Endoscope-Assisted Transmaxillosphenoidal Approach to the Sellar and Parasellar Regions: An Anatomic Study

Combined Endoscopic Endonasal Transclival and Contralateral Transmaxillary Approach to the Petrous Apex and the Petroclival Synchondrosis: Working "Around the Corner" of the Internal Carotid Artery-Quantitative Anatomical Study and Clinical Applications

The endoscopic contralateral transmaxillary (CTM) approach has been proposed as a potential route to widen the corridor posterolateral to the internal carotid artery (ICA). In this study, we first refined the surgical technique of a combined multiportal endoscopic endonasal transclival (EETC) and CTM approach to the petrous apex (PA) and petroclival synchondrosis (PCS) in the dissection laboratory, and then validated its applications in a preliminary surgical series. The combined EETC and CTM approach was performed on three cadaver specimens based on four surgical steps: (1) the nasal, (2) the clival, (3) the maxillary and (4) the petrosal phases. The CTM provided a "head-on trajectory" to the PA and PCS and a short distance to the surgical field considerably furthering surgical maneuverability. The best operative set-up was achieved by introducing angled optics via the endonasal route and operative instruments via the transmaxillary corridor exploiting the advantages of a non-coaxial multiportal surgery. Clinical applications of the combined EETC and CTM approach were reported in three cases, a clival chordoma and two giant pituitary adenomas. The present translational study explores the safety and feasibility of a combined multiportal EETC and CTM approach to access the petroclival region though different corridors.

Analysis of the Prechiasmatic Sulcus in Chiari Malformation Type I

OBJECTIVE

To assess morphologic features of the prechiasmatic sulcus (PS) in Chiari malformation type I (CM-I).

METHODS

Computed tomography images were obtained in patients with CM-1 (mean age: 21.26 ± 16.46 years; sex: 25 females and 17 males) and 58 healthy control subjects (mean age: 28.12 ± 22.60 years; sex: 29 females and 29 males). The following parameters were measured to determine the anatomy of the PS: planum length, sulcal length, sulcal angle (SA), and interoptic distance. Considering sulcal length and SA measurements, 4 types of PS were identified: narrow-steep-groove (NSG), narrow-flat-groove (NFG), wide-steep-groove, and wide-flat-groove.

RESULTS

SA was greater in the CM-I group (32.80 ± 18.21°) compared with the control group (23.05 ± 14.53°) (P = 0.004), but the other parameters were similar in both groups. Distribution ranking of PS types was as follows: NFG (31%) > NSG (26.20%) > wide-steep-groove (23.80%) > wide-flat-groove (19%) in the CM-I group; wide-flat-groove (37.90%) > wide-steep-groove (20.70%) = NFG (20.70%) = NSG (20.70%) in the control group. Distribution rate of PS types relative to both groups showed that the classification system was not affected by CM-I (P = 0.226).

CONCLUSIONS

SA value was approximately 25% greater in the CM-I group than in the control group; thus, CM-I patients had more vertical groove. The percentage of narrow-type (NSG + NFG) PS in the CM-I group was higher than in the control group.

History, Current Techniques, and Future Prospects of Surgery to the Sellar and Parasellar Region

The sellar and parasellar region can be affected by diverse pathologies. The deep-seated location and surrounding critical neurovascular structures make treatment challenging; there is no singular, optimal approach for management. The history and development of transcranial and transsphenoidal approaches by pioneers in skull base surgery were largely aimed at treating pituitary adenomas, which are the most common lesions of the sella. This review explores the history of sellar surgery, the most commonly used approaches today, and future considerations for surgery of the sellar/parasellar region.

Lost or fragmented bony septum of the optic canal facing the sphenoid sinus: a histological study using elderly donated cadavers

PURPOSE

To histologically describe a direct contact (the so-called dehiscence) of the optic nerve (ON) and/or internal carotid artery (ICA) to the mucosa of posterior paranasal sinuses represented by the sphenoid sinus (SS).

METHODS

Observations of histological sections of unilateral or bilateral skull bases (parasellar area and orbital apex) from 22 elderly cadavers were made.

RESULTS

A bony septum was less than 300 µm between the SS and ICA and 200 µm between the SS and optic nerve. Parts of the septa were sometimes absent due to fragmentation and holes of the bony lamella (2/22 facing the ICA; 4 facing the ICA in combination with an absent bony septum facing the nerve). In these dehiscence sites, the SS submucosal tissue attached to a thick sheath (50-100 µm in thickness) enclosing the optic nerve and ophthalmic artery and/or the ICA adventitia (50-200 µm in thickness). The ICA sometimes contained a sclerotic plaque that attached to or even protruded into the SS. With or without dehiscence, the SS mucosa was always thin (50-100 µm in thickness) and accompanied no mononuclear cellular infiltration or tumor.

CONCLUSIONS

A thin bony septum of the optic nerve or ICA had been notable as a danger point during surgery, but even a 0.05-mm-thick bone lamella might be an effective barrier against cellular infiltration or bacterial invasion from the SS. Fragmentation and holes of the bony lamella in 4 cadavers might allow cellular invasion to the optic nerve. Accordingly, unknown immunological cross talks might occur to cause demyelination.

Evaluation of the Cranial Aperture of the Optic Canal on Cone-Beam Computed Tomography Images and its Clinical Implications for the Transcranial Approaches

OBJECTIVE

This study aimed to investigate morphometric properties of the cranial aperture (CA) of the optic canal.

METHODS

Cone-beam computed tomography images of 400 individuals (200 males and 200 females) aged 37.32 ± 15.87 years were retrospectively examined to assess the morphometry and morphology of the CA.

RESULTS

The height and width of CA were found as 4.22 ± 0.74 mm and 7.27 ± 1.15 mm, respectively. The distances between the CA and the midsagittal line, the anterior and lateral boundaries of the anterior skull base were measured as 5.77 ± 1.32 mm, 64.97 ± 6.36 mm, and 41.00 ± 4.05, respectively. The angle of the optic canal in the sagittal plane was measured as 7.57° ± 3.95°, whereas in the horizontal plane as 38.96° ± 4.36°. The aperture shape was defined as the tear-drop (413 foramina, 51.62%), triangular (180 foramina, 22.50%), oval (158 foramina, 19.75%), round (30 foramina, 3.75%), and polygonal (19 foramina, 2.38%).

CONCLUSIONS

The authors observed that the diameters, and angulations of the CA may change relative to gender and the shape. The anatomic features of CA are important for the positioning of the patient's head, the choice of the appropriate surgical approach or equipment, and the detection of anatomical landmarks during interventions. In this context, our dataset may be beneficial for surgeons helpful as a reference for radiological evaluations.

Impact of C-shaped skin incision on surgical operability in the retrosigmoid approach: when a good start is half of the job

BACKGROUND

The retrosigmoid approach (RSA) is one of the routes of choice to approach tumors and vascular lesions of the cerebellopontine angle. Among different types of skin incisions and soft tissue dissection techniques, the most widely used variants comprise the straight/lazy S-shaped and the C-shaped incisions. Several reports discuss advantages in terms of functional and clinical outcomes of the C-shaped incision, but scientific considerations about the critical impact of this kind of incision on surgical operability are still extremely limited.

OBJECT

Authors comparatively analyze the advantage provided by C-shaped incision in RSA in terms of anatomic exposure and surgical operability, compared with straight/lazy S-shaped one.

METHODS

A comparative microanatomical laboratory investigation was conducted. The operability score (OS) was applied for quantitative analysis of surgical operability.

RESULTS

C-shaped incision, providing a significant reduction of the overall working distance (-13%) together with an overall increase of the maneuverability area (+ 204.9%), did improve the conizing effect on the surgical corridor. It optimized overall maneuverability of surgical instruments, in terms of angle of attack (+ 27.7%), as well as maneuverability arc (+ 122%), on the entire surgical field. C-shaped incision ensured good operability on all surgical targets (OS ranging from 2 to 3), most significantly improving surgical maneuverability at the porus trigeminus and internal acoustic meatus.

CONCLUSION

C-shaped incision in the RSA significantly improves anatomic exposure and surgical operability as compared with straight/lazy S-shaped incision.

Comparative Anatomical Study of Fronto-Orbito-Zygomatic and Fronto-Temporal Approach to the Central Skull Base

ABSTRACT

Despite the advances in microsurgery and neuroanatomy, surgery of the central skull base still represents a challenge. Fronto-temporal approach has represented the mainstay of surgical approaches to this region. With advances in skull base surgery, orbital and zygomatic extensions were added to fronto-temporal approach to improve exposure minimizing brain retraction.The authors compared fronto-temporal and fronto-orbitozygomatic approaches to the central skull base by using the previously described operability score, to three different anatomical targets: the ipsilateral anterior clinoid process, the contralateral anterior clinoid process, and the ipsilateral posterior clinoid process.Based on the measurements taken, fronto-orbitozygomatic approache showed higher values at all 3 targets. The reported values were critically discussed.The operability score has been reported as an effective method to compare surgical approaches. The present study demonstrated the maximal possibility of exposure of the two approaches. Based on the strong variability of this anatomical region, especially because of the different pathologies, the authors suggest considering the operability score as a further tool to better define the best surgical approach to this anatomical region.

Transcranial extradural subtemporal repair for sphenoid sinus lateral recess meningoencephalocele: technical note

Cranial meningoencephalocele is a rare condition consisting of the herniation of meninges, CSF, and brain tissue through a cranial or skull base defect. Sphenoid sinus lateral recess meningoencephalocele is of particular interest due to the complex anatomy surrounding the bone defect and their demanding surgical management. In this technical note, we reported a step-by-step description of a rare case of sphenoid sinus lateral recess meningoencephalocele causing headache due to recurrent cerebrospinal fluid leak treated with a subtemporal craniotomy with extradural middle cranial fossa drilling and meningoencephalocele removal with multilayer reconstruction. The transcranial route is a safe and effective treatment for sphenoid sinus lateral recess meningoencephalocele repair. The subtemporal extradural approach allows for an optimal exposure of the relevant anatomy minimizing risks and improving the possibility to perform an effective multilayer skull base reconstruction.

Endoscope-Assisted Neuroportal Transcerebellar Approach to the Fourth Ventricle: An Anatomical Study

BACKGROUND AND STUDY AIMS

 Minimally invasive approaches to deep-seated lesions still represent a fundamental issue in modern neurosurgery. Tubular retractors allow to enhance the operability of intraventricular lesions, minimizing the risk of damages to brain parenchyma. Increasing interest for portal devices has been mainly focused on supratentorial pathologies, while transportal approaches in the posterior cranial fossa have been rarely described. In the present study, the authors aimed to investigate the surgical exposure and operability obtained with a microsurgical neuroportal transcerebellar approach targeting the fourth ventricle, assisted by endoscopic exploration.

MATERIAL AND METHODS

 Six cadaveric specimens were provided for anatomical microsurgical dissection and Vycor ViewSite Brain Access System was used as tubular retractor. Surgical feasibility of the neuroportal transcerebellar approach was demonstrated through a definable and measurable parameter, the operability score.

RESULTS

 The neuroport provided a surgical corridor away from eloquent structures to target the whole fourth ventricle cavity, preventing injury to cerebellar nuclei and white matter pathways and, potentially, minimizing the risk of surgical morbidity. Maximal operability was reached in the pontomedullary junction and medullary area of the ventricular floor. Transportal endoscopic assistance contributed to a further extension of surgical exposure in blind spots, corresponding to the ipsilateral lateral recess, the uppermost part of the fourth ventricle, and the obex.

CONCLUSION

 The neuroportal transcerebellar approach represents a viable alternative route to the fourth ventricle, avoiding vermian splitting or subarachnoid dissection of the cerebellomedullary cistern. Endoscopic assistance enhances the exposure of the surgical field and accomplishes a valid instrument for intraventricular orientation to ease microsurgical procedures.

Assessment of the Optic Foramen Shape and Size in Human Fetuses

OBJECTIVE

This study was aimed to obtain data on the dimensions of the optic foramen in human fetuses for early childhood surgeries.

METHODS

Twenty-five formalin-fixed fetuses (16 boys and 9 girls) with average age 21.68 ± 3.12 gestational weeks (range, 16-28 weeks) in the inventory of Anatomy Department, Faculty of Medicine were included in the study. The surface area, width, and height of the optic foramen were bilaterally measured using a digital image analysis software.

RESULTS

The forms of the optic foramen were described as oval shaped (72%, 36 foramina) and round shaped (28%, 14 foramina). The surface area, width, and height of the optic foramen were found as 2.40 ± 1.02 mm, 1.83 ± 0.59 mm, and 1.58 ± 0.36 mm, respectively. The measurements of the parameters related to the optic foramen were not statistically different in terms of sides and sexes (P > 0.05). Linear functions for the height, width and surface area of the optic foramen were calculated as: y = 0.711 + 0.040 × weeks, y = -0.019 + 0.086 × weeks, and y = -0.400 + 0.129 × weeks, respectively.

CONCLUSION

The linear functions in this study can be used to estimate the dimensions of the optic foramen. The calculated regression equations, representing the growth dynamic of the optic foramen showed that the surface area, width, and height were increasing according to gestational ages between 16 and 28 weeks. Microanatomical knowledge related to the optic foramen may be beneficial for surgeons to avoid iatrogenic injury in infants and for anatomists to understand the development of the fetal skull base.

Endoscopic sublabial transmaxillary approach to the inferior orbit: pearls and pitfalls-A comparative anatomical study

OBJECTIVE

Although orbital surgery has always represented a challenge for neurosurgeons, keyhole and endoscopic techniques are gradually surging in popularity maximizing functional and esthetic outcomes. This quantitative anatomical study first compared the surgical operability achieved through three endoscopic approaches within the inferior orbit: the endoscopic sublabial transmaxillary (ESTMax), the endoscopic endonasal transethmoidal (EETEth), and the endoscope-assisted lateral orbitotomy (ELO).

METHODS

Each of these approaches was performed bilaterally on five specimens. We described the ESTMax step-by-step, underlining its advantages and pitfalls in comparison with EETEth and ELO. Then, we assessed surgical measurements and operability in ESTMax, EETEth, and ELO.

RESULTS

The ESTMax provided the most favorable operative window (278.9 ± 43.8 mm²; EETEth: 240.8 ± 21.5 mm², p < 0.001; ELO: 263.1 ± 19.8 mm², p = 0.006), the broadest surgical field area (415.9 ± 26.4 mm²; EETEth: 386.7 ± 30.1 mm², p = 0.041; ELO: 305.2 ± 26.3 mm², p < 0.001), surgical field depths significantly shorter than EETEth (p < 0.001) but similar to ELO, the widest surgical angles of attack (45°-65°; EETEth: 20°-30°, p < 0.001; ELO: 25°-50°, p < 0.001), and the greatest surgical mobility areas (EETEth: p < 0.001; ELO: p < 0.001). Furthermore, the ESTMax allowed multi-angled exposure and handy maneuverability around all the inferior intraorbital targets. Small anterior antrostomy, blunt intraorbital dissections, direct targets' approach, orbital floor reconstruction, and maxillary bone flap replacement may limit the ESTMax morbidity rates.

CONCLUSIONS

The ESTMax is a minimally invasive "head-on" orbital approach that exploits endoscopic surgery advantages avoiding the cranio-orbital and trans-nasal approach limitations and possible complications. It represents a promising alternative to EETEth and ELO because of its optimal operability for resecting lesions extending into the entire inferior orbit.

Chiasmatic Ridge: Incidence, Classification, and Clinical Implications

OBJECTIVE

The study aimed to identify the chiasmatic ridge (CR) morphology and to discuss its surgical significance.

METHODS

The suprasellar region of 90 adult dry skulls with unknown ages, sexes, or nationalities was examined to record the shape and incidence of the CR.

RESULTS

The CR was found in 14 (15.56%) of 90 dry skulls. The ridge was classified into 3 types, taking into account its shape, incidence (presence/absence), and the risk of residual tumor formation. The absence of the CR was named as Type 1 (76 cases, 84.44%). The bony extension without a hidden area was identified as Type 2 (8 cases, 8.89%), while the bony extension with a hidden area as Type 3 (6 cases, 6.67%).

CONCLUSION

Type 3 CR (which has an evident hidden area beneath the ridge) should be taken into account by neurosurgeons to eliminate possible residual tumor risk during removal of tumors (eg, meningioma) with subfrontal or supraorbital approaches.

Anatomic features of the cranial aperture of the optic canal in children: a radiologic study

OBJECTIVE

This study aimed to peruse anatomic features of the cranial aperture of the optic canal (CAOC) for obtaining an extended morphometric dataset in children.

METHODS

Computed tomography images of 200 children were included in this retrospective work to analyze the shape, location and diameters of the CAOC.

RESULTS

The CAOC area, width and height were observed as 17.53 ± 2.80 mm², 6.12 ± 0.84 mm, and 4.35 ± 0.64 mm, respectively. The angle of the optic canal in axial plane was found as 39.28 ± 5.13°, while in sagittal plane as 16.01 ± 6.76°. The distance between the CAOC and the midsagittal line was 7.17 ± 1.48 mm. The CAOC was measured as 54.04 ± 5.23 mm and 42.55 ± 3.28 mm away from the anterior and lateral boundary of the anterior skull base, respectively. The CAOC shape was described as the tear-drop (186 foramina, 46.5%), triangular (156 foramina, 39%), oval (47 foramina, 11.8%), and round (11 foramina, 2.8%).

CONCLUSION

The depth, angle and diameter measurements belonging to the CAOC were changing according to its shape or demographic data (e.g., sex and age). Therefore, preoperative radiologic evaluation containing the shape, location and size of the CAOC should be considered by multidisciplinary operating teams in terms of surgical interventions such as implant positioning.

Surgical Management of Giant Intracranial Aneurysms: Overall Results of a Large Series

OBJECTIVE

To review and discuss surgical treatment options for giant intracranial aneurysms (GIAs), focusing on indications, technical aspects, and results, along with some illustrative cases.

METHODS

We reviewed the data of 82 consecutive patients surgically managed between January 2000 and December 2019 for treatment of a GIA.

RESULTS

Male sex and hemorrhage at presentation were prevalent. The average follow-up was 81.2 ± 45 months. The anterior circulation was involved in 76.8% of GIAs. If the GIA showed a clear neck, minimal atherosclerosis, or intrasaccular thrombosis, and ≤2 branches arising from the neck, it was reconstructed. This procedure was possible in 78% of cases. The technique also involved temporary clipping, remodeling, and thrombectomy, as well as fragmentation techniques. Angioarchitectural features other than these techniques underwent bypass and aneurysm trapping. Most bypasses were extracranial to intracranial and high flow. Flow capacity, collateral circulation, and availability of the donor vessel mainly affected the choice of the type of bypass. Overall, successful exclusion of the GIA was 91.4%. The need for retreatment and complication rate were 3.6% and 19.5%, respectively. A good overall outcome (modified Rankin Scale score 0-3) was achieved in 84.2% of patients, and mortality was 10%.

CONCLUSIONS

Microneurosurgical techniques still maintain a significant role for most GIAs, with a high durability and acceptable rate of morbidity and mortality. Clip reconstruction is the first-line surgical treatment option, whereas bypass is indicated in cases of planned or unplanned sacrifice of the parent artery to prevent long-term ischemic complications.

A Computed Tomography Study of the Prechiasmatic Sulcus Anatomy in Children

PURPOSE

To investigate the characteristics of the prechiasmatic sulcus in children aged between 1-20 years.

METHODS

Patient files of 200 children admitted to the university hospital on 2019 were analyzed, retrospectively. The computed tomography images of patients were used to obtain anatomical knowledge containing prechiasmatic sulcus types and dimensions.

RESULTS

The measurements related to the sulcal length (6.94 ± 1.25 mm) and sulcal angle (31.01 ± 18.13°) showed that the sulcal length did not alter in children between 1 and 20 years, whereas the sulcal angle did not vary from infancy to prepubescent period, but it was decreasing in postpubescent period. In 29 patients, the sulcal length was observed to divide into 2 parts with an evident angle. The interoptic distance and planum length were found as follows: 14.70 ± 2.85 mm and 14.84 ± 4.12 mm, respectively. The order of PS types was observed as type 4 (26.5%, 53 cases) > type 2 (26%, 52 cases) > type 1 (24%, 48 cases) > type 3 (23.5%, 47 cases).

CONCLUSIONS

The sulcal length did not vary in children, whereas the sulcal angle decreased with an irregular pattern. The sulcal angle decreased after prepubescent period, possibly due to the sphenoid sinus pneumatization and spheno-occipital synchondrosis. The sulcal length angle mostly in infants and young children may cause surgical orientation difficult during the resection of tumors using transcranial approaches.

Fetal Anatomy of the Optic Strut and Prechiasmatic Sulcus with a Clinical Perspective

OBJECTIVE

The main objective of the study was to show the morphologic features of optic strut (OS) and prechiasmatic sulcus (PS) in the fetal skull base with a surgical anatomical perspective.

METHODS

Twenty-three fetal cadavers (9 female, 14 male) with an average age of 21.70 ± 3.12 (range: 16-28) weeks of gestation in the inventory of the Anatomy Department were included in the study. Measurements were made with a digital image analysis software and goniometer.

RESULTS

The sulcal length, interoptic distance, planum length, and sulcal angle were detected as follows: 3.91 ± 0.74 mm, 6.88 ± 1.04 mm, 6.55 ± 1.51 mm, and 24.52 ± 9.51°, respectively. Considering the location of the posteromedial margin of OS according to PS, OS was identified as the sulcal in 56.5% (13 cases), postsulcal in 30.4% (7 cases), and asymmetric in 13% (3 cases). According to the sulcal length and angle, PS was identified as type 1 in 26.1% (6 cases), type 2 in 21.7% (5 cases), type 3 in 30.4% (7 cases), and type 4 in 21.7% (5 cases).

CONCLUSIONS

Our findings suggest that the sulcal length and angle reach adult size in utero. Taking into account the fetal and the gathered adult measurements, the high percentage of steep angle compared to flat angle show that after birth, PS become more flat, probably depending on the variations of the sphenoid sinus pneumatization. Thus, more studies conducted on the alterations in PS and OS types relative to the pneumatization are needed in terms of patient positioning, selection of appropriate surgical approach, and intraoperative decision-making.

Temporal Galeofascial Flap for Reconstruction After Transmaxillary Approaches to the Clival Region

BACKGROUND

A paramount concern after transmaxillary approaches has been skull base reconstruction. Regional pedicled flaps represent the best reconstructive option. We have described a technique to harvest a lateral-based multilayered vascularized flap for skull base reconstruction after resection of large tumors using the transmaxillary transpterygoid approach (TMTPA).

METHODS

We performed a cadaver study using the TMTPA to harvest the combined temporal galeofascial flap (CTGF). The first layer, with major sealing capabilities, is composed by a temporoparietal galeal-pericranial flap. The second layer is composed by temporal muscle fascia to provide mechanical support for flap dural engrafting.

RESULTS

The CTGF provides excellent coverage of both the clival dural lining and the ipsilateral pterygopalatine fossa structures (×1.6). The CTGF is pliable and easy to harvest. It offers great flexibility in flap content and design, providing a large quantity of vascularized tissue. The vascular pedicle derives from the superficial temporal vessels, which can ensure flap trophism.

CONCLUSIONS

CTGF represents an effective option as a regional multilayered pedicled flap for skull base reconstruction after resection of clival tumors using the TMTPA. The flap pedicle, owing to its anatomical location, will often be preserved even after repeated microsurgical or endoscopic procedures, providing a technical alternative for reconstruction even in patients who have undergone multiple surgeries with low residual availability of regional flaps.

Evolution of transmaxillary approach to tumors in pterygopalatine fossa and infratemporal fossa: anatomic simulation and clinical practice

BACKGROUND

The endoscopic transnasal approach has been proven to have advantages on the removal of the tumors in pterygopalatine fossa (PPF) and infratemporal fossa (ITF). Herein, this study aimed to describe a modified approach for resection of the tumors in these areas, both in cadaveric specimen and clinical patients.

METHODS

The 20 adult cadaveric specimens and five patients with tumors in PPF and ITF were enrolled in this study. For the cadaveric specimens, ten were simulated anterior transmaxillary approach and ten were performed modified endoscopic transnasal transmaxillary approach. The exposure areas were compared between two groups and main anatomic structure were measured. Surgery was operated in the five patients with tumors of PPF and ITF to verify the experience from the anatomy. Perioperative management, intraoperative findings and postoperative complications were recorded and analyzed.

RESULTS

The modified endoscopic transnasal transmaxillary approach provided as enough surgical exposure and high operability to the PPF and ITF as the anterior transmaxillary approach did. The diameter of maxillary artery in the PPF was 3.77 ± 0.78 mm (range: 2.06-4.82 mm), the diameter of middle meningeal artery in the ITF was 2.79 ± 0.61 mm (range: 1.54-3.78 mm). Four patients who suffered schwannoma got total removal and one of adenocystic carcinoma got subtotal removal. The main complications were facial numbness and pericoronitis of the wisdom tooth. No permanent complication was found.

CONCLUSIONS

With the widespread use of neuroendoscopy, the modified endoscopic transnasal transmaxillary approach is feasible and effective for the resection of tumors located in PPF and ITF, which has significant advantages on less trauma and complications to the patients.

Endoscope-assisted contralateral transmaxillary approach to the clivus and the hypoglossal canal: technical case report

Clival lesions are still considered surgically complex due to their anatomical location. Critical structures, such as the internal carotid arteries (ICAs), cavernous sinuses, cranial nerves, and brainstem, may be encased within the lesion. Although advances in endoscopic endonasal approaches have provided new routes to these lesions, exposure and resection of clival tumors through the endonasal route remain a technical challenge. Here, the authors report a left-sided endoscopic transmaxillary approach to access the right aspect of the clivus and the hypoglossal canal.A 35-year-old woman presented with progressive right 6th cranial nerve palsy. MRI revealed a contrast-enhancing right petroclival chondrosarcoma that involved Meckel's cave and extended into the right hypoglossal canal. An endoscopic-contralateral-transmaxillary approach through a left sublabial incision was used to access the right petroclival region and right hypoglossal canal. A left maxillary osteoplastic flap was elevated to expose the left maxillary sinus. This was followed by a left medial maxillectomy, gaining access to the left posterior nasal cavity. The posterior third of the left inferior turbinate and nasal septum were removed to access the right side of the petroclival region. Near-total resection was achieved without any vascular or neurological complications. A thin shell of residual tumor was left behind due to involvement of vital structures, such as the ICA, and further treated with proton-beam radiotherapy.The endoscopic-contralateral-transmaxillary approach provides a direct surgical corridor and good lateral visualization of the skull base vasculature. This approach allows wide maneuverability around the ICA and hypoglossal canal, which, in this case, allowed maximal tumor resection with full preservation of neurological function.

Three-Dimensional Printed Skull Base Simulation for Transnasal Endoscopic Surgical Training

OBJECTIVE

Transnasal endoscopic skull base surgery (SBS) presents a major challenge for inexperienced neurosurgeons because of the complicated anatomic structures, 2-dimensional endoscopic view, limited operative field, and required skills. We designed a personalized multimaterial and multicolor three-dimensional (3D)-printed SBS simulation to reproduce the complex anatomy of the skull base. The fidelity and feasibility for anatomic education and surgical training were assessed.

METHODS

Two-dimensional computer tomography and magnetic resonance images were collected from a 42-year-old healthy male volunteer. After 3D modeling and spatial alignment, personalized SBS simulations were produced using a multimaterial 3D printer. The fidelity of the models was assessed by 3 experienced neurosurgeons, and the effects for anatomic education and surgical training were evaluated by 10 resident trainees. Both evaluations were based on 5-point Likert questionnaires.

RESULTS

The mean scores for fidelity of tissue structure ranged from 3.7 to 4.7, and scores for aid in anatomic education and surgical training ranged from 3.5 to 4.9.

CONCLUSION

The 3D-printed SBS simulation is a practical, economical, high-fidelity model. It has great potential for anatomic education and operative training in transnasal endoscopic surgery.

Visualization of cerebrospinal fluid-filled spaces in the cavernous sinus using magnetic resonance imaging

The cavernous sinus (CS) has been extensively studied and is commonly acknowledged as a dural venous sinus. There have been no reports documenting cerebrospinal fluid (CSF)-filled spaces in the CS. Here, we explore such structures in the CS using magnetic resonance imaging (MRI). A total of 183 patients underwent T2-weighted or constructive interference steady-state (CISS) sequence MRI. Imaging data from coronal sections were analyzed. Of the 183 patients, 26.8% had CSF-filled spaces in the CS. These spaces appeared to communicate with the suprasellar cistern through dural defects found in the superior wall of the CS, and also appeared to surround the cavernous portion of the internal carotid artery (ICc) and pituitary gland, and further be adjacent to the oculomotor and trigeminal cisterns. Dural defects were identified in 81.6% of patients, with CSF-filled spaces adjacent to the oculomotor and trigeminal cisterns found in 81.6% and 12.2% of patients, respectively. The distribution of these spaces could be classified into four types based on their topographical relationships with the ICc, namely the circumferential, medial, lateral, and superior types. The circumferential and medial types were the most frequently found and comprised >80% on both sides. The CS may involve CSF-filled spaces in physiological conditions that are formed through dural defects in the superior wall and adjacent cranial nerve cisterns. These findings are critical when considering approaches to the CS, modes of lateral extension of pituitary tumors, and CSF dynamics in the CS.