase approach can provide an ideal exposure to the petroclival and ventrolateral brainstem regions via the endoscope with less damaging of the normal structures. It can be used to treat the lesions located in those areas through the natural gap combined with the drilling of petrous apex bone.

Microsurgical Treatment of Posterior Cerebral Circulation Aneurysms Via Keyhole Approaches

To explore the techniques of microsurgical treatment for posterior cerebral circulation aneurysms via keyhole approaches and assess its feasibility. A total of 27 patients with 28 posterior cerebral circulation aneurysms were treated surgically by keyhole approaches; 24 patients presented with subarachnoid hemorrhage and 3 with headache. Of these 27 patients, 15 patients were treated via the supraorbital keyhole approach, 6 via the retrosigmoid keyhole approach, 3 via the subtemporal keyhole approach, 2 via median suboccipital approach, and 1 via the pterional keyhole approach. Of the 28 posterior cerebral circulation aneurysms, 24 aneurysms were clipped and 4 trapped; 23 aneurysms clipped completely, and 1 had residual aneurysm. Glasgow Outcome Scores at discharge revealed 25 patients had a good recovery; 1 patient was slightly disabled, and 1 patient was severely disabled. Of 15 patients treated via the supraorbital keyhole approach, to make a wider operative space, drilling of anterior clinoid process (2 patients) and posterior clinoid process (3 patients) was performed; posterior communicating artery was cut off (1 patient). For 3 patients with multiple aneurysms, complete occlusion was achieved via the same approach at one-stage. Individualized keyhole approaches for posterior cerebral circulation artery aneurysms are safe and effective. The anterior clinoid process or posterior clinoid process could be drilled to offer a wide operative space for clipping. The use of multiple working windows is very helpful for controlling the parent artery and clipping the aneurysm.

A Percutaneous Transtubular Middle Fossa Approach for Intracanalicular Tumors

In cases of small intracanalicular tumors (≤ 1.5 cm), the middle fossa approach (MFA) provides the ability for adequate tumor removal with preservation of existing auditory function. Application of a minimally invasive tubular retractor in this approach may help mitigate the risk of postoperative seizures, aphasia, and venous complications by minimizing intraoperative retraction of the temporal lobe. We propose a minimally invasive microscopic and/or endoscopic percutaneous transtubular MFA for the management of intracanalicular tumors. Subtemporal keyhole craniectomies were performed on 5 preserved cadaveric heads (10 sides), with 6 sides previously injected with a synthetic tumor model. A ViewSite Brain Access System tubular retractor (Vycor Medical, Inc., Boca Raton, Florida, USA) was used to provide minimal temporal retraction and protection of the surrounding anatomy. An extradural dissection of the internal auditory canal was performed under microscopic and endoscopic visualization with a minimally invasive surgical drill and tube shaft instruments, the intracanalicular tumors were removed, and degree of resection was assessed. All 10 approaches were completed successfully through the tubular retractor with minimal retraction of the temporal lobe. Excellent visualization of the structures within the internal auditory canal was achieved with both the microscope and 3-dimensional endoscope. On the 6 synthetic intracanalicular tumors resected, 5 gross total (Grade I) and 1 near total (Grade II) resections were achieved. A percutaneous transtubular MFA is a feasible minimally invasive option for resection of small intracanalicular tumors with potential preservation of auditory function, reduced temporal retraction, and enhanced protection of surrounding structures.

Microsurgical fenestration and cystoperitoneal shunt through preauricular subtemporal keyhole craniotomy for the treatment of symptomatic middle fossa arachnoid cysts in children.

The optimal surgical treatment for symptomatic middle fossa arachnoid cyst is still controversial. The most leading therapeutic options include cyst shunting and fenestration (endoscopic, microsurgical). We present our experience on surgical treatments of arachnoid cysts. A retrospective data review of 16 children who underwent keyhole craniotomy for microsurgical fenestration and shunting of middle fossa arachnoid cysts between 1999 and 2012 was performed after institutional review board approval. The average patient age was 6.1 years. The average follow-up period was 36.5 months. There were ten male and six female patients in the series. Indications for surgery included intractable headaches (50%), increasing in cyst size (18.75%), and seizures (31.25%). All patient records were reviewed for their clinical presentation, classification, cyst resolution, symptom resolution, and cyst outcomes. After surgery, all patients underwent assessments of clinical and radiological improvement. Postoperative complications were observed in two cases: progressively resolving monoparesia in one case and resolving epileptic seizure with monotherapy in the other. All patients had a satisfactory clinical outcome, and in 87.5%, there was either a decrease in the size or a complete disappearance of the MFAC. Nevertheless, three (18.75%) of all patients needed shunt revision because of shunt dysfunction. Complication related to surgical technique was cerebrospinal fluid leak which spontaneously resolved in one patient. Microsurgical fenestration with keyhole craniotomy to provide passage between cysts to basal cisterns together with cystoperitoneal shunting during the same operation is still an effective and safe method in cases with symptomatic middle fossa arachnoid cysts in children.

Anterior Clinoidectomy to Anterior Petrosectomy through Modified Subtemporal Pterional Keyhole Approach

Anterior Clinoidectomy to Anterior Petrosectomy through Modified Subtemporal Pterional Keyhole Approach

3D Endoscopic Transtubular Anterior Petrosectomy for Petroclival Meningiomas: Assessment of Resection in Varying Tumor Volumes Utilizing a Synthetic Tumor Model

Background: Surgical excision of petroclival meningiomas remains a challenge for neurosurgeons. The complex anatomy of the petroclival region and the location of the target lesion are the main determinates when selecting an optimal surgical approach. Extradural anterior petrosectomies are commonly used in the resection of petroclival meningiomas, though the application of temporal retraction carries the risk of the venous complications. Endoscopic anterior clinoidectomies have recently been proposed to access lesions of this region. We investigate a less invasive 3D endoscopic anterior transpetrosal approach through a subtemporal keyhole craniotomy using a minimally invasive tubular retractor system for the management of petroclival meningiomas.

Endoscopic Reconstruction of the Middle Cranial Fossa Through a Subtemporal Keyhole Using a Pedicled Deep Temporal Fascial Flap

Reconstruction of the skull base is essential to prevent postoperative leakage of cerebrospinal fluid (CSF). However, a reliable method of reconstructing the middle cranial fossa via a subtemporal keyhole is not available. To determine whether less invasive reconstruction of the middle cranial fossa under endoscopic guidance with a pedicled deep temporal fascia approach via a subtemporal keyhole is feasible and useful. The middle cranial fossa in 4 fresh cadaver heads was reconstructed with a 4-mm 0° rigid endoscope. A subtemporal skin incision (subtemporal incision) was followed by 2 small skin incisions (temporal line incisions) made on the superior temporal line. The endoscope was inserted through the temporal line incisions, and then the deep temporal fascia was separated from the superficial temporal fascia and temporal muscle under endoscopic view. A pedicled flap was harvested from the subtemporal incision and applied to the middle cranial fossa after subtemporal keyhole craniotomy. The pedicled deep temporal fascial flap was flexible, long, and large enough to overlay skull base defects. This purely endoscopic technique using a pedicled deep temporal fascial flap provided reliable reconstruction of the middle cranial fossa through a subtemporal keyhole. This technique would also be applicable in preventing CSF leakage or treating traumatic, acquired nontraumatic, or congenital encephalocele in the middle cranial fossa.

The posterior subtemporal keyhole approach combined with the transchoroidal approach to the ambient cistern: microsurgical anatomy and image-guided quantitative analysis

The aim of this study is to describe microsurgical anatomy and to quantitatively analyze exposure using the posterior subtemporal keyhole (PSK) approach combined with the transchoroidal keyhole (TCK) approach to the ambient cistern. We determined the proper location of craniotomy of such combined keyhole approach on 16 sides of cadaver heads. The PSK approach and the TCK approach were performed in the same minicraniotomy to observe microanatomic features and to quantitatively measure exposure limits of the ambient cistern and related structures using image-guided system. Some superficial and bone landmarks could be used to find the proper location of such combined minicraniotomy. In the PSK approach, the exposure distances of the trigeminal nerve and the anterior portion of the P2 segment (P2a) were 10.02 ± 0.76mm and 16.32 ± 2.02mm, respectively. The superior, inferior, anterior, and posterior exposure limit of brainstem from the intersection point of the lateral mesencephalic sulcus and pontomesencephalic sulcus was 7.5 ± 0.19mm, 11.04 ± 0.27mm, 15.72 ± 0.52mm, and 10.16 ± 0.38mm, respectively. In the TCK approach, the vertical distances between the taenia fimbriae and the lateral geniculate body without and with mild caudal retraction of the hippocampus were 5.28 ± 0.46mm and 11.18 ± 0.57mm, respectively. The linear exposure distances of the posterior portion of the P2 segment (P2p) or P3 segment were 12.14 ± 1.88mm. Except of one case, the P2p could be exposed using the TCK approach. The midpoint of the medial edge of the parahippocampal gyrus on the coronal magnetic resonance images provides landmark to choose the appropriate approach. The PSK combined with the TCK approach can simultaneously expose the lower and upper ambient cistern in a proper minicraniotomy.

Combined endoscope-assisted translabyrinthine subtemporal keyhole approach for vestibular Schwannoma and auditory midbrain implantation: Cadaveric study

Conclusions: The combined endoscope-assisted translabyrinthine subtemporal keyhole approach can expose the internal auditory canal, cerebellopontine, and inferior colliculus satisfactorily in the same surgical setting. As a minimally invasive approach, this can be considered an effective method for removal of vestibular schwannoma and auditory midbrain implantation in the same surgical setting, while avoiding retraction of the cerebellum and serious adverse events and complications. Objectives: Patients with neurofibromatosis type II are the initial candidates for auditory midbrain implantation; the appropriate surgical approach should allow for tumor removal and electrode implantation in the same surgical setting. Here, we demonstrate the possibility of the combined endoscope-assisted translabyrinthine subtemporal keyhole approach to achieve this aim. Methods: Five formalin-fixed cadaver heads were used to simulate surgical procedures in 10 sides, by means of microscopy and endoscopy. The relationship between concerned structures was identified. Results: With the help of an endoscope, we exposed the internal auditory canal and cerebellopontine through a translabyrinthine approach and the inferior colliculus through a subtemporal keyhole approach. This double approach can be combined to expose the internal auditory canal and cerebellopontine and inferior colliculus satisfactorily in the same surgical setting. This combined approach can avoid retraction of the cerebellum and reduce serious adverse events and complications.

Opening cranial cisterns in anterior subtemporal keyhole approach to superior petroclival region:anatomic study and comparative analysis

Objective To quantitatively compare the exposure areas and angles in anterior subtemporal keyhole approach to superior petroclival region before and after cranial cisterns opening. Methods The study was carried out on 20 sides of cadaver heads. With application of a navigation system, the exposure area in superior clivus, the ventrolateral area in brain stem around BA, the linear exposure of the posterior petroclinoid fold and BA trunk, and the approach angles to BA tip were evaluated. Results The exposure area in superior clivus （ 136. 7 ± 19. 8 ） mm^2, the ventrolateral area in brain stem （ 222. 8 ± 25.8 ） mm^2, the linear exposure of the posterior petroclinoid fold （ 11.5 ±0. 6 ） mm, and BA trunk （10. 3± 2.0 ）mm, and the approach angles in the vertical axis to BA tip（ 13.7 ± 1.7 ）°were significantly greater after opening cranial nerve cisterns. But the approach angles in the horizontal axis to BA tip were indifferent. Conclusions The exposure areas and angles of anterior subtemporal keyhole approach to superior petroclival region can be increased after opening cranial nerve cisterns. Key words: Subtemporal; Keyhole approach; Cranial nerve cisterns ; Superior petroclival region

Opening cranial cisterns by the anterior subtemporal keyhole approach to the superior petroclival region: anatomical study and comparative analysis

Background Without drilling the bony structures, simple incision of the tentorium dorsal to the porus of trochlear nerve by the anterior subtemporal keyhole approach provides narrow exposure in the superior petroclival region. This study was designed to measure and compare the areas of exposure, linear distances, and angles of approach in the superior petroclival region before and after opening cranial cisterns. Methods The study was carried out on 20 sides of cadaver heads. With the use of a navigation system, the area of exposure in the dorsum sella and clivus, the ventrolateral area of exposure in brainstem around the BA, the linear exposure of the posterior petroclinoid fold and BA trunk, and the angles of approach to BA tip were evaluated. The length of oculomotor cistern and trochlear cistern, the distance of oculomotor porus between trochlear porus, the linear exposure of the trigeminal nerve, and the angle to the most inferior medial point in clivus were also measured. Results The area of exposure in the dorsum sella and clivus (157.6 ± 27.2mm 2), the ventrolateral area of exposure in brainstem around BA (249.5 ± 29.7mm 2), the linear exposure of the posterior petroclinoid fold (11.5 ± 0.6 mm) and BA trunk (10.3 ± 2.0 mm), and the angle of approach in the vertical axis to the BA tip (13.7° ± 1.7°) were significantly greater after opening cisterns. The angles of approach in the horizontal axis to the BA tip (24.5° ± 1.1° vs 24.7° ± 0.8°) were not statistically different. The length of oculomotor cistern and trochlear cistern, the distance of oculomotor porus and trochlear porus, the linear exposure of the trigeminal nerve, and the angle of approach to the most inferior medial point in clivus were 6.7 ± 1.3 mm, 10.7 ± 2.4 mm, 9.6 ± 2.3 mm, 15.8 ± 1.4 mm, and 13.0° ± 1.5°, respectively. Conclusion The areas of exposure, linear distances, and the angles of approach in the superior petroclival region can be increased after opening cranial cisterns by the anterior subtemporal keyhole approach.