Transosseous Veins of the Temporal Bone: Connection Between Middle and Posterior Cranial Fossa Venous Structures.

BACKGROUND: The veins and dural venous sinuses of the skull base are important to understand in terms of imaging findings, diagnoses, and surgery. However, to date and to the best of our knowledge, the transosseous veins of the petrous part of the temporal bone have not been studied. METHODS: Ten latex-injected adult cadaveric specimens (20 sides) were dissected to identify the intraosseous and transosseous veins. The petrous part of the temporal bone was drilled away, and the petrous part of the internal carotid artery and the veins of the middle and posterior cranial fossa adjacent to the petrous part of the temporal bone were exposed. RESULTS: Transosseous veins traveling through the petrous part of the temporal bone were identified on all 20 sides. In general, these were most concentrated near the anterior and posterior parts of the petrous part of the temporal bone. Most traveled more or less vertically from the petrous ridge and related superior petrosal sinus internally through the petrous part of the temporal bone toward the inferior petrosal sinus or horizontally, uniting the veins of the floor of the middle cranial fossa with the veins of the posterior cranial fossa. These transosseous veins connected the veins in the middle cranial fossa with the veins of the posterior cranial fossa. Most (70%) of these transosseous veins were also found to have small connections to the internal carotid venous plexus. CONCLUSIONS: To the best of our knowledge, previous studies have not reported on transosseous veins of the temporal bone or described their anatomy of connecting the veins of the middle and posterior cranial fossae.

Prenatal visualisation of the torcular herophili by means of a Doppler technology highly sensitive for low-velocity flow in the expert assessment of the posterior fossa: a prospective study.

OBJECTIVE: To evaluate the usefulness of a Doppler technology highly sensitive for low-velocity flow in the antenatal imaging of the torcular herophili (TH) in the second trimester of pregnancy. DESIGN: Prospective study. SETTING: Referral Fetal Medicine Unit. POPULATION: Non-consecutive series of singleton pregnancies submitted to antenatal neurosonogram between 20 and 28 weeks of gestation. METHODS: A midsagittal section of the fetal brain was obtained by insonating through the anterior fontanelle, then the MV-Flow™ and LumiFlow™ presets were selected to visualise the TH as the posterior confluence of the superior sagittal sinus and the straight sinus. MAIN OUTCOME MEASURES: Evaluation of the anatomic relationship of the TH with the 'transpalatal line' joining the upper bony palate to the fetal skull. RESULTS: A total of 99 pregnant women were recruited, including one fetus with open spina bifida, one with Dandy-Walker malformation (DWM) and two with Blake's pouch cysts. In normal fetuses, the TH appeared to lie on or just below the 'transpalatal line'. In the cases of Blake's pouch cyst, the position of the TH appeared normal if compared with controls, whereas in DWM a supra-elevated position of the TH in respect of the transpalatal line was demonstrated. Finally, in the fetus with Chiari II malformation the TH was identified below the 'transpalatal plane'. CONCLUSIONS: Prenatal ultrasound visualisation of the TH by means of newly developed Doppler technologies characterised by high sensitivity for low-velocity flow is feasible and allows the indirect evaluation of the insertion of cerebellar tentorium in the second trimester. TWEETABLE ABSTRACT: Prenatal imaging of the torcular herophili using a Doppler technology highly sensitive for low-velocity flow.

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, 20 mm 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.

Lateral nasal wall flap for endoscopic reconstruction of the skull base: anatomical study and clinical series.

BACKGROUND: The lateral nasal wall (LNW) flap provides vascularized endonasal reconstruction primarily in revision surgery. Although the harvesting technique and reconstructive surface have been reported, the arterial supply to the LNW flap and its clinical implications is not well defined. This study presents anatomical dissections to clarify the vascular supply to this flap, and the associated clinical outcomes from this reconstructive technique. METHODS: The course and branching pattern of the sphenopalatine artery (SPA) to the LNW were studied in 6 vascular latex-injected heads (11 LNW flaps total). Patients undergoing an LNW flap since 2008 were identified and the underlying pathology, indication, flap viability, and clinical outcomes were retrospectively analyzed. RESULTS: The inferior turbinate artery arises from the LNW artery and divides into 2 branches at the most posterior aspect of the inferior turbinate bone. A smaller-caliber superficial branch travels anteriorly and branches to the LNW. A larger dominant branch travels into the inferior meatus and tangentially supplies the nasal floor. Twenty-four patients with sellar or posterior cranial fossa (PCF) defects were reconstructed with an LNW flap. Postoperative contrast enhancement of the LWN flap was identified in 95.5% of cases. Postoperative cerebrospinal fluid (CSF) leaks were identified in 6 cases. CONCLUSION: Blood supply to the nasal floor by the dominant inferior meatus branch is more robust than the supply to the anterior LNW by the superficial arterial branch. The LNW flap is the preferred vascularized reconstructive option to the PCF and sella in the absence of a nasoseptal flap (NSF).

Dural arteries of the dorsoclival area.

OBJECTIVE: 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. METHODS: Using a colored silicone mix preparation, fifteen sides of eight cranial bases were studied using 4-20× magnification of the surgical microscope. RESULTS: 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. CONCLUSION: Dural arterial supply of the dorsoclival area is very opulent. Its knowledge is important for surgical approaches and endovascular procedures.

Clivus Hemangioma in a Pediatric Patient: Case Report.

BACKGROUND: Hemangiomas are benign blood vessels tumors that represent less than 1% of all the bone neoplasms. Calvarial hemangiomas are mainly solitary lesions commonly located in the frontal and parietal bone; however, they may occur in any skull region. These tumors increase in size over a period of months to years before they start showing their first symptoms such as headache, bone deformity, and pathological fractures. Differential diagnosis with osteosarcoma should be considered. Surgical resection with a safety margin is a standard treatment of the cranial hemangioma. Furthermore, radiotherapy has proven to stop the tumor's growth but not its size. CASE DESCRIPTION: We treated an 11-year-old male who had a rare case of a capillary hemangioma located in the clivus bone. The patient underwent 2 endoscopic endonasal resection because of tumor recurrence. Surgical safety margins are highly recommended, but this procedure could not be performed because of the tumor's location. After the second relapse, the oncology team decided to initiate radiotherapy. At 6-month follow-up, the tumor reduced its size and remained unchanged. CONCLUSIONS: Surgical safety margins are highly important to prevent recurrence in this type of bone tumors. Skull base hemangiomas are a big challenge when you want to achieve these safety margins. We believe that a combined treatment of surgery and radiotherapy should be considered as the main treatment.

Emissary veins prevalence and evaluation of the relationship between dural venous sinus anatomic variations with posterior fossa emissary veins: MR study.

PURPOSE: The aim of this study was to find the prevalence of emissary veins and to compare the visibility of these emissary veins with the anatomic variations of the dural venous sinuses detected in magnetic resonance venography (MRV). MATERIALS AND METHODS: All MR images of two hundred twenty patients were evaluated retrospectively. Posterior cranial fossa emissary veins diameter measurements were performed in the axial plane. The anatomic variations of the venous sinuses in MRVs of all patients were recorded. Accordingly, the presence of the emissary veins was compared with the dural venous sinus anatomic variations. p < 0.05 was considered statistically significant. An inter-observer reliability analysis was performed. RESULTS: The prevalence of emissary veins in MRI was found in the right mastoid emissary vein (MEV) 82.7% and left MEV 81.4%. Occipital emissary vein (OEV) was present in 63 patients (28.6%) for the first radiologist (R1), and it was present in 61 patients (27.7%) for the second radiologist (R2) (K = 0.978). A statistically significant correlation was detected between the diameter of the left MEV and gender (p < 0.05) for both radiologists. There was a statistically significant difference between the left MEV and OEV and transverse sinus anatomic variations. CONCLUSION: MR imaging is a noninvasive and irradiating imaging method for detecting posterior fossa major emissary veins, and we recommend using MR imaging for preoperative evaluation of posterior fossa major emissary veins and related dural venous sinuses.

Transclival Venous Circulation: Anatomic Study.

INTRODUCTION: The clivus is a small, central area of the basal cranium with limited surgical access and high morbidity associated with pathologies of its surrounding structures. Therefore thorough knowledge and understanding of the anatomy in this region are crucial for the success of treatments and interpretation of imaging. As to our knowledge, there is no extant cadaveric examination of the transclival veins, so the present study was performed. METHODS: Fifteen lightly embalmed adult heads underwent blue latex injection of the left and right internal jugular veins. Special attention was given to the presence or absence of transclival vessels. When transclival veins were identified, their intracranial source, point of penetration of the clivus and anterior connections were documented. RESULTS: Ten (66.7%) specimens were found to have transclival veins. These connected the basilar venous plexus to the retropharyngeal venous plexus on all specimens. Eight of the 10 specimens had multiple transclival veins, and 2 had only 1 vessel. The majority of the transclival veins were found penetrating the clivus at its lower one third. However, 2 specimens also had transclival veins that pierced the clivus at its upper one third. CONCLUSIONS: An improved understanding of the skull base and its venous drainage can assist clinicians and surgeons in better understanding normal, pathologic, and variant anatomy in this region.

Risk Assessment of Hemorrhage of Posterior Inferior Cerebellar Artery Aneurysms in Posterior Fossa Arteriovenous Malformations.

BACKGROUND: Posterior fossa arteriovenous malformations (AVMs) are associated with increased risk of rupture and severe consequences from such rupture. The hemorrhagic risk of prenidal aneurysms (anr) on the posterior inferior cerebellar artery (PICA) may exceed that of the AVM in posterior fossa AVMs fed by PICA (PICA-AVM). OBJECTIVE: To characterize the relative risks of aneurysm and AVM hemorrhage in patients with posterior fossa AVMs. METHODS: We retrospectively reviewed patients diagnosed with AVM. Patients with posterior fossa AVMs were divided into 3 groups: PICA-AVM with prenidal aneurysm (PICA-AVM-anr group), PICA-AVM without prenidal aneurysm (PICA-AVM group), and AVMs without PICA feeder with/without aneurysm (AVM-only group). Patient and lesion characteristics and treatment outcomes were compared. ANOVA and chi squared tests were used for statistical analyses. RESULTS: Our cohort included 85 patients. Mean age was 45.3 ± 18.1 yr, with 43(50.6%) female patients. Fifty-one patients (60.0%) had hemorrhagic presentation, and 27 (31.8%) experienced acute hydrocephalus. Patients in the PICA-AVM-anr group (n = 11) were more likely to present with aneurysmal subarachnoid hemorrhage (SAH; P = .005) and less likely to have AVM rupture (P < .001). Ten (90.9%) patients presented with hemorrhage, 6 (60.0%) of which resulted from aneurysm rupture. Of these 6, 5 (83.3%) had acute hydrocephalus. No patients with AVM rupture had hydrocephalus. Eight (72.7%) received aneurysm treatment prior to AVM treatment. There were no significant differences in post-treatment outcomes dependent on treatment order. CONCLUSION: In addition to relatively higher risk of AVM rupture from infratentorial location and prenidal aneurysm, a higher risk of aneurysm rupture rather than AVM rupture was observed in patients with PICA-AVM-anr complex.

Visualization of the Abducens Nerve in its Petroclival Segment Using Contrast-Enhanced FIESTA MRI: The Size of the Petroclival Venous Confluence Affects Detectability.

PURPOSE: Visualization of the abducens nerve in its petroclival segment still remains challenging. We aimed to investigate the detectability of the petroclival segment of the abducens nerve and to evaluate the role of the size of the petroclival venous confluence (PVC) in the visibility of the nerve using contrast-enhanced fast imaging employing steady-state acquisition (FIESTA) magnetic resonance imaging (MRI). METHODS: We retrospectively evaluated the contrast-enhanced FIESTA images of 237 patients (female/male: 127/110; mean age: 49.0 ± 14.7). Two radiologists divided the imaging findings of the petroclival segments of the abducens nerves into three groups: 0 (not visualized), 1 (partially visualized), and 2 (completely visualized). Another radiologist measured the anteroposterior diameter of the PVC from the clival bony surface to the inner layer of dura at the dural entrance level of the abducens nerve. One-way analysis of variance, Tukey's test, and receiving operating curve analysis were performed. RESULTS: Among 474 abducens nerves, 76 were classified as group 0 (76/474, 16.03 %), 100 were classified as group 1 (100/474, 21.10 %), and 298 were classified as group 2 (298/474, 62.87 %). There was significant difference in mean anteroposterior diameters of the PVC for each group (group 0, 0.95 mm; group 1, 1.80 mm; group 2, 2.51 mm). The cut-off values for the differentiation of group 0 from group 1 and group 1 from group 2 were found to be 1.35 and 2.09 mm, respectively. CONCLUSIONS: Abducens nerve in its petroclival segment can be reliably identified using contrast-enhanced FIESTA MRI especially in those with a greater anteroposterior diameter of the PVC.

Traumatic Frontal Epidural Hematoma Caused by Multiple Arterial Injuries in the Anterior Fossa.

BACKGROUND: This case report illustrates the need to evaluate the possibility of multiple arterial sources when presented with a frontal epidural hematoma associated with facial trauma. CASE DESCRIPTION: The patient presented after being struck in the face by a baseball. Computed tomography of the brain revealed a large frontal epidural hematoma. Intraoperatively, bleeding from a frontal branch of the middle meningeal artery was encountered and cauterized, and the hematoma was removed. Routine follow-up imaging performed the next day showed a residual frontal hematoma; however, the epidural hematoma was in a more medial location than the initial hematoma. The patient was taken back to the operating room; after frontal lobe retraction and extensive exploration, a different source of bleeding from posterior ethmoidal artery feeders was encountered. After the second operation, the patient's hematoma did not recur, and he was discharged home with no neurologic deficits 3 days later. CONCLUSIONS: We report a case of an epidural hematoma caused by 2 distinct arterial feeders. We discuss radiologic review and operative management of anterior fossa epidural hematomas and stress the importance of considering arterial bleeding from sources other than the middle meningeal artery in anterior fossa epidural hematomas. We discuss the utility of preoperative angiography for these patients and reinforce the need for acute postoperative imaging to ensure successful operative and patient outcomes.

[Vascular pathologies and vascular anatomical variants of the posterior cranial fossa]. / Gefäßpathologien und -normvarianten der hinteren Schädelgrube.

CLINICAL/METHODICAL ISSUE: The posterior fossa is the location of some specific vascular pathologies and vascular anatomical variants that are important for radiologists to know and recognize. Vascular malformations that are also found in the supratentorial region have some divergent characteristics in the posterior fossa. PRACTICAL RECOMMENDATIONS: Knowledge of the vascular anatomy of the posterior fossa and its variants is important for an understanding of vascular pathologies.

Traumatic basilar artery entrapment with patency of pontine perforators and absence of significant brainstem infarction: report of an unusual case.

We report a rare case of entrapment of the basilar artery into the sphenoid bone caused by a longitudinal fracture of the clivus. Using high resolution three-dimensional flat panel angiography, we show preservation of the basilar artery perforators in spite of severe stenosis of the entrapped segment of the basilar artery. There were no obvious signs and symptoms of posterior fossa stroke clinically or radiographically as far as could be assessed under given clinical circumstances.

[The specific features of the anatomical structure of the artery of labyrinth (an anatomical and topographical study)].

The objective of the present work was to study syntopy of the artery of labyrinth using block-preparations of the posterior cranial fossa, variants of its branching-off from the vertebro-basiliar basin (VBB), and peculiar features of its anatomical structure. A total of 12 block-preparations of the posterior cranial fossa were available for the investigation. They were preliminarily stained with red latex and fixed in a three-point system. These procedures were followed by retrosigmoid craniotomy, opening of dura mater in the supero-lateral part of the cerebellomedulllary cistern, traction of the cerebellum, and blunt separation of the basiliar artery (BA). Variants of branching of the antero-inferior cerebellar artery (AICA) and branching of the artery of labyrinth from AICA were studied. It was shown that the artery of labyrinth branches off from the antero-inferior cerebellar artery in 100% of the cases. The latter artery formed a loop in 14% of the cases (3 ears). The average diameter of the labyrinth artery was 0.32 mm and its mean area 0.06 sq.cm. The artery of labyrinth branched off from the posterior para-stem segment of the antero-inferior cerebellar artery in 42.6% of the cases (9 ears), and from the anterior para-stem segment of AICA in 14.2% of the cases (3 ears). Within the conventional «rhombus¼, the artery of labyrinth was straight in 76.2% of the cases (16 ears) and arc-shaped in 23.8% (4 ears).

An Unusually Benign Course of Extensive Posterior Circulation Occlusion.

BACKGROUND: Acute basilar artery occlusion is associated with poor outcome. In a few cases, occlusion occurs over a period allowing adequate collateral circulation to the posterior fossa. We describe a rare presentation with transient loss of consciousness (LOC) in a patient with extensive occlusion of the posterior circulation. METHODS: Case report. RESULTS: We describe a 70-year-old right-handed man with a history significant for atrial fibrillation and dolichoectasia of the basilar artery. Fourteen years ago, he had a small infarction in the pons resulting in right hemiparesis. Magnetic resonance angiogram at that time showed mild intracranial atherosclerosis. He was treated with warfarin for secondary stroke prevention. He presented to our emergency department after a witnessed spell of LOC after a large meal. On regaining consciousness, he had 2 episodes of emesis. Examination revealed only a spastic right hemiparesis from the old stroke in the pons. Cerebral angiogram showed absent flow in the mid and distal basilar arteries, both posterior cerebral arteries, and both posterior communicating arteries with bilateral stenoses of internal carotid arteries. His international normalized ratio in the emergency department was 1.1. He was treated with intravenous heparin and did well. Three months later, he underwent stent treatment of the worsening stenosis (90%) of the right internal carotid artery. CONCLUSIONS: Occasionally, collateral circulation has the potential to maintain adequate perfusion to the posterior fossa in severe cases of posterior circulation occlusion and diffuse intracranial atherosclerotic disease. Careful patient selection is essential before planning any endovascular intervention.

Management of ruptured posterior fossa arteriovenous malformations.

OBJECTIVE: Posterior fossa arteriovenous malformations (pAVMs) are rare and because of their location at or close to vital structures, their treatment remains challenging despite overall improvements in the management of cerebrovascular lesions. We reviewed our recent series of ruptured pfAVMs in search of guiding principles in the management of these complex lesions. METHODS: This is a retrospective series of consecutive patients admitted for a ruptured pfAVM from 2002 to 2013. We analyzed clinical and radiological data, as well as initial and definitive management. Outcome was assessed using the modified Rankin Scale (mRS) at 6 months. RESULTS: The study included 34 patients (19 women and 15 men). Upon admission, 79% of patients presented with an intra-cerebellar hematoma, 42% of which required urgent drainage. Hydrocephaly was also present in 82% of patients, 56% of which required emergency ventriculostomy. There was an aneurysm associated with the AVM in 47% of cases. In 38% of the cases, the aneurysm was the source of the hemorrhage. Only 68% of patients were amenable to undergo treatment of the AVM: 24% exclusively by surgery, 9% by embolization, 3% by radiosurgery, and 32% using combined means. Five patients died within the first week: one as a direct result of the severity of the hemorrhage, and the other four due to re-bleeding before treatment. Outcome was favorable (mRS 0-2) in 71% of patients. CONCLUSION: Patients with a ruptured pfAVM are often comatose upon admission, requiring emergency live-saving surgical treatment. An associated aneurysm is often the source of bleeding which if dealt with immediately, offers time to plan the most appropriate strategies to eliminate the AVM. Nevertheless, early re-bleeding is frequent, and a cause of concern as it often leads to death. Despite the gravity of the clinical condition upon admission, outcome is favorable for those amenable to treatment.

The Dorello canal: historical development, controversies in microsurgical anatomy, and clinical implications.

Interest in studying the anatomy of the abducent nerve arose from early clinical experience with abducent palsy seen in middle ear infection. Primo Dorello, an Italian anatomist working in Rome in the early 1900s, studied the anatomy of the petroclival region to formulate his own explanation of this pathological entity. His work led to his being credited with the discovery of the canal that bears his name, although this structure had been described 50 years previously by Wenzel Leopold Gruber. Renewed interest in the anatomy of this region arose due to advances in surgical approaches to tumors of the petroclival region and the need to explain the abducent palsies seen in trauma, intracranial hypotension, and aneurysms. The advent of the surgical microscope has allowed more detailed anatomical studies, and numerous articles have been published in the last 2 decades. The current article highlights the historical development of the study of the Dorello canal. A review of the anatomical studies of this structure is provided, followed by a brief overview of clinical considerations.

Occlusion of a clival dural arteriovenous fistula using a novel approach through the foramen ovale.

Dural arteriovenous fistulas (DAVFs) are abnormal connections between arteries and veins that are classified by location, morphology or direction of venous drainage. Treatment of DAVFs is undertaken in patients with severe symptoms or those with retrograde cortical venous drainage and/or venous ectasia. Much is written regarding the treatment of DAVFs involving the transverse sigmoid sinuses, cavernous sinus and tentorium, but little is written concerning the treatment of clival DAVFs. We demonstrate a novel transforaminal percutaneous approach through the foramen ovale as a viable method to occlude a clival vein. Specialised software was used to create a safe trajectory to the DAVF via the foramen ovale. The patient then underwent successful occlusion of the clival DAVF, thus further increasing the neurointerventionalist's armamentarium when attempting to treat difficult to reach clival DAVFs.

High-resolution STIR for 3-T MRI of the posterior fossa: visualization of the lower cranial nerves and arteriovenous structures related to neurovascular compression.

OBJECTIVE: Preoperative evaluation of small vessels without contrast material is sometimes difficult in patients with neurovascular compression disease. The purpose of this retrospective study was to evaluate whether 3D STIR MRI could simultaneously depict the lower cranial nerves--fifth through twelfth--and the blood vessels in the posterior fossa. MATERIALS AND METHODS: The posterior fossae of 47 adults (26 women, 21 men) without gross pathologic changes were imaged with 3D STIR and turbo spin-echo heavily T2-weighted MRI sequences and with contrast-enhanced turbo field-echo MR angiography (MRA). Visualization of the cranial nerves on STIR images was graded on a 4-point scale and compared with visualization on T2-weighted images. Visualization of the arteries on STIR images was evaluated according to the segments in each artery and compared with that on MRA images. Visualization of the veins on STIR images was also compared with that on MRA images. Statistical analysis was performed with the Mann-Whitney U test. RESULTS: There were no significant differences between STIR and T2-weighted images with respect to visualization of the cranial nerves (p > 0.05). Identified on STIR and MRA images were 94 superior cerebellar arteries, 81 anteroinferior cerebellar arteries, and 79 posteroinferior cerebellar arteries. All veins evaluated were seen on STIR and MRA images. There were no significant differences between STIR and MRA images with respect to visualization of arteries and veins (p > 0.05). CONCLUSION: High-resolution STIR is a feasible method for simultaneous evaluation of the lower cranial nerves and the vessels in the posterior fossa without the use of contrast material.