Dural arteriovenous malformation in a child with Bannayan-Riley-Ruvalcaba Syndrome

Intracranial arteriovenous malformations (AVM) are a rare feature of Bannayan-Riley-Ruvalcaba syndrome (BRRS). Palencia et al reported a case of intracranial arteriovenous malformation in a child with BRRS in a Spanish journal in 1986. However, the occurrence of dural AVM in a patient with BRRS has not since been addressed in the literature. Advancements in imaging and therapeutic embolization, and the ability now to screen for phosphatase and tensin homologue (PTEN) mutations allow us to detect and manage these patients sooner. Early detection of intracranial AVMs is necessary because of the risk for progression to venous ischemia and resultant neurologic damage. We present the case of a child with headaches and periorbital venous congestion due to a dural AVM with bilateral venous outflow occlusion who was treated with multiple embolizations, now with interval remission of headache symptoms.     

Dural arteriovenous fistula causing primary intraventricular haemorrhage

Primary intraventricular haemorrhage is a rare presentation of a dural arteriovenous fistula. We describe the case of a 52-year-old woman with a past history of idiopathic intracranial hypertension who presented with sudden-onset severe headache The CT scan on admission showed primary intraventricular haemorrhage with no associated haemorrhage in the brain parenchyma or the extra-axial compartment The cerebral angiogram demonstrated a dural arteriovenous fistula involving the left sigmoid and transverse sinuses which was successfully embolised transvenously. Subependymal venous congestion and rupture secondary to retrograde venous drainage has been proposed as the cause for this presentation.     

Emergent headaches during pregnancy: correlation between neurologic examination and neuroimaging

BACKGROUND AND PURPOSE: Emergent evaluation of the pregnant headache patient requires rational selection of acute neuroimaging studies, yet guidelines do not exist. We investigated the demographic and clinical features that are predictive of intracranial pathologic lesions on neuroimaging studies in pregnant women with emergent headaches.MATERIALS AND METHODS: We conducted a retrospective review of demographic factors, clinical features, and radiologic findings in a consecutive case series of 63 pregnant women emergently evaluated with a chief complaint of headache, including those with previous headache histories. Clinical data were abstracted from emergency department records, hospital course, and discharge summaries. Multivariate logistic regression analysis examined predictors of intracranial pathologic lesions on emergent neuroimaging studies.RESULTS: Multiparous African American women constituted 63% of the case subjects. Headaches were frequently accompanied by photophobia (59%), nausea (52%), vomiting (37%), and occasionally with fever (11%), meningismus (9%), or seizures (7%). A total of 43% of case subjects had abnormal neurologic examination findings. Emergent neuroimaging, including noncontrast head CT and MR imaging, revealed an underlying headache etiology in 27%, including cerebral venous thrombosis, reversible posterior leukoencephalopathy, pseudotumor, and intracranial hemorrhage. The odds of having intracranial pathologic lesions on neuroimaging were 2.7 times higher in patients with abnormal results on neurologic examination (P = .085).CONCLUSIONS: Emergent neuroimaging studies may reveal an underlying headache etiology in 27% of pregnant women. Further research with a larger sample size is needed to determine what clinical factors are predictive of a pathologic condition on neuroimaging studies.

Headache is a common neurologic complaint among women of childbearing age.¹ The prevalence of headaches during pregnancy has been reported to be as high as 35%.² Although most headaches are unrelated to an intracranial pathologic lesion, some headaches may herald ominous diagnoses, including eclampsia, stroke, tumor, subarachnoid hemorrhage, or cerebral venous thrombosis. Emergent evaluation of headache in the pregnant patient requires rational selection of acute neuroimaging studies, yet guidelines do not exist. Often, the decision to investigate a headache in a pregnant patient through neuroimaging is based on the presence or absence of focal neurologic findings; however, there are no data to support this practice. We investigated the demographic factors, clinical presentations, and examination findings of pregnant women with headaches presenting to an emergency department in an academic center. Our hypothesis was that abnormal findings on neurologic examination would be predictive of an intracranial pathologic condition on acute neuroimaging studies.     

Going high with preexisting neurological conditions

This review presents the potential impact of high altitude exposure on preexisting neurological conditions in patients usually living at low altitude. The neurological conditions include permanent and transient ischemia of the brain, occlusive cerebral artery disease, cerebral venous thrombosis, intracranial hemorrhage and vascular malformations, multiple sclerosis, intracranial space-occupying lesions, dementia, extrapyramidal disorders, migraine and other headaches, and epileptic seizures. New developments in diagnostic work-up and treatment of preexisting neurological conditions are also mentioned where applicable. For each neurological disorder, the authors developed absolute and relative contraindications for a trip to high altitude. These recommendations are not based on the results of controlled randomized trials, but mainly on case reports, pathophysiological considerations, and extrapolations from the low altitude situation.     

Primary cough headache, primary exertional headache, and primary headache associated with sexual activity: a clinical and radiological study

Introduction

The purposes of this study are to describe clinical features of primary cough headache, primary exertional headache, and primary headache associated with sexual activity and to evaluate potential association with abnormalities in the cerebral or cervical venous circulation.

Methods

This multicentre, observational, non-interventional consecutive cohort study included patients fulfilling ICHD-II criteria for primary cough headache (N?=?10), primary exertional headache (N?=?11), or primary headache associated with sexual activity (N?=?20), as well as 16 headache-free controls. Each patient was evaluated clinically and underwent craniocervical MRV of the cranial circulation. All scans were interpreted centrally by blinded raters, using the Farb criteria proposed for idiopathic intracranial hypertension. Stenosis was defined as a Farb score <3 in left or right transverse sinuses or jugular veins.

Results

In all primary headache groups, headaches were most frequently diffuse, severe, or very severe. Headache duration was significantly shorter in patients with cough headache (median 6.5 versus 20 and 60 min). An exploitable magnetic resonance venogram was obtained for 36 patients. Stenosis was detected in none of the control group, but in 5/7 patients with primary cough headache group, 2/10 patients with primary exertion headache, and 12/19 patients with primary headache associated with sexual activity. The frequency of stenosis was significantly different from the control group in the primary cough headache and primary headache associated with sexual activity groups.

Conclusions

Headaches provoked by cough and sexual activity are possibly associated with venous abnormalities in a significant subgroup of affected patients. As the literature shows conflicting results, this venous stenosis can be considered as a promoting factor.     

Vascular hydraulics associated with idiopathic and secondary intracranial hypertension

BACKGROUND AND PURPOSE: The radiologic diagnosis of idiopathic intracranial hypertension (IIH) is one of exclusion, with no reproducible positive features described in the imaging literature. Because MR venography is prone to flow artifacts, diagnosis of secondary intracranial hypertension (SIH) can also be problematic. Vascular hydraulics can be useful for diagnosis of these conditions when measured by invasive or sonographic means. The purpose of this study was to measure vascular flow and pulsatility characteristics with a noninvasive MR imaging method. METHODS: Twelve patients with clinical and lumbar puncture findings of IIH or SIH and 12 control subjects were examined with MR venography and MR flow quantification studies of the cerebral arteries and veins. Total cerebral, superior sagittal sinus (SSS), and straight sinus blood flows were measured. Pulsatility indices from the arterial and venous flow for all patients were compared using the Student t test. RESULTS: MR venography confirmed that seven of the 12 patients had venous outflow obstruction, and thus, SIH. The remaining five patients had IIH. All patients showed reduced sinus pulsatility compared with that of the control group; reductions of 42% in the SSS and 32% in the straight sinus were noted (P =.0001 and.005, respectively). In the IIH group, total blood flow was 46% higher than that in the control group (P =.0002), and SSS flow was normal. In the SIH group, total blood flow was normal; however, SSS flow was reduced by 25% (P =.003). CONCLUSION: Reduced venous sinus pulsatility is a marker of intracranial hypertension secondary to raised venous sinus pressure. When suspicion of IIH or SIH exists and the MR venogram is difficult to interpret, raised total blood flow indicates IIH, whereas reduced SSS flow indicates SIH.     

Use of Phase-Contrast MRA to Assess Intracranial Venous Sinus Resistance to Drainage in Healthy Individuals

BACKGROUND AND PURPOSE:Resistance to blood flow in the cerebral drainage system may affect cerebral hemodynamics. The objective of the present study was to use phase-contrast MRA to quantify resistance to drainage of blood across branches of the venous sinus tree and to determine whether the resistance to drainage values correlated with internal jugular vein outflows.MATERIALS AND METHODS:We performed whole-head phase-contrast MRA and 2D phase-contrast MR imaging in 31 healthy volunteers. Vascular segmentation was applied to the angiograms, and the internal jugular vein velocities were quantified from the flow images. Resistance to drainage across branches of the venous sinus tree was calculated from the segmented angiograms, by using the Poiseuille equation for laminar flow. Correlations between the values of resistance to drainage and internal jugular vein outflow measurements were assessed by using the Spearman ρ.RESULTS:The overall mean resistance to drainage of the venous sinus tree was 24 ± 7 Pa s/cm³. The mean resistance to drainage of the right side of the venous sinus tree was 42% lower than that of the left side (P < .001). There were negative correlations between the values of resistance to drainage and internal jugular vein outflows on both the left side of the venous sinus tree (R = −0.551, P = .002) and the right side (R = −0.662, P < .001).CONCLUSIONS:Phase-contrast MRA is a noninvasive means of calculating the resistance to drainage of blood across the venous sinus tree. Our approach for resistance to drainage quantification may be of value in understanding alterations in the cerebral venous sinus drainage system.

The cerebral venous sinus system is characterized by anatomic variations¹ associated with marked interindividual variability in blood drainage patterns.² The venous compartment is generally compliant, whereas the walls of the sinuses tend to be rigid. In comparison with the intracranial arterial system, the venous sinus system has received less attention in the imaging-based evaluation of cerebrovascular diseases in clinical research, possibly because the pathologies that affect the intracranial venous sinus system are less common than those affecting the arterial system and often present a broad spectrum of clinical manifestations.³ However, alterations in cerebral hemodynamics are known to be associated with abnormal drainage in the cerebral venous sinus system. For example, impaired intracranial drainage is widely cited as one of the prime causes in idiopathic intracranial hypertension,^4–7 intracranial dural arteriovenous fistula malformation,⁸ communicating and noncommunicating hydrocephalus,^9,10 and multiple sclerosis.¹¹ Nevertheless, a suspected case of venous stenosis must be assessed with caution¹² because misinterpretation can lead to a nonindicated operation (with all its associated non-negligible risks). This point is clearly illustrated by the debate over the involvement of jugular venous stenosis in the pathogenesis of multiple sclerosis. In multiple sclerosis, it has been shown that percutaneous transluminal angioplasty of extracranial veins with suspected alterations is ineffective, may exacerbate underlying disease activity, and can lead to serious complications.¹³In clinical practice, intraluminal vessel defects and/or pathologic flow velocities of the intracranial drainage system are usually evaluated by using contrast-enhanced or unenhanced MR imaging,⁵ CTA,¹⁴ DSA,¹⁵ or transcranial Doppler sonography.¹⁶ Although unenhanced vascular imaging techniques are less sensitive than contrast-enhanced techniques, they may be of value for an initial evaluation of the venous system in neonates or in patients who are allergic to contrast agents or have kidney dysfunction. Unenhanced 3D phase-contrast MRA (PC-MRA) offers several advantages: It is relatively rapid, is often appropriate for patient follow-up, and is associated with a lower complication rate.^17,18 The results of patient evaluations usually show that a narrower luminal cross-section can produce higher flow resistance and therefore a decrease in flow and an increase in pressure—at least in the region adjacent (proximal) to the lesion. Moreover, venous sinus manometry has shown an elevated sagittal sinus pressure and a significant drop in transverse sinus pressure in patients with idiopathic intracranial hypertension.¹⁹ Other researchers have shown that most patients with idiopathic intracranial hypertension have normal blood flow in the superior sagittal sinus.⁷The mechanisms linking the cerebral venous outflow rate to intracranial pressure have not been characterized, to our knowledge. However, it is possible that structural factors (such as an increase in the resistance to drainage [Rd] of blood across the branches of the venous sinus pathways) may impact intracranial venous outflow, as has been demonstrated in patients with venous outflow obstruction (in whom an elevated venous back pressure resulted in elevated venous resistance²⁰). It is generally assumed that the pressure drop for driving axial flow across a tube increases with the flow resistance. Thus, an increase in venous sinus flow resistance would require an increase in upstream flow pressure for a constant volume flow through this drainage system to be maintained. Hence, the cumulative effects of the Rd across segments of the venous sinus pathways may have a role in cerebral hydrodynamics in general and in intracranial pressure and cerebral compliance in particular.While the association between intracranial hydrodynamics and the geometric characteristics of the venous sinus system appears to be strong, we are not aware of any quantitative data on the resistance to blood flow in the cerebral drainage system. The objective of the present study was therefore to calculate the Rd of blood across the major dural sinuses and internal jugular veins (IJVs) in healthy volunteers by using phase-contrast MR angiography. We used the well-established Poiseuille equation for laminar flow to calculate the Rd from the PC-MRA data. Furthermore, we explored the relationship between the values of Rd and the IJV flows measured by cine phase-contrast MR imaging.     

Modeling intracranial pressures in microgravity: the influence of the blood-brain barrier

INTRODUCTION: A majority of astronauts experience symptoms of headache, vomiting, nausea, lethargy, and gastric discomfort during the first few hours or days after entering a microgravity environment. Due to similarities in symptoms and their time evolution, it has been hypothesized that some of these conflicts are related to the development of benign intracranial hypertension in these individuals in microgravity. METHODS: This hypothesis was tested using a validated mathematical model that embeds the intracranial system in whole-body physiology. This model was used to predict steady-state intracranial pressures in response to various cardiovascular stimuli associated with microgravity, including changes in arterial pressure, central venous pressure, and blood colloid osmotic pressure. The model also allowed alterations of the blood-brain barrier due to factors such as gravitational unloading and increased exposure to radiation in space to be considered. RESULTS: Simulations predicted that intracranial pressure will increase significantly if, combined with a drop in blood colloid osmotic pressure, there is a reduction in the integrity of the blood-brain barrier in microgravity. DISCUSSION: These results suggest that in some otherwise healthy individuals microgravity environments may elevate intracranial pressure to levels associated with benign intracranial hypertension, producing symptoms that can adversely affect crew health and performance.     

The controversial entity of brain herniations into arachnoid granulations: A report of three cases with literature review

Brain herniation into arachnoid granulation (BHAG) is a quite recently described controversial entity in terms of both etiology and clinical significance. It comprises a herniation of brain tissue into a presumed preexisting arachnoid granulation in dural venous sinuses, calvarium, meningeal or diploic veins. Most often described as an incidental finding in patients examined for unrelated pathologies, some BHAGs can possibly be related to headache, epilepsy or conditions with increased intracranial pressure such as idiopathic intracranial hypertension (IIH) or pseudotumor cerebri (PTC). The number of reported cases is low and there are only three more recently published observational studies on this subject with results lacking statistical significance due to relatively few BHAGs analyzed. Therefore, BHAGs still need an increased focus from both the radiologists and clinicians and more published studies and cases are necessary to help in understanding their factual meaning, clinical and treatment implications. In this article we describe three new cases of BHAGs to the literature, with patients presenting with different symptoms.     

Meta-Analysis of CSF Diversion Procedures and Dural Venous Sinus Stenting in the Setting of Medically Refractory Idiopathic Intracranial Hypertension

BACKGROUND AND PURPOSE:In medically refractory idiopathic intracranial hypertension, optic nerve sheath fenestration or CSF shunting is considered the next line of management. Venous sinus stenosis has been increasingly recognized as a treatable cause of elevated intracranial pressure in a subset of patients. In this article, we present the results of the largest meta-analysis of optic nerve sheath fenestration, CSF shunting, and dural venous sinus stenting. This is the only article that compares these procedures, to our knowledge.MATERIALS AND METHODS:We performed a PubMed search of all peer-reviewed articles from 1988 to 2014 for patients who underwent a procedure for medically refractory idiopathic intracranial hypertension.RESULTS:Optic nerve sheath fenestration analysis included 712 patients. Postprocedure, there was improvement of vision in 59%, headache in 44%, and papilledema in 80%; 14.8% of patients required a repeat procedure with major and minor complication rates of 1.5% and 16.4%, respectively. The CSF diversion procedure analysis included 435 patients. Postprocedure, there was improvement of vision in 54%, headache in 80%, and papilledema in 70%; 43% of patients required at least 1 additional surgery. The major and minor complication rates were 7.6% and 32.9%, respectively. The dural venous sinus stenting analysis included 136 patients. After intervention, there was improvement of vision in 78%, headache in 83%, and papilledema in 97% of patients. The major and minor complication rates were 2.9% and 4.4%, respectively. Fourteen additional procedures were performed with a repeat procedure rate of 10.3%. Three patients had contralateral stent placement, while 8 had ipsilateral stent placement within or adjacent to the original stent. Only 3 patients required conversion to CSF diversion or 2.2% of patients with stents.CONCLUSIONS:Patients with medically refractory idiopathic intracranial hypertension have traditionally undergone a CSF diversion procedure as the first intervention. This paradigm may need to be re-examined, given the high technical and clinical success and low complication rates with dural venous sinus stenting.

Idiopathic intracranial hypertension (IIH), previously referred to as pseudotumor cerebri and benign intracranial hypertension, is a syndrome defined by elevated intracranial hypertension without radiographic evidence of a mass lesion in the brain.¹ The overall prevalence of IIH in North America has been estimated to be 0.9–1.07/100,000^2,3; however, in women with obesity between 20 and 44 years of age, the prevalence rises to 15–19/100,000.²Although headache is the most common presenting symptom, seen in 92%–94% of patients,^4,5 IIH also represents a significant cause of chronic headaches. In some patients, there may be vision changes,^6–9 which, if not corrected, may progress to permanent visual loss.^10,11The standard medical treatment includes weight loss, acetazolamide, diuretics, and repeat high-volume lumbar punctures. In patients with medically refractory IIH or progressive visual loss, a CSF-diversion procedure (lumboperitoneal shunt, ventriculoperitoneal shunts, or optic nerve sheath fenestration) is considered the next line of management.^9,12CSF diversion procedures in the setting of medically refractory IIH have been described in the literature dating back to 1955, by Jackson and Snodgrass.^13,14 These studies are level 3 evidence, comprising case series and individual case reports. There are no prospective randomized controlled studies on lumboperitoneal shunt, ventriculoperitoneal shunts, or optic nerve sheath fenestration, to our knowledge.Venous sinus stenosis has been increasingly recognized as a treatable cause of elevated intracranial pressure. Venous sinus stent placement was first described by Higgins et al.¹⁵ During the past 20 years, an increasing number of case reports and larger case series have described dural venous sinus stent placement, and reported high rates of technical success and favorable clinical outcomes.^6,7,16–21In this article, we present the results of the largest meta-analysis of optic nerve sheath fenestration, CSF diversion procedure, and venous sinus stent placement for medically refractory IIH from 1988 to present. We then compare these interventions with a focus on symptom improvement, complications, and the need for repeat procedures.     

Cerebral angiographic findings of spontaneous intracranial hypotension

We report a case of spontaneous intracranial hypotension that underwent cerebral angiography. The angiogram showed prominence of the veins and venous phase of the angiogram. This is thought to be secondary to decreased intracranial pressure and subsequent dilation of the venous system to attempt to replace the lost intracranial CSF volume. In situations in which the typical clinical presentation is not present and additional examinations such as cerebral angiography are performed, these findings may be helpful to direct the physicians involved toward the correct diagnosis.     

Angiographic features of spontaneous intracranial hypotension

The imaging characteristics of spontaneous intracranial hypotension have been well described in the clinical and imaging literature. We present a case of spontaneous intracranial hypotension with typical clinical and laboratory features that were thought to be suspicious for a ruptured aneurysm. Blood in the CSF in conjunction with headaches led to cerebral angiography that showed diffuse enlargement of cortical and medullary veins. The angiographic findings were diagnostic of spontaneous intracranial hypotension and consistent with the Monro-Kellie hypothesis.     

Spontaneous intracranial hypotension: clinical and neuroimaging findings in six cases with literature review

Spontaneous intracranial hypotension (SIH) is an uncommon but increasingly recognized syndrome. Orthostatic headache with typical findings on magnetic resonance imaging (MRI) are the key to diagnosis. Delayed diagnosis of this condition may subject patients to unnecessary procedures and prolong morbidity. We describe six patients with SIH and outline the important clinical and neuroimaging findings. They were all relatively young, 20-54 years old, with clearly orthostatic headache, minimal neurological signs (only abducent nerve paresis in two) and diffuse pachymeningeal gadolinium enhancement on brain MRI, while two of them presented subdural hygromas. Spinal MRI was helpful in detecting a cervical cerebrospinal fluid leak in three patients and dilatation of the vertebral venous plexus with extradural fluid collection in another. Conservative management resulted in rapid resolution of symptoms in five patients (10 days-3 weeks) and in one who developed cerebral venous sinus thrombosis, the condition resolved in 2 months. However, this rapid clinical improvement was not accompanied by an analogous regression of the brain MR findings that persisted on a longer follow-up. Along with recent literature data, our patients further point out that SIH, to be correctly diagnosed, necessitates increased alertness by the attending physician, in the evaluation of headaches.     

Reversibility of venous sinus obstruction in idiopathic intracranial hypertension

Elevated intracranial intravenous pressure seems to be of importance in pseudotumor cerebri syndromes, either as a cause (secondary intracranial hypertension) or as a consequence (idiopathic intracranial hypertension) of increased intracranial pressure. We present 3 case reports in which diagnostic imaging before and after CSF diversion provided evidence that narrowing of the transverse sinuses is a secondary phenomenon. Stent angioplasty of the venous sinuses should not be considered a therapeutic approach in these cases.     

MRI findings in lumbar puncture headache syndrome: abnormal dural-meningeal and dural venous sinus enhancement.

Intracranial hypotension (IH) is a treatable cause of persistent headaches. Persistent cerebrospinal fluid (CSF) leak at a lumbar puncture (LP) site may cause IH. We present postcontrast MRI of a patient with post-lumbar-puncture headache (LPHA) showing abnormal, intense, diffuse, symmetric, contiguous dural-meningeal (pachymeningeal) enhancement of the supratentorial and infratentorial intracranial dura, including convexities, interhemispheric fissure, tentorium, and falx. MRI also showed abnormal dural venous sinus enhancement, a new finding in LPHA, suggesting compensatory venous expansion. Thus, IH and venodilatation may play a role in the development of LPHA.     

Correction of the influence of clinostatic hypokinesis on encephalitic circulatory dynamics during the sleep in patients with hypertensive disease

During the sleep person is in the state of antiorthostasis, this state provokes vascular cerebral abnormalities (night cerebral hypervolemia). The nature of encephalon blood supply is changing in this horizontal state, in the result there is lowering of hydrostatic blood pressure, rise of the encephalon blood supply and more difficult venous outflow. 60 patients with essential hypertension (1-2 phases) at the age of 64.2 +/- 1.8 years which were in the state of slightly raised upper segment of the head and body during night sleep were examined. By the method of the cerebral venous hemocirculation defined. Conclusion. Cerebral arterial blood flow of examined patients has increased by 25-30% during the sleep, the changes of arterial and cerebral venous hemocirculation have attended hypervolemia. Being in the state of upper (by 10-15 degrees) head of the bed decreases blood redistribution and decreases the extension of cerebral blood circulation's acute abnormalities.     

Travel to high altitude during pregnancy: frequently asked questions and recommendations for clinicians

The effects of altitude on pregnancy have been extensively studied in high altitude residents, but there is a lack of knowledge concerning the pregnant altitude visitor. Exposure to hypoxia results in physiologic responses which act to preserve maternal and fetal oxygenation. However, these reactions are limited and maternal/fetal complications may be observed, especially in association with exercise. Certain pre-existing conditions or risk factors of hypertension/preeclampsia and/or fetal growth restriction are contra-indications for traveling to high altitude, especially after 20 weeks. The acclimatization process has to be respected to avoid acute mountain sickness without taking drugs, and at least a few days of acclimatization are required before exercising.     

The anatomy of collateral venous flow from the brain and its value in aetiological interpretation of intracranial pathology

For more than a century, available data concerning collateral venous outflow from the brain have received insufficient attention, as existing theories did not assign practical importance to them. Ideas concerning arterial blood supply and circulation of cerebrospinal fluid were considered more relevant. But available data afford a schematic model of cerebral venous outflow that does have important pathophysiological consequences. Principal outflow through the internal jugular veins can be substituted completely by the large vertebral plexuses, through communications at the cranial base. Emissary veins of the skull vault are small and few in number. Outflow from the deep venous system through the great vein of Galen can be substituted by choroidal, thalamic and striate anastomoses toward the basal vein. So-called intracerebral venous anastomoses through the centrum semiovale towards the convexity are nonexistent or negligible. Instead, a venous watershed exists separating paraventricular white matter from a layer of subcortical white matter. In most infants, the cavernous sinus is not yet connected to the cerebral veins. Once such communications have been formed, important collateral pathways exist through basal and Sylvian veins via the cavernous sinus to the pterygoid plexuses. Simultaneous hindrance of principal and collateral venous outflow will lead to elevated venous pressure and eventual insufficiency of cerebral blood flow (CBF). This will cause increased intracranial pressure, and ventricular enlargement due to periventricular atrophy. The slow phase of the two-compartment model of CBF coincides with the paraventricular white matter area of the deep venous system. In the neonate CBF was found to be still very low, and in the two compartments CBF increases at a different rate to a maximum in childhood. In hydrocephalus, measurement of CBF in the slow deep compartment, rather than the fast cortical one, will be most informative. Received: 11 July 1995 Accepted: 8 September 1995     

Accelerated myelination associated with venous congestion

Magnetic resonance imaging is currently the gold standard in the assessment of brain myelination. The normal pattern of brain myelination conforms to a fixed chronological sequence. Focal accelerated myelination is a usual pathological state and previously has only been associated with Sturge‐Weber syndrome. The purpose of our study is to describe alternate causes for accelerated myelination. We retrospectively reviewed serial MR scans, MR angiography, conventional angiography and the clinical progress of three children with accelerated myelination. Two patients with accelerated myelination had an underlying cerebral sinovenous thrombosis. The third patient had Sturge‐Weber syndrome. Our study strongly suggests that cerebral venous thrombosis with the consequent restriction of venous outflow could be a key factor in the induction of accelerated myelination. We recommend that in patients with accelerated myelination, the search for an underlying etiology should include careful evaluation of the intracranial vascular pathology, especially cerebral venous thrombosis.     

Quantifying the effect of posture on intracranial physiology in humans by MRI flow studies

PURPOSE: To quantify the effect of posture on intracranial physiology in humans by MRI, and demonstrate the relationship between intracranial compliance (ICC) and pressure (ICP), and the pulsatility of blood and CSF flows. MATERIALS AND METHODS: Ten healthy volunteers (29+/-7 years old) were scanned in the supine and sitting positions using a vertical gap MRI scanner. Pulsatile blood and CSF flows into and out from the brain were visualized and quantified using time-of-flight (TOF) and cine phase-contrast techniques, respectively. The total cerebral blood flow (tCBF), venous outflow, ICC, and ICP for the two postures were then calculated from the arterial, venous, and CSF volumetric flow rate waveforms using a previously described method. RESULTS: In the upright posture, venous outflow is considerably less pulsatile (57%) and occurs predominantly through the vertebral plexus, while in the supine posture venous outflow occurs predominantly through the internal jugular veins. A slightly lower tCBF (12%), a considerably smaller CSF volume oscillating between the cranium and the spinal canal (48%), and a much larger ICC (2.8-fold) with a corresponding decrease in the MRI-derived ICP values were measured in the sitting position. CONCLUSION: The effect of posture on intracranial physiology can be quantified by MRI because posture-related changes in ICC and ICP strongly affect the dynamics of cerebral blood and CSF flows. This study provides important insight into the coupling that exists between arterial, venous, and CSF flow dynamics, and how it is affected by posture.