Dorsum Sellae Research Articles

Osseous arteriovenous fistulas in the dorsum sellae, clivus, and condyle

Arteriovenous fistulas (AVFs) located in the cavernous sinus (CS), clivus, and condyle can be osseous shunts in nature. Here, we reviewed the angioarchitecture, clinical characteristics, and treatment results of AVFs in these lesions. Twenty-five patients with 27 lesions who underwent rotational angiography in our department between May 2013 and December 2019 were reviewed. We examined 20 CS AVFs, 2 clival AVFs, and 5 condylar AVFs. We divided the anatomical shunted pouches into five locations: the dorsum sellae (posteromedial of the CS), posterolateral wall of the CS, lateral wall of the CS, clivus, and condyle. We divided the AVFs into three categories: intraosseous, transitional, and nonosseous shunts. We analyzed the characteristics and treatment results. A total of 33 shunted pouches or points were identified in 27 lesions. The dorsum sellae (n = 16) was the most frequent location. Fourteen AVFs (88%) in the dorsum sellae were osseous (intraosseous or transitional) shunts. All AVFs in the clivus or condyle were also osseous shunts. Eleven lesions (92%) of intraosseous and all lesions of transitional shunts exhibited bilateral external carotid artery involvement as feeders. Ten lesions (83%) of intraosseous shunts were treated with selective transvenous embolization of the shunted pouch with or without additional partial embolization of the sinus. Eleven (92%) intraosseous shunts were completely occluded, and symptom resolution was achieved in all intraosseous shunts. Most of the CS AVFs with shunted pouches in the dorsum sellae and all of the AVFs in the clivus and condyle share similar characteristics.

Tailoring the surgical corridor to the basilar apex in the pretemporal transcavernous approach: morphometric analyses of different neurovascular mobilization maneuvers.

The pretemporal transcavernous approach (PTA) provides optimal exposure and access to the basilar artery (BA); however, the PTA can be invasive when vital neurovascular structures are mobilized. The goal of this study was to evaluate mobilization strategies to tailor approaches to the BA. After an orbitozygomatic craniotomy, 10 sides of 5 cadaveric heads were used to assess the surgical access to the BA via the opticocarotid triangle (OCT), carotid-oculomotor triangle (COT), and oculomotor-tentorial triangle (OTT). Measurements were obtained, and morphometric analyses were performed for natural neurovascular positions and after each stepwise expansion maneuver. An imaginary line connecting the midpoints of the limbus sphenoidale and dorsum sellae was used as a reference to normalize the measurements of BA exposure and to facilitate the clinical applicability of this technique. In the OCT, the exposed BA segment ranged from - 1 ± 3.9 to + 6 ± 2.0mm in length in its natural position. In the COT, the accessible BA segment ranged from - 4 ± 2.3 to - 2 ± 3.0mm in length in its natural position. Via the OTT, the accessible BA segment ranged from - 7 ± 2.6 to - 5 ± 2.8mm in length in its natural position. In the OCT, COT, and OTT, a posterior clinoidectomy extended the exposure down to - 6 ± 2.7, - 8 ± 2.5, and - 9± 2.9mm, respectively. This study quantitatively evaluated the need for the expansion maneuvers in the PTA to reach BA aneurysms according to the patient's anatomical characteristics.

The Size of the Sella Turcica in Skeletal Class I, Class II, and Class III using FACAD Software- South Indian Population Study

Background: The sella turcica is a saddle-shaped bony structure in which anterior wall is formed by tuberculum sellae and posterior wall is formed by dorsum sellae. Lateral cephalometric landmark, sella, is of paramount importance in the field of orthodontics and dentofacial orthopaedics for diagnosis, treatment planning and assessment of skeletal maturation. * Significant literature is available indicating that large variations occur in the shape and size of sella turica among the three different types of skeletal malocclusion classes.* Studies have been conducted in different regions to evaluate the shape and size of sella turcica in different skeletal malocclusions therefore, the aim of this study is to describe the shape and measure the size of the sella turcica in south Indian subjects with different skeletal types. Materials and Methodology: Lateral cephalometric radiographs of 60 subjects (30 males and 30 females); 20 Class I, 20 Class II, and 20 Class III. The sella turcica on each lateral cephalometric was analysed using FACAD ortho software tracing to measure the linear dimensions of length, depth, and anteroposterior dimension. One-way analysis of variance was performed to study the relationship between skeletal type and sella size. Result: Skeletal class III subjects presented with a statistically significant difference in the depth of sella turcica on comparison with skeletal class II (p>0.01). There was statistically insignificant difference found in the anteroposterior dimension and length of sella turcica in skeletal class I, class II and class III. Conclusion: When the size of sella turcica was compared with skeletal type, a statistically significant difference was found in depth skeletal Class II and Class III subjects.

Ossification around intercavernous sinus: An osteological finding that can complicate trans – sphenoidal surgery

The aim of the study was to document an anatomical variation around the sella turcica which was unique and lacked any reference in the literature. A low lying osseous bar connecting the right middle clinoid process to the midpoint of the right lateral border of the dorsum sella was observed in a human skull specimen. The osseous bar was forming a foramen close to the floor of the sella, and the structure in association with this part of sella is the inferior intercavernous sinus. Measurements of the sella turcica bridge (STB), carotico-clinoid foramen (CCF), interclinoid foramen (ICF) on both sides and that of the ossified bar and foramen formed by itself were taken with the help of ImageJ software. The values observed for the measurements of different parameters of STB and its components, for CCF and ICF were bilaterally different. While the values for the osseous bar and foramen formed by it cannot be compared because of its unilateral occurrence. The presence of foramen around the inferior intercavernous sinus may lead to difficulty in performing procedures like transsphenoidal surgery (TSS) or extended TSS (eTSS) while extracting intradural lesions, thus increasing the chances of haemorrhage.

Incidentally detected sellar spine in a patient with Cushing’s syndrome: a case report

Sellar spine, a bony spur extending anteriorly from the dorsum sellae, is a very rare anatomical variant. Several hypotheses regarding its etiology have been proposed, including the strongly supported theory of a cephalic ossified notochordal remnant. Sellar spine is usually detected incidentally in patients who have no definite symptoms, but several cases have reportedly accompanied endocrinopathies such as precocious puberty, hypopituitarism, or galactorrhea/oligomenorrhea. However, no published reports have described sellar spine in a patient with Cushing’s syndrome. We herein report a case of sellar spine detected during the evaluation of Cushing’s disease in a 29-year-old woman who underwent inferior petrosal sinus sampling, computed tomography, magnetic resonance imaging, and exploratory surgery. There was no evidence of a pituitary microadenoma, but a sellar spine was present in the operative field. Thus, the sellar spine might have caused Cushing’s syndrome in this case, although the exact mechanism is unknown.

Anatomical location of the abducens nerves (VI) in the ventral approach of clival tumors.

The aim of this work was to determine reliable anatomical landmarks for locating and preserving the abducens nerves (6th cranial nerves) during trans-facial or trans-nasal endoscopic approaches of skull base tumors involving the clivus and the petrous apex. In order to describe this specific anatomy, we carefully dissected 10 cadaveric heads under optic magnification. Several measurements were taken between the two petro-sphénoidal foramina, from the bottom of the sella and the dorsum sellae. The close relationship between the nerves and the internal carotid artery were taken into account. We defined a trapezoid area that allowed drilling the clivus safely, preserving the 6th cranial nerve while being attentive to the internal carotid artery. The caudal part of this trapezium is, on average, 20mm long at mi-distance between the two petro-sphenoidal foramina. The cranial part is at the sella level, a line between both paraclival internal carotid arteries. Oblique lateral edges between the cranial and caudal parts completed the trapezium.

Squamous suture obliteration: frequency and investigation of the associated skull morphology.

This study aimed to investigate the frequency of squamous suture (SqS) obliteration, to estimate the involvement of the major calvarial sutures and those surrounding the temporal squama, and to inspect the neuro- and basicranium for deformities. A series of 211 dry skulls of contemporary adult males were macroscopically observed. The skulls with closed SqS were scanned using an industrial µCT system. Digital morphometry of the skulls with obliterated SqS was performed by recording the 3D coordinates of anatomic landmarks and calculation of linear distances, angles and indices. Obliteration of SqS was observed in 3 (1.42%) skulls. One skull showed bilateral SqS obliteration. The other two cases were unilateral, one right-sided and one left-sided. SqS obliteration seems to be co-ordinated with the closure of the parietomastoid suture, partially related to the closure of the occipitomastoid, sphenoparietal and sphenofrontal sutures, and independent from the closure of the sphenosquamosal suture and the major calvarial sutures. No severe disproportions in the skull configuration were observed in the three investigated cases. The major differences in the complimentary hemicrania concern the parietal and occipital parts of the skull vault. Dorsum sellae erosion, an indicator for raised intracranial pressure, was observed in all three cases.

Fourth Ventricular Outflow Obstruction in an Infant with Ileal Atresia and Laryngomalacia: Endoscopic Management

AbstractFourth ventricle outflow obstruction (FVOO) is a rare cause of obstructive hydrocephalus. In this study, we described a case of idiopathic FVOO with ileal atresia and laryngomalacia which was managed with endoscopic third ventriculostomy (ETV) and re-endoscopy. We also described the techniques of fenestration of Liliequist membrane and partial removal of arachnoid membrane over dorsum sella (DS) to prevent closure of fenestration and recurrence of hydrocephalus. The patient was a 4-month-old infant presented with progressively increasing head size, feeding difficulty, respiratory distress, and tense fontanel. The infant had a history of laparotomy for ileal atresia. CT scan showed panventriculomegaly due to FVOO. ETV with fenestration of Liliequist membrane was done on emergency basis. After operation, the patient improved clinically and radiologically. Four weeks later, the patient returned with recurrent hydrocephalus. Endoscopic reoperation showed closure of fenestration in arachnoid membrane (Lilieqiest membrane). Endoscopic refenestration with partial excision of arachnoid on DS was done. The patient again recovered radiologically and clinically till last follow-up. In idiopathic FVOO, ETV with wide fenestration of Liliequist membrane, preferably with partial removal of arachnoid on DS, may be very useful in treating hydrocephalus (HCP) and preventing recurrent HCP even in infants.

MON-240 Histologically Proven Lymphocytic Hypophysitis with Marked Improvement on Glucocorticoid Therapy

Background: Lymphocytic hypophysitis (LH) is a rare autoimmune disorder characterized by lymphocytic infiltration of the pituitary gland. The disease predominantly affects women, with >50% of cases presenting during pregnancy or postpartum.1 LH is often associated with other autoimmune conditions, primarily thyroiditis, and adrenalitis.2 Clinical case: A 27-year-old female presented with secondary amenorrhea for eight months. Workup revealed hyperprolactinemia (PRL 65 ng/mL) and a heterogenous pituitary mass measuring 3.3 cm in the largest dimension. Cabergoline was initiated for a presumed prolactinoma. Laboratory evaluation was significant for hypogonadotropic hypogonadism (estradiol <50 pg/mL, progesterone <1 ng/mL, FSH 2.9 mIU/mL, LH 0.45 mIU/mL) despite normalization in prolactin. She was also found to have Hashimoto’s thyroiditis (FT4 0.7 ng/dL, TSH 8.2 uU/mL with positive TPO antibodies) and was started on levothyroxine.Repeat imaging demonstrated a 2.4 cm heterogenous expanding sellar mass with soft tissue extension to the dorsum sella concerning for a meningioma. Visual field testing was intact without evidence of chiasmal compression. She underwent trans-sphenoidal pituitary decompression surgery which was terminated prematurely due to the presence of extensive fibrous tissue in the sella. Pathology was consistent with LH. Immunohistochemical staining was positive for lymphocytic markers CD3 and CD20, confirming marked infiltration of inflammatory B-cells and T-cells. Her postoperative course was notable for panhypopituitarism. In view of the pathological findings of LH, she was started on a high dose of 40mg of prednisone daily. Within two months, sellar magnetic resonance imaging revealed a homogenous normal-appearing pituitary with a reduction in soft tissue mass in the sellar and suprasellar region. Oral contraceptive therapy was initiated for sex hormone replacement with the resumption of menses. Prednisone was gradually tapered to 5mg/day, and she was subsequently transitioned to maintenance hydrocortisone for central adrenal insufficiency. Discussion: LH is a rare chronic inflammatory disease that should be considered in the differential diagnosis of a non-secreting pituitary mass, especially if occurring in young women presenting during pregnancy or postpartum. The condition is associated with preferential destruction of corticotroph and thyrotroph cells.3 Appropriate management remains controversial. High dose glucocorticoid therapy, to which our patient responded to dramatically, has been shown to be beneficial in reducing mass effect. Optimal treatment involves surgical resection of the pituitary mass to decompress surrounding structures.3

Hybrid antero-lateral transcondylar approach to the clivus: a laboratory investigation and case illustration.

Surgical treatment of lesions involving the ventral craniovertebral junction (CVJ) and the lower clivus, traditionally involved complex lateral or transoral approaches to the skull base. However, mid or upper clivus involvement requires more extensive lateral approaches. Recently, the endoscopic endonasal approach (EEA) has become the standard for upper CVJ lesions and medial clival, and a valuable alternative for those tumors extending in its upper third as well as laterally. However, the EEA is associated with an increased risk of post-operative CSF leakage and infection when the tumor is characterized by an intradural extension. Furthermore, whenever the tumor has significant lateral and/or inferior extension below the odontoid process, the chances for a complete resection decrease. To analyze the extent of exposure of a hybrid microscopic-endoscopic transcondylar antero-lateral approach to the CVJ and clival region, and to verify its effectiveness in terms of mid and upper clival access. Five silicone-injected cadaver heads were used. Following a standard antero-lateral approach, condylectomy and jugular tubercle drilling were performed, after which angled endoscopes were utilized to extend the bone resection to the clivus. A volumetric assessment of the amount of clival removal was carried out. A case of CVJ chordoma operated through this approach is presented. The hybrid antero-lateral transcondylar approach provides adequate exposure of the ventral CVJ, up to the dorsum sellae and the sphenoid sinus, the contralateral petrous apex, and the contralateral paraclival internal carotid artery (ICA). Approximately 60% of the total clival volume can be removed with this approach. The main limitation is the limited visualization of the ipsilateral paraclival ICA and petrous apex. The hybrid antero-lateral transcondylar approach is a valuable surgical option for CVJ tumor extending from C2 to the mid and upper clivus.

Variant sella morphology and pituitary gland height in adult patients with Chiari II malformation: potential pitfall in MRI evaluation

PurposeTo systematically evaluate the sella morphology and pituitary gland height on brain MRI of Chiari II malformation (C2M) patients to understand the observed high incidence of apparent enlargement of the pituitary gland. MethodsBrain MRIs of C2M patients at a single tertiary care adult institution were retrospectively reviewed. We also evaluated two age and gender-matched control groups-patients with normal brain MRI (C1 group) and chronic ventricular shunts (C2 group). The heights of tuberculum sella, dorsum sella, and pituitary gland were measured and compared. The presence or absence of dural thickening was noted. Results21 patients were included in each group. In C2M group, a pituitary adenoma was suggested on 24% of the MRIs. The dorsum sella was significantly smaller in the C2M group (4.8 mm) compared to both the C1 group (7.4 mm, p < 0.001) and the C2 group (7.1 mm, p < 0.001). The pituitary gland was also larger in the cranial-caudal dimension in C2M group (8.6 mm) as compared to both the C1 group (6.6 mm, p < 0.01) and the C2 group (6.0 mm, p < 0.001). One C2M patient with a pituitary gland<10 mm was suggested to have a pituitary adenoma on outside MRI, although a normal pituitary gland was seen on pathology. ConclusionC2M patients have shallow sella which can accentuate the pituitary gland height. The mean pituitary height was larger in C2M patients, but no functional pituitary pathology was present. It is important to consider sella morphology when evaluating the pituitary gland of C2M patients to avoid unnecessary medical and surgical interventions.

Anatomical Assessment of the Endoscopic Assisted Lateral Supraorbital Approach and Endoscopic Endonasal Transclival Approach to Basilar Apex Aneurysms.

To assess the feasibility of using an endoscopic-assisted lateral supraorbital (LSO) approach and an endoscopic endonasal transclival approach (EETA) for basilar apex (BAX) aneurysms. Ten cases with LSO approaches, with or without posterior clinoidectomy and endoscopic assistance, and 10 cases with EETA, with or without drilling of the dorsum sellae, were performed on 20 cadaveric heads. Anatomical exposure and surgical freedom at the BAX were evaluated. Anatomical exposure provided by the LSO approach was limited to the BAX and ipsilateral posterior cerebral artery (PCA) and increased with a mean value of 5.0 mm after posterior clinoidectomy; the basilar artery, contralateral PCA, and superior cerebellar arteries (SCAs) were visualized in all cases. Accordingly, surgical freedom was larger. Endoscopic assistance provided a significant increase in basilar artery exposure; however, surgical freedom did not increase markedly. The main advantage of EETA was the greatest exposure of the basilar artery. With drilling of the dorsum sellae, anatomical exposure increased by a mean value of 3.4 mm, and provided the greatest amount of surgical freedom and visualization of the basilar artery terminal bifurcation and of the SCAs in all cases. The endoscopic-assisted LSO approach and the EETA may represent a feasible approach for treatment of BAX aneurysms lying within 5.0 mm below and within 3.4 mm above the dorsum sellae.

Commentary: Endoscopic Endonasal Transpituitary Gland Approach for Resection of Dorsum Sellae Meningioma - Technical Case Report.

Commentary: Endoscopic Endonasal Transpituitary Gland Approach for Resection of Dorsum Sellae Meningioma - Technical Case Report.

The morphology of Sella Turcica in individuals with different skeletal malocclusions – A cephalometric study

AimsThe aim of the study was to analyze the morphology and expedient the linear dimensions of Sella Turcica among Indian individuals having Skeletal Class I, Class II and Class III pattern, and then to determine if differences exist with different skeletal patterns. Methods and materialThe lateral cephalogram of 150 patients (75 males and 75 females), aged 18–30 years who reported for various treatments of malocclusions were studied. Statistical analysis usedAnalysis were done by ANOVA with Tukey's t-test, SPSS version 17.0 was used. P < 0.05 was considered as significant. ResultsThe normal morphology of the sella turcica were seen in 85 of the 150 individuals which was highest (56.66%) in the study group, an oblique anterior wall was present in 11.33% of the subjects, an irregular dorsum sella and sella turcica bridge were seen in 10% of the subjects, pyramidal shaped sella were seen in 6.66% and 5.33% of the subjects had double-contoured sella turcica. No significant difference between males or females in terms of diameter, depth or length was evident. A significant difference was observed among different skeletal patterns and the diameter of sella. ConclusionsThe normal morphology of the sella turcica was seen in approximately 57% of the individuals. The larger diameter values were seen in the skeletal Class III subjects, while the smaller diameter values were observed in the Class II subjects.

Prevalence and Clinical Implications of the Primitive Trigeminal Artery and its Variants: A Meta-Analysis

The primitive trigeminal artery (PTA) is the most common and the largest persistent carotid-basilar anastomosis. Primitive trigeminal artery variants (PTAVs) are anastomoses between the internal carotid artery and cerebellar arteries. These vessels pose a risk of hemorrhagic or ischemic complications during neurosurgical procedures in the parasellar and intrasellar regions. The aim of this study was to determine the prevalence of both PTA and PTAVs and their clinically important anatomic features. Major electronic databases were thoroughly searched for studies on PTA and PTAV. References in the included articles were also evaluated. Data regarding prevalence, laterality, origin, course patterns, and associated anomalies were extracted and pooled into a meta-analysis. A total of 39 studies (110,866 patients) were included in the meta-analysis. The total pooled prevalence estimate of PTA and PTAVs combined was 0.4% (95% confidence interval [CI], 0.3-0.5). Individually, PTA was present in 0.3% of patients and PTAV in 0.2%. Both arteries most often originated from the C4 internal carotid artery and took a course lateral to the dorsum sellae. The anterior inferior cerebellar artery type was the predominant PTAV (72.1%). Basilar artery hypoplasia was found in 42.5% of patients with a PTA. PTA and PTAVs are rare vessels, but they are clinically important because they can contribute to trigeminal neuralgia. Knowledge of the potential course of these arteries is essential in neuroradiology and neurosurgery, especially in minimally invasive procedures such as the endoscopic endonasal transsphenoidal approach to the pituitary gland and the percutaneous gasserian ganglion procedure.

Dural arteries of the dorsoclival area.

In the literature, there is a lack of complete description of dural arteries of the dorsoclival area with contradictory data. However, dorsoclival area is a site of tumors and vascular malformation or the skull base. That is why, the knowledge of dural arteries is very important. Using a colored silicone mix preparation, fifteen sides of eight cranial bases were studied using 4-20× magnification of the surgical microscope. Dorsoclival area is supplying by three arterial complexes, internal carotid artery complex with always the dorsal meningeal artery for the superior two-third of the clivus, medial clival artery for the dorsum sellae, the external carotid artery complex with the hypoglossal and jugular branches of the ascending pharyngeal artery for the inferior one-third of the clivus, and the vertebral artery complex with the anterior meningeal artery for the most inferior part of the clivus and the anterior edge of the foramen magnum. Moreover, there are many anastomoses between those three arterial complexes at this area. Dural arterial supply of the dorsoclival area is very opulent. Its knowledge is important for surgical approaches and endovascular procedures.

Surgical Nuances of Endoscopic Endonasal Upper Clivectomy for Radical Resection of Central Skull Base Tumors: Two-Dimensional Operative Videos

Abstract INTRODUCTION With routine endoscopic endonasal approach (EEA) for resection of skull base tumors, it is difficult to remove tumors that extend behind the posterior clinoid process (PCP) and dorsum sellae due to the limited exposure. Critical neurovascular structures (internal carotid artery, cavernous sinus, pituitary gland), PCP and dorsum sellae obstruct tumor visualization. Posterior clinoidectomy gives an excellent wider operative view and allows radical resection of tumors in the retrosellar area, prepontine and interpeduncular cisterns. We modified the endoscopic posterior clinoidectomy for safer endonasal extradural posterior clinoidectomy and applied it in 44 patients with parasellar and retrosellar tumors. This is the largest clinical series of endonasal extradural posterior clinoidectomy in which the clinical outcomes were evaluated. METHODS An extradural upper clivectomy (with complete posterior clinoidectomies) following lateral retraction of the paraclival internal carotid artery and extradural pituitary transposition were applied while preserving the blood supply and venous drainage of the pituitary gland. No violation to the cavernous sinuses. In cases with prominent posterior clinoid process, a midline sellar dura cut was added to facilitate its extradural exposure. Forty-four consecutive patients, in whom this technique was performed, between 2016 and 2018 at Osaka City University Hospital, were reviewed. The pathology included 19 craniopharyngiomas, 7 chordomas, 6 meningiomas, 6 pituitary adenomas, 4 chondrosarcomas, and 2 miscellaneous. Utilization and effectiveness of this approach were further demonstrated with neuroimaging. RESULTS On radiological examination, the surgical field was 2.2 times wider in cases with bilateral posterior clinoidectomies than in cases without posterior clinoidectomy. Upper clivectomies were successfully applied in all patients without permanent neurovascular injury, with better maneuverability and greater resection rate of the tumors. Four patients experienced transient postoperative abducens nerve paresis, and one patient experienced transient postoperative oculomotor nerve paresis; nevertheless, the deficits recovered within 3 mo. CONCLUSION The extended EEA with extradural upper clivectomy creates an extra-working space and allows adequate accessibility with safe surgical maneuverability to remove tumors that extend behind the posterior clinoid and dorsum sellae.

Clinical classification of clival chordomas for transnasal approaches.

Endoscopic endonasal approaches (EEAs) are ideal for most chordomas, but there is little information regarding the practical clinical classification of clival chordomas to guide surgery with EEAs. This article investigates a relatively concise and practical clinical classification system for clival chordomas and summarizes the clinical characteristics and operative key points of different clinical types. Here, 55 patients with clival chordomas treated through EEAs from 2012 to 2017 were retrospectively reviewed. Depending on the origin of the notochord and the growth pattern of the tumor, with our introduced Wang's line, these cases of clival chordoma were divided into types I-IV. There were 14 cases of type I-A, 7 cases of type I-B, 10 cases of type II, 10 cases of type III-A, 7 cases of type III-B, and 7 cases of type IV. The gross total resection (GTR) rate of primary and recurrent type I tumors was 64% and 25%, and residual tumors were found mainly in cases with involvement of the cavernous sinus or the posterior upper part of the dorsum sella. The GTR rate of primary and recurrent type II tumors was 85% and 66.6%, respectively. Residual tumors were found in cases with involvement of the petrous apex. The GTR rate of primary and recurrent type III tumors was 75% and 20%, and residual tumors were found in cases with involvement of the parapharyngeal space and dorsal side of C1-2. Residual type I-B and type III-B tumors were found when there was BA or VA adhesion or brain stem invasion. Our new classification method proposed here can be used to guide the resection of clival chordomas through EEAs.

Surgical implementation and efficacy of endoscopic endonasal extradural posterior clinoidectomy.

The endoscopic endonasal approach (EEA) for skull base tumors has become an important topic in recent years, but its use, merits, and demerits are still being debated. Herein, the authors describe the nuances and efficacy of the endoscopic endonasal extradural posterior clinoidectomy for maximal tumor exposure. The surgical technique included extradural posterior clinoidectomy following lateral retraction of the paraclival internal carotid artery and extradural pituitary transposition. In cases with prominent posterior clinoid process, a midline sellar dura cut was added to facilitate extradural exposure. Forty-four consecutive patients, in whom this technique was performed between 2016 and 2018 at Osaka City University Hospital, were reviewed. The pathology included 19 craniopharyngiomas, 7 chordomas, 6 meningiomas, 6 pituitary adenomas, 4 chondrosarcomas, and 2 miscellaneous. Utilization and effectiveness of this approach were further demonstrated with neuroimaging. Extradural posterior clinoidectomies were successfully applied in all patients without permanent neurovascular injury and with better maneuverability and greater resection rate of the tumors. Four patients experienced transient postoperative abducens nerve paresis, and 1 patient experienced transient postoperative oculomotor nerve paresis; however, the patients with deficits recovered within 3 months. On radiological examination, the surgical field was 2.2 times wider in cases with bilateral posterior clinoidectomy than in cases without posterior clinoidectomy. The extended EEA with extradural posterior clinoidectomy creates an extra working space and allows adequate accessibility with safe surgical maneuverability to remove tumors that extend behind the posterior clinoid and dorsum sellae.

The braincase of Syllomus aegyptiacusLydekker, 1899 (Reptilia, Testudines) from the Middle Miocene Calvert Formation of Virginia

The braincase of the marine turtle Syllomus aegyptiacus (Calvert Formation, Virginia, Middle Miocene) is described and figured in detail for the first time. It reveals a ventral crest on the basisphenoid, a high dorsum sellae, an almost subequal diameter of the canals for the internal and lateral carotid arteries at a cross break and a canalis caroticus lateralis and internus that are still far separated from each other at level of the dorsum sellae. The braincase is compared to other known braincases of fossil and extant chelonioid turtles.