Bilateral thalamic developmental venous variations (DVVs) draining into same internal cerebral vein: a case report and review with emphasis on DVVs with outflow restriction.

Developmental venous variations (DVVs) are anatomic variations of normal transmedullary veins which are often discovered incidentally. Although they are accepted as benign compensatory venous drainage systems, they may become symptomatic or clinically significant due to flow-related causes. The fragile venous drainage systems increase vulnerability to in-out flow alterations. Increased inflow or decreased outflow causes rise in venous pressure, which may subsequently produce ischemic symptoms. Obstruction or stenosis of the collector vein is the most common cause of decreased outflow of a DVV. However, in the absence of collecting vein stenosis, venous hypertension may still exist due to volume overload. In case of multiple DVVs with single combined drainage pathway, functional outflow restriction may occur due to diminished capability of the vessel to adapt to pressure changes. In this report, we present a case with bilateral thalamic DVVs, which cause parenchymal amorphous calcification and drain into the left internal cerebral vein. A review of the literature on DVVs with outflow restriction including pathophysiological mechanisms is also discussed.

Petrosquamosal sinus: clinical characteristics based on radiologic and operative findings.

OBJECTIVE: Petrosquamosal sinus (PSS) is an embryonic emissary vein of the temporal bone connecting the intracranial and extracranial venous networks, which is present in some variants of venous cerebral drainage. The aim of the present study was to analyze 20 cases of PSS and to present its clinical characteristics and implications. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. INTERVENTION: Diagnostic. MAIN OUTCOME MEASURE: By reviewing retrospective medical records and TBCT findings, a total of 20 PSS cases were found. Based on the shapes of PSS demonstrated on TBCT, PSS was classified into tortuous and straight types. The course and thickness of PSS were also investigated. The average thicknesses of PSS between tortuous and straight types were compared. RESULTS: The mean age of the patients was 54.1 ± 16.2 years. The study group consisted of 7 male (35.0%) and 13 female (65.0%) patients. Eleven cases were found on the right side and 8 cases on the left side. The mean diameter of the bony canal that PSS courses on TBCT was 2.57 ± 0.88 mm. Its maximal and minimal diameters were 4.2 and 0.7 mm. The average diameter of tortuous type PSSs (3.04 ± 0.75 mm) was significantly larger compared with that of straight-type PSSs (2.09 ± 0.76 mm) (p < 0.05). CONCLUSION: Preoperative identification of PSS using TBCT may be important for safe mastoid surgery. The presence of PSS should be identified with thorough examination of radiographic findings before mastoid surgery.

The intracranial bridging veins: a comprehensive review of their history, anatomy, histology, pathology, and neurosurgical implications.

INTRODUCTION: The intracranial bridging veins are pathways crucial for venous drainage of the brain. They are not only involved in pathological conditions but also serve as important landmarks within neurological surgery. METHODS: The medical literature on bridging veins was reviewed in regard to their historical aspects, embryology, histology, anatomy, and surgery. CONCLUSION: Knowledge on the intracranial bridging veins and their dynamics has evolved over time and is of great significance to the neurosurgeon.

[Genetic factors related to intracranial arteriovenous malformations]. / Les facteurs génétiques associés aux malformations artério-veineuses cérébrales.

Genetic studies are interesting not only in the diagnosis and screening of new cases within a family harboring a particular disease, but also in understanding the underlying genetic and molecular factors related to that disease. Such studies revealed 3 categories of cerebral arteriovenous malformations in relationship to possible genetic factors. The first one concerns cerebral arteriovenous malformations in relationship to inherited diseases where a genetic support is clearly identified. Hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber disease) represents the most classical picture. The second category corresponds to familial cases of cerebral arteriovenous malformations were several members and relatives of the same family harboring the pathology without clear demonstration of any genetic basis. The third category includes cerebral arteriovenous malformations described in association with neurocutaneous disorders issued from maldevelopment events. Sturge-Weber disease and Wyburn-Mason syndrome best illustrate this category. A review of these categories will help in a better understanding of some genetic issues related to cerebral arteriovenous malformations.

Variations of the superficial middle cerebral vein: classification using three-dimensional CT angiography.

BACKGROUND AND PURPOSE: Classification of variations of the superficial middle cerebral vein (SMCV) remains ambiguous. We propose a new classification system based on embryologic development for preoperative examination. METHODS: Three-dimensional CT angiography was used to evaluate 500 SMCVs (in 250 patients). The outflow vessels from the SMCV were classified into seven types on the basis of embryologic development. The 3D CT angiograms in axial stereoscopic and oblique views and multiple intensity projection images were evaluated by the same neurosurgeon on two occasions. Inconsistent interpretations were regarded as equivocal. RESULTS: Three-dimensional CT angiography clearly depicted the SMCV running along the lesser wing or the middle cranial fossa. However, the outflow vessel could not be confirmed as the sphenoparietal, cavernous, or emissary type in 39 (8%) of the sides. SMCVs running in the middle cranial fossa to join the transverse sinus or superior petrosal sinus were accurately identified. SMCVs were present in 456 sides: 62% entered the sphenoparietal sinus or the cavernous sinus and 12% joined the emissary vein. Nine vessels were the superior petrosal type, 10 the basal type, 12 the squamosal type, and 44 the undeveloped type. CONCLUSION: Three-dimensional CT angiography can depict the vessels and their anatomic relationship to the bone structure, allowing identification of the SMCV variant in individual patients. Preoperative planning for skull base surgery requires such information to reduce the invasiveness of the procedure. With the use of our classification system, 3D CT angiography can provide exact and practical information concerning the SMCV.

Neurovascular developmental interaction: a specific form of vascular maldevelopment in the malformed brain. I. An experimental study and proposal of a new teratological concept.

The process of the development of the intracranial vessels was studied by means of immunohistochemical analysis of factor VIII in normal and exencephalic chick fetuses. The results revealed that the development of blood vessels in exencephalic brain was far advanced beyond the norm, with intense immunoreactivity to factor VIII on postincubation day 16 exceeding that on day 21 in normal controls. Compared with results regarding the direction of the overgrowth in the neuronal maturation process in the previous study using the chick exencephaly model, the findings of overmatured blood vessels were compatible with NSE- and somatostatin-positive elements that appeared especially in the overgrowth foci. The results of the present study suggested the pathogenic development of the "area cerebrovasculosa" in the neural placode as a phenomenon consequent upon hypervascularization in response to neuronal overgrowth, as seen in human cases of exencephaly or anencephaly. We emphasize the significance of this specific phenomenon in the development of the fetal central nervous system, namely neurovascular developmental interaction.

Embryology of the cerebral vasculature.

Although much remains to be learned about the embryology of the intracranial vasculature, much of the developmental pathways of the intracranial vascular system are now apparent. Understanding these pathways offers the potential to appreciate the nature of such arterial anomalies as the azygos anterior cerebral artery and the trigeminal artery and such venous anomalies as the vein of Galen malformation and the venous angioma.

Cavernous angioma does not exist?

12 cases of cerebral "venous angioma" are reported; pathological, clinical and radiological features of the lesion are reviewed. "Venous angioma" should be regarded as a developmental anatomic variation of the venous drainage system of the white matter. Its clinical significance is controversial, although it has been reported to cause hemorrhage, seizures, progressive neurological deficits, headaches. The clinical presentation of our patients was variable and, in some of them, dependent also on associated lesions. An hematoma was found in three patients, infarction in one and tumor in one. Angiography, CT and MRI demonstrated the typical appearance of the anomaly. Surgery was performed in one patient harboring a significant cerebellar hematoma and the coexistence of a cavernoma was pathologically confirmed. Venous developmental anomalies are often identified as the source of symptoms due to other conditions, that should be treated independently sparing the anomaly.