Biomedical subjects

D A Nichols

Publications and source records attributed to D A Nichols.

At least 37 records · Page 2Linked to original sources

PubMed1997

Resection of a large temporooccipital parenchymal arteriovenous fistula by using deep hypothermic circulatory bypass. Case report.

The authors believe this to be the first published case in which a deep hypothermic cardiopulmonary bypass was used to facilitate resection of a large parenchymal arteriovenous fistula. The use of this procedure facilitated resection of the lesion by allowing compression and manipulation of large venous varices that were overlying the deeper arterial feeding vessels. The surgical rationale, technique, and intra- and postoperative management are discussed.

Adult↗

PubMed1997

Intra-arterial thrombolysis in acute basilar artery thromboembolism: the initial Mayo Clinic experience.

OBJECTIVE: To investigate the feasibility of intra-arterial thrombolysis in acute basilar artery thrombosis. DESIGN: We reviewed a consecutive series of patients in whom intra-arterial thrombolysis was performed during the period from 1994 to 1996. MATERIAL AND METHODS: Intra-arterial thrombolysis with urokinase was done in an attempt to recanalize the basilar artery in a series of nine patients with basilar artery thrombosis admitted to the neurologic intensive care unit. At the time of initial assessment, all nine patients had major neurologic deficits attributable to brain-stem ischemia, including two patients with locked-in syndrome. RESULTS: Recanalization of the basilar artery system was successful in seven of the nine patients (a range of 2 to 13 hours after the ictus). Failure to recanalize the basilar artery occurred in two patients, who died after progressing to coma. Complete recovery or only minimal neurologic deficits were demonstrated in five of the nine patients. Despite recanalization of the basilar artery, two patients had no major change in their neurologic function, and both ultimately had severe ataxia and were fully dependent on others. A cerebellar hemorrhage occurred in one patient but without clinical worsening. Two patients had a retroperitoneal hematoma. CONCLUSION: Intra-arterial thrombolysis with urokinase in acute basilar artery occlusion resulted in recanalization in seven of the nine patients (78%). Five of the nine patients recovered fully, including two patients who had had locked-in syndrome. In light of the devastating natural course of acute basilar artery occlusion, these initial results are encouraging and indicate that intra-arterial thrombolysis may be a useful emergency treatment, even in patients with prolonged symptoms of ischemia (up to 12 hours).

Adult↗

PubMed1996

The role of radiosurgery and particulate embolization in the treatment of dural arteriovenous fistulas.

Over the past 5 years 29 patients with dural arteriovenous fistulas (AVFs) were treated by the authors using the Leksell radiosurgical gamma knife unit. Within 2 days after radiosurgery, 17 patients with AVFs that exhibited retrograde pial or cortical venous drainage (12 patients) and/or produced intractable bruit (eight patients) underwent particulate embolization of external carotid feeding vessels. The rationale for this treatment strategy was that radiosurgery was expected to cause obliteration of most fistulas after 12 to 36 months. In patients with bruit, ocular symptoms, or in those at risk for hemorrhage, treatment with embolization after radiosurgery kept the fistulas angiographically visible for radiosurgical targeting yet offered palliation of symptoms and temporary, partial protection from hemorrhage during the latency period. In 12 patients, preobliteration embolization immediately reduced (10 patients) or eliminated (two patients) retrograde pial venous drainage. To date, no lesion has hemorrhaged after treatment. Angiography 1 to 3 years posttreatment in 18 patients showed total obliteration of 13 fistulas (72%) and partial obliteration of five (28%). Radiosurgery, followed by embolization when retrograde pial venous drainage, intractable bruit, and/or major external carotid artery supply is present, appears to be a promising treatment for selected patients with symptomatic dural AVFs.

Adult↗

PubMed1996

Percutaneous transcatheter embolization of coronary arteriovenous fistulas.

Coronary artery fistulas are infrequently encountered vascular communications that are either congenital or due to cardiac trauma. Most patients with these anomalies are asymptomatic, but late complications can occur and include congestive heart failure, myocardial ischemia, arrhythmias, and endocarditis. Therefore, many investigators have recommended surgical repair, even for asymptomatic patients. Although coronary arteriovenous fistulas pose many challenges to interventional cardiologists, early experiences suggest that these abnormal vessels can be successfully obliterated percutaneously; thus, the patient is spared the risks and morbidity associated with cardiac surgical intervention. Herein we present two cases that illustrate many of the technical issues involved in successful transcatheter embolization of coronary artery fistulas.

Adult↗

PubMed1995

Childhood dural arteriovenous fistulae of the posterior dural sinuses: three case reports and literature review.

We report three cases of posterior dural sinus arteriovenous fistulae in pediatric patients and a literature review of 18 additional cases. These lesions carry a grave prognosis with a reported mortality of 38% and with an historical anatomic cure of only approximately 9%. With advanced neurointerventional techniques and increased knowledge of their pathophysiology, these highly complicated lesions can be more safely treated with a strategy that involves extensive preoperative embolization and surgical excision. The importance of delaying direct surgery with conservative measures or interventional radiological treatment, including preoperative transarterial and transvenous embolization, is critical in the management of these lesions.

Cerebral Angiography↗

PubMed1995

Spontaneous carotid-jugular fistula and carotid dissection in a patient with multiple intracranial arachnoid cysts and hemifacial atrophy: a generalized connective tissue disorder? Case report.

The authors report a case of a 45-year-old woman with pulsatile tinnitus who was found to have an unusual spontaneous fistula between the petrous internal carotid artery and internal jugular vein. The fistula resolved spontaneously, possibly related to daily manual compression of the ipsilateral common carotid artery. The patient also had a contralateral carotid artery dissection, multiple intracranial arachnoid cysts, and hemifacial atrophy. Her medical history was significant for easy bruisibility, abnormal scarring, and mitral valve prolapse. This association appears unique and may represent a previously underscribed generalized connective tissue disorder.

Aortic Dissection↗

PubMed1995

Interim report on the radiosurgical treatment of cerebral arteriovenous malformations. The influence of size, dose, time, and technical factors on obliteration rate.

During the authors' initial 4-year experience with radiosurgery using the Leksell cobalt-60 gamma unit, they treated 121 patients with cerebral arteriovenous malformations (AVMs). The radiosurgical dose to the margin of the nidus was 20 Gy for lesions less than 2.0 cm in diameter (volume < or = 4.2 cm3); 18 Gy for malformations 2.1 to 3.0 cm in diameter (volume 4.2-14.1 cm3); and 16 Gy for malformations greater than 3.0 cm (volume > 14.1 cm3). Fifty-one patients underwent follow-up angiography between 1 and 3 years after treatment, and complete obliteration of the nidus was confirmed in 38 (74.5%) of these patients. Thirty-two (74.4%) of 43 AVMs with volumes of 10 cm3 or less and six (75%) of eight larger AVMs (volume 11-30 cm3) showed complete obliteration. Analysis of the time course of AVM nidus shrinkage and obliteration showed that most of the radiosurgically induced effect had occurred by 36 months after treatment. Retrospective analysis of the dose plans for 10 AVMs that were not obliterated by 36 months after gamma knife radiosurgery at the authors' institution (eight cases) or elsewhere (two cases) revealed that six AVMs had not been covered completely by the prescribed isodose. Six (5%) of the 121 patients developed neurological deficits as a direct result of radiosurgical treatment. The authors infer from these data that malformations up to 30 cm3 in volume (approximately 4.0 cm in average diameter) can be treated effectively with an acceptably low complication rate using a radiosurgical dose of 16 Gy to the margin of the nidus. The obliteration rate for the larger malformations that were treated with a dose of 16 to 18 Gy appears to be similar to that for smaller ones treated with 18 to 20 Gy. As more experience accrues using radiosurgery to treat AVMs, patient selection criteria and the variables associated with successful obliteration of the nidus should become more clearly defined.

Adolescent↗

PubMed1995

Medical and surgical management of intracranial aneurysms.

OBJECTIVE: To examine the medical and surgical aspects of intracranial aneurysms, including the pathogenesis, clinical manifestations, management of subarachnoid hemorrhage (SAH), and indications for surgical intervention. DESIGN: This review presents the classification of intracranial aneurysms, defines specific aneurysms, and analyzes the Mayo Clinic experience with surgical treatment of cerebral aneurysms. MATERIAL AND METHODS: Intracranial aneurysms are classified by cause, size, site, and shape. The clinical grading systems for SAH, the most common manifestation, are as follows: modified Botterell, Hunt and Hess, and World Federation of Neurological Surgeons. Surgical options are direct clipping, interventional neuroradiologic treatment, proximal ligation or trapping of aneurysms, and wrapping or coating of aneurysms. Although the timing of surgical intervention after SAH is controversial, it should be based on the clinical grade, site of the aneurysm, and patient's medical condition. RESULTS: The frequency of intracranial aneurysms is estimated to be 1 to 8% in the general population, and 90% of patients have SAH. After SAH, 8 to 60% of patients die before they get to a hospital. After hospitalization, the mortality rate is 37%, severe disability is 17%, and outcome is favorable in 47%. The current trend for surgical treatment is early after SAH. The Mayo Clinic experience with 1,947 patients who underwent surgical treatment because of aneurysmal SAH or for aneurysmal repair between 1969 and 1990 is as follows: 1,445 had an excellent outcome, 231 had a good outcome, 171 had a poor outcome, and 100 died. CONCLUSION: Aggressive management can be beneficial for many patients with severe neurologic injury after SAH by preventing rerupture of the aneurysm, attenuating the severity and sequelae of vasospasm, and decreasing the surgical complications.

Aged↗

PubMed1995

Stereotactic radiosurgical treatment of cerebral arteriovenous malformations. Gamma Unit Radiosurgery Study Group.

OBJECTIVE: To assess the role of clinical factors, size of lesion, site of involvement, and radiation dose in patients with cerebral arteriovenous malformations (AVMs) who underwent stereotactic radiosurgical treatment. DESIGN: We reviewed the results in 121 patients with cerebral AVMs treated with the Leksell "Gamma Knife" between January 1990 and December 1993 at the Mayo Clinic in Rochester, Minnesota. MATERIAL AND METHODS: The following strict dose-volume protocol was used: AVMs 2.0 cm or smaller in diameter (volume, 4.2 cm3 or less) received 20 Gy to the margin of the nidus, those between 2.1 and 3.0 cm in diameter (4.3 to 14.1 cm3) received 18 Gy to the margin, and those that exceeded 3.0 cm in diameter (more than 14.1 cm3) received 16 Gy to the margin. Lesions that involved the brain stem received a radiosurgical dose of 18 Gy or less to the margin. Patients participated in regular follow-up clinical and imaging studies for up to 55 months. RESULTS: Follow-up cerebral angiography in 43 patients demonstrated total obliteration of the AVM nidus in 31 (72.1%), including 5 of 7 (71.4%) who had AVMs with a volume larger than 10 cm3. Clinical follow-up revealed that 111 patients (91.7%) had a stable or improved outcome, 3 had a nonfatal AVM hemorrhage, 2 suffered a fatal hemorrhage, and 2 died of causes not directly attributed to the AVM or radiosurgical treatment. Two patients had new or increased, nondisabling neurologic deficits as a result of treatment, and one patient had a temporary partial eyelid ptosis. CONCLUSION: Our findings suggest that previous theories about the relationship between AVM size and rate of obliteration after radiosurgical treatment may need revision. Our experience confirms that radiosurgical treatment for cerebral AVMs is safe and effective, even in cases for which the latency period before obliteration is longer than 2 years.

Adolescent↗

PubMed1994

Endovascular treatment of intracranial aneurysms.

OBJECTIVE: To examine the techniques, reported experiences, and advantages and disadvantages associated with the endovascular treatment of intracranial aneurysms. DESIGN: We review the endovascular techniques used for the treatment of intracranial aneurysms and the sequelae of subarachnoid hemorrhage, which have evolved during the past 10 years. MATERIAL AND METHODS: Two broad categories of endovascular therapy for intracranial aneurysms are described: occlusion of the parent artery and preservation of the parent artery by selective occlusion of the aneurysm with balloons or metallic coils. The Mayo protocol for testing tolerance of patients before permanent balloon occlusion of the parent artery is described, as are the types of aneurysms most amenable to this treatment. In addition, use of balloon angioplasty for cerebral vasospasm after subarachnoid hemorrhage is reviewed. RESULTS: Recent improvements in microcatheter technology have facilitated the safe navigation of percutaneously introduced catheters in the intracranial circulation and selective catheterization of intracranial aneurysms. Surgically difficult aneurysms are now being treated with endovascular techniques more frequently than in the past. Early results from animal experiments and human trials have shown that selective occlusion of aneurysms with metallic coils may have a role in the treatment of intracranial aneurysms. Balloon angioplasty of symptomatic cerebral vasospasm has demonstrated improvement in neurologic function in approximately 70% of patients. CONCLUSION: As technology continues to improve and as greater experience is obtained, interventional neuroradiologists will continue to have an increasingly important role in the treatment of intracranial aneurysms.

Angiography, Digital Subtraction↗

PubMed1994

Carotid artery occlusion: positive predictive value of duplex sonography compared with arteriography.

PURPOSE: Duplex ultrasonography is an accurate, noninvasive method for diagnosing, characterizing, and classifying atherosclerotic stenoses of the extracranial carotid artery system. To date, however, no large series has studied the predictive value of duplex sonography in the diagnosis of carotid artery occlusion, an important consideration, given the marked difference in clinical treatment between patients with high-grade stenosis (surgical therapy) and those with occlusive disease (nonsurgical therapy). METHODS: We retrospectively reviewed 158 patients with 174 occluded carotid artery segments (examined over a 6 1/2-year period) to determine the predicative value of duplex sonography in differentiating carotid artery occlusion from high-grade stenosis. RESULTS: All patients had arteriographic correlation. Duplex ultrasonography had a positive predictive value of 92.5% (7.5% false-positive rate; 95% confidence interval, 3.6% to 11.4%) in establishing a diagnosis of carotid artery occlusion. Further analysis revealed no significant improvement in the false-positive rate with the addition of color Doppler flow imaging to high-resolution B-mode scanning and pulsed Doppler spectral analysis. Predictive value increased to 96.7% (95% confidence interval, 90.7% to 99.3%) over the last 2 years of the study, a statistically significant improvement. CONCLUSIONS: We believe that duplex ultrasonography is an acceptably accurate method for diagnosing carotid arterial occlusion in most patients. Arteriography should be reserved for patients with symptoms who are surgical candidates to identify those who may still have a surgically correctable high-grade stenosis.

Aged↗

PubMed1994

Perimesencephalic subarachnoid hemorrhage. Additional perspectives from four cases.

BACKGROUND: Nonaneurysmal perimesencephalic hemorrhage, a distinct form of subarachnoid hemorrhage, is a recently described variant of intracranial hemorrhage. We describe two patients who presented with unusual features of this type of subarachnoid hemorrhage and also two patients who had a perimesencephalic pattern of hemorrhage due to a ruptured posterior circulation aneurysm. CASE DESCRIPTIONS: The first patient, a 41-year-old woman with perimesencephalic hemorrhage, underwent an exploratory craniotomy because angiography had suggested an anomaly of the basilar tip. No source of hemorrhage could be identified at the time of surgery. The second patient was a 3-year-old boy who presented with opisthotonos and who was found to have a perimesencephalic hemorrhage. Angiography revealed no source for the hemorrhage. The third patient, a 54-year-old man, had a perimesencephalic pattern of subarachnoid hemorrhage from a vertebrobasilar junction aneurysm associated with a fenestration that was missed on the initial angiographic study. The fourth patient, a 43-year-old man, suffered a perimesencephalic pattern of subarachnoid hemorrhage from a small posterior cerebral artery aneurysm, which had not been recognized on two angiograms. CONCLUSIONS: These patients elaborate on the clinical spectrum of subarachnoid hemorrhage with a perimesencephalic pattern. First, a negative exploratory craniotomy suggests that the source of nonaneurysmal perimesencephalic hemorrhage may not be arterial. Second, nonaneurysmal perimesencephalic hemorrhage may also occur in children. Finally, the index of suspicion for a posterior circulation aneurysm should remain high in patients who present with a perimesencephalic pattern of subarachnoid hemorrhage, and these aneurysms may rise from unusual locations.

Adult↗

PubMed1994

Electronic animal identification for controlling feed delivery and detecting estrus in gilts and sows in outside pens.

The objective of the present study was to evaluate the feasibility of delivering feed and detecting estrous behavior by computer-controlled equipment in a nonconfinement environment. In Exp. 1, gilts were assigned to treatment when detected pregnant by ultrasound at 30 to 35 d after artificial insemination. They were assigned to be fed individually in stalls once/day (0830) with a scoop (controls, n = 20) or with an electronic sow feeding station (ESF, n = 20). The ESF gilts received their feed in 98.6-g aliquots at 80-s intervals as they visited the feeding station. Control vs ESF gilts did not differ (P > .8) for backfat (2.2 vs 2.1 cm) or weight (170 vs 172 kg) before farrowing, total and live pigs/litter (9.3 and 8.7 vs 9.1 and 8.8), or litter birth weight (12.7 vs 12.1). In Exp. 2, proceptive behavior, as measured by visits to a boar's pen, were recorded electronically, and observed estrus was evaluated in two groups of sows during their first (n = 11) and second and third (n = 19) estrous cycles and in one group of gilts (n = 14). A partition prevented visual and physical contact between the boar and the visiting females except where the electronic estrus detection (EED) station was installed. Feed delivery software was used to monitor boar visitation even though no feed delivery equipment was present at the boar pen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1994

Intracranial dural arteriovenous fistulae: angiographic predictors of intracranial hemorrhage and clinical outcome in nonsurgical patients.

This long-term follow-up study of 54 patients clarifies the angiographic predictors of intracranial hemorrhage (ICH) and clinical outcome in individuals with unoperated intracranial dural arteriovenous fistulae (AVF's). All of these patients were examined at the Mayo Clinic between 1976 and 1989, and all available cerebral arteriograms were reviewed by a neuroradiologist. Follow-up information was obtained for 52 patients (96%) until death or treatment intervention, or for at least 1 year after diagnosis, with a mean follow-up period of 6.6 years. Throughout this 6.6-year follow-up period, ICH related to dural AVF occurred in five of the 52 patients, for a crude risk of hemorrhage of 1.6% per year. The risk of hemorrhage at the time of mean follow-up examination was 1.8% per year. Angiographic examination revealed several characteristics that were considered potential predictors of ICH during the follow-up period. Lesions of the petrosal sinus and straight sinus had a higher propensity to bleed, although the small numbers in the series precluded a definite conclusion. A person suffering from a dural AVF with a venous varix on a draining vein had an increased risk of hemorrhage, whereas no hemorrhage was seen in the 20 patients without a varix (p < 0.05). Lesions draining into leptomeningeal veins had an increased occurrence of hemorrhage, although this increased risk was not statistically significant. Patients' initial symptoms were compared to those at follow-up evaluation. Pulsatile tinnitus improved in more than half of the 52 patients, and resolved in 75% of those showing some improvement. Individuals without a sinus or venous outflow occlusion at initial cerebral angiography were more likely to improve or remain stable (89%), whereas patients with an occlusion showed infrequent improvement (11%; p < 0.05).

Adult↗

PubMed1994

Blinded prospective evaluation of sensitivity of MR angiography to known intracranial aneurysms: importance of aneurysm size.

PURPOSE: To determine the sensitivity of time-of-flight and phase-contrast MR angiography for the detection of intracranial aneurysms. METHODS: Sixteen patients with 27 intracranial aneurysms previously identified with conventional angiography and 19 control patients were examined with three-dimensional time-of-flight, three-dimensional phase-contrast MR angiography, and standard MR imaging. Subvolumes of the carotid and posterior circulations, source images, and standard MR images were blindly interpreted by three experienced neuroradiologists. RESULTS: Detection of an aneurysm by a given sequence was defined as at least two of the three blinded readers identifying the aneurysm. The sensitivities of the sequences based on all 27 aneurysms were: transaxial T1, 25.9%; T2, 48.1%; PC, 44.4%; and TF, 55.6%. Two of 3 aneurysms detected with T2 but not MR angiography had adjacent blood products. Five millimeters appeared to be a critical size; the sensitivities for aneurysms greater than or equal to 5 mm were: T1, 37.5%; T2, 62.5%; PC, 75%; and TF, 87.5%. CONCLUSIONS: Three-dimensional time-of-flight MR with 512 x 256 matrix is more sensitive than three-dimensional phase-contrast or standard MR imaging for detection of aneurysms. Retrospectively, aneurysms 3 mm or larger can be identified with MR angiography; however, prospectively, 5 mm is the critical size for detection.

Adult↗

PubMed1993

Imaging spectrum of thrombo-occlusive vascular disease associated with antiphospholipid antibodies.

The association of antiphospholipid antibodies with unexplained thrombo-occlusive vascular disease is well known but often remains unrecognized. The most well-studied clinical manifestation is venous thrombosis, but arterial occlusive disease involving multiple sites is also well documented. Twenty-six cases of thrombo-occlusive disease were observed in 22 patients over a 3-year period. Magnetic resonance imaging and angiography were used to make the diagnoses. None of the patients who underwent angiography or venography developed thrombolytic disease related to the puncture site. This group of patients with antiphospholipid antibody syndrome had a wide distribution of arterial and venous thrombotic disease. Radiologists should consider antiphospholipid antibody syndrome in the differential diagnosis when evaluating thrombo-occlusive vascular disease that is unexpected or occurs without risk factors. Knowledge of antiphospholipid antibody status has important implications for prognosis and therapy.

Adult↗

PubMed1993

Ocular motor nerve palsies in spontaneous dissections of the cervical internal carotid artery.

Cranial nerve palsies affecting ocular motor function in patients with spontaneous cervical internal carotid artery dissections are rare. Among 155 patients with spontaneous dissections of the cervical internal carotid artery, four (2.6%) had transient third, fourth, or sixth cranial nerve palsy. The third nerve was involved in two patients, the fourth nerve in one, and the sixth nerve in one. Three patients had ipsilateral headache or facial pain, one had bilateral headaches, and three had oculosympathetic palsy. None had any associated cerebral or retinal ischemic symptoms. Cervical internal carotid artery dissection should be included in the differential diagnosis of palsies of the third, fourth, or sixth cranial nerve, especially when associated with ipsilateral headache or facial pain. Interruption of the nutrient arteries supplying these cranial nerves could explain their involvement by internal carotid artery dissection.

Adult↗

PubMed1993

Occlusive hyperemia: a theory for the hemodynamic complications following resection of intracerebral arteriovenous malformations.

An alternative theory is proposed to explain the brain edema and hemorrhage that may occur after resection of high-flow intracerebral arteriovenous malformations (AVM's). This theory, termed "occlusive hyperemia," is based on a retrospective analysis of operative dictations along with postoperative imaging studies (191 angiograms and 273 computerized tomography scans) in 295 cases of intracerebral AVM's operated on at the Mayo Clinic between 1970 and 1990. In this series, 34 cases (12%) of postoperative deterioration were documented, of which 15 were due to incomplete resection of the AVM. Of the remaining 19 cases, six had brain edema alone and 13 had hemorrhage with edema, despite complete excision of the AVM. In these 19 cases, the AVM's were greater than 6 cm in diameter in 10 patients, between 3 and 6 cm in six, and less than 3 cm in three. Obstruction of the venous drainage system was observed in 14 (74%) of the 19 cases. Ten of these 14 were due to obstruction of the primary venous drainage of the brain parenchyma immediately surrounding the lesions, while four were due to obstruction of other venous structures. In no case was a rapid circulation identified on postoperative angiograms. The flow pattern was slow or stagnant in former AVM feeders and their parenchymal branches. It is proposed that postoperative intracranial hemorrhage and/or brain edema in AVM patients may be due to: 1) obstruction of the venous outflow system of brain adjacent to the AVM, with subsequent passive hyperemia and engorgement; and 2) stagnant arterial flow in former AVM feeders and their parenchymal branches, with subsequent worsening of the existing hypoperfusion, ischemia, and hemorrhage or edema into these areas. Supportive hemodynamic evidence for this theory was derived from the literature.

Adult↗