Tumor Embolization through Meningohypophyseal and Inferolateral Trunks is Safe and Effective.

BACKGROUND AND PURPOSE: Skull base tumors are commonly supplied by dural branches of the meningohypophyseal and inferolateral trunks. Embolization through these arteries is often avoided due to technical challenges and inherent risks; however, successful embolization can be a valuable surgical adjunct. We aimed to review the success and complications in our series of tumor embolizations through the meningohypophyseal and inferolateral trunks. MATERIALS AND METHODS: We performed a retrospective review of patients with tumor treated with preoperative embolization at our institution between 2010 and 2020. We reviewed the following data: patients' demographics, tumor characteristics, endovascular embolization variables, and surgical results including estimated blood loss, the need for transfusion, and operative time. RESULTS: Among 155 tumor embolization cases, we identified 14 patients in whom tumor embolization was performed using the meningohypophyseal (n = 13) or inferolateral (n = 4) trunk. In this group of patients, on average, 79% of tumors were embolized. No mortality or morbidity from the embolization procedure was observed in this subgroup of patients. The average estimated blood loss in the operation was 395 mL (range, 200-750 mL). None of the patients required a transfusion, and the average operative time was 7.3 hours. CONCLUSIONS: Some skull base tumors necessitate embolization through ICA branches such as the meningohypophyseal and inferolateral trunks. Our series demonstrates that an effective and safe embolization may be performed through these routes.

Arterial and Venous 3D Fusion AV-3D-DSA: A Novel Approach to Cerebrovascular Neuroimaging.

DSA is the standard imaging technique for evaluation of cerebrovascular conditions. However, One drawback is its limitation in depicting a single angiographic phase at a time. We describe a new 3D-DSA algorithm, which we call arterial and venous-3D-DSA, which allows the concurrent yet distinct display of the arterial and venous structures, which may be useful for different clinical and educational purposes.

Dural Venous Channels: Hidden in Plain Sight-Reassessment of an Under-Recognized Entity.

BACKGROUND AND PURPOSE: Tentorial sinus venous channels within the tentorium cerebelli connecting various cerebellar and supratentorial veins, as well as the basal vein, to adjacent venous sinuses are a well-recognized entity. Also well-known are "dural lakes" at the vertex. However, the presence of similar channels in the supratentorial dura, serving as recipients of the Labbe, superficial temporal, and lateral and medial parieto-occipital veins, among others, appears to be underappreciated. Also under-recognized is the possible role of these channels in the angioarchitecture of certain high-grade dural fistulas. MATERIALS AND METHODS: A retrospective review of 100 consecutive angiographic studies was performed following identification of index cases to gather data on the angiographic and cross-sectional appearance, location, length, and other features. A review of 100 consecutive dural fistulas was also performed to identify those not directly involving a venous sinus. RESULTS: Supratentorial dural venous channels were found in 26% of angiograms. They have the same appearance as those in the tentorium cerebelli, a flattened, ovalized morphology owing to their course between 2 layers of the dura, in contradistinction to a rounded cross-section of cortical and bridging veins. They are best appreciated on angiography and volumetric postcontrast T1-weighted images. Ten dural fistulas not directly involving a venous sinus were identified, 6 tentorium cerebelli and 4 supratentorial. CONCLUSIONS: Supratentorial dural venous channels are an under-recognized entity. They may play a role in the angioarchitecture of dural arteriovenous fistulas that appear to drain directly into a cortical vein. We propose "dural venous channel" as a unifying name for these structures.

Cerebral Venous Thrombosis Associated with COVID-19.

Despite the severity of coronavirus disease 2019 (COVID-19) being more frequently related to acute respiratory distress syndrome and acute cardiac and renal injuries, thromboembolic events have been increasingly reported. We report a unique series of young patients with COVID-19 presenting with cerebral venous system thrombosis. Three patients younger than 41 years of age with confirmed Severe Acute Respiratory Syndrome coronavirus 2 (SARS-Cov-2) infection had neurologic findings related to cerebral venous thrombosis. They were admitted during the short period of 10 days between March and April 2020 and were managed in an academic institution in a large city. One patient had thrombosis in both the superficial and deep systems; another had involvement of the straight sinus, vein of Galen, and internal cerebral veins; and a third patient had thrombosis of the deep medullary veins. Two patients presented with hemorrhagic venous infarcts. The median time from COVID-19 symptoms to a thrombotic event was 7 days (range, 2-7 days). One patient was diagnosed with new-onset diabetic ketoacidosis, and another one used oral contraceptive pills. Two patients were managed with both hydroxychloroquine and azithromycin; one was treated with lopinavir-ritonavir. All patients had a fatal outcome. Severe and potentially fatal deep cerebral thrombosis may complicate the initial clinical presentation of COVID-19. We urge awareness of this atypical manifestation.

Toward a Better Understanding of Dural Arteriovenous Fistula Angioarchitecture: Superselective Transvenous Embolization of a Sigmoid Common Arterial Collector.

BACKGROUND AND PURPOSE: Our aim was to propose a conceptually new angioarchitectural model of some dural arteriovenous fistulas based on subset analysis of transverse and sigmoid type lesions. The "common collector" notion argues for convergence of multiple smaller caliber arterial vessels on a common arterial collector vessel within the sinus wall. Communication of this single collector (or constellation of terminal collectors) with the sinus proper defines the site of arteriovenous fistula, which can be closed by highly targeted embolization, preserving the sinus and avoiding unnecessary permeation of indirect arterial feeders. MATERIALS AND METHODS: One hundred consecutive dural arteriovenous shunts were examined. Thirty-six transverse/sigmoid fistulas were identified within this group and analyzed for the presence of a common arterial collector as well as other parameters, including demographics, grade, treatment approach, and outcome. RESULTS: A common collector was identified in nearly all Cognard type I lesions (15 fistulas with 14 single collector vessels seen) and progressively less frequently in higher grade fistulas. Identification of the common collector requires careful angiographic analysis, including supraselective and intraprocedural angiographies during treatment, and final embolic material morphology. CONCLUSIONS: Detailed evaluation of imaging studies allows frequent identification of a vascular channel in the sinus wall, which we argue reflects a compound, common arterial channel (rather than a venous collector) with 1 or several discrete fistulous points between this vessel and the sinus proper. Targeted closure of this channel is often feasible, with sinus preservation and avoidance of embolic material penetration into arteries remote from fistula site.

Toward Better Understanding of Flow Diversion in Bifurcation Aneurysms.

BACKGROUND AND PURPOSE: Flow diversion is being increasingly used to treat bifurcation aneurysms. Empiric approaches have generally led to encouraging results, and a growing body of animal and ex vivo literature addresses the fate of target aneurysms and covered branches. Our prior investigations highlighted the dynamic nature of metal coverage provided by the Pipeline Embolization Device and suggested strategies for creating optimal single and multidevice constructs. We now address the geometric and hemodynamic aspects of jailing branch vessels and neighboring target aneurysms. MATERIALS AND METHODS: Fundamental electric and fluid dynamics principles were applied to generate equations describing the relationships between changes in flow and the degree of vessel coverage in settings of variable collateral support to the jailed territory. Given the high complexity of baseline and posttreatment fluid dynamics, in vivo, we studied a simplified hypothetic system with minimum assumptions to generate the most conservative outcomes. RESULTS: In the acute setting, Pipeline Embolization Devices modify flow in covered branches, principally dependent on the amount of coverage, the efficiency of collateral support, and intrinsic resistance of the covered parenchymal territory. Up to 30% metal coverage of any branch territory is very likely to be well-tolerated regardless of device or artery size or the availability of immediate collateral support, provided, however, that no acute thrombus forms to further reduce jailed territory perfusion. CONCLUSIONS: Basic hemodynamic principles support the safety of branch coverage during aneurysm treatment with the Pipeline Embolization Device. Rational strategies to build bifurcation constructs are feasible.

Curative cerebrovascular reconstruction with the Pipeline embolization device: the emergence of definitive endovascular therapy for intracranial aneurysms.

Endovascular, endosaccular, coil embolization has emerged as an established therapy for both ruptured and unruptured cerebral aneurysms. However, many aneurysms are not cured using conventional endovascular techniques. Coil embolization often results in incomplete aneurysm occlusion or recanalization in the ensuing months after treatment. The Pipeline embolization device (PED; Chestnut Medical) represents a new generation endoluminal implant which is designed to treat aneurysms by reconstructing the diseased parent artery. Immediately after implantation, the PED functions to divert flow from the aneurysm, creating an environment conducive to thrombosis. With time, the PED is incorporated into the vessel wall as neointimal-endothelial overgrowth occurs along the construct. Ultimately, this process results in the durable complete exclusion of the aneurysm from the cerebrovasculature and a definitive endoluminal reconstruction of the diseased parent artery.

Rapid intracranial clot removal with a new device: the alligator retriever.

BACKGROUND AND PURPOSE: Despite availability of an approved drug to treat acute cerebral ischemia, most patients with stroke do not realize a good outcome. A method that would rapidly increase or restore cerebral perfusion before irreversible cell death should improve patient outcomes. MATERIALS AND METHODS: We recently had the opportunity to treat 6 middle-aged-to-elderly patients who presented with signs and symptoms of acute cerebral ischemia, by mechanically removing their (predominantly) middle cerebral artery clots by using a new retrieval device that had been previously approved by the US Food and Drug Administration for intravascular retrieval of foreign bodies. During a 2-month period, the 6 patients were treated in 5 separate institutions. No patient had an unsuccessful attempt at clot removal. The cases were collected by personal communication with each operator. RESULTS: In all instances, use of the device resulted in rapid clot removal. Each patient had a large improvement in National Institutes of Health Stroke Scale score. Two of the 6 patients had experienced failure of another clot retrieval device, and 3 patients required no systemic thrombolytics, reducing the likelihood of one of the most feared complications of stroke therapy, intracranial hemorrhage. SUMMARY: We believe that use of this device may result in improved outcomes for patients with acute ischemic stroke. In our limited experience, it provided a rapid, safe, and effective means for achieving revascularization.

Rapid stent-supported revascularization in acute ischemic stroke.

We report the case of a patient with an acute middle cerebral artery occlusion emergently revascularized with a Neuroform self-expanding stent.

Prostaglandins activation of erythropoietin production and erythroid progenitor cells.

A model is presented postulating a role for prostaglandins E and prostacyclin in kidney generation of erythropoietin and the activation of the erythroid progenitor cell (CFU-E) compartment by erythropoietin (Ep). Several criteria have been met to prove that prostanoids mediate erythropoiesis: 1) several E-type prostaglandins (PGE2, 15-methyl prostaglandin E2, 16,16-dimethyl E2, 6-keto-E1 and PGE1) produced a significant increase in radioiron incorporation in red cells of exhypoxic polycythemic mice; 2) prostaglandin E2 increased kidney production of erythropoietin in the isolated perfused dog kidney; 3) arachidonic acid, a precursor for all bisenoic prostaglandins, increased kidney production of erythropoietin in the isolated perfused dog kidney which was blocked by pretreatment with the cyclo-oxygenase inhibitor drug indomethacin; 4) hypoxemic perfusion of the isolated perfused dog kidney increased kidney production of erythropoietin and produced an elevation in prostacyclin in the perfusates; 5) albuterol, a beta-2 adrenergic agonist, produced a significant increase in perfusate levels of erythropoietin and PGE in the isolated perfused dog kidney; 6) renal ischemia increased Ep and PGE levels in renal venous plasma which was blocked by pretreatment with indomethacin; 7) prostaglandin E2 and arachidonic acid produced a significant increase in erythroid colonies (CFU-E) in vitro in normal mouse bone marrow; 8) E-type prostaglandins (15-methyl E2) increased in vivo erythroid colony (CFU-E) formation in bone marrows of post-hypoxic polycythemic mice; and 9) injections of 15-methyl E2 daily for six weeks in normal and hypoxic mice produced a significant elevation in the total circulating red cell mass. These studies indicate that hypoxic stimulation of kidney production of erythropoietin may be related to the generation of prostacyclin (PGI2). On the other hand, albuterol and ischemic (reduction in renal blood flow) stimulation of kidney production of erythropoietin involves prostaglandins of the E type. In addition, E-type prostaglandins were found to enhance the effects of erythropoietin in activating erythroid progenitor cells (CFU-E) in the bone marrow. We postulate from our model that prostaglandins E and prostacyclins are involved in the mechanism of kidney production of erythropoietin as well as the activation of the Ep-responsive cell (ERC) compartment.

Endoluminal Reconstruction for Nonsaccular Aneurysms of the Proximal Posterior Cerebral Artery with the Pipeline Embolization Device.

BACKGROUND AND PURPOSE: Treatment options for nonsaccular posterior cerebral artery aneurysms include a range of surgical and endovascular reconstructive and deconstructive methods. However, no truly satisfactory treatment option is available to date for lesions arising from the P1 and P2 segments. The purpose of the present case series is to investigate both the efficacy and safety of the Pipeline Embolization Device in treating these challenging aneurysms. MATERIALS AND METHODS: We present a series of 6 consecutive patients who underwent endoluminal reconstruction with the Pipeline Embolization Device for nonsaccular P1 or P2 segment aneurysms between January 2009 and June 2013. RESULTS: Aneurysm location included the P1 segment in 2 patients and the P2 segment in 4 patients. Mean aneurysm diameter was 23 mm (range, 5-44 mm). Mean length of the arterial segment involved was 10 mm (range, 6-19 mm). Clinical presentation included mass effect in 4 patients and perforator stroke and subacute aneurysmal subarachnoid hemorrhage in 1 patient each. Endovascular reconstruction was performed by using 1 Pipeline Embolization Device in 5 patients and 2 overlapping Pipeline Embolization Devices in the remaining patient. Angiographic aneurysm occlusion was immediate in 1 patient, within 6 months in 4 patients, and within 1 year in the remaining patient. Index symptoms resolved in 4 patients and stabilized in the remaining 2. No new permanent neurologic sequelae and no aneurysm recurrence were recorded during the mean follow-up period of 613 days (range, 540-725 days). CONCLUSIONS: Endovascular reconstruction with the Pipeline Embolization Device for nonsaccular aneurysms arising from the P1 and P2 segments compares favorably with historical treatment options in terms of occlusion rate, margin of safety, and neurologic outcome.

Anterior choroidal artery patency and clinical follow-up after coverage with the pipeline embolization device.

BACKGROUND AND PURPOSE: Endoluminal reconstruction with the Pipeline Embolization Device is an effective treatment option for select intracranial aneurysms. However, concerns for the patency of eloquent branch arteries covered by the Pipeline Embolization Device have been raised. We aimed to examine the patency of the anterior choroidal artery and clinical sequelae after ICA aneurysm treatment. MATERIALS AND METHODS: We prospectively analyzed all patients among our first 157 patients with ICA aneurysms treated by the Pipeline Embolization Device who required placement of at least 1 device across the ostium of the anterior choroidal artery. The primary outcome measure was angiographic patency of the anterior choroidal artery at last follow-up. Age, sex, type of aneurysm, neurologic examination data, number of Pipeline Embolization Devices used, relationship of the anterior choroidal artery to the aneurysm, and completeness of aneurysm occlusion on follow-up angiograms were also analyzed. RESULTS: Twenty-nine aneurysms requiring placement of at least 1 Pipeline Embolization Device (median = 1, range = 1-3) across the anterior choroidal artery ostium were identified. At angiographic follow-up (mean = 15.1 months; range = 12-39 months), the anterior choroidal artery remained patent, with antegrade flow in 28/29 aneurysms (96.5%), while 24/29 (82.7%) of the target aneurysms were angiographically occluded by 1-year follow-up angiography. Anterior choroidal artery occlusion, with retrograde reconstitution of the vessel, was noted in a single case. A significant correlation between the origin of the anterior choroidal artery from the aneurysm dome and failure of the aneurysms to occlude following treatment was found. CONCLUSIONS: After placement of 36 Pipeline Embolization Devices across 29 anterior choroidal arteries (median = 1 device, range = 1-3 devices), 1 of 29 anterior choroidal arteries was found occluded on angiographic follow-up. The vessel occlusion did not result in persistent clinical sequelae. Coverage of the anterior choroidal artery origin with the Pipeline Embolization Device, hence, may be considered reasonably safe when deemed necessary for aneurysm treatment.

Foreign Body Emboli following Cerebrovascular Interventions: Clinical, Radiographic, and Histopathologic Features.

Foreign material emboli following cerebral, cardiac, and peripheral catheterizations have been reported since the mid-1990s. Catheter coatings have been frequently implicated. The most recent surge of interest in this phenomenon within the neurointerventional community is associated with procedures using flow-diversion devices for the treatment of cerebral aneurysms. Following coil-supported Pipeline embolization in 4 cases and stent-supported coiling in 1, 5 patients developed multiple subcentimeter enhancing lesions, usually with surrounding edema and variable magnetic susceptibility in the vascular territories of the treated aneurysms. Conventional angiography findings were unrevealing. Laboratory work-up showed mild CSF protein elevation with no leukocytosis. Brain biopsy in 2 cases revealed granulomatous angiitis encasing foreign material, identical in stain appearance to a polyvinylpyrrolidone catheter coating. Corticosteroid administration typically produced clinical improvement. A heterogeneous radiographic and clinical course was noted, with rise and fall in the number of enhancing lesions in 2 patients and persistence in others. The etiology may be related to widespread adoption of increasingly sophisticated catheterization techniques.

The New York Islands AVM Study: design, study progress, and initial results.

BACKGROUND AND PURPOSE: Prospective population-based data on the incidence of brain arteriovenous malformation (AVM) hemorrhage are scarce. We studied lifetime detection rates of brain AVM and incident AVM hemorrhage in a defined population. METHODS: The New York islands (ie, Manhattan Island, Staten Island, and Long Island) comprise a 9,429,541 population according to the 2000 census. Since March 15, 2000, all major New York islands hospitals have prospectively reported data on consecutive patients living in the study area with a diagnosis of brain AVM and whether the patient had suffered AVM hemorrhage. Patients living outside the ZIP code-defined study area were excluded from the study population. RESULTS: As of June 14, 2002, 284 prospective AVM patients (mean+/-SD age, 35+/-18 years; 49% women) were encountered during 21,216,467 person-years of observation, leading to an average annual AVM detection rate of 1.34 per 100,000 person-years (95% CI, 1.18 to 1.49). The incidence of first-ever AVM hemorrhage (n=108; mean age, 31+/-19 years; 45% women) was 0.51 per 100,000 person-years (95% CI, 0.41 to 0.61). The estimated prevalence of AVM hemorrhage among detected cases (n=144; mean age, 33+/-19 years; 50% women) was 0.68 per 100,000 (95% CI, 0.57 to 0.79). CONCLUSIONS: Our prospective data, spanning 27 months, suggest stable rates for AVM detection and incident AVM hemorrhage. Approximately half of AVM patients may suffer intracranial hemorrhage.

Correlates of arterial-filling patterns in the intracarotid amobarbital procedure.

OBJECTIVE: To determine behavioral correlates of anterior cerebral artery (ACA) and posterior cerebral artery (PCA) perfusion patterns in the intracarotid amobarbital sodium procedure. DESIGN: Multivariate analysis of covariance and partial correlations of behavioral measures to ACA crossflow and PCA filling. SETTING: Angiography and the intracarotid amobarbital procedure at a comprehensive epilepsy center. SUBJECTS: Forty-two patients with intractable epilepsy (right-hemisphere seizure focus [n-23]; left-hemisphere seizure focus [n = 19]). MEASUREMENTS: Internal carotid angiography was performed both at a standard injection rate (8 mL of contrast per second) and at 1 mL/s, which matched the rate of the subsequent amobarbital injection. The degree of ipsilateral PCA and contralateral ACA filling were graded on a seven-point scale and compared with postinjection behavior, language, and memory measures. RESULTS: The ACA crossflow did not correlate significantly with that of any measure. The degree of PCA-filling pattern correlated significantly only with the level of consciousness (r = .31, P < .004), but it was not significant after accounting for the effects of seizure laterality, injection side, and amobarbital dosage. Neither ACA crossflow nor PCA filling correlated significantly with memory. The degree of ACA and PCA filling was overestimated at standard angiography (8 mL of contrast medium per second) injection rates. CONCLUSIONS: Although the degree of PCA filling correlates mildly with the level of consciousness postinjection, possibly by perfusion of thalamic or mesencephalic branches, it is not reliably predictive and is less contributory than the injection side and seizure laterality. The PCA filling is not required to produce valid memory assessment in the intracarotid amobarbital procedure, and ACA crossflow is not predictive of behavioral responses.

Visual symptoms with dural arteriovenous malformations draining into occipital veins.

OBJECTIVE: To determine the cause of the visual dysfunction and effect of treatment on dural arteriovenous malformations (DAVMs) that secondarily involve the occipital lobe. BACKGROUND: DAVMs are an infrequent cause of visual dysfunction that should be amenable to treatment if diagnosed before permanent visual field loss. METHODS: The records of seven patients with cerebral visual disturbances associated with DAVMs were analyzed with attention to visual symptoms, visual field testing, and vascular anatomy. RESULTS: Sudden visual loss occurred in five patients, two with a hemorrhage and one with a venous infarct in the occipital lobe. Fortification images occurred in three patients, two of whom had palinopsia (one with de novo formed visual hallucinations). Homonymous quadrantic or hemianoptic field defects, some fluctuating, were found in six patients. Angiography revealed each DAVM was supplied solely by dural arteries and drained into occipital pial veins due to retrograde blood flow through the sites near or in the wall or lumen of the dural venous channels that normally drain the occipital lobe. Unlike DAVMs in other locations, only two patients had occlusion of an adjacent venous sinus. These patients, particularly the two with posterior fossa DAVMs remote to the occipital lobe, clearly demonstrate the visual and neurologic dysfunction resulting from venous hypertension. In six patients, intra-arterial embolization of the arterial feeders and nidus (one patient required additional surgery) resulted in resumption of normal occipital venous emptying. No further visual episodes occurred in five of these six patients. The visual fields normalized in three patients and improved in one with venous infarct but were unchanged in both patients with a hemorrhage. CONCLUSIONS: DAVMs that drain into occipital veins cause field loss and other visual disturbances because of venous hypertension in the occipital lobe, which can be reversed by occluding the DAVM nidus. If a venous infarct or hemorrhage has not caused irreversible damage, visual recovery should be complete.

Balloon-assisted coil embolization of wide-necked aneurysms of the internal carotid artery: medium-term angiographic and clinical follow-up in 22 patients.

BACKGROUND AND PURPOSE: The management of broad-necked cerebral aneurysms by Guglielmi detachable coils (GDCs) is technically challenging owing to a variety of factors, including difficulty in defining the aneurysm/parent vessel interface angiographically and problems in achieving complete occlusion, later predisposing the aneurysm to regrowth/recanalization. We sought to determine whether the use of intraluminal balloons to remodel the parent vessel/aneurysm interface during GDC embolization would provide a safe means of improving the efficacy of endovascular treatment of broad-necked aneurysms. METHODS: Twenty-two saccular aneurysms of the internal carotid artery were treated with GDCs by using balloon remodeling techniques. All aneurysms were characterized by wide necks or were small with unfavorable neck/fundus ratios and required balloon assistance for coil embolization. Patients were followed up both clinically and angiographically. RESULTS: By using a microcatheter-mounted nondetachable balloon to provide a temporary barrier across the aneurysmal neck, we were able to deploy GDCs safely within a variety of aneurysms. Among the 22 patients treated, aneurysmal occlusion on follow-up angiography (mean, 19 months) was found in 17 of 20 patients (two patients died and no follow-up studies were available). Observed or suspected thromboembolic events occurred in four of 22 patients, resulting in one permanent deficit. Twenty of the 22 patients had good to excellent clinical outcomes. CONCLUSION: Although balloon-assisted coiling of cerebral aneurysms requires manipulation of a second microcatheter and an inflatable balloon, increasing its technical complexity, we believe that this method has utility in treating broad-necked aneurysms and small aneurysms that are otherwise suboptimally managed by conventional GDC deployment.

De novo aneurysm formation after stereotactic radiosurgery of a residual arteriovenous malformation: case report.

We report a case of a 19-year-old woman who underwent radiosurgical treatment of a residual arteriovenous malformation. Nine months after treatment, repeat angiography revealed a de novo paranidal aneurysm that was treated endovascularly. We postulate that changes in flow dynamics or vessel integrity after radiosurgery contributed to the formation of her de novo aneurysm.

Angiographic abnormalities in progressive multifocal leukoencephalopathy: an explanation based on neuropathologic findings.

BACKGROUND AND PURPOSE: Progressive multifocal leukoencephalopathy (PML) is typically occult at angiography and fails to enhance on MR images. After observing angiographic abnormalities characterized by arteriovenous shunting and pathologic parenchymal blush in patients with AIDS-related PML, often in the absence of contrast enhancement on MR images, we hypothesized that there might be distinct changes in the cerebral microvasculature that account for the reduction in vascular transit time (arteriovenous shunting) in the absence of blood-brain barrier dysfunction. METHODS: The imaging studies and neuropathologic specimens of six patients with biopsy-proved PML were reviewed retrospectively. In all patients contrast-enhanced MR imaging and CT, followed by cerebral angiography, were performed before stereotactically directed biopsy. The angiograms were evaluated for the presence of vascular displacement, pathologic parenchymal blush, arteriovenous shunting, and neovascularity. The CT and MR studies were reviewed for the presence of enhancement of the PML lesions. Biopsy specimens were examined for the presence of necrosis, perivascular inflammation, and neovascularity. RESULTS: All patients had oligodendrocytic intranuclear inclusions diagnostic of PML, together with perivascular inflammation and neovascularity to a varying extent; no other neuropathologic processes were identified. Angiographic abnormalities, characterized by a pathologic parenchymal blush and arteriovenous shunting, were identified in four of the six patients. In only one of these cases, however, was abnormal enhancement identified on cross-sectional imaging studies (MR and CT), and this patient had florid perivascular inflammatory infiltrates histologically. CONCLUSION: The pathologic parenchymal blush and arteriovenous shunting seen angiographically in some patients with PML reflect small-vessel proliferation and perivascular inflammatory changes incited by the presence of the JC virus in infected oligodendrocytes.