Causes of Pulsatile Tinnitus and Treatment Options.

Pulsatile tinnitus (PT) requires detailed workup to evaluate for an underlying structural cause. With advances in neuroimaging, structural venous abnormalities that can cause PT have becoming increasingly recognized. A number of anomalies, including dural arteriovenous fistulas, idiopathic intracranial hypertension, transverse sinus stenosis, sigmoid sinus wall abnormalities, jugular venous anomalies, and hypertrophied emissary veins, have been implicated in flow disruption and turbulence in the vicinity of auditory structures, resulting in PT. Endovascular treatment options, including stenting, coiling, and embolization with liquid agents, have demonstrated high efficacy and safety. These treatments can lead to symptomatic relief in carefully selected cases.

The sphenopterygoid canal and pterygoid foramen.

BACKGROUND: In human anatomy, there are well-known the foramina of the greater sphenoidal wing, the foramen rotundum, the foramen ovale, the foramen spinosum, as well as the inconstant sphenoidal emissary foramen of Vesalius and the foramen of Arnold. Different canals are found in several species of rodents, such as the alisphenoid and sphenopterygoid (SPC) canals. METHOD: It was re-explored an archived computed tomography angiogram of a 60 y.o. female case. RESULTS: Bilateral superior recesses of the pterygoid fossae (SRPF) and a right SPC were found. The SRPF on each side penetrated the non-lamellar pterygoid root and superiorly reached the sphenoidal sinus wall. Upper fibres of medial pterygoid muscles were inserted into each SRPF. An unexpected SPC was found on the right side. It opened superiorly on the lateral side of the foramen rotundum and inferiorly at a pterygoid foramen in the superior end of the posterior margin of the lateral pterygoid plate. A sphenoidal emissary vein traversed that SPC to drain into the pterygoid plexus. CONCLUSION: The SRPF and SPC could also be found in humans. As the sphenoidal emissary veins are surgically relevant, they should not be further regarded as exclusively crossing the foramen of Vesalius but also the SPC.

Occipital emissary vein existence and its impact on the diagnosis of idiopathic intracranial hypertension in pediatric patients.

PURPOSE: This study aimed to investigate the efficacy of occipital emissary vein (OEV) detection in the diagnosis of idiopathic intracranial hypertension (IHH) in the pediatric age group, and to compare the prevalence and luminal diameter of OEV in patients with IHH and in healthy control subjects. METHODS: Conventional magnetic resonance imaging findings were assessed in the patients with IHH and in healthy control subjects who were under the age of 18, by two observers. The presence and luminal dimension of OEV and transverse sinus stenosis were also evaluated and compared between these two groups with magnetic resonance venography techniques. RESULTS: The rate of OEV existence was 7 times higher in the IIH group compared to the control group based on the second observer outcome (p = 0.010, OR = 7.0), with a very good interobserver agreement (Ƙ = 0.85). The dimension of OEV ranged between 0.6 and 2.5 mm. There was no correlation found between the opening pressure and the dimension of OEV (p = 0.834). CONCLUSION: In conclusion, OEV existence could be an additional radiological finding for diagnosing IHH among pediatric patients, alongside other conventional findings.

Arteriovenous malformation with unique drainage through the emissary vein of the foramen ovale: illustrative case.

BACKGROUND: As part of the laterotrigeminal venous system (LTVS), the emissary vein of the foramen ovale (EVFO) is an underrecognized venous structure communicating between the cavernous sinus and pterygoid plexus. The sphenobasal sinus is an anatomical variation of the sphenoparietal sinus that drains directly into the EVFO. The authors present the case of a ruptured arteriovenous malformation (AVM) with a unique drainage pattern through the sphenobasal sinus and EVFO. OBSERVATIONS: A 9-year-old female initially presented with loss of consciousness and was subsequently found to have a ruptured AVM in the left basal frontal area. She underwent an immediate decompressive hemicraniectomy, with a computed tomography angiogram demonstrating a unique anatomical variation in which the sphenobasal sinus communicated with the EVFO and LTVS. The final venous drainage returned to the pterygoid plexus and external jugular vein. Postoperatively, the patient made a substantial recovery, with generalized right-sided weakness remaining as the sole deficit. LESSONS: The authors present the case of a ruptured AVM with unique venous drainage into the sphenobasal sinus and EVFO, for which the current literature remains limited. As exemplified by this illustrative case, technique modification may be warranted in the setting of this unique anatomical variation to avoid venous sinus injury.

An anatomical study of the sigmoid sinus artery: Application to the transmastoid approach.

INTRODUCTION: We aimed to investigate the morphological features of the artery that traverse the sigmoid sinus's lateral surface and to discuss this structure's clinical relevance. METHODS: Ten sides from five cadaveric Caucasian heads were used for gross anatomical dissection to investigate the morphological features of the sigmoid sinus artery (SSA), and additional five sides were used for histological observation. RESULTS: The SSA was found on eight out of ten sides (80%). The mean diameter of the SSA was 0.3 mm. The mean distance from the tip of the mastoid process to the artery was 20.3 mm. Histological observation identified extradural and intradural courses of SSA. The intradural course was further categorized into protruding and non-protruding types. In the protruding type, the SSA traveled within the dura but indented into the bone, making it more or less an intraosseous artery. In the non-protruding type, the SSA traveled within the dura but did not protrude into the bone but rather indented into the lumen of the SS. In all sections, both intradural and extradural courses were identified simultaneously. CONCLUSIONS: When the mastoid foramen is observed, it does not always only carry an emissary vein but also an artery. The SSA could be considered a "warning landmark" during bone drilling for the transmastoid approach.

Anatomical study of the mastoid foramina and mastoid emissary veins: classification and application to localizing the sigmoid sinus.

The mastoid foramen (MF) is located on the mastoid process of the temporal bone, adjacent to the occipitomastoid suture or the parietomastoid suture, and contains the mastoid emissary vein (MEV). In retrosigmoid craniotomy, the MEV has been used to localize the position of the sigmoid sinus and, thus, the placement of the initial burr hole. Therefore, this study aimed to examine the exact location and variants of the MF and MEV to determine if their use in localizing the sigmoid sinus is reasonable. The sample in this study comprised 22 adult dried skulls (44 sides). MF were identified and classified into five types based on location, prevalence, whether they communicated with the sigmoid sinus and exact entrance into the groove of the sigmoid sinus. The diameters and relative locations of the MF in the skull were measured and recorded. Finally, the skulls were drilled to investigate the course of the MEV. Additionally, ten latex-injected sides from human cadavers were also dissected to follow the MEV, especially in cases with more than one vein. We found that type I MFs (single foramen) were the most prevalent (50%). These MFs were mainly located on the occipitomastoid suture; only one case on the right side was adjacent to the parietomastoid suture. Type II (paired foramina) was the second most prevalent (22.73%), followed by type III (13.64%), type 0 (9.09%), and type IV (4.55%). The diameter of the external opening in a connecting MF (2.43 ± 0.79) was twice that of a non-connecting MF (1.14 ± 0.56). Interestingly, on one side, two MFs on the external surface shared a single internal opening; the MEV bifurcated. MFs followed three different courses: ascending, almost horizontal, and descending. Regardless of how many external openings there were for the MF, these all ended at a single opening in the groove for the sigmoid sinus. For cadaveric specimens with multiple MEVs, all terminated in the sigmoid sinus as a single vein, with the more medial veins terminating more medially into the sinus. Based on our study, the MF/MEV can guide the surgeon and help localize the deeper-lying sigmoid sinus. Knowledge of this anatomical relationship could be an adjunct to neuronavigational technologies.

Prevalence, morphology, morphometry and associated clinical implications of mastoid emissary veins: narrative review.

The mastoid emissary vein connects the posterior auricular vein to the sigmoid sinus and varies in size, number, location, and course, resulting in clinical complications. This study was conducted in response to the vast clinical implications associated with this vein. The aim of this review is to highlight and describe the prevalence, varied morphology, and morphometry of the mastoid emissary vein, how these varied parameters cause clinical complications, and how these can be rectified and avoided. A literature survey was conducted using various databases and different terms related to mastoid emissary vein were used to search the literature. Pitfalls related to surgery in the vicinity of this vein and their remedies were elucidated. The literature search revealed that the prevalence, morphology, and morphometry of mastoid emissary veins vary immensely and are responsible for morbidity and mortality. Pre-operative identification of mastoid veins is thus essential and so multidetector computed tomography of the temporal bone should be scheduled before planning surgery.

A veia emissária mastóidea que conecta a veia auricular posterior ao seio sigmoide pode variar em tamanho, número, localização e curso, resultando em complicações clínicas. O objetivo desta revisão é destacar e descrever a prevalência, variação morfológica e morfometria da veia emissária mastóidea, além de como esses parâmetros causam complicações clínicas e como corrigi-las e reduzi-las. Foram conduzidas buscas em diversas bases de dados utilizando diferentes termos relacionados à veia emissária mastóidea. As armadilhas relacionadas a procedimentos cirúrgicos realizados nas proximidades dessa veia e as respectivas soluções foram descritas. A pesquisa na literatura revelou que a prevalência, a morfologia e a morfometria da veia emissária mastóidea variam imensamente, sendo responsáveis ​​por alta morbidade e mortalidade. Portanto, a identificação da veia mastóidea deve ser realizada no pré-operatório através de tomografia computadorizada multidetectores do osso temporal, antes do planejamento cirúrgico.

Preservation of Enlarged Mastoid Emissary Vein during Microvascular Decompression for Trigeminal Neuralgia Accompanied by Abnormal Venous Drainage: A Technical Case Report.

During microvascular decompression (MVD) for trigeminal neuralgia (TGN), the mastoid emissary veins (MEV) are routinely sacrificed using the suboccipital retrosigmoid approach. The technical nuances when the MEV is an important collateral venous pathway for the obstructive internal jugular vein (IJV) have not been described thus far. Herein, we demonstrate for the first time a modified surgical technique for MVD to preserve the MEV. A 62-year-old man with a 10-year history of TGN refractory to carbamazepine was referred to our hospital for MVD. Preoperative imaging revealed that the superior cerebellar artery was the offending vessel. Computed tomography angiography also revealed that his contralateral IJV pathway was hypoplastic, and the ipsilateral pathway was severely stenosed by the external compression of the elongated styloid process and the transverse process of the first cervical vertebra. The ipsilateral MEV and the connecting occipital veins were enlarged as the sole collateral pathways of intracranial venous drainage. A modified MVD technique, including an upside-down L-shaped skin incision, layer-by-layer dissection of the occipital muscles, and denuding of the intraosseous part of the MEV, was used to cure the TGN with the preservation of the venous pathway. After surgery, the pain completely diminished without any complications. In conclusion, such technical modifications would be applicable in cases where the MEV needs to be preserved during posterior fossa surgery. Preoperative screening of the venous system is also recommended.

Osteological Study of the Parietal Foramen in the Adult Human Skull Bones and its Clinical and Surgical Correlations / Estudio Osteológico del Foramen Parietal en los Huesos del Cráneo Humano Adulto y sus Correlaciones Clínicas y Quirúrgicas

SUMMARY: Parietal emissary foramina (PEF) are small holes, which are localized between the middle and posterior thirds of the parietal bone posterior surface close to the sagittal suture. PEF are important structures that protect the parietal emissary vein, which passes through it. During neurosurgery procedures, parietal foramina (PF) knowledge is crucial. This work aimed to evaluate presence and location of the PF in the skull of an adult human. Moreover, measure the distance amidst PF and the sagittal suture's midline to ascertain its clinical repercussions. 74 adult human skulls, without gross pathology, were observed for the PF's existence. The PF's and sagittal suture's midline distance were measured. According to the PF patterns of presence, five groups were distributed. Finally, specimens were photographed and subjected to statistical analysis. The PF was absent in 7 skulls (9.5 %). There were 9 skulls (12.2 %) exhibited central parietal foramen where the parietal foramen lies on the sagittal suture. 17 skulls (23 %) showed right unilateral parietal foramen, whereas 15 skulls (20.3 %) demonstrated left unilateral parietal foramen. The final 26 skulls (35.1 %) exhibited bilateral parietal foramen. This descriptive study supplies valuable information of PF variations, which is crucial for neurosurgeons in modifying surgical techniques and procedures to alleviate injury to PF-emerging structures such as emissary veins.

Los forámenes emisarios parietales (FEP) son pequeños orificios que se localizan entre los tercios medio y posterior de la superficie posterior del hueso parietal, cerca de la sutura sagital. Los FEP son estructuras importantes que protegen la vena emisaria parietal, que lo atraviesa. Durante los procedimientos de neurocirugía, el conocimiento de los forámenes parietales (FP) es crucial. Este trabajo tuvo como objetivo evaluar la presencia y ubicación del FP en el cráneo de hombres adultos, además, medir la distancia entre el FP y la línea mediana de la sutura sagital para conocer su repercusión clínica. Se examinaron 74 cráneos humanos adultos, sin patología grave, para determinar la existencia del FP. Se midió la distancia de la línea mediana de la sutura sagital y del FP. De acuerdo con los patrones de presencia del FP, se distribuyeron en cinco grupos. Finalmente, los especímenes fueron fotografiados y sometidos a análisis estadístico. El PF estaba ausente en 7 cráneos (9,5 %). Hubo 9 cráneos (12,2 %) que presentaban un PF central localizándose en la sutura sagital. 17 cráneos (23 %) presentaban un FP unilateral derecho, mientras que 15 cráneos (20,3 %) se observó un FP unilateral izquierdo. Los 26 cráneos restantes (35,1 %) exhibieron FP bilaterales. Este estudio descriptivo proporciona información valiosa sobre las variaciones del FP, que es fundamental para los neurocirujanos en el momento de modificar las técnicas y los procedimientos quirúrgicos para aliviar las lesiones de las estructuras emergentes del FP, como las venas emisarias.

Clinical applications of the mastoid emissary vein.

PURPOSE: During retrosigmoid craniotomy, the mastoid emissary vein (MEV) can be a source of considerable bleeding during the operation, especially when the larger diameter MEV or sigmoid sinus is torn. In this study, we evaluated the relevant structure of the MEV for their anatomy and applied the data in surgery to summarize their clinical significance. METHODS: The posterior craniocervical regions of 15 silicon-injected Chinese human cadaver specimens were dissected to expose the MEV and adjacent structures. Fifty-one patients who were scheduled to undergo retrosigmoid craniotomy were selected. All patients underwent preoperative routine CT of the head. The relevant data were collected on cadaveric anatomy and CT. Eventually, all patients underwent retrosigmoid craniotomy and the MEV was observed during the operation. RESULTS: In cadaver specimens, the prevalence of the MEV was 90.0%. It originated from the middle and lower parts of the posterior wall of the sigmoid sinus and extended in the posterior direction in the mastoid process, usually having 1-2 external openings (86.7%) and only 1 internal opening. The intraosseous courses of the MEV were classified as straight and curved. The straight type accounted for 57.9%, and the curved type for 42.1%. The mean diameter of the MEV was 1.84 ± 0.85 mm, and the straight length of the MEV inside the mastoid process was 11.93 ± 3.58 mm. In 16.7% and 6.7% of all cadaver specimens, the MEV diameter was greater than 2.5 and 4 mm, respectively. In 51 patients (bilateral), routine head CT scan showed the MEV in 49.0% of the patients, and the MEV diameter was greater than 2.5 and 4 mm, respectively, in 17.6% (18/102) and 3.9% (4/102) of the cases. During surgery (unilateral) in the 51 patients, 48 had the MEV and 3 had no MEV. None of the patients had sigmoid sinus tears or massive bleeding. CONCLUSION: In the process of retrosigmoid craniotomy, detailed anatomical knowledge of the MEV, well-planned CT scan, and meticulous microsurgical techniques are key for successful operation, which can reduce the occurrence of complications.

Prevalence, morphology, morphometry and associated clinical implications of mastoid emissary veins: narrative review / Prevalência, morfologia, morfometria e implicações clínicas das veias emissárias mastóideas: uma revisão narrativa

Abstract The mastoid emissary vein connects the posterior auricular vein to the sigmoid sinus and varies in size, number, location, and course, resulting in clinical complications. This study was conducted in response to the vast clinical implications associated with this vein. The aim of this review is to highlight and describe the prevalence, varied morphology, and morphometry of the mastoid emissary vein, how these varied parameters cause clinical complications, and how these can be rectified and avoided. A literature survey was conducted using various databases and different terms related to mastoid emissary vein were used to search the literature. Pitfalls related to surgery in the vicinity of this vein and their remedies were elucidated. The literature search revealed that the prevalence, morphology, and morphometry of mastoid emissary veins vary immensely and are responsible for morbidity and mortality. Pre-operative identification of mastoid veins is thus essential and so multidetector computed tomography of the temporal bone should be scheduled before planning surgery.

Resumo A veia emissária mastóidea que conecta a veia auricular posterior ao seio sigmoide pode variar em tamanho, número, localização e curso, resultando em complicações clínicas. O objetivo desta revisão é destacar e descrever a prevalência, variação morfológica e morfometria da veia emissária mastóidea, além de como esses parâmetros causam complicações clínicas e como corrigi-las e reduzi-las. Foram conduzidas buscas em diversas bases de dados utilizando diferentes termos relacionados à veia emissária mastóidea. As armadilhas relacionadas a procedimentos cirúrgicos realizados nas proximidades dessa veia e as respectivas soluções foram descritas. A pesquisa na literatura revelou que a prevalência, a morfologia e a morfometria da veia emissária mastóidea variam imensamente, sendo responsáveis ​​por alta morbidade e mortalidade. Portanto, a identificação da veia mastóidea deve ser realizada no pré-operatório através de tomografia computadorizada multidetectores do osso temporal, antes do planejamento cirúrgico.

Radiological and Morphometric Study of the Emissary Foramens and Canal in the Posterior Cranial Fossa of the Human Skull with Its Neurosurgical Significance.

Objective The posterior condylar canals (PCCs), posterior condylar veins (PCVs), occipital foramen (OF), and occipital emissary vein (OEV) are potential anatomical landmarks for surgical approaches through the lateral foramen magnum. We performed the study to make morphometric and radiological analyses of the various emissary foramens and vein in the posterior cranial fossa. Methods Morphometric study were performed on 95 dry occipital bones and radiological analyses on computed tomography (CT) angiography images of 150 patients. The number of OFs on both sides was recorded and PCC length and mean diameters of the internal and external orifices of PCC were measured for bony specimens. Prevalence of PCV and PCV size was investigated using CT angiography. Results Mean PCC length was higher in the left side (9.85 ± 2.5). Mean diameter of the internal orifice and the external orifice diameter were almost the same. The majority of PCCs (75-79.33%) had 2 to 5 mm diameter; only 4 to 9.2% were small in size (< 2 mm). In CT angiography, PCV was not identified in 23 (15.33%) patients. PCVs were located bilaterally in 105 (70%) and unilaterally in 22 (20.5%) patients. Only 11.3% of PCVs were large in size (> 5 mm), 80% of PCVs were medium sized (2-5 mm), and 8.6% were small sized (< 2 mm). Conclusion Normal values of OF, PCC, PCV, and OEV could serve as a future reference for the understanding of the physiology of craniocervical venous drainage, which is necessary to avoid surgical complications and can also serve as a guide to surgical interventions for pathologies of the posterior cranial fossa, such as tumors and injuries.

Aberrant drainage of posterior condylar emissary vein and abnormal orifice of hypoglossal canal: surgical implications in the transcondylar fossa approach for VA-PICA junction aneurysm.

BACKGROUND: The posterior condylar emissary vein (PCEV) and posterior condylar canal (PCC) are anatomical landmarks for identifying important structures like jugular tubercle and occipital condyle in surgical approach to the foramen magnum and condylar fossa. Several anatomical variations have been described. Drainage into the jugular bulb is found to be commonest. METHOD: A 70-year-old patient with unruptured vertebral artery-posterior inferior cerebellar artery (PICA) junction aneurysm-underwent surgical clipping via transcondylar fossa approach. RESULT: Preoperative computed tomography demonstrated an abnormal communication existed between the left-sided PCC and hypoglossal canal (HC). The PCEV was identified draining into a dilated venous channel/pouch at the "hip" of sigmoid sinus (junction of sigmoid sinus and jugular bulb). Intra-operatively, an occipital artery-PICA bypass was performed. The PCEV was skeletonized, coagulated, and divided to achieve hemostasis. The lateral and cranial drilling around PCC was successful at safeguarding the underlying contents of HC (in medial and caudal extent). CONCLUSION: Preoperative angiography and detailed morphometric analysis of the PCC were helpful in planning surgical approach-identifying and controlling the PCEV, and skeletonization of the PCC without compromising the hypoglossal nerve and anterior condylar emissary vein.

Characteristics and Management of Dilated Mastoid Emissary Veins: A Case Report and Literature Review.

INTRODUCTION: The mastoid emissary vein (MEV) describes a transosseous connection between the sigmoid dural venous sinus and the suboccipital venous plexus. In cases of outflow stenosis or malformation, the MEV may become dilated and a source of pulsatile tinnitus (PT) amenable to treatment. We describe a case of PT secondary to MEV treated successfully via endovascular coil embolization and conduct a systematic review of the literature. METHODS: We performed a systematic review without meta-analysis of studies involving management of dilated MEV on January 14, 2022, and describe a case of PT secondary to an enlarged MEV treated via coil embolization. RESULTS: A total of 13 studies were selected for full review. Reports identified MEV presenting as PT in 60% (12 of 20) of cases, intraoperative hemorrhage in mastoid surgery in 15% (3 of 20), a compressive scalp mass in 10% (2 of 20), and thrombophlebitis, facial swelling, or an incidental finding in 5% (1 of 20) each. Forty-five percent (9 of 20) underwent treatment, with all experiencing symptom resolution or improvement. Surgery included transvenous coil embolization in 33.3% (3 of 9), flap reconstruction in 22.2% (2 of 9), and surgical packing, ligation, and thrombectomy in 11.1% (1 of 9) each. Dilated MEV was reported concurrently with impeded drainage pathways in 35% (7 of 20) of reports. CONCLUSIONS: Dilated MEV has been reported as an etiology of pulsatile tinnitus and appears amenable to treatment via open and endovascular means. Endovascular coil embolization appears to offer effective symptom resolution, however, available literature exists only in case reports and small series. Further investigation is highly warranted.

Bilateral Pulsatile Tinnitus Caused by Bilateral Dilated Mastoid Emissary Vein.

Pulsatile tinnitus is a rhythmic type of tinnitus. Most cases are caused by vascular disorders and present as synchronous with the patient's heartbeat. A dilated mastoid emissary vein may cause pulsatile tinnitus. Here, we report the first case of bilateral pulsatile tinnitus caused by dilated bilateral mastoid emissary vein. The patient suffered from bilateral pulsatile tinnitus for 2 years. His bilateral tinnitus disappeared temporarily when the bilateral mastoid processes were compressed. Temporal bone computed tomographic (CT) showed the bilateral dilated mastoid emissary canals. Cranial Magnetic resonance venograms (MRV) showed the bilateral dilated mastoid emissary veins. We explained the risk of surgery to the patient. Because the patient could tolerate his tinnitus and did not have a hemangioma or tumor, he did not choose to undergo surgery.

Introducing the Posterior Condylar Emissary Vein as an Effective Surgical Landmark for Optimizing the Standard Retrosigmoid Approach: An Anatomo-Imaging Study.

OBJECTIVE: There is a lack of definite anatomical landmarks for the inferior extension of the standard retrosigmoid approach. In this study, we evaluated whether the posterior condylar emissary vein (PCEV) can be used as an intraoperative landmark for optimizing the surgical corridor. METHODS: We performed the standard retrosigmoid approach on 5 formalin-fixed and latex-injected cadaveric specimens and measured the distance between the PCEV near its bony canal and the vertebral artery (VA). In addition, vascular reconstructions of thin-sliced preoperative computed tomography (CT) scans were studied in 40 patients and the relationship between these 2 vessels was evaluated. An illustrative case is also included. RESULTS: The PCEV was consistently identified on both sides of cadaveric specimens and in 87.5% and 82.5% of the left and right sides of the included CT scans, respectively. The average distance between the part of the PCEV near its osseous canal and the VA was measured to be between 8.4 mm and 8.6 mm in the specimens and between 9.2 mm and 9.3 mm in the CT scans. This distance offers a safe and effective plane of dissection during the standard retrosigmoid approach and allows easy access to the foramen magnum. CONCLUSIONS: The PCEV near its bony canal proved to be an easy, straightforward, safe, and effective operative landmark with which the surgeon can extend the soft tissue dissection and bony exposure towards the foramen magnum. This maneuver provides ample access to the cisterna magna for cerebrospinal fluid drainage and increases visibility and surgical maneuverability to the entire cerebellopontine angle.

Anatomical observation and significance of the parietal foramen in Chinese adults.

BACKGROUND: This study aimed to investigate the incidence, number, diameter, and relative location of the parietal foramen (PF) as well as communication of intracranial and extracranial orifices and their direction, and sagittal suture morphology and length. MATERIALS AND METHODS: A total of 280 dry Chinese adult skull specimens from the Department of Anatomy, Southern Medical University, were observed and measured. The occurrence rate and quantity of the PF near the sagittal suture were recorded. The aperture of the PF, the vertical distance between PF and sagittal suture, and the linear distance between PF and lambda were measured using a Vernier calliper. The length of the sagittal suture was measured by a flexible ruler; the direction and communication of intracranial and extracranial orifices were detected using a probe. RESULTS: The total incidence of the PF was 82.86%, slightly higher on the right side than on the left side. The single-foramen type was the most prevalent. The mean diameter of the PF on the left and right sides were 1.02 ± 0.72 mm and 1.07 ± 0.67 mm, respectively, and the diameter of the PF on the sagittal suture was 1.77 ± 0.44 mm. The mean vertical distance between the PF and the sagittal suture was 5.90 ± 2.78 mm and 5.85 ± 2.75 mm on the left and right sides, respectively. The shape of the sagittal suture in the PF area was primarily dentate shaped, with an average arc length of χ = 124.36 ± 7.76 mm, of which the majority were completely healed type. The intracranial and extracranial communication was 39.97%, and the majority of the PF were anteromedial direction. CONCLUSIONS: The current study provided an anatomical basis for imaging diagnosis and neurosurgery by investigating the incidence, diameter, and relative location of the PF and intracranial and extracranial communication and direction.

Transcondylar Fossa Approach for Resection of Anterolateral Foramen Magnum Meningioma: 2-Dimensional Operative Video.

Among the posterolateral corridors to the ventral foramen magnum (FM), the transcondylar fossa (supracondylar transjugular tubercle) approach (TCFA) is indicated for lesions lying anteriorly to the dentate ligament and above the jugular foramen and hypoglossal canal.1-13 It involves the drilling of the condylar fossa, namely the exocranial surface of the jugular tubercle. Despite the anatomic variability of the condyle and posterior condylar emissary vein,14,15 they are important landmarks for the TCFA. The extradural jugular tuberculectomy has no risk of iatrogenic mechanical instability compared with the transcondylar approach. This 2-dimensional operative video (Video 1) aims to show the key technical aspects of the TCFA through the case description of an anterolateral FM meningioma. A 35-year-old male patient with a left anterolateral FM meningioma underwent TCFA in a semisitting position. Drilling of the condylar fossa led to an extradural resection of the jugular tubercle. Posterior condylar emissary veins connecting the sigmoid sinus/jugular bulb with the vertebral venous plexus marked the lateral limit of the approach. Through a suprahypoglossal working corridor, the meningioma was debulked and dissected. Postoperative magnetic resonance imaging confirmed complete resection of the tumor, and the patient was discharged neurologically intact on the third postoperative day. TCFA is a valuable technical option for selected anterolateral FM meningiomas. The perfect knowledge and intraoperative use of specific anatomic landmarks are critical to safely perform the TCFA while maximizing the exposure of the surgical target and decreasing the risk of postoperative mechanical instability of the craniovertebral junction.