Development Of Arteriovenous Malformations Research Articles

Anesthetic implications for the parturient with hereditary hemorrhagic telangiectasia

To review the effects of hereditary hemorrhagic telangiectasia (HHT) in the parturient and the anesthetic management of such patients during pregnancy and delivery. A literature search (1966-2008) was performed using Medline and EMBASE databases. Bibliographies of retrieved articles were searched for additional sources. Hereditary hemorrhagic telangiectasia affects 1 in 5000-8000 people. It is a genetic condition in which vascular dysplasia affects many organs particularly the pulmonary, cerebral, gastrointestinal, and spinal vasculature. A large proportion of women with HHT have uneventful pregnancies. However, women can present in pregnancy with clinically silent but potentially life-threatening features of the disorder including fatal hemorrhage from ruptured arteriovenous malformations (AVMs), systemic emboli, and high output cardiac failure secondary to arteriovenous shunting. Literature on the anesthetic management of HHT in pregnancy is limited. Both general and regional anesthetic techniques have been successfully performed in these patients, but are reliant on identifying the presence of specific AVMs; avoidance of cardiovascular instability; and prophylaxis against systemic emboli secondary to pulmonary AVM shunting. The presence of spinal AVMs is considered a relative contraindication to regional techniques. As with other systemic AVMs, these can develop and increase in size during pregnancy with implications for the timing of screening and surveillance. An understanding of the presence and potential development of life-threatening AVMs during pregnancy is imperative for anesthesiologists caring for parturients with HHT. Even in the asymptomatic patient, a high index of suspicion should be maintained, screening performed where possible and anesthetic technique adapted accordingly.

De Novo Cerebral Arteriovenous Malformation: Case Report and Literature Review

We describe a rare case of a de novo cerebral arteriovenous malformation (AVM) in a 9-year-old girl. MR imaging at 6 years of age demonstrated band heterotopia. Follow-up MR imaging 3 years later demonstrated a new 3.5-cm AVM in the left parietol-occipital region, confirmed by conventional angiography. This report, along with limited previous reports, suggests that AVMs can be acquired lesions and that AVM development is a dynamic process extending into the postnatal period.

Arteriovenous Malformation

Object. Important central nervous system (CNS) manifestations in patients with hereditary hemorrhagic telangiectasia (HHT) include arteriovenous malformations (AVMs) and dural arteriovenous fistulas (DAVFs). Hereditary hemorrhagic telangiectasia is caused by germline mutations of two genes: ENG (HHT Type 1) and ACVRL1 (HHT Type 2). The ENG gene variations have been associated with the formation of intracranial aneurysms. The authors studied whether sequence variations in ACVRL1 or ENG are associated with the development of clinically sporadic arteriovenous dysplasias and aneurysms of the CNS. Methods. The coding sequence (in 44 patients with AVMs and 27 with aneurysms) and the 5′ end and the polyA site (in 53 patients with AVMs) of the ACVRL1 gene were analyzed for sequence variations using direct sequencing and single-strand conformational polymorphism analysis. One ENG and three ACVRL1 gene polymorphisms were genotyped using restriction enzyme–based analysis in 101 patients with sporadic AVMs and DAVFs of the CNS, 79 patients treated for intracranial aneurysms, and 202 control volunteers. The authors identified a statistically significant association between the IVS3 −35A/T polymorphism in intron 3 of the ACVRL1 gene and the development of AVMs and DAVFs (p = 0.004; odds ratio [OR] 1.73; 95% confidence interval [CI] 1.19–2.51; after adjustments for age and sex), but not aneurysms (crude OR 0.82; 95% CI 0.55–1.18). Conclusions. The results of this study link ACVRL1 (HHT Type 2 gene) to the formation of the clinically sporadic variants of vascular malformations of the CNS most commonly seen in patients with HHT, that is, AVMs and DAVFs.

Association of a polymorphism of the ACVRL1 gene with sporadic arteriovenous malformations of the central nervous system

Important central nervous system (CNS) manifestations in patients with hereditary hemorrhagic telangiectasia (HHT) include arteriovenous malformations (AVMs) and dural arteriovenous fistulas (DAVFs). Hereditary hemorrhagic telangiectasia is caused by germline mutations of two genes: ENG (HHT Type 1) and ACVRL1 (HHT Type 2). The ENG gene variations have been associated with the formation of intracranial aneurysms. The authors studied whether sequence variations in ACVRL1 or ENG are associated with the development of clinically sporadic arteriovenous dysplasias and aneurysms of the CNS. The coding sequence (in 44 patients with AVMs and 27 with aneurysms) and the 5' end and the polyA site (in 53 patients with AVMs) of the ACVRL1 gene were analyzed for sequence variations using direct sequencing and single-strand conformational polymorphism analysis. One ENG and three ACVRL1 gene polymorphisms were genotyped using restriction enzyme-based analysis in 101 patients with sporadic AVMs and DAVFs of the CNS, 79 patients treated for intracranial aneurysms, and 202 control volunteers. The authors identified a statistically significant association between the IVS3 -35A/T polymorphism in intron 3 of the ACVRL1 gene and the development of AVMs and DAVFs (p = 0.004; odds ratio [OR] 1.73; 95% confidence interval [CI] 1.19-2.51; after adjustments for age and sex), but not aneurysms (crude OR 0.82; 95% CI 0.55-1.18). The results of this study link ACVRL1 (HHT Type 2 gene) to the formation of the clinically sporadic variants of vascular malformations of the CNS most commonly seen in patients with HHT, that is, AVMs and DAVFs.

Recurrence of cerebral arteriovenous malformations in children: Report of two cases and review of the literature

Background Angiography is considered the standard to assess the treatment success of cerebral arteriovenous malformations (AVMs). When postoperative angiograms show neither residual nidus nor early draining veins, patients are considered cured, and the risks of hemorrhage are eliminated. However, this notion is challenged by the development of recurrent AVMs in children. In our report, 2 children developed recurrent AVMs after undergoing complete resection, which was documented by postoperative angiography. We review other similar cases reported in the literature to help establish guidelines for postoperative monitoring. Methods In this retrospective review, 36 children underwent complete surgical resection of cerebral AVMs that were documented by intra- or postoperative angiography. After a follow-up period ranging from 1 to 17 years, rates of recurrence were assessed. Results Although angiographic documentation showed complete resection, 2 children developed recurrences 3 and 5 years later. Among these 36 children, the recurrence rate was 5.5% at follow-up (mean 9 years). Conclusions Based on our data and review of the literature, intra- or early postoperative angiography is essential to exclude the presence of a residual nidus but does not ensure cure of the AVMs in children. If postoperative angiographic scans are obtained too early, postoperative changes may prevent the detection of a residual nidus. Therefore, we recommend that angiographic scans be obtained intraoperatively or early postoperatively to document complete resection and again at 1 and 5 years after surgical resection.

Redefined role of angiogenesis in the pathogenesis of dural arteriovenous malformations.

To investigate the role of angiogenesis in the pathogenesis of dural arteriovenous malformations (AVMs), 40 rats underwent common carotid artery-external jugular vein (CCA-EJV) anastomosis, bipolar coagulation of the vein draining the transverse sinus, and sagittal sinus thrombosis to induce venous hypertension. Fifteen rats underwent a similar surgical procedure, but venous hypertension was not induced. The 55 rats were divided into seven groups. Four groups, each containing 10 rats, underwent induced venous hypertension. The other three groups, each containing five rats, did not undergo induced venous hypertension. After 1, 2, or 3 weeks, dura mater was obtained from one group of hypertensive rats and from one group of nonhypertensive rats and was assayed for angiogenic activity (rabbit cornea bioassay). The remaining group of 10 hypertensive rats was not assayed to determine if sampling affected dural AVM formation. Unlike rats without CCA-EJV anastomosis, rats with CCA-EJV anastomosis had significantly increased postoperative sagittal sinus pressures (p < 0.0001). Mean angiogenesis indices were significantly greater in rats with venous hypertension than in rats without venous hypertension (p = 0.004). Dural AVMs formed in 42% of the 55 rats and facial AVMs formed in 51%. Angiogenic activity correlated positively with venous hypertension (p = 0.74). Development of dural AVMs correlated positively with both venous hypertension (p = 0.0009) and angiogenic activity (p = 0.04). These data indicate that venous hypertension may induce angiogenic activity either directly or indirectly by decreasing cerebral perfusion and increasing ischemia, and that dural AVM formation may be the result of aberrant angiogenesis.

Postsurgical Development of Dural Arteriovenous Malformations after Transpetrosal and Transtentorial Operations

The authors present a case of mixed pial and dural arteriovenous malformations (AVMs) in the transverse and the sigmoid sinuses, which developed 2 years after the resection of a trigeminal neuroma via the transpetrosal and transtentorial approach. To the best of our knowledge, this is the first case of the delayed development of dural AVMs after transpetrosal and transtentorial surgery. The cause of acquired dural AVMs is discussed, and the potential risk of delayed development of dural AVMs after transpetrosal and transtentorial surgery is described.

Patterns of peptide-containing perivascular nerves in the circle of Willis: their absence in intracranial arteriovenous malformations

Using standard immunohistochemical techniques and an improved procedure for whole-mount vascular preparations, the authors describe the pattern and density of innervation of calcitonin gene-related peptide (CGRP)-like, neuropeptide Y (NPY)-like and vasoactive intestinal polypeptide (VIP)-like immunoreactivity in major arteries of postmortem adult human circles of Willis. Calcitonin gene-related peptide-, NPY-, and VIP-LI exhibited a variety of varicose and nonvaricose single axons, and small and large perivascular nerve bundles. Although the density of innervation within each vascular segment was highly variable, the pattern of innervation for each neuropeptide observed was consistent throughout the circle of Willis. With the use of human and rat circles of Willis as positive control preparations, the lack of CGRP-LI, NPY-LI, and VIP-LI in vessel segments taken from five cases of intracranial arteriovenous malformations (AVMs) is also reported. It is concluded that adult human circles of Willis exhibit CGRP-LI, NPY-LI, and VIP-LI perivascular nerves. In addition, intracranial AVMs do not possess these peptide-containing nerves that, in animals, normally mediate neurogenic control in the cerebrovasculature. It is hypothesized that this lack of innervation, and hence neurotrophic influence, may contribute to the development of AVMs.