Symptoms Of Idiopathic Intracranial Hypertension Research Articles

Quality of life at 6 months in the Idiopathic Intracranial Hypertension Treatment Trial.

To examine the changes in vision-specific and overall health-related quality of life (QOL) at 6 months in participants with idiopathic intracranial hypertension (IIH) and mild visual loss enrolled in the Idiopathic Intracranial Hypertension Treatment Trial (IIHTT) and to determine the signs and symptoms of IIH that mediate the effect of acetazolamide on QOL. We assessed QOL using the National Eye Institute Visual Function Questionnaire-25 (NEI-VFQ-25), the 10-Item NEI-VFQ-25 Neuro-Ophthalmic Supplement, and the 36-Item Short Form Health Survey (SF-36). We examined associations among changes in QOL measures over 6 months, treatment status, and changes in signs and symptoms using linear and structural equation models. Among the 165 participants with IIH (86 randomized to acetazolamide, 79 to placebo), beneficial effects of acetazolamide were seen on all QOL scales evaluated, as well as on the Near Activities (5.60 points, p = 0.03), Social Functioning (3.85 points, p = 0.04), and Mental Health (9.82, p = 0.04) subscales of the NEI-VFQ-25. Positive acetazolamide-related effects on QOL appeared to be primarily mediated by improvements in visual field, neck pain, pulsatile tinnitus, and dizziness/vertigo that outweighed the side effects of acetazolamide. The marked reductions in baseline QOL seen among patients with mild visual loss from IIH are improved by treatment with acetazolamide. When combined with acetazolamide-associated improvements in visual field and other aspects of IIH, our findings with respect to QOL provide further support from the IIHTT in favor of acetazolamide to augment a dietary intervention in the treatment of IIH with mild visual loss (clinicaltrials.gov: NCT01003639).

Optimizing ventriculoperitoneal shunt placement in the treatment of idiopathic intracranial hypertension: an analysis of neuroendoscopy, frameless stereotaxy, and intraoperative CT.

Cerebrospinal fluid shunting can effectively lower intracranial pressure and improve the symptoms of idiopathic intracranial hypertension (IIH). Placement of ventriculoperitoneal (VP) shunts in this patient population can often be difficult due to the small size of the ventricular system. Intraoperative adjuvant techniques can be used to improve the accuracy and safety of VP shunts for these patients. The purpose of this study was to analyze the efficacy of some of these techniques, including the use of intraoperative CT (iCT) and frameless stereotaxy, in optimizing postoperative ventricular catheter placement. The authors conducted a retrospective review of 49 patients undergoing initial ventriculoperitoneal shunt placement for the treatment of IIH. The use of the NeuroPEN Neuroendoscope, intraoperative neuronavigation, and iCT was examined. To analyze ventricular catheter placement on postoperative CT imaging, the authors developed a new grading system: Grade 1, catheter tip terminates optimally in the ipsilateral frontal horn or third ventricle; Grade 2, catheter tip terminates in the contralateral frontal horn; Grade 3, catheter terminates in a nontarget CSF space; and Grade 4, catheter tip terminates in brain parenchyma. All shunts had spontaneous CSF flow upon completion of the procedure. The average body mass index among all patients was 37.6 ± 10.9 kg/m2. The NeuroPEN Neuroendoscope was used in 44 of 49 patients. Intraoperative CT scans were obtained in 24 patients, and neuronavigation was used in 32 patients. Grade 1 or 2 final postoperative shunt placement was achieved in 90% of patients (44 of 49). In terms of achieving optimal postoperative ventricular catheter placement, the use of iCT was as effective as neuronavigation. Two patients had their ventricular catheter placement modified based on an iCT study. The use of neuronavigation significantly increased time in the operating room (223.4 ± 46.5 vs. 190.8 ± 31.7 minutes, p = 0.01). There were no shunt infections in this study. The use of iCT appears to be equivalent to the use of neuronavigation in optimizing ventricular shunt placement in IIH. Additionally, it may shorten operating room time and limit overall costs.

Ophthalmological symptoms of idiopathic intracranial hypertension: Importance for diagnosis and clinical course

Ophthalmological symptoms, particularly papilledema and transient visual obscuration as well as pulsatile head and ear noises are hallmarks of idiopathic intracranial hypertension also known as pseudotumor cerebri. Pronounced asymmetrical and unilateral papilledema are common occurrences in patients with idiopathic intracranial hypertension. Distension of the optic nerve sheath indicates increased intracranial pressure, which need to be confirmed by lumbar puncture. The presence of papilledema indicates increased intracranial pressure but its absence does not exceed it. Previous and long-standing papilledema obviously induces changes of the optic disc which prevent the further development of major disc swelling. The development of visual atrophy can mimic a regression of papilledema. In cases of marked papilledema visual loss may be caused by nonarteritic, ischemic optic neuropathy or macular edema. Visual obscuration is present in the vast majority of cases of pronounced chronic papilledema and is an indication of long-standing increased intracranial pressure. Most patients with pseudotumor cerebri and papilledema show only mild visual field defects, such as an enlarged blind spot and/or relatively mild arcuate defects, which regress after reduction of the intracranial pressure. Some patients, however, experience a relatively rapid progression of substantial visual field defects and optic atrophy requiring immediate and effective medicinal treatment. Ophthalmological symptoms are frequently key criteria for idiopathic intracranial hypertension. More attention should be paid to these signs and the diagnostic approach should be multidisciplinary.

Neurologische Symptome, Diagnostik, Differenzialdiagnose und medikamentöse Therapie des Pseudotumor cerebri

Persistent headache and loss of visual acuity combined with papilledema are the predominant symptoms of idiopathic intracranial hypertension (IIH). The clinical signs are not different from those seen in other diseases with elevated intracranial pressure. To differentiate primary and secondary forms of increased intracranial pressure neuroimaging procedures and analysis of cerebrospinal fluid (CSF) are absolutely essential according to national and international guidelines. Lumbar puncture reveals an elevated opening pressure in cases of IIH as the only pathological finding. Treatment options are serial lumbar punctures combined with body weight reduction as well as medication with carbonic anhydrase inhibitors, such as acetazolamide and topiramate or diuretic therapy with furosemide. In some patients surgical options, e.g. optic nerve sheath fenestration, CSF shunting procedures including ventriculoperitoneal and lumboperitoneal shunt systems and bariatric surgery also have to be considered. In recent years modern neuroradiological procedures have also been applied (e.g. venous stenting in cases of sinus obstruction) in some centers.

The Utility of Computed Tomography in Shunted Patients with Idiopathic Intracranial Hypertension Presenting to the Emergency Department

Shunted patients with idiopathic intracranial hypertension (IIH) often present to the emergency department (ED) for symptoms related to their disease. Although brain imaging with computed tomography (CT) is often performed, particularly in the current medicolegal environment, its utility during these ED visits is unclear. The ED visits of all shunted adult patients with IIH from 2003-2015 were retrospectively reviewed. ED visits not related to IIH were excluded from our study. Thirty-one patients visited the ED 171 times for IIH symptoms. Five patients had greater than 10 ED visits. Twenty-five (81%) patients had 131 visits involving a CT scan, while six (19%) patients were not scanned. The majority of scans (n = 126, 96%) showed no change; five (4%) scans detected new noncritical pathologies. On the basis of CT findings alone, treatment changes occurred in three (2.3%) instances. Of the 131 visits with a CT scan, twenty-five (19%) visits resulted in management changes; of the 40 ED visits without a CT scan, four (10%) visits resulted in a management change (P = 0.23). In our cohort, CT imaging rarely showed a change in pathology or affected the management of patients with IIH. There was no difference in the rate of management changes between those patients who underwent a CT scan and those who did not. Given the risk of cumulative radiation exposure and cost of CT scans, CT imaging should be used when there is concern for visual dysfunction and the utility of CT imaging in the ED for the workup of other symptoms related to IIH must be explored further.

Endovascular Stenting for Idiopathic Intracranial Hypertension

Transverse sinus stenosis (TSS) is often observed in patients with idiopathic intracranial hypertension (IIH). Studies show that all symptoms of IIH can be resolved by transverse sinus stent placement. We present a case of a 39-year-old woman diagnosed with IIH presented with papilledema and severe headaches. The consideration of interventional management was necessitated by the preceding failure of several months of medical treatment. Her vascular imaging demonstrated stenosis of the transverse sinus and her intracranial venous pressure measurements indicated elevated pressure with a high pressure gradient across the stenosis. She underwent transverse sinus stent placement across the stenotic segment. After this intervention, her symptoms improved and her intracranial pressure normalized. The imaging follow-up revealed efficacious patency of the stent. Based on a mathematical model, we suggest that a Starling-like resistor demonstrating a collapsible transverse sinus can permanently be replaced by a rigid-walled sinus upon employment of an endovascular stent in the stenotic transverse sinus, which should be considered as an alternative to other surgical procedures for IIH patients.

Cervical puncture and perimedullary cistern shunt placement for idiopathic intracranial hypertension: An alternative to lumbar cistern or cerebral ventricular catheter placement a report of two cases.

Objective:Idiopathic intracranial hypertension (IIH) is a syndrome characterized by increased intracranial pressure (ICP) in the absence of an identifiable cause, and if untreated, can result in permanent vision loss. In symptomatic IIH patients, cerebrospinal fluid (CSF) diversion can lower ICP and protect vision; however, currently used CSF diversion systems are prone to malfunction in this population.Materials and Methods:In two IIH patients with histories of numerous prior shunt revisions that presented with proximal ventriculoperitoneal shunt malfunction, ICP reduction was achieved by an alternative surgical cerebrospinal fluid (CSF) diversion technique: Fluoroscopically guided, percutaneous placement of a catheter in the premedullary cistern and subsequent connection to the valve and distal shunt system.Results:Postoperatively, both patients’ papilledema resolved, headaches improved, and the shunts were working well at 3-month follow-up. At 1-year follow-up, one patient was well without papilledema or symptom recurrence, and the second patient had the shunt system removed by an outside surgeon.Conclusion:This technique may hold promise as an alternative shunting strategy in IIH patients with numerous proximal shunt failures or who are poor candidates for ventricular and lumbar shunts.

What is the best imaging modality in evaluating patients with unilateral pulsatile tinnitus?

What is the best imaging modality in evaluating patients with unilateral pulsatile tinnitus?

Idiopathic intracranial hypertension from the perspective of headache center

Idiopathic intracranial hypertension (IIH) is a pathological state defined as an increase of intracranial pressure in the absence of a causative pathological process. The aim of this study was to evaluate the clinical features of the patients with IIH diagnosed in our Headache Center according to the current knowledge of this disorder. In the retrospective and cross-sectional analysis of 3395 patients we present 12 newly diagnosed IIH patients, ten women and two men, aged from 19 to 51, with obtained values of cerebrospinal fluid pressure between 250 and 680 mm of water. The symptoms of IIH clinical presentation have been headache, reported by 92% of patients; papilledema, noted in 67%; and cranial nerve impairment (25%). The results obtained from presented patients confirmed the presence of headache features that are included in criteria for headache attributed with IIH in majority of them: progressive, daily, diffuse, non-pulsatile headache with aggravation by coughing or straining. Decrease of pain intensity after lumbar puncture was noted in all patients. We notice the relatively small proportion of patients with headache attributed to IIH among the patients treated in our Headache Center. The prevalence of IIH is not low and headache is the most frequent presenting symptom; therefore, we could only conclude that some chronic headache patients refractory for treatment are patients with IIH.

Headache prevalence and clinical features in patients with idiopathic intracranial hypertension (IIH)

Headache is a key symptom of idiopathic intracranial hypertension (IIH). Operational diagnostic criteria for "Headache attributed to IIH" are included in the international classification of headache disorders, the ICHD-2. The association of IIH with obesity was established by several reports. We investigate the prevalence of headache and its main clinical features in a clinical sample of IIH patients. The possible correlations between the presence of headache and body mass index (BMI) and intracranial pressure (ICP) levels were studied in a consecutive clinical series of patients, in whom diagnosis of IIH was confirmed by exclusion of secondary forms and by the evidence of increased ICP. Differences for age, BMI, and ICP between patients with and without headache and between males and females were assessed with Mann-Whitney U test. Spearman's correlation analysis was used to assess relationships between age, BMI, and ICP. P value < 0.05 was used to set statistical significance. 40 patients entered the study (9 males, 31 females; mean age 39, 8 years, SD 13.2). Headache was reported by 75 % patients. Those characteristics which are included in the present international diagnostic criteria for "Headache attributed to IIH" were reported by a remarkable proportion of the studied patients, but not by all. On the other hand, some headache features usually attributed to migraine forms, and which are not among the required criteria were present in some patients: pulsating quality and unilateral distribution of pain in around 20 %, and migrainous associated symptoms in more than 40 % of the sample. According to statistical analyses, no differences were found for age, BMI, and ICP between patients with and without headache. Our results confirmed the strong association between headache and IIH. Although no significant correlations between some of the key features of IIH were found in this study, we suggest that further studies on larger series--possibly with a longitudinal evaluation--are needed, to help clinicians in categorizing different subgroups among IIH patients as well as in identifying the main factors influencing the prognosis of this disorder.

Hypertension intracrânienne idiopathique : stent ou non

The pathogenesis and treatment paradigm for idiopathic intracranial hypertension (IIH) are controversial. Transverse sinus stenosis is seen in the majority of patients with IIH and appears to play a role in the disease process. The debate continues as to whether transverse sinus stenosis is a primary or secondary process relative to raised intracranial pressure. While the role of transverse sinus stenosis in IIH pathogenesis remains controversial, modeling studies suggest that stent placement within a transverse sinus stenosis with a significant pressure gradient should decrease cerebral venous pressure, improve CSF resorption in the venous system, and thereby reduce intracranial (CSF) pressure, improving the symptoms of IIH and reducing papilledema. Beside the classical surgical treatments, venous sinus stenting could be a treatment option for many patients with IIH. However, additional work, preferably controlled prospective studies, needs to be performed to prove its safety and efficacy. The goal of this article is to review the current literature on dural venous sinus stenting.

Pediatric Idiopathic Intracranial Hypertension and Extreme Childhood Obesity

To estimate the magnitude of the association between overweight, moderate, and extreme childhood obesity and the risk of idiopathic intracranial hypertension (IIH). Risk estimates were obtained from the Kaiser Permanente Southern California Children's Health Study (n = 913 178). Weight classes were assigned by body mass index specific for age and sex. A combination of electronic database searches followed by complete medical records review was used to identify all children diagnosed with IIH between 2006 and 2009. We identified 78 children with IIH, the majority of whom were girls (n = 66, 84.5%), age 11-19 (n = 66, 84.5%), non-Hispanic Whites (n = 37, 47.4%), and overweight or obese (n = 57, 73.1%). The adjusted ORs and 95% CIs of IIH with increasing weight class were 1.00, 3.56 (1.72-7.39), 6.45 (3.10-13.44), and 16.14 (8.18-31.85) for underweight/normal weight (reference category), overweight, moderately obese and extremely obese 11-19 year olds, respectively (P for trend < .001). Other independent IIH risk factors included White non-Hispanic race/ethnicity for all age groups and female sex, but only in older children. Overweight/obese children also had more IIH symptoms at onset than normal weight children. We found that childhood obesity is strongly associated with an increased risk of pediatric IIH in adolescents. Our findings suggest that the childhood obesity epidemic is likely to lead to increased morbidity from IIH particularly among extremely obese, White non-Hispanic teenage girls. Our findings also suggest careful screening of these at risk individuals may lead to earlier detection and opportunity for treatment of IIH.

Headache in patients with idiopathic intracranial hypertension: a pilot study to assess applicability of ICHD-2 diagnostic criteria

Headache is one of the most common symptoms of idiopathic intracranial hypertension (IIH). The aim of this study was to investigate the applicability of the diagnostic criteria for "Headache attributed to IIH" included in the current classification of headache disorders, particularly as far as the main headache features. A consecutive clinical series of IIH patients with demonstration of increased intracranial pressure by lumbar puncture in the recumbent position were enrolled. Among a total of 22 patients, headache was reported by 14. The proportion of patients reporting the main headache features required by diagnostic criteria were: 93 % for daily or nearly-daily occurrence; 71.5 % for diffuse/non-pulsating pain; 57 % for aggravation by coughing/straining. Thus, these three headache features, at least one of which is required for diagnosis of headache attributed to IIH, were present in the vast majority of our sample, suggesting that their inclusion should be regarded as appropriate. The analysis of our results may suggest possible changes in the current ICDH-2 criteria for headache attributed to IIH, based on the following considerations: the existence of remarkable differences as far as the relative frequency of each headache feature; the fact that diffuse and non-pulsating pain-included in the current classification as a single requirement-were not always found together; the high frequency of migrainous associated symptoms (nausea or photophobia-phonophobia were present in 71.5 % cases).

Primary spontaneous cerebrospinal fluid rhinorrhea: a symptom of idiopathic intracranial hypertension?

The authors aim to identify the characteristics of primary spontaneous CSF rhinorrhea and propose a hypothesis for its pathogenesis. Between 2003 and 2009, 21 patients diagnosed with primary spontaneous CSF rhinorrhea underwent surgery in the authors' hospital. The clinical aspects were retrospectively reviewed, and their characteristics were analyzed. There were 18 women and 3 men, whose ages ranged from 37 to 74 years (mean 53 years). Body mass index (BMI) ranged from 22 to 58.8 kg/m(2) (mean 31.2 kg/m(2)). Eighteen patients (85.7%) were overweight, and 18 (85.7%) suffered from headache or tinnitus before rhinorrhea. Radiological images revealed fully or partially empty sellae in 14 patients (66.7%). The preoperative intracranial pressure (ICP) ranged from 11 to 28 cm H(2)O (mean 17.6 cm H(2)O), while the postoperative ICP ranged from 21 to 32 cm H(2)O (mean 25.5 cm H(2)O, p < 0.01). An endoscope-assisted transnasal approach was chosen for the repair. Postoperatively, in 95.2% of patients a cure was achieved. Rhinorrhea recurred in only 1 patient, and a leakage from a new defect occurred in another patient 4 years after the operation. Both patients underwent additional surgery, which was successful. The follow-up period varied from 5 to 75 months with a mean of 34 months. All patients had direct or indirect evidence of elevated ICP, most patients presented with symptoms of idiopathic intracranial hypertension (IIH), and most patients were women and obese. Primary spontaneous CSF rhinorrhea may be due to IIH, and it is a rare symptom of IIH. When treating or monitoring these patients during follow-up, ICP should be controlled, and other symptoms of IIH should be noted.

Lennox-Gastaut Syndrome and idiopathic intracranial hypertension

Lennox-Gastaut Syndrome is a severe childhood epilepsy syndrome characterised by the diagnostic triad of a slow spike and wave pattern on electroencephalogram, multiple seizure types and developmental delay. Idiopathic intracranial hypertension is a syndrome characterised by raised cerebrospinal fluid pressure in the absence of an intracranial mass lesion or ventricular dilatation and often headache. We present the first reported case of Lennox-Gastaut Syndrome associated with symptomatic idiopathic intracranial hypertension in a 15 year old male, requiring cerebrospinal fluid diversion by means of ventriculoperitoneal shunting.

Absence of aquaporin-4 antibodies in patients with idiopathic intracranial hypertension

The pathophysiology of abnormal cerebrospinal fluid (CSF) dynamics in idiopathic intracranial hypertension (IIH) is not clear [1]. In healthy individuals, CSF is mostly formed in the choroid plexus with small contributions from extrachoroidal tissues, including ependymal surfaces of the brain and the capillary–astrocyte complex in the blood-brain barrier. It is reabsorbed into the dural venous sinuses through the arachnoid villi, although other sites are increasingly being recognised [10]. Several theories have been suggested to explain the aetiology of raised CSF pressure in IIH, including increased CSF production, impaired CSF absorption, obstruction of dural venous sinuses and increased brain volume due to cerebral oedema [6]. More recently, the potential role of proinflammatory CSF profiles have been suggested in some studies [2, 5]. Aquaporins are a recently discovered family of transmembrane water channels which play an important role in water homeostasis in the central nervous system (CNS) and are thought to be involved in the pathophysiologic mechanisms of cerebral oedema [3]. Aquaporin (AQP)-1 is natively expressed in the choroid plexus and contributes to water transport across the choroidal epithelium during CSF secretion. AQP-4 is more widely distributed within the CNS, including the choroid plexus [13] and ependymal cells of the ventricles [9]. Bloch et al. [4] suggested that AQP-4 could facilitate CSF absorption in hydrocephalus. Recently, antibodies to AQP-4 have been suggested to play a role in the pathogenesis of neuromyelitis optica (NMO) [11]. We hypothesised that a dysfunction of AQP-4 expression could affect CSF secretion or absorption and potentially contribute to the pathogenesis of IIH. In this study, we utilised a recently described anti-AQP-4 antibody assay [14] to look for AQP-4 antibodies in the serum and CSF of patients with IIH. We were not able to investigate the role of anti-AQP-1 antibodies because such an assay is currently not available. Paired CSF and serum samples from 10 female symptomatic IIH patients [mean age 31.8 ± 7.8 years; mean body mass index (BMI) 33.4 ± 6.9 kg/m] who were diagnosed according to the updated modified Dandy criteria [8] and 10 female control subjects (mean age: 35.8 ± 12.1 years; mean BMI: 31.7 ± 8.8 kg/m) were examined for anti-AQP-4 antibodies. Control subjects were patients who presented with headache and had lumbar puncture to exclude subarachnoid haemorrhage or raised intracranial pressure, and who were subsequently diagnosed with migraine or tension-type headache. The study was approved by South Yorkshire research ethics committee and all participants provided written informed consent. S. Dhungana A. Ismail B. Sharrack Department of Neurology, Sheffield Teaching Hospitals NHS Trust, University of Sheffield, Sheffield, UK

Bariatric surgery for the treatment of idiopathic intracranial hypertension

The purpose of this study was to review the literature on the effectiveness of bariatric surgery for obese patients with idiopathic intracranial hypertension (IIH) with regard to both symptom resolution and resolution of visual deficits. The published literature was reviewed using manual and electronic search techniques. Data from each relevant manuscript were gathered, analyzed, and compared. These included demographic data, pre- and postoperative symptoms, pre- and postoperative visual field deficits, bariatric procedure type, absolute weight loss, changes in body mass index, and changes in CSF opening pressure. Eleven relevant publications (including 6 individual case reports) were found, reporting on a total of 62 patients. The Roux-en-Y gastric bypass was the most common bariatric procedure performed. Fifty-six (92%) of 61 patients with recorded postoperative clinical history had resolution of their presenting IIH symptoms following bariatric surgery. Thirty-four (97%) of 35 patients who had undergone pre- and postoperative funduscopy were found to have resolution of papilledema postoperatively. Eleven (92%) of 12 patients who had undergone pre- and postoperative formal visual field testing had complete or nearly complete resolution of visual field deficits, and the remaining patient had stabilization of previously progressive vision loss. In 13 patients both pre- and postoperative CSF pressures were recorded, with an average postoperative pressure decrease of 254 mm H(2)O. Changes in weight loss and body mass index varied depending on the reported postoperative follow-up interval. The published Class IV evidence suggests that bariatric surgery may be an effective treatment for IIH in obese patients, both in terms of symptom resolution and visual outcome. Prospective, controlled studies are necessary for better elucidation of its role.

Indikation und Technik der Optikusscheidenfensterung

An optic nerve sheath fenestration is indicated when papilloedema leads to progressive visual loss despite previous, conservative measures and when no cause of increased intracranial pressure can be indentified and eliminated. This rather rare constellation usually occurs in idiopathic intracranial hypertension. The procedure is performed via a medial transconjunctival orbitotomy. If headaches and neurologic symptoms other than visual deterioration prevail, the placement of a ventricular shunt is preferred. This review covers the symptoms of idiopathic intracranial hypertension and optic nerve sheath fenestration with its technical aspects and results.

Predicting the Development of Postoperative Symptoms of Idiopathic Intracranial Hypertension based on Preoperative Radiologic Findings

Predicting the Development of Postoperative Symptoms of Idiopathic Intracranial Hypertension based on Preoperative Radiologic Findings

Idiopathic Intracranial Hypertension in a Pediatric Population: A Retrospective Analysis of the Initial Imaging Evaluation

There are few studies in the pediatric population regarding the use of magnetic resonance venography to rule out cerebral venous sinus thrombosis in patients presenting with signs and symptoms of idiopathic intracranial hypertension. The purpose of this study was to compare the clinical characteristics of children with presumed idiopathic intracranial hypertension who did and did not undergo venography during their evaluation at a single children's hospital. The authors found that 45 of 68 (66%) patients underwent magnetic resonance venography. Five of 45 (11%) venography studies revealed a thrombosis. There were no significant clinical differences within patients based on the completion of venography or the presence of thrombosis. Larger studies are needed to identify risk factors for thrombosis in children with presumed idiopathic intracranial hypertension, as well as factors influencing physician decision making in the use of magnetic resonance venography in this evaluation.