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Anil K. Lalwani, Christopher F. Dowd and Van V. Halbach

✓ Dural arteriovenous fistulas of the transverse/sigmoid sinus usually cause pulse-synchronous bruit but may present catastrophically. Current systems for classifying these vascular malformations do not consider obstruction of venous outflow, which increases the risk of intracranial hemorrhage due to retrograde flow via cortical veins. The authors have developed a grading system based on the severity of venous restrictive disease determined by superselective angiography. In a retrospective analysis of 25 patients with dural arteriovenous fistulas of the transverse/sigmoid sinus treated between 1988 and 1990, the grade of venous restrictive disease reflected the clinical presentation. Visual symptoms and central nervous system hemorrhage were more common in patients with cortical venous drainage and more severe distal venous occlusion (Grade 3: 31% and 31%, respectively; Grade 4: 67% and 100%, respectively) than in patients with cortical venous drainage and mild-to-moderate venous restrictive disease (Grade 2: 13% and 0%, respectively) or those without venous outflow (Grade 1: 0% and 0%, respectively). These preliminary results suggest that this grading system may be useful for predicting the risk of catastrophic clinical presentation and for guiding therapeutic decision-making in patients with dural arteriovenous fistulas of the transverse/sigmoid sinus. A prospective study of a larger number of patients is needed to validate the predictive value of this new grading system.

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Christopher F. Dowd, Van V. Halbach and Randall T. Higashida

The field of interventional neuroradiology has experienced remarkable technological developments in microcatheters and embolic materials during the past two decades. The realm of meningioma therapy has benefited handsomely from the combination of these technical improvements and the knowledge of experienced practitioners in this field. Transarterial embolization has become a standard procedure in the preoperative management of meningiomas. The authors describe the indications, pretreatment evaluation, techniques, and outcomes when preoperative angiography and embolization are performed in the treatment of these tumors.

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G. Edward Vates, Kevin C. Wang, David Bonovich, Christopher F. Dowd and Michael T. Lawton

✓ Bow hunter stroke, which is characterized by transient vertebrobasilar ischemia brought on by head turning, is an unusual condition usually caused by structural abnormalities at the craniocervical junction. The authors present a case in which compression of the left vertebral artery (VA) at the C4–5 level was caused by a laterally herniated intervertebral disc. A 56-year-old man presented with a 6-month history of dizziness and syncope when he turned his head 45° or more to the left. Transcranial Doppler (TCD) ultrasonography demonstrated decreased blood flow through the left VA, and angiography revealed an occlusion of the left VA at the C4–5 level, both when the patient turned his head to the left. Via an anterior cervical approach, the VA canal was unroofed through the transverse foramina to decompress the left VA at C4–5; intraoperatively, the left VA was found to be compressed by a laterally herniated cervical disc fragment. To the best of the authors' knowledge this is the first report of a laterally herniated cervical disc causing bow hunter stroke. The use of TCD may be of value in the diagnosis and management of the disorder, and herniated cervical disc must be included in the roster of potential causes for this rare disease.

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Perry P. Ng, Randall T. Higashida, Sean Cullen, Reza Malek, Van V. Halbach and Christopher F. Dowd

Interventional neuroradiology is a less invasive modality than open neurosurgery for the treatment of a wide range of neurovascular disorders. Refinements in technique and improvements in the design of microcatheters, guide wires, and embolic materials have yielded superior clinical outcomes and provided an impetus to treat more of these lesions endovascularly rather than surgically. Endovascular therapy is the standard of care for direct and indirect carotid artery cavernous sinus fistulas and may also be curative for dural arteriovenous fistulas (AVFs) in other locations.

The authors provide review of the clinical features, pathophysiology, and management of intracranial AVFs focusing on contemporary endovascular treatment options.

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Cameron G. McDougall, Van V. Halbach, Christopher F. Dowd, Randall T. Higashida, Donald W. Larsen and Grant B. Hieshima

✓ Preliminary experience using electrolytically detachable coils to treat basilar tip aneurysms in 33 patients is described. The most frequent presentation was subarachnoid hemorrhage (SAH) in 23 patients. All patients were referred after neurosurgical assessment and exclusion as candidates for surgical clipping of their aneurysms. At the time of initial treatment complete aneurysm occlusion was achieved in seven (21.2%) of 33 patients. In 17 of the patients (51.5%), greater than 90% but less than 100% aneurysm occlusion was achieved. Angiographic follow up (mean 11.7 months) was available in 19 patients. At follow-up angiography four (21%) of 19 aneurysms were 100% occluded and 12 (63.2%) of 19 were more than 90% but less than 100% occluded.

The mean clinical follow-up time in treated patients surviving beyond the initial treatment period is 15 months. One patient suffered major permanent morbidity from thrombosis of the basilar tip region a few hours after coil placement. One patient treated following SAH experienced further hemorrhage 6 months later. No other patient suffered direct or indirect permanent morbidity as a consequence of this method of treatment.

The authors believe that this technique is a reasonable alternative for patients who are not candidates for conventional surgical treatment or in whom such treatment has failed. This study's follow-up period is brief and greater experience with long-term follow-up study is mandatory.

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Van V. Halbach, Christopher F. Dowd, Randall T. Higashida, Peter A. Balousek, Samuel F. Ciricillo and Michael S. B. Edwards

Object. In this study the authors report on the results of endovascular treatment for mural-type vein of Galen malformations (VGMs) in a group of infants.

Methods. Eight children (six infants and two neonates) who suffered from symptoms caused by a mural-type VGM were treated by means of endovascular therapy. Their age at the time of treatment ranged from 13 days to 19 months (mean 7.6 months). Two neonates and three infants who presented with hydrocephalus and increased head circumference, one of whom was stabilized with a shunt, underwent elective closure of the malformations 3, 4, 6, 6, and 13 months later, respectively. Two patients presented with hemorrhage; one had an intraventricular hemorrhage (IVH) on the 1st day of life and one, a 5-month-old infant, suffered a large parenchymal hemorrhage and an IVH; both patients were immediately cured by means of endovascular techniques. One child presented with a seizure and cortical venous drainage that were treated immediately. Eleven separate treatment sessions were conducted; eight via transarterial femoral access and the remaining three via a transvenous approach. Two patients were treated by using transfemoral transvenous embolization with fibered coils, and one patient required a transtorcular transvenous approach to permit complete closure of the fistula with electrolytically detachable coils. The embolic devices used included silk suture emboli (three patients), electrolytically detachable coils (three patients), and fibered platinum coils (seven patients). In seven patients, complete closure was demonstrated on postembolization arteriographic studies. The eighth patient had stagnant flow in a giant 6-cm varix treated with arterial and venous coils but has not yet undergone follow-up studies. Late follow-up arteriography was performed in four patients at times ranging from 11 to 24 months postprocedure. In one patient, thrombosis of the malformation and shrinkage of the varix were confirmed on follow-up computerized tomography scanning. The remaining three patients have not yet undergone follow-up angiographic examination. Two asymptomatic complications occurred, including separation of the distal catheter, which was removed with a snare device, and a single platinum coil that embolized to the lung, producing no symptoms in 101 months of clinical follow up. The follow-up period ranged from 3 to 105 months, with a mean of 52 months.

Conclusions. Endovascular therapy is the treatment of choice for mural-type VGMs and offers a high rate of cure with low morbidity.

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Tomoaki Terada, Randall T. Higashida, Van V. Halbach, Christopher F. Dowd, Mitsuharu Tsuura, Norihiko Komai, Charles B. Wilson and Grant B. Hieshima

✓ Dural sinus thrombosis has been hypothesized as a possible cause of dural arteriovenous fistulas (AVF's). The pathogenesis and evolution from thrombosis to actual development of an AVF are still unknown. To study dural fistula formation, a surgically induced venous hypertension model in rats was created by producing an arteriovenous shunt between the carotid artery and the external jugular vein. The external jugular vein beyond the anastomosis was ligated 2 to 3 months after surgery and angiography was performed to identify any new acquired AVF's.

Forty-six male Sprague-Dawley rats, each weighing approximately 300 gm, were used for this study. In Group I, 22 rats underwent a common carotid artery anastomosis to the external jugular vein, which is the largest draining vein from the transverse sinus via the posterior facial vein, followed by proximal external jugular vein ligation. In Group II, 13 rats underwent the same surgical procedure, followed by contralateral posterior facial vein occlusion. Group III served as the control group, in which 11 rats underwent only unilateral external jugular vein occlusion with or without contralateral posterior facial vein occlusion. The shunts in Groups I and II were ligated at 2 to 3 months following surgery, and transfemoral angiography was performed immediately before and after occlusion.

New acquired AVF's had developed in three rats (13.6%) in Group I, three rats (23.1%) in Group II, and no rats (0%) in Group III. One of these newly formed fistulas was located at the dural sinus, analogous to the human dural AVF. The other five were located in the subcutaneous tissue, including the face and neck. The dural AVF in the rat was present on follow-up angiography at 1 week after the bypass occlusion. It is concluded that chronic venous hypertension of 2 to 3 months' duration, without associated venous or sinus thrombosis, can induce new AVF's affecting the dural sinuses or the subcutaneous tissue.

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Adel M. Malek, Van V. Halbach, Stephen Holmes, Constantine C. Phatouros, Philip M. Meyers, Christopher F. Dowd and Randall T. Higashida

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Randall T. Higashida, Fong Y. Tsai, Van V. Halbach, Christopher F. Dowd, Tony Smith, Kenneth Fraser and Grant B. Hieshima

✓ Transluminal angioplasty for hemodynamically significant stenosis (> 70%) involving the posterior cerebral circulation is now being performed by the authors in selected cases. A total of 42 lesions affecting the vertebral or basilar artery have been successfully treated by percutaneous transluminal angioplasty techniques in 41 patients. The lesions involved the proximal vertebral artery in 34 cases, the distal vertebral artery in five, and the basilar artery in three. Patients were examined clinically at 1 to 3 and 6 to 12 months after angioplasty. Three (7.1%) permanent complications occurred, consisting of stroke in two cases and vessel rupture in one. There were four (9.5%) transient complications (< 30 minutes): two cases of vessel spasm and two of cerebral ischemia. Clinical follow-up examination demonstrated improvement of symptoms in 39 cases (92.9%). Radiographic follow-up studies demonstrated three cases (7.1 %) of restenosis involving the proximal vertebral artery; two were treated by repeat angioplasty without complication, and the third is being followed clinically while the patient remains asymptomatic.

In patients with significant atherosclerotic stenosis involving the vertebral or basilar artery territories, transluminal angioplasty may be of significant benefit in alleviating symptoms and improving blood flow to the posterior cerebral circulation.