Biomedical subjects

P Purdy

Publications and source records attributed to P Purdy.

18 recordsLinked to original sources

PubMed2000

Idiopathic ischemic cerebral infarction in childhood: depiction of arterial abnormalities by MR angiography and catheter angiography.

BACKGROUND AND PURPOSE: We report our experience with MR imaging, MR angiography, and catheter angiography in children with acute idiopathic cerebral infarction and suggest that catheter angiography may still play an important role in this setting. METHODS: During the past 8 years, 18 children with idiopathic cerebral infarction underwent MR imaging and catheter angiography; 17 were also studied with MR angiography. MR imaging was done within 34 hours after onset of hemiplegia or seizures or both. Sixteen patients underwent catheter angiography within 36 hours of MR imaging; 12 studies were performed within 22 hours. Two patients underwent catheter angiography, in both cases within 72 hours. Infarcts were compared with arterial abnormalities seen at catheter angiography, and the results of MR angiography were compared with those seen at catheter angiography. RESULTS: Comparing MR angiography with catheter angiography, we found the positive predictive value of MR angiography for arteriopathy was 100%, with a negative predictive value of 88%. MR angiography was equivalent to catheter angiography in the detection and depiction of proximal middle cerebral artery disease; however, depiction of disease in the internal carotid artery (ICA) and detection of peripheral embolic disease were better with catheter angiography than MR angiography. CONCLUSION: Basal ganglia lesions associated with ICA disease by MR angiography should probably be studied with digital subtraction angiography, as MR angiography did not depict the length and severity of ICA disease as well as catheter angiography did. Hemispheric infarcts should be studied with catheter angiography, as emboli may occur in the absence of heart disease; the circle of Willis may be uninvolved with embolic disease, and MR angiography is not sensitive to emboli in small peripheral intracranial arteries.

Acute Disease↗

PubMed1999

Aneurysm retreatment after Guglielmi detachable coil and nondetachable coil embolization: report of nine cases and review of the literature.

OBJECTIVE: Guglielmi detachable coil embolization of cerebral aneurysms is becoming increasingly used to manage certain intracranial lesions based on aneurysm geometry, patient condition, and patient and surgeon preferences. Aneurysm recurrences or incomplete initial treatments are not uncommon, making repeat treatment necessary using either surgical or endovascular techniques. METHODS: Between January 1993 and June 1998, 1025 cerebral aneurysms were managed by the authors at a single hospital. One hundred twenty-four of these lesions were treated using Guglielmi detachable coils, and one was managed with nondetachable coils. During the follow-up period, eight patients who underwent embolization at our institution and one who underwent embolization elsewhere received repeat treatment. Five were approached surgically, and four underwent re-embolization. All charts and films were reviewed retrospectively to determine patient outcome and clinical success. RESULTS: No patient in the subgroup of this clinical study suffered a permanent complication from initial aneurysm coiling, no episodes of subsequent bleeding occurred, and no complications resulted from any subsequent therapies. The anatomic results were excellent, and all aneurysms were totally or near totally obliterated. CONCLUSION: Subtotal initial coil embolization of aneurysms can be managed safely using a variety of surgical and endovascular techniques. Our approach to this predicament, lessons we have learned, and a review of the literature are herein discussed.

Adult↗

PubMed1998

Subarachnoid hemorrhage during arteriovenous malformation embolization as a result of vessel wall "sandblasting".

OBJECTIVE: Preoperative selective particulate embolization of arteriovenous malformations can make subsequent surgical resection of such lesions safer for the patient and easier for the surgeon. Nevertheless, embolization carries intrinsic risks, which include subarachnoid hemorrhage. We report two cases of subarachnoid hemorrhage during particulate embolization that we think was attributable to catheter positioning near a vessel curve and subsequent denudation of the vessel wall to the degree that hemorrhage was induced.

Adult↗

PubMed1997

Does electrothrombosis occur immediately after embolization of an aneurysm with Guglielmi detachable coils?

Current options for treating cerebral aneurysms include surgical clipping and placement of Guglielmi detachable coils (GDCs). The latter system is reported to induce acute aneurysmal occlusion by a mechanism of electrothrombosis. We report our observations in the case of a ruptured aneurysm treated with GDCs and then surgically exposed 2 hours later. The lack of thrombus within the aneurysm and around the coils led us to question the mechanism of action of GDCs.

Aneurysm, Ruptured↗

PubMed1996

Intracavernous carotid artery aneurysms: the possible importance of angiographic dural waisting. A case report.

BACKGROUND: Cavernous carotid aneurysms are generally benign entities. Certain indications exist for their treatment, however, including transient ischemic events, subarachnoid hemorrhage or risk of subarachnoid hemorrhage, epistaxis or its risk, ophthalmoplegia, pain, and progressive visual loss. We feel certain angiographic features may indicate a greater likelihood that cavernous carotid aneurysms extend into the subarachnoid space, thus making their rupture a life-threatening event. METHODS: A case report of an intracavernous carotid aneurysm, which at surgery extended into the subarachnoid space, is described. RESULTS: In this particular case, deformation of the aneurysm (waisting) as seen at angiography was in retrospect an indication that the cavernous carotid aneurysm extended into the subarachnoid space, either through the dural ring or through the eroded dural roof of the cavernous sinus. This finding was verified at surgery when the lesion was explored and trapped. CONCLUSION: Angiographic waisting of a cavernous carotid aneurysm may indicate that the aneurysm extends into the subarachnoid space. Such extension means that rupture would be a life-threatening event. While deformation of the aneurysm may be secondary to compression against the optic nerve or anterior clinoid process with an intact layer of dura overlying the aneurysm, the neurosurgeon confronted with such findings should analyze such lesions carefully and consider surgical exploration.

Aged↗

PubMed1995

Treatment of dural sinus thrombosis using selective catheterization and urokinase.

Thrombosis of the cerebral dural venous sinuses, cortical draining veins, and deep cerebral veins is a rare clinical finding. Because of its low incidence and multiple etiologies, the optimum therapy for this condition will only be elucidated by a multicenter, randomized prospective study. At our institution, we favor early and aggressive management of cerebral venous sinus thrombosis with transfemoral, venous intradural infusions of the fibrinolytic agent urokinase. To date, treatment of only 13 patients using this technique has been reported in the English literature. This report adds 12 more such treated patients. Despite the presence of preinfusion infarcts in 5 patients, four of which were hemorrhagic, we incurred no major therapeutic morbidity. Functional sinus patency was achieved in 11 of 12 patients, with our only true failure occurring in an individual with symptoms of at least 2 months' duration. Good to excellent clinical outcome was achieved in 10 of 11 patients (one newborn had inadequate follow-up).

Adult↗

PubMed1995

Lesion localization in periodic lateralized epileptiform discharges: gray or white matter.

We analyzed the results of neuroimaging studies in patients with periodic lateralized epileptiform discharges (PLEDs) or bilateral independent periodic lateralized epileptiform discharges (BIPLEDs) for localization of lesions in gray or white matter to determine if "cortical isolation" is a critical mechanism in the pathogenesis of this phenomena. We assessed 32 patients who had undergone computed tomography (CT) exclusively and 8 patients who had undergone magnetic resonance imaging (MRI) with or without CT. The superior resolution necessary for adequate lesion localization allowed use of only the MRI scans from the 8 patients. Six patients had scans with cortical and subcortical gray and white matter lesions, and 1 patient had a cortical gray matter lesion only. One patient had an indeterminate scan. No patient had white matter lesions only. Our findings in patients with PLEDs and BIPLEDs correlate with postmortem data in patients with generalized periodic EEG patterns that show consistent localization of lesions in the gray matter. These findings do not support cortical isolation as the critical or sole mechanism in PLEDs or BIPLEDs.

Adult↗

PubMed1995

Elevated transcranial Doppler ultrasound velocities following therapeutic arterial dilation.

BACKGROUND: Elevated transcranial Doppler (TCD) velocities seen after cerebral angioplasty are commonly interpreted as evidence of residual or recurrent stenosis but may conceivably arise from hyperemia and require different clinical management. SUMMARY OF REPORT: Four cases of abnormally elevated mean TCD velocities obtained after therapeutic arterial dilation with either balloon angioplasty or intra-arterial administration of papaverine are described. In each case, cerebral angiography revealed a dilated vessel, suggesting that hyperemia and impaired autoregulation were the causes of the high velocities. CONCLUSIONS: These examples suggest that high TCD velocities after vessel dilation may be produced by unpredictable amounts of vessel narrowing and flow alteration. Although a normalizing TCD velocity after angioplasty suggests effective vessel dilation, high velocities may be due partly to hyperemia and cannot be interpreted as arising solely from recurrent stenosis.

Adult↗

PubMed1994

Interdisciplinary evaluation of cerebral hemodynamics in the treatment of arteriovenous fistulae associated with giant varices.

The techniques for the treatment of intracranial arteriovenous fistulae include angiographic balloon occlusion of the fistula as well as direct surgical attack. Regardless of the method, the occurrence of severe hyperemia caused by a lack of autoregulation after obliteration of the fistula remains a significant concern. We report the use of single photon emission computed tomography and transcranial Doppler studies to assess the occurrence of hyperemia during trial balloon occlusion of such fistulae in two patients. Single photon emission computed tomography and transcranial Doppler studies confirmed the lack of hyperemia during the test occlusion, allowing consideration of treatment plans involving acute fistula occlusion without the difficulty imposed by gradual occlusion and permitting a more accurate evaluation of risk. The purpose of this report is to illustrate how clinical evaluation of intracranial hemodynamics can contribute significantly to treatment decisions.

Adult↗

PubMed1994

Prediction of tolerance to carotid artery occlusion using transcranial Doppler ultrasound.

Surgical sacrifice of the carotid artery is a frequently anticipated event during the treatment of certain aneurysms and tumors. The ability to predict tolerance to carotid artery occlusion is therefore of benefit when planning procedures in which the carotid artery is at risk. A trial of carotid artery occlusion using an angiographic balloon during concurrent neurological examination or blood flow studies is an accepted method for testing tolerance, but it carries the risks of an angiogram and cannot be performed at the bedside. Transcranial Doppler ultrasound (TCD) is a noninvasive modality that permits measurement of blood velocity in cerebral vessels. The immediate effects of carotid artery occlusion on middle cerebral artery (MCA) perfusion can be obtained by insonating this artery during manual carotid artery compression. To compare the TCD response to carotid artery compression with the data obtained with more formal testing, the MCA of 22 patients was insonated during manual carotid artery compression and the results compared with the clinical tolerance to balloon occlusion in all patients and to blood flow studied by single photon emission computerized tomography before or during balloon occlusion in 14 of the 22 patients. Surgery was planned to treat giant unruptured aneurysms in 17 cases, intracranial tumors in three, a carotid-cavernous fistula in one, and a carotid artery injury in one. Fifteen patients showed a reduction in TCD flow velocities by no more than 65%; of these, 14 (93%) clinically tolerated the balloon occlusion test. Of the seven patients showing a TCD flow velocity decrease of more than 65%, six (86%) developed a transient focal deficit during the occlusion. It is concluded that the change in MCA velocity measured with TCD studies during manual carotid artery occlusion is a useful predictor of the clinical and blood flow responses to a trial of carotid artery occlusion with an angiographic balloon.

Adult↗

PubMed1993

Postpartum cerebral angiopathy. Is there a role for sympathomimetic drugs?

BACKGROUND: Postpartum cerebral angiopathy is associated with the use of of ergot alkaloids. The exact mechanism is unclear but may be related to their sympathomimetic properties, as evidenced in patients already on other ergot derivatives who deteriorated only after taking additional sympathomimetic drugs. We postulate that sympathomimetic agents, independent of ergot alkaloids, may produce the same complication. CASE DESCRIPTION: A postpartum patient, initially presenting with headaches, subsequently manifested rapid neurological deterioration after ingesting isometheptene, a sympathomimetic drug. She was not on any ergot derivative but presented similar clinical and radiological manifestations. She experienced increased headache severity, visual disturbance, and seizures associated with multiple segmental cerebral vasoconstriction on angiography and increased T2-weighted signal in the occipital areas on magnetic resonance imaging. CONCLUSIONS: This case is additional evidence that sympathomimetic actions of some drugs, such as ergot derivatives and isometheptene, may lead to postpartum cerebral angiopathy. Documentation of medication used by postpartum women suffering similar complications is needed to verify these findings.

Adult↗

PubMed1992

The transcranial Doppler appearance of acute carotid artery occlusion.

Transcranial Doppler ultrasound is a noninvasive technique of cerebral blood velocity measurement that is being increasingly used to detect untoward hemodynamic changes. In this report, we describe striking transcranial Doppler ultrasound changes occurring in 2 patients after cervical carotid artery occlusion that led to cerebral infarction. These changes consist of the sudden appearance of a Doppler signal of extremely low pulsatility and moderately high velocity in the middle cerebral artery distribution. In 1 patient, this signal was the first sign of carotid occlusion. We suggest that these transcranial Doppler ultrasound changes can provide an early warning of carotid artery compromise.

Acute Disease↗

PubMed1990

Transcranial Doppler ultrasound as a guide to graded therapeutic occlusion of the carotid artery.

Although gradual carotid artery occlusion is an accepted and effective treatment for some surgically inaccessible intracranial aneurysms, there are no specific guidelines to determine the optimal amount of carotid artery narrowing at each adjustment. The technique of transcranial Doppler ultrasound, however, allows continuous measurement of blood velocity in the middle cerebral artery as the carotid artery is narrowed, so that hemodynamic effects and development of collateral flow can be immediately assessed at the bedside at each adjustment of the carotid artery diameter. This case report describes the use of transcranial Doppler to guide the rate of carotid occlusion in a patient with an unclippable giant aneurysm of the carotid artery. Sudden carotid occlusion and gradual occlusion at the usual rate were not tolerated by the patient, but repeatedly tightening the clamp until the first signs of attenuation of the Doppler signal allowed an expedient occlusion without complication. Transcranial Doppler ultrasound can provide a useful dynamic guide to gradual therapeutic carotid occlusion.

Carotid Arteries↗

PubMed1990

Intracarotid hydroxyethyl methacrylate solution causing stroke in dogs.

Hydroxyethyl methacrylate (HEMA) has been advocated as a polymerizing solution with which to prevent deflation of detachable balloons in interventional neuroradiology. It is pertinent to know if unpolymerized HEMA would have untoward effects if accidentally released into the carotid artery by balloon rupture or deflation. Seven mongrel dogs underwent transfemoral catheterization of the common carotid artery and subsequent injection of HEMA solution in volumes of 1 cc in five dogs, 2 cc in one, and 4 cc in one. Angiography performed at the time of injection revealed evidence of intravascular thrombosis as well as possible spasm. Three surviving animals were sacrificed at 48 hours; the brains were fixed and examined histopathologically. One brain was normal and one was autolyzed and could not be examined. Five of the seven animals had histopathologically documented cerebral infarctions of varying size. No foreign substance was seen within the blood vessels to suggest intravascular polymerization. The animals injected with 2 or 4 cc HEMA solution did not survive 48 hours. Literature review reveals little documentation of the toxicology of intravascular HEMA. With its increasing popularity as a compound for polymerization in detachable balloons introduced into the brain, further investigations are warranted to understand the physical properties of the compound and potential risks of its use.

Animals↗

PubMed1988

Head computed tomographic scans in women with eclampsia.

From 1980 to 1986, head computed tomographic scans were performed in 49 women with eclampsia managed according to the standardized regimen used at Parkland Memorial Hospital. Abnormal radiographic findings were seen in 14 (29%). Although this incidence may have been affected by the temporal relationship of the scan to the seizure, it was greatly impacted by technical resolution obtained with succeeding improved equipment. In the last 3 years of the study more than a third of these scans showed some abnormality, and in 1986, using "fourth-generation" equipment, half were abnormal. These areas of radiographic hypodensity correspond to those with petechial hemorrhages and local edema that have been described at autopsy in women who died after eclamptic episodes. All women recovered fully despite ominous findings in some. We conclude that the clinical utility of tomography in women with otherwise "uncomplicated eclampsia" is limited because these findings seldom alter management.

Brain↗

PubMed1987

Cerebral location of international 10-20 system electrode placement.

We employed CT scanning to correlate scalp markers placed according to the international 10-20 system with underlying cerebral structures. Subjects were 12 normal volunteers. Measurements included assessment for cranial asymmetry to determine the effect of skull asymmetry on cortical location of electrodes. Results were correlated with the cortical histological map of Brodmann. Primary cortical locations agree well with previously published data and provide cortical localization in greater detail than previous studies. Variability of cortical electrode location was substantial in some cases and not related to cranial asymmetry. The results indicate that CT scanning or other neuroimaging techniques which reveal detailed cerebral anatomy would be potentially highly useful in defining the generators of electrocerebral potentials recorded from the scalp.

Adult↗

PubMedDate not supplied

A technique for computer-guided stereotaxis without preoperative head fixation.

A CT-guided stereotactic method is described which uses a standard BRW frame for probe insertion but which does not require frame fixation to the skull during the localizing scan. The patient is instead scanned wearing three radiopaque scalp markers, and new software utilized to obtain BRW coordinates. Acceptable accuracy for targets greater than one centimeter in diameter was obtained in phantom trials and in three case reports. This technique may be helpful for stereotactic targets greater than one centimeter in diameter and when preoperative head fixation is not desirable or possible.

Brain↗

PubMedDate not supplied

Effects of inhaled stable xenon on cerebral blood flow velocity.

The effects of inhaled stable xenon gas on cerebral blood flow were studied with 23 transcranial Doppler examinations performed in 13 normal volunteers while breathing, 25, 30, or 35% xenon for 5 min. Doppler velocities from the middle cerebral artery rose significantly during inhalation in 85% of subjects and 78% of studies and decreased significantly in 15% of subjects and 17% of studies. These different velocity responses may represent different responses of pial vasculature to xenon. The mean velocity rise among those studies showing a significant increase was 38 +/- 3.6% (SEM). The velocity rise began 2 min after the start of xenon inhalation and increased rapidly, so that the velocities measured at the four times at which scans were obtained in our xenon CT protocol (0, 1.5, 3, and 5 min after the start of xenon inhalation) were significantly different. A consistent fall in the pulsatility of the Doppler waveform as the velocity increased provided evidence for xenon-induced vasodilation of the small-resistance vessels as the cause of the increase in flow velocity. Most subjects became mildly hyperventilated, so that the observed changes could not be attributed to hypercapnia. Inhalation of 25, 30, or 35% xenon for 5 min induces a delayed but significant rise in cerebral blood velocity. This suggests that cerebral blood flow itself may be rapidly changing during the process of xenon CT scanning. These changes may compromise the ability of the xenon CT technique to provide reliable quantitative measurements of cerebral blood flow.

Administration, Inhalation↗