Arteriovenous Malformations Nidus Research Articles

Phase-contrast MR angiography of vascular malformations of the spinal cord at 0.5 T.

Preliminary experience with phase-contrast magnetic resonance (MR) angiography at 0.5 T applied in 12 cases of vascular malformations of the spinal cord is reported. There were six intramedullary arteriovenous malformations (AVMs), four perimedullary fistulas, and two dural arteriovenous fistulas with perimedullary drainage, all proved with x-ray angiography. The small size of the vessels and their location within a bony structure presented a technical challenge. Serpentine vascular signal patterns were identified within the spinal canal in all cases, showing good correlation with the x-ray angiographic pattern. Relative to spin-echo images, MR angiograms allowed better visualization of the venous drainage. The nidus of intramedullary AVMs was more difficult to recognize. The ability to manipulate the velocity-encoding value allows better characterization of flow speed. The results underline the two dimensions of the phase-contrast technique, which provides both anatomic images and dynamic information about vascular malformations. MR angiography does not replace selective x-ray angiography, which is indispensable for therapeutic strategy (endovascular procedure or surgery), but it can be considered a valuable alternative to x-ray angiography during follow-up.

Gamma knife radiosurgery による脳動静脈奇形の治療戦略: 体積の重要性について

Successful gamma knife radiosurgery depends on the volume of nidus of cerebral arteriovenous malformations (AVMs). Because of lower possibility of obliteration of large AVMs treated by gamma knife radiosurgery, embolization therapies were carried out in 10 cases out of 50 AVMs to reduce the volume of nidus before gamma knife radiosurgery. The strategy is as follows: 1) when the volume of nidus is less than 5ml, gamma knife radiosurgery is selected as the first treatment. 2) when the volume of nidus is from 5 to 10ml, embolization is recommended in selective cases in which the procedure seems to be safely performed. 3) When the volume of nidus is over 10ml, embolization should be tried in all cases. In this strategy, it is essential to evaluate the accurate volume of nidus before gamma knife radiosurgery to decide whether embolization should be carried out or not. Angiography with painless fixation of Leksell frame was thought to be best procedure to meansure the accurate volume of nidus before gamma knife radiosurgery.

MR imaging of head and neck vascular malformations

Between 1980 and 1990, 150 patients with cervicofacial vascular malformations were studied at the authors' institution with computed tomography, plain radiography, and angiography. Since 1989, 34 of these patients have also undergone magnetic resonance (MR) imaging. Capillary-venous hemangiomas seem to be the best indication for the adjunctive use of MR imaging. The venous pouches, characteristic of this type of lesion, cause elevated signal intensity, well seen on the T2-weighted images. Excellent fat and muscle differentiation with MR imaging allows appreciation of the depth of extension of these lesions and their delimitation from normal tissue. Arteriovenous malformations (AVMs) are characterized by serpentine signal voids, indicative of the high flow rate of these lesions. Delimitation of the AVM nidus in the midst of the afferent and efferent dilated vessels is often difficult. Study of immature angiomas with MR imaging should be restricted to lesions in specific locations (eg, orbital, laryngeal). Lymphatic malformations showed either tissular or cystic signal intensity changes. MR imaging does not replace other studies but represents an important complementary study for the delineation and diagnosis of deep extensions of vascular malformations, allowing better planning of therapy.

Persistent nidus blood flow in cerebral arteriovenous malformation after stereotactic radiosurgery: MR imaging assessment.

Stereotactic radiosurgery has become a major force in the treatment of arteriovenous malformations (AVMs) of the brain. After treatment, obliteration of flow through the malformation occurs in 75%-85% of cases within 2 years, assuming the entire AVM nidus can be encompassed by the radiation field. Because the follow-up period is relatively long, a noninvasive means to assess residual transnidus blood flow is desirable. The authors report favorable findings after a comparative analysis of 85 posttreatment magnetic resonance images and 27 follow-up cerebral arteriograms in 34 patients treated with stereotactic radiosurgery. The authors found that transnidus flow can be determined from apparent signal intensity differences between tandem two-dimensional gradient-recalled echo images obtained first without and then with gradient moment nulling (flow compensation), with empirically derived pulse parameters. This method provides a means to monitor the reduction in AVM matrix size and to assess the extent of persistent arteriovenous shunting (ie, blood flow) across the nidus.

Hemodynamics of the central nervous system arteriovenous malformation nidus during particulate embolization

We have modelled the hemodynamics of the nidus of the central nervous system (CNS) arteriovenous malformation (AVM) during the process of particulate embolization. The model accurately reproduces the visually apparent incremental slowing observed during such embolization of CNS AVMs. The model is simple and proposes that the nidus is composed of many identical microchannels. As the microchannels are occluded by particles at a constant rate, the rate of change of flow reduction with each bolus of emboli constantly increases exponentially. A rapid reduction in apparent flow rate occurs immediately prior to complete occlusion. With a more accurate understanding of the working of the nidus of CNS AVMs we can increase the safety of therapeutic particulate embolization.

Radiosurgery of cerebral arteriovenous malformations with the dynamic stereotactic irradiation

From December 1986 through December 1988, 33 patients with inoperable arteriovenous malformation (AVM) were treated in our center with the dynamic stereotactic radiosurgery, which uses a standard 10 MV isocentric linear accelerator. There were 18 females and 15 males with a median age of 26 years (range: 9–69) and a median follow-up time of 16 months (range: 7–32). The arteriovenous malformation volumes treated ranged from 0.2 to 42 cm 3. The prescribed doses at the isocenter varied from 50 to 55 Gy and were given as a single fraction in the majority of the patients ( 31 33 ). Late complications consisting of intracranial bleeding and/or hemiparesis were observed in three patients. To date, 21 patients underwent repeat angiographic studies at 1 year post-treatment. A complete obliteration of the lesion was achieved in 38% of these patients. For the patients whose arteriovenous malformation nidus was covered by a minimum dose of 25 Gy, the total obliteration rate was 61.5% (8/13), whereas none of the patients who had received less than 25 Gy at the edge of the nidus obtained a total obliteration. Our preliminary analysis at I year post-radiosurgery reveals results comparable to those previously reported for other radiosurgical techniques for the same follow-up period.

Radiation Therapy for Arteriovenous Malformations: A Review

Abstract There have been numerous case reports and series of patients treated with partial brain irradiation, linear accelerator-based radiosurgery, gamma knife radiosurgery, and Bragg peak therapy for inoperable arteriovenous malformations (AVMs). These cases are summarized and compared. There is convincing evidence that radiation therapy does have a role in obliterating carefully chosen inoperable lesions. The changes that occur in vessel walls after radiation are reviewed. Data about x-ray and gamma radiation are mostly historical and difficult to evaluate because of the techniques of partial brain irradiation. There is a lack of data about the volume of AVM treated and the minimum dose delivered to the AVM nidus. For gamma knife, heavy particle, and linear accelerator therapy, more complete data are available. The incidence of hemorrhage during the first 2 years after treatment, when radiation-induced vascular changes are proposed to occur, is approximately 2.6% per year for gamma knife therapy, 2% per year for proton beam therapy, 2.3% per year for helium beam therapy, and 2.3% per year for linear accelerator therapy. These rates are similar to the recurrence rate for hemorrhage of 2.2 to 3% per year expected based on the natural history of untreated AVMs. If AVM obliteration after therapy is not achieved, the incidence of recurrent hemorrhage remains between 2% per year after treatment with gamma knife therapy. The incidence of hemorrhage for all patients treated was reported as 0.15% per year in one study and 20% over 8 years in a follow-up study using proton beam therapy. Mortality from hemorrhage after treatment was 0.6% after gamma knife therapy, 2.3% after helium beam therapy, and 2 to 5% after proton beam therapy. These figures for mortality are all lower than the 11% observed for the natural history of untreated AVMs. Permanent neurological deficits experienced as a complication of radiation occurred in 2 to 3% of patients treated with gamma knife therapy, 4% of patients treated with helium beam therapy, 1.7% of patients treated with proton beam therapy, and 3% of patients treated with stereotactic linear accelerator therapy. Proton beam therapy has been used for both small and large lesions. The majority of lesions in patients treated with gamma knife, helium beam, and linear accelerator therapy have been small (usually less than 3.0 cm average diameter) lesions. In these patients with small inoperable lesions treated with accurately directed fields of isocentric radiation, the greatest incidence of AVM obliteration has been observed on follow-up angiograms. Larger lesions may undergo vascular wall thickening with subsequent protection from recurrent hemorrhage, but more data are needed to support this hypothesis.

Radiation therapy for arteriovenous malformations

There have been numerous case reports and series of patients treated with partial brain irradiation, linear accelerator-based radiosurgery, gamma knife radiosurgery, and Bragg peak therapy for inoperable arteriovenous malformations (AVMs). These cases are summarized and compared. There is convincing evidence that radiation therapy does have a role in obliterating carefully chosen inoperable lesions. The changes that occur in vessel walls after radiation are reviewed. Data about x-ray and gamma radiation are mostly historical and difficult to evaluate because of the techniques of partial brain irradiation. There is a lack of data about the volume of AVM treated and the minimum dose delivered to the AVM nidus. For gamma knife, heavy particle, and linear accelerator therapy, more complete data are available. The incidence of hemorrhage during the first 2 years after treatment, when radiation-induced vascular changes are proposed to occur, is approximately 2.6% per year for gamma knife therapy, 2% per year for proton beam therapy, 2.3% per year for helium beam therapy, and 2.3% per year for linear accelerator therapy. These rates are similar to the recurrence rate for hemorrhage of 2.2 to 3% per year expected based on the natural history of untreated AVMs. If AVM obliteration after therapy is not achieved, the incidence of recurrent hemorrhage remains between 2% per year after treatment with gamma knife therapy. The incidence of hemorrhage for all patients treated was reported as 0.15% per year in one study and 20% over 8 years in a follow-up study using proton beam therapy. Mortality from hemorrhage after treatment was 0.6% after gamma knife therapy, 2.3% after helium beam therapy, and 2 to 5% after proton beam therapy. These figures for mortality are all lower than the 11% observed for the natural history of untreated AVMs. Permanent neurological deficits experienced as a complication of radiation occurred in 2 to 3% of patients treated with gamma knife therapy, 4% of patients treated with helium beam therapy, 1.7% of patients treated with proton beam therapy, and 3% of patients treated with stereotactic linear accelerator therapy. Proton beam therapy has been used for both small and large lesions. The majority of lesions in patients treated with gamma knife, helium beam, and linear accelerator therapy have been small (usually less than 3.0 cm average diameter) lesions. In these patients with small inoperable lesions treated with accurately directed fields of isocentric radiation, the greatest incidence of AVM obliteration has been observed on follow-up angiograms.(ABSTRACT TRUNCATED AT 400 WORDS)

Intracranial vascular lesions: optimization and clinical evaluation of three-dimensional time-of-flight MR angiography.

The clinical value of three-dimensional time-of-flight magnetic resonance (MR) angiography was prospectively evaluated in 26 patients with congenital intracranial vascular lesions; 12 had arteriovenous malformations (AVMs), and 14 had venous angiomas. In the initial phase of the study the entire region of interest was imaged with one large acquisition volume (60-120-mm-thick slab). Later, the angiograms were obtained with adjacent but slightly overlapping, 30-mm-thick slabs, which clearly improved vascular detail. Gadolinium enhancement slightly improved depiction of veins but not of arteries. MR angiograms were compared with available conventional angiograms and MR studies. The topography of the AVM nidus was equally well appreciated on the MR as on the conventional angiograms. However, in six of 12 patients the hyperdynamic afferent arteries were incompletely shown on MR angiograms because of incomplete rephrasing. In three patients, venous drainage was also incompletely visualized. Compared with conventional MR studies, MR angiography offered the same detection rate but better anatomic insight. Thirteen of the 14 venous angiomas were also identified on MR angiograms. Detailed imaging, however, necessitated gadolinium enhancement and thin-slab acquisition.

微小脳動静脈奇形

A total of 259 patients with arteriovenous malformation (AVM) who had undergone cerebral angiography were evaluated in this study. The patients were divided into two groups, those with cryptic AVM and those with larger AVM. Age distributions, onset patterns, initial symptoms and symptoms on admission were compared. Group I was for cases of angiographic nidus ?1.0 cm. Group II consisted of cases in which angiographic early venous filling was the only abnormal finding, and diagnosed AVM histopathologically. In Group III, there was no angiographic abnormal finding, and the diagnosis of AVM was obtained from excised specimens histopathologically, and so-called “angiographically occult AVM.” Group I, II, and III included cryptic AVM. Group IV was the control group: the nidus of AVM was larger (>1.0 cm).There were 72 cases in Group I (27.8%), 13 cases in Group II (5.0%), 22 cases in Group III (8.5%), and 152 cases in Group IV (58.7%). There was a total of 107 cases of cryptic AVM in Groups I, II, and III. This was 41.3% of the total cases of AVM.Results were as follows: 1) Average age of patients with cryptic AVM was 37.4 years, compared with 35.5 years for patients with larger AVM. Age distribution of patients with cryptic AVM ranged from the teens through the 30s. For patients with larger AVM, age distribution peaked in the 30s.2) Onset patterns of cryptic AVM were analyzed by studying the existence of hemorrhage on CT scan. In Group I, hemorrhage was the cause of AVM in 56 cases (87.5%), and in all cases in Group II and III the AVM was triggered by hemorrhage. Hemorrhage was the cause of cryptic AVM in 89 cases (91.8%), while patients with symotoms other than hemorrhage, such as convulsions, accounted for a slight 8.2% of cryptic AVM. However, in Group IV, hemorrhage was the cause of larger AVM in 88 cases (65.2%), while 47 cases (34.8%) had no hemorrhage.In the 177 cases of all hemorrhagic AVM, cryptic AVM accounted for 50.3%.3) Headache was the most common initial symptom (44.9%) of patients with cryptic AVM. But convulsions was as few as 10.3%. With larger AVM, convulsions were characteristic in 23.7%. It is interesting that cryptic AVM, on admission, disturbance of consciousness about doubled, to 27.2%.To conclude, over 90% of cases of cryptic AVM had an onset pattern with hemorrhage. This figure would be higher than in cases of larger AVM.

脳動静脈奇形周囲に存在する血管の形態学的特徴について

脳動静脈奇形周囲に存在する血管の形態学的特徴について

Choroid plexus arteriovenous malformation in a full-term neonate

A full-term newborn infant with intracranial hemorrhage secondary to an arteriovenous malformation (AVM) of the choroid plexus is presented. Although angiography was not undertaken before surgery, a vascular nodule containing an AVM nidus was found in the hematoma wall. The authors stress that an AVM should be considered as a cause of intracranial hemorrhage and that the hematoma wall be searched thoroughly in neonates without predisposing factors.

Stereotactic Gamma Radiosurgery for Intracranial Vascular Malformations and Tumors: Report of the Initial North American Experience in 331 Patients

We reviewed the initial experience with 331 consecutive patients treated during the first 2 years of operation of the University of Pittsburgh Gamma Unit. Among 178 patients with vascular malformations, 161 had angiographically demonstrable arteriovenous malformations, and 17 had angiographically occult malformations. Patients with tumors included 123 with histologically benign, predominantly extra-axial neoplasms and 30 with malignant, predominantly intra-axial neoplasms. When the arteriovenous malformation nidus could be covered with at least the 50% isodose line and a dose to the margin greater than or equal to 20 Gy, 60% were obliterated within 1 year. Patients with benign tumors and well-circumscribed malignant tumors did not experience tumor growth within the radiosurgical treatment volume. The role of radiosurgery is expanding to include primary treatment of larger lesions than was formerly possible and adjunctive treatment of more complex arteriovenous malformation and tumors.

Embolization of Cerebral Arteriovenous Malformations with Bucrylate

The experience with embolization of intracerebral arteriovenous malformations (AVMs) with bucrylate (isobutyl-2-cyanoacrylate) in 29 patients is reported. In 9 cases (31%) less than 1/3 of the AVM nidus was occluded, in 12 (41%) 1/3 to 2/3, in 4 (14%) more than 2/3, and total occlusion was only seen in 3 cases (10%). One patient was never embolized, owing to procedure complications. At follow-up angiography in 20 patients, partial revascularization was found in 11 AVMs and further occlusion in 2. Complications occurred in 11 cases (38%). Five patients (17%) suffered from hemorrhage: 2 died, one deteriorated severely and 2 recovered. Unintentional embolization or edema resulted in neurologic deficits in 6 patients (21%), permanent in 3 and reversible in 3. Symptomatic improvement was initially found in 13 patients (45%) but was stable only in 9. In 9 patients (38%) embolization was followed by elective surgery or irradiation. The best results were obtained in small and medium-sized AVMs (< 6 cm) while ther...

Embolization of Cerebral Arteriovenous Malformations with Bucrylate

The experience with embolization of intracerebral arteriovenous malformations (AVMs) with bucrylate (isobutyl-2-cyanoacrylate) in 29 patients is reported. In 9 cases (31%) less than 1/3 of the AVM nidus was occluded, in 12 (41%) 1/3 to 2/3, in 4 (14%) more than 2/3, and total occlusion was only seen in 3 cases (10%). One patient was never embolized, owing to procedure complications. At follow-up angiography in 20 patients, partial revascularization was found in 11 AVMs and further occlusion in 2. Complications occurred in 11 cases (38%). Five patients (17%) suffered from hemorrhage: 2 died, one deteriorated severely and 2 recovered. Unintentional embolization or edema resulted in neurologic deficits in 6 patients (21%), permanent in 3 and reversible in 3. Symptomatic improvement was initially found in 13 patients (45%) but was stable only in 9. In 9 patients (38%) embolization was followed by elective surgery or irradiation. The best results were obtained in small and medium-sized AVMs (less than 6 cm) while there was a high risk of complications and an uncertain palliative effect in large AVMs.

Neurovascular lesions and endovascular therapy: the role of MR.

Magnetic resonance imaging (MRI) studies were performed on 27 patients with vascular lesions of the central nervous system before and after embolization with either IBCA, polyvinyl alcohol foam particles, Avitene (microfibrillar collagen) or balloons. Thirteen pial brain arteriovenous malformations (AVMs), 3 brain AV fistulas, 2 giant aneurysms, 5 dural AVMs, 1 vertebro-vertebral fistula and 3 meningiomas were studied. The pre-embolization MR demonstrated the nidus and venous drainage of all pial AVMs. MR failed to detect 3 out of 5 dural AVMs using only spin echo sequences. A draining vein alone was seen in the remaining two cases. MR was superior to CT in detecting contiguous parenchymal changes such as atrophy, reversible ischemia, and mass effect in the pre-embolization studies. Following embolization, MR demonstrated partial or complete obliteration of the vascular nidus in all 13 pial AVMs. The embolized area was seen as an area of increased signal consistent with thrombus where previously there had been signal void. Ischemic or edematous changes in the brain parenchyma following embolization were seen on MR more easily than on CT scans. MR was accurate in the assessment of aneurysm patency, degree of thrombosis and balloon position in both giant aneurysms, and AV fistulae. These MR findings had an impact on patient management. MR will be an increasingly useful tool in the diagnosis and management of a number of neurovascular diseases requiring endovascular intervention.

Local cerebral blood flow measurement using 123I-IMP SPECT in patients with cerebrovascular diseases.

Three dimensional tomographic images of local cerebral blood flow (1CBF) using single photon emission computed tomography (SPELT) were obtained with N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) and 133Xe in 19 subjects: seven with ruptured aneurysm, one with unruptured giant aneurysm, five with arteriovenous malformation (AVM), six with moyamoya disease. This study concerned a comparison between the two methods of 133Xe inhalation and 123I-IMP intravenous injection. Clinical and morphological (angiography, CT scan) findings were used for reference. The SPECT image showed low 1CBF earlier and larger than CT scan abnormalities in patients with cerebral vasospasm following subarachnoid hemorrhage. 133Xe 1CBF images showed high flow areas in giant aneurysm and nidus of AVM but 123I-IMP SPECT showed decreased activity in these areas. Low activity area with 123I-IMP around the large AVM may indicate an intracerebral steal phenomenon or decreased metabolism. In the patients with moyamoya disease, CT scan demonstrated minimal changes, but large areas of decreased 1CBF were demonstrated with both 133Xe and 123I-IMP. The patients with intracerebral hematoma had a definite defect area of 1CBF corresponding to the hematoma on CT scan and a large area of decreased activity around the hematoma. 133Xe ICBF and 123I-IMP SPECT maps correspond well with each other under certain conditions, but they differed in the points of spatial resolution and true nutritional blood flow. 123I-IMP may give an image of other functions more important than cerebral blood flow.

第4脳室lateral recess AVMの摘出術

A case of arteriovenous malformation (AVM) of the left lateral recess of the fourth ventricle is presented in this paper.The patient, an eight-year-old girl complaining of vomiting and vertigo, was admitted to our hospital with horizontal nystagmus and ataxic gait. Computerized tomography (CT) scans and angiograms demonstrated an AVM of the lateral recess of the fourth ventricle, which was fed predominantly by the choroidal branches of the left posterior inferior cerebellar artery, and drained by the petrosal vein. At first, the patient underwent resection of the nidus through the midline approach. Postoperative CT scans, however, demonstrated a residual nidus of AVM in the area of the left cerebellar peduncle and a probable draining vein in the left cerebellopontine angle. Therefore, a second operation was designed for the lateral approach. The residual AVM was found in the middle and inferior cerebellar peduncle being supplied by the choroidal branches of the left anterior inferior cerebellar artery and small branches of the left superior cerebellar artery at the cerebellopontine angle and in the lateral recess of the fourth ventricle. Postoperative angiograms revealed complete obliteration of the AVM, although CT scans demonstrated a small hematoma in the lateral recess of the fourth ventricle. The patient was discharged with mild hearing disturbance and dysmetria on the left side, which disappeared six months later.Operative techniques as well as the surgical indication for the posterior fossa AVM are discussed and a review of the literature is given.

Clinical Application of Cerebral Endovascular Balloon Catheter for Arteriovenous Malformation

A case of occipital arteriovenous malformation (AVM), successfully treated by using a detachable balloon catheter, was reported. The patient was a 25-year-old female who developed a photogenic seizure. Selective left internal carotid angiography showed an AVM in the occipital lobe (Luessenhop Grade II). Selective angiography using a non-detachable balloon catheter (elimination method) was performed for the detailed preoperative examination. A tolerance test during the temporary occlusion of each feeder was performed. At the same time the oxygen content of arterial and internal jugular blood was measured before and after occlusion of main feeders. Just before the operation, selective embolization of the main feeding arteries from the posterior cerebral artery with a detachable balloon was performed. The angiography following embolization showed devascularization of two-thirds of the AVM nidus. Surgical resection was performed without difficulty. Total blood loss was estimated to be less than 200 ml. Embolization using a detachable balloon catheter seemed to be an effective adjunctive treatment prior to operative removal of AVM.

TRICYCLIC ANTIDEPRESSANT POISONING IN CHILDREN

The MR images, CT scans, and angiograms of 15 consecutive patients with intracranial, supratentorial arteriovenous malformations (AVMs) were studied retrospectively. The three imaging techniques were evaluated separately to assess their utility in defining the size, characteristics, and location of the AVM nidus, its arterial supply, and venous drainage. The studies were also evaluated for their ability to show associated parenchymal abnormalities, the presence of mass effect, and changes occurring after embolization.MR was superior to both CT and angiography in showing the exact anatomic relationships of the nidus, feeding arteries, and draining veins, as well as in demonstrating the extent of AVM nidus obliteration after embolization. MR was more sensitive than CT in revealing associated parenchymal abnormalities and subacute hemorrhage. Because of flow-related artifacts and low sensitivity in distinguishing calcification from rapid flow and/or hemosiderin, MR seemed to have a low sensitivity for detecting old hemorrhage within an AVM nidus. Angiography is still needed in the planning of either surgical or endovascular treatment of AVMs.