Arterial Vascular Structures Running Through Retrotransverse Foramen and Retrotransverse Groove of the Atlas Vertebrae.

OBJECTIVE: Retrotransverse foramen (RTF) and retrotransverse groove (RTG) are anatomic variations of the atlas (C1) vertebrae. RTF contains an anastomotic vein connecting atlanto-occipital and atlanto-axodian venous sinuses. The purpose of this study was to analyze the arterial vascular structures running though the RTF and RTG. METHODS: Three-dimensional volume rendered computed tomography angiography (3D VR CTA) images of 427 patients (264 men, 163 women; age 17-87 years) were reviewed and evaluated using the RadiAnt DICOM Viewer (version 5.0.2; Medixant, Poznan, Poland). The incidence of RTF or RTG, the incidence of the V3 segment of vertebral artery variants, and the artery vascular structures inside the RTF and RTG anatomic variation of C1 were analyzed. RESULTS: Fifty (11.7%) atlases presented RTF anatomical variant; 113 (26.5%) atlases presented RTG anatomical variants. The incidence of the V3 segment of vertebral artery variants was 0.94% (4 of 427). Three (0.7%) were persistent first intersegmental artery and 1 (0.2%) was the fenestration of the vertebral artery on left side. In 4 cases of C1 vertebral artery V3 segmental variants, there were no RTF and RTG. No artery vascular structure was found in RTF or RTG. CONCLUSIONS: The RTF or RTG of C1 was a common anatomical variant. No arterial vascular structure runs though the RTF or RTG. The presence of C1 RTF and RTG variants had no effect on the V3 segmental course of the vertebral artery. Preoperative understanding of these variations using 3D CTA are helpful for the safe execution of the upper cervical posterior approach surgeries.

Foramen Magnum Dural Arteriovenous Fistulas: Clinical Presentations and Treatment Outcomes, A Case-Series of 12 Patients.

BACKGROUND: Dural arteriovenous fistulas (DAVFs) are usually seen in relation to the venous sinuses, but in certain rare instances fistulas may not drain directly into the venous sinuses but rather drain into the cortical veins. This rare form of DAVF may present with either intracranial hemorrhage or myelopathy. The mode of clinical presentation is influenced by the venous outflow into either intracranial drainage or caudally intraspinal drainage. OBJECTIVE: To evaluate the clinical presentations, angioarchitectural characteristics, and treatment of 12 patients who presented with DAVF in the region of the foramen magnum. METHODS: In this case series we reviewed clinical charts, radiological images, and operative notes of 12 patients who were diagnosed of foramen magnum DAVF from December 1993 until April 2017. The angiographic studies were analyzed for feeding arteries, the location of the shunt, the venous drainage patterns, and the presence of venous side aneurysms. RESULTS: Twelve patients were angiographically confirmed with foramen magnum DAVFs. They included 11 males and 1 female (M:F = 11:1). Mean age of 55.6 yr ranging between 42 yr and 71 yr of age. Eight patients presented with progressive myelopathy, 3 patients with posterior fossa intracranial hemorrhage, and 1 patient presented with lower cranial nerve IX and XII palsies due to mass effect. CONCLUSION: A dural arteriovenous shunt, which may be located in the region of the foramen magnum, should be suspected in those cases of subarachnoid hemorrhage in the posterior fossa or progressive myelopathy mimicking spinal DAVF.

Three-dimensional analysis of foramen magnum and its adjacent structures.

The goal of this effort is to evaluate the anatomy of the foramen magnum (FM) using 3-dimensional computed tomography (3D CT), and determine whether or not the anatomical features of vascular structures and condylar foramen (CF) affect the types of FM.The CT angiography records of 101 patients (44 men and 57 women) were retrospectively examined in this study. Details of the FM, CF, and the vertebral and basilar arteries were examined using maximum intensity projection and 3D rendering images. The average age of the 101 patients was 45.28 ± 16.3 years. The 8 types of FM, in order of their frequency of occurrence, are as follows: round (19 cases; 18.8%), 2 semicircles (18; 17.8%), egg-shaped (15; 14.9%), hexagonal (14; 13.9%), tetragonal (11; 10.9%), oval (11; 10.9%), pentagonal (9; 8.9%), and irregular (4; 4%). There was no statistically significant relationship between the anatomical features of the vertebral and basilar arteries and the CF with the different types of FM (P ≥ 0.05). In our study, the diameter of the anteroposterior (AP) FM was 34.7 ± 3.6 mm, and the transverse (T) diameter was 29.5 ± 2.5 mm. The AP and T diameters were significantly higher in men than in women (P = 0.006 and P ≤ 0.001, respectively).Our study revealed that 3D CT is a safe and easy method for visualizing the anatomical structure of the FM and neighboring structures. Furthermore, this study was the first to demonstrate that there is no correlation between the 8 types of FM and the vertebral artery, basilar artery, and CF.

Bilateral cervical spinal dural arteriovenous fistulas with intracranial venous drainage mimicking a foramen magnum dural arteriovenous fistula.

We describe a unique case of bilateral cervical spinal dural arteriovenous fistulas mimicking an intracranial dural arteriovenous fistula near the foramen magnum. We review its detection via MRI and digital subtraction angiography and subsequent management through surgical intervention. Pitfalls in diagnostic angiography are discussed with reference to accurate location of the fistula site. The venous anastomotic connections of the posterior midline spinal vein to the medial posterior medullary vein, posterior fossa bridging veins, and dural venous sinuses of the skull base are discussed with reference to problem-solving in this complex case. The mechanism of myelopathy through venous hypertension produced by spinal dural fistulas is also emphasized.

Endovascular treatment for dural arteriovenous fistula at the foramen magnum: report of five consecutive patients and experience with balloon-augmented transarterial Onyx injection.

BACKGROUND: Foramen magnum dural arteriovenous fistulas (DAVF) with perimedullary venous drainage represent a small minority of intracranial DAVF, and only a number of small series with limited cases have been reported. The purpose of this retrospective study is to summarize experience of transarterial Onyx embolisation in the treatment of these lesions, with emphasis on the balloon-augmented technique. METHODS: Five consecutive patients with DAVF at the foramen magnum were treated by transarterial embolisation using the Onyx system. Their symptoms included myelopathy (n=4) and SAH (n=1). Suppliers were from the vertebral artery (VA) (n=4), occipital artery (OA) (n=4), and ascending pharyngeal artery (APA) (n=2), with drainage to the perimedullary veins. After catheterization of the dilated supplier, the fistulous connections, proximal draining veins and appropriate distal segment of the feeders of these DAVF were transarterial embolized using Onyx-18. In three patients, balloon-augmented technique was used to assist embolisation. The technical feasibility of the procedure, angiographic results, and clinical outcome were evaluated. RESULTS: In every case, complete obliteration was achieved. Neither intraprocedural vessel rupture nor other procedure-related complications occurred. The results remained stable in all patients on follow-up angiograms (mean, 7.2 months). At the last clinical follow-up (mean, 17.6 months), two patients showed complete resolution of the initial symptoms, and three patients showed significant improvement. CONCLUSION: We found that Onyx embolisation is a feasible and safe alternative to open surgery in the treatment of selective DAVF at the foramen magnum. The balloon-augmented technique widens indications for transarterial Onyx packing of these lesions, and improved safety of the procedure.

Concurrent dural and perimedullary arteriovenous fistulas at the craniocervical junction: case series with special reference to angioarchitecture.

OBJECT: Dural arteriovenous fistulas (DAVFs) and perimedullary arteriovenous fistulas (PAVFs) are uncommonly associated in the craniocervical junction. The purpose of this study was to describe the clinical and angiographic characteristics of such concurrent lesions. METHODS: Authors reviewed 9 cases with a coexistent DAVF and PAVF at the craniocervical junction. Clinical presentation, angiographic characteristics, intraoperative findings, and treatment outcomes were assessed. RESULTS: All patients (male/female ratio 5:4; mean age 66.3 years) presented with subarachnoid hemorrhage. Angiography revealed that 8 patients had both a DAVF and PAVF on the same side, whereas 1 patient had 3 arteriovenous fistulas, 1 DAVF, and 1 PAVF on the right side and 1 DAVF on the left side. All of the fistulas shared dilated perimedullary veins (anterior spinal vein, 7 cases; anterolateral spinal vein, 2 cases) as a main drainage route. The shared drainage route was rostrally directed in 8 of 9 cases. Eight patients exhibited an arterial aneurysm on the distal side of the feeding arteries to the PAVF, and the aneurysm in each case was intraoperatively confirmed as a bleeding point. One patient had ruptured venous ectasia at the perimedullary fistulous point. All patients underwent direct surgery via a posterolateral approach. No recurrence was observed in the 4 patients who underwent postoperative angiography, and no rebleeding event was recorded among any of the 9 patients during the follow-up period (mean 38.4 months). CONCLUSIONS: The similarity of the angioarchitecture and the close anatomical relationship between DAVF and PAVF at the craniocervical junction suggested that these lesions are pathogenetically linked. The pathophysiological mechanism and anatomical features of these lesions represent a unique vascular anomaly that should be recognized angiographically to plan a therapeutic strategy.

Anatomic variations of sphenopalatine artery and minimally invasive surgical cauterization procedure.

BACKGROUND: Sphenopalatine artery (SPA) ligation or cauterization stands to be one of the most common management options of refractory epistaxis. Ramification pattern of SPA as it passes through sphenopalatine foramen (SPF) has not been clearly established. The aim of this study is to investigate situations in which middle meatal approach may fail due to anatomic variations of SPA and to define a minimally invasive surgical cauterization procedure. Anatomic variations of SPA were determined by microdissection of 20 adult sagittally cross-sectioned head specimens. METHODS: Branching characteristics of SPA and its anatomic relations were evaluated and anatomic variations were noted. RESULTS: SPA was generally (80%) forming branches within SPF before entering into the nasal cavity. In 20% of the specimens, SPF was located superior to the horizontal lamella of the middle turbinate, and accessory foramen was present in 10%. In 10% of the cases, the posterior lateral nasal branch was situated as two branches in a deep sulcus in the middle meatus. CONCLUSION: The ramification pattern of SPA can not be fully exposed without resection of the posterior part of the middle turbinate via the middle meatal approach. Two-step procedures are advocated in reducing failure rates. Previously defined two-step procedures are relatively invasive. A less invasive procedure is defined based on the variations of SPA and SPF.

Microsurgical anatomy of the facial nerve trunk.

Dissection and manipulation of the facial nerve (FN) trunk between its exit from the cranial base through the stylomastoid foramen (SMF) and its bifurcation is a critical step in various otologic, plastic and neurosurgical procedures. This study demonstrates the anatomical relationships and variability of the FN trunk with emphasis on some important morphometric data, particularly with relevance to hypoglossal-facial nerve anastomosis (HFA). Bilateral microsurgical dissection was performed on twenty-three human cadavers fixed with formalin. The whole trunk of the FN was exposed, its diameter at the SMF and its length were measured, its branches were observed and the site of its bifurcation was determined. Anastomotic connections with other nerves and blood supply of the trunk were studied. The FN invariably emerged from the cranial base through the SMF. Its diameter upon its emergence from the foramen was 2.66 +/- 0.55 mm. Two branches consistently originated from the trunk: the posterior auricular nerve and the nerve to the digastric muscle. Less consistent were the communicating branch with the glossopharyngeal nerve and the nerve to the stylohyoid muscle. The bifurcation of the FN occurred before its penetration into the parotid gland in 15% of cases and within the gland in 85%. The length of the FN trunk was 16.44 +/- 3.2 mm. Anastomoses between the FN and other nerves were observed in one-third of the dissections. The blood supply to the FN trunk was provided by the stylomastoid artery that was identified in 91% of cases. Understanding the microsurgical anatomy of the FN trunk is essential for performing any surgical procedure in the relevant region. Surgical implications of this study are presented with emphasis on HFA surgery.

Extreme lateral transcondylar approach to the skull base.

In this study, the authors present their experience of using extreme later transcondylar approach (ELTC) for treating 7 patients with lesions in the anterolateral foramen magnum, upper cervical spine and cerebellopontine angle reaching upto jugular foramen. The tumours included meningiomas, neurofibromas (2 cases each), chondrosarcoma, epidermoid and aneurysmal bone cyst (one case each). The approach was used alone, in combination with retrolabyrinthine presigmoid approach in a patient with lower cranial nerve neurofibroma extending extracranially through the jugular foramen, or in combination with partial C1-C3 laminectomy in two patients with meningiomas situated anterolateral to the cord from the foramen magnum to C3. In two patients with extradural vertebral artery (VA) entrapment by a chondrosarcoma and aneurysmal bone cyst respectively, the vertebral artery was ligated distal to the tumour. The tumours were totally excised in five cases and partially in two. There was no preoperative mortality. The major complications included cerebrospinal fluid leak from the wound (3 cases) and increase in lower cranial nerve paresis (2 cases). At follow up, ranging from 6 months to 2 years, 5 patients showed no tumour recurrence. There was improvement in neurological status. One patient, with a partially excised aneurysmal bone cyst, showed no added deficits or increase in the tumour size. However, there was a massive regrowth in the patient with chondrosarcoma after 6 months. This technique provided a wide surgical exposure with direct visualization of the tumour-anterior cord interface, early proximal control of the VA and preservation of lower cranial nerves.

Midline and far lateral approaches to foramen magnum lesions.

Twenty patients with foramen magnum lesions were operated upon in the last 5 years at Postgraduate Institute of Medical Education and Research, Chandigarh. The common presenting features were quadriparesis, quadriplegia, diminished sensations, neck pain and respiratory insufficiency. The lesions encountered were meningiomas, neurofibromas, posterior inferior cerebellar artery aneurysms, neurenteric cyst and chordoma. Patients with posterior or posterolaterally placed lesions were operated by the midline posterior approach while those with anterior or anterolateral lesions were managed by the far lateral approach. All mass lesions were excised completely and the aneurysms were clipped. Seventeen patients made good neurological recovery while three died. The latter three patients presented very late. The merits of various surgical approaches to the foramen magnum are discussed.

Microsurgical anatomy of the suboccipital segment of the vertebral artery.

The craniocervical regions of seven cadavers (14 sides) injected with silicone rubber were dissected under a Zeiss OPMI surgical microscope. The present study provides a detailed description of the suboccipital segment of the vertebral artery, with particular attention to its loops, branches, supporting osteofibrous structures, adjacent nerves, and surrounding venous structures. Several ligaments fixating the vertebral artery to surrounding structures, which have not been described in previous anatomical studies, were found. The authors propose an anatomically based subdivision of the suboccipital segment of the vertebral artery into five subsegments: infraforaminal, foraminal, supraforaminal, horizontal, and intramembranous. Measurements of surgically and clinically important features were obtained. Surgical approaches to this region are suggested based on a more informed understanding of the local anatomy.

[Intradural hematoma of the foramen magnum associated with factor XIII deficiency]. / Hématome intradural du foramen magnum associé à un déficit en facteur XIII.

A 50-year-old woman, with a history of IgG monoclonal gammapathy, presented with meningitis and intradural hematoma of the foramen magnum associated with factor XIII deficiency. The patient died postoperatively of diffuse haemorrhage. Inhibitors to factor XIII are extremely rare and are congenital or acquired. Patients with factor XIII inhibitor can experience severe bleeding, and many died of cerebral haemorrhage. The role of this defect is discussed. We recommend an extensive investigation of haemostasis for patients with both episode of haemorrhagic disorder and monoclonal gammapathy.

Giant posterior inferior cerebellar artery aneurysm associated with foramen magnum syndrome.

The case of a giant distal posterior inferior cerebellar artery (PICA) aneurysm which caused foramen magnum syndrome is presented. A 67-year-old male was referred for evaluation of a posterior fossa mass lesion on MRI scan. Craniotomy was performed which revealed a giant and completely thrombosed aneurysm of the distal PICA, which was subsequently excised intact. This report adds giant aneurysm of the PICA to the list of posterior fossa lesions reported which cause foramen magnum syndrome.

Extracranial aneurysm of the posterior inferior cerebellar artery: case report.

The authors report the unusual case of an aneurysm arising from the extracranial portion of the left posterior inferior cerebellar artery (PICA). The patient was a 39-year-old woman who developed a subarachnoid hemorrhage. The hemorrhage was in the basal, ambient, and Sylvian cisterns, but not in the ventricles. There were no focal neurological deficits, and the clinical grading was 1. On cerebral angiograms, the PICA was found to originate from the vertebral artery as low as 17.9 mm below the foramen magnum and to enter into the spinal canal through the intervertebral foramina of C1-C2. The artery went up to the posterior fossa and had only the cranial loop with an absence of the caudal loop. The saccular aneurysm hung on the initial segment of the PICA and was located at the C1 level. The patient developed motor aphasia and hemiparesis on the right side 15 days after onset, and an infarction was disclosed in the boundary zones of the left parietal lobe on a computed tomographic scan. The aneurysm was successfully obliterated by a neck clipping 2 months later, and the patient was discharged in good condition. The literature discussing PICA aneurysms in the extracranial, as well as distal, portion is reviewed.

Microanatomy of retia mirabilia of bowhead whale foramen magnum and mandibular foramen.

The morphology of vessels of the cervical rete mirabile near the region of the foramen magnum of the bowhead whale, Balaena mysticetus, as well as of retial vessels of the mandibular foramen was studied by light and transmission electron microscopy. A comparison of arterial and venous components of the mandibular rete revealed considerable arterial branching and arteriovenous anastomoses. Although the small arteries of bowhead retia contained the same layers found in nonretial arteries, several distinctive morphologic features were evident. These included wide separation by collagenous connective tissue and small size of individual smooth muscle cells of the tunica media. These myocytes also contained considerable perinuclear glycogen and communicated minimally with adjacent myocytes by small foot-like cytoplasmic appendages as well as branching of basement membranes. Ganglia-like neural plexuses were observed within the tunica media of arterial retia. Endothelial cells lining the intima demonstrated loose peripheral edges which frequently projected into the vessel lumen, and these cells rested upon a subjacent layer of reticular fibers. It is known for some species that the retial supply to the brain in whales largely supplants an internal carotid arterial supply and that the spinal cord is supplied by retia. The physiologic role of the bowhead mandibular retia remains unknown. The retia mirabilia of cetaceans are considered as one of the morphologic adaptations which modulate hemodynamics during diving and resurfacing. The morphologic features of these vessels in the bowhead whale, as revealed by electron microscopy, appear to reflect the capability to respond in a slow but sustained manner to diving, and the large glycogen deposits may help sustain vascular myocyte metabolism during prolonged submersion.

[The emissaries of the human skull (author's transl)]. / Die Emissarien des menschlichen Schädels.

The range of hemodynamic conductivity of the venous outlets of the skull, called emissary veins, and factors influencing them have been explored in 888 closed and 210 opened human skulls: Exept the condylar canal and the mastoid emissary vein only emissary veins joined to cranial nerves are of importance. The straighter the connection to the heart the wider the related emisary vein tends to be, which explains the predominance of the right emissary veins in the occipital cranial fossa. The right and the left jugular vein as well as the jugular and the mastoid emissary vein compensate each other. The influence of constitutional factors is shown by the sex difference in the conductivity of the jugular veins corresponding to the sex difference of the mean cerebral weight.