Biomedical subjects

E S Kwan

Publications and source records attributed to E S Kwan.

29 records · Page 2Linked to original sources

PubMed1987

Clinical features and mechanism of occipital infarction.

To clarify the clinical features and mechanism of infarction in the posterior cerebral artery territory, we investigated 35 consecutive patients who presented with homonymous visual field defects and occipital infarction documented by computed tomography. Cerebral angiographic findings in 23 patients, and the clinical features of rare transient ischemic attacks and maximal deficit occurring at stroke onset, were consistent with embolism of the posterior cerebral artery. Visual field defects were the only neurological abnormality in 17 patients; the remainder had additional findings. Three patients had a major brainstem stroke. Stroke in the posterior cerebral artery territory was found in a heterogeneous group of patients, although embolism was the most common stroke mechanism. Several distinct patient groups were identified: cardiac source embolism (10 patients), vertebrobasilar atheroma with local embolism (6), migraine (5), systemic illness with presumed coagulopathy (3), and "unknown source embolism" after negative cardiac investigation (11 patients). During follow-up, 26 patients had no further neurological events (the majority on anticoagulation or antiplatelet treatment), 3 suffered new strokes, and 6 died.

Basilar Artery↗

PubMed1987

Basilar artery stenosis: middle and distal segments.

We report the clinical features and prognosis in nine patients with angiographically documented basilar artery stenosis of the middle and distal segments. Six patients had transient ischemic attacks (TIAs), and in two this was their only clinical manifestation. The TIAs in four patients included two or more of the following symptoms: dizziness, diplopia, perioral numbness, dysphagia, weakness, or loss of consciousness. Two other patients had isolated symptoms of transient dizziness and unilateral weakness. Seven patients had posterior circulation strokes, preceded by TIAs in four. Basilar artery occlusive disease can affect any segment of the artery. The short-term prognosis of middle and distal basilar artery stenosis was good especially when patients were treated with warfarin or platelet antiaggregants.

Aged↗

PubMed1987

Intracarotid chemotherapy with 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) in 5% dextrose in water in the treatment of malignant glioma.

After radiotherapy, 20 patients, 18 with documented progression of malignant glioma and 2 with Grade II astrocytoma, received a total of 52 courses of intracarotid 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) at a dose of 150 mg/m2 dissolved in 5% dextrose in water. The patients were treated at 6-week intervals for a maximum of five courses of chemotherapy per patient. Response to treatment was analyzed on computed tomographic scans by measuring the volume of the enhancing tumor and any central low density. From these data, tumor doubling times ranging from 110 to 968 days were obtained. An 11 to 60% reduction in enhancing tumor volume was noted in 8 patients, 2 of whom had a greater than 50% decrease in tumor volume. One patient had no change in tumor volume 110 weeks after the initiation of BCNU chemotherapy. Four patients had tumor in more than one vascular territory; tumor growth was arrested in the perfused territory, but continued in the nonperfused area. In 1 of the 4 patients, tumor also grew along a shunt catheter tract and spread over the surface of the ipsilateral hemisphere. One patient developed clinically asymptomatic leukoencephalopathy after five courses of BCNU. Two patients had postradiation leukoencephalopathy before BCNU treatment. Seventeen patients had peritumoral low density with mass effect after BCNU; thus, the true incidence of BCNU-related leukoencephalopathy could not be determined. All patients experienced transient unilateral orbital pain during the infusion and scleral erythema that lasted for several hours afterward. Loss of vision was noted in 2 patients, although it seemed to be related to the therapy in only 1 patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1987

Intradural spinal lipomas.

Intradural spinal lipomas are rare, and their origin is unknown. Although the clinical presentation may not be distinctive, the neuroradiographic presentation is. Total excision is usually not possible, although subtotal resection is easily accomplished using an ultrasonic aspirator.

Adult↗

PubMed1987

Chiari II malformation: MR imaging evaluation.

The purpose of this study was to explore the value of high-detail MR imaging in the diagnosis of the Chiari II malformation. Twenty-four patients with known Chiari II malformation as diagnosed by CT scanning were evaluated with cranial MR scans. Two patients also had spine scans. The sagittal-plane images were the most informative, and abnormalities of the telencephalon, diencephalon, mesencephalon, rhomboencephalon, upper spinal cord, and mesencephalon were shown extremely well. We found MR to be an easy and accurate method for demonstrating the abnormalities of the Chiari II malformation, and it is our procedure of choice.

Adolescent↗

PubMed1986

Globoid cell leukodystrophy: cranial computed tomography and evoked potentials.

The evoked potentials and cranial computed tomographic (CT) scan findings in a case of early infantile globoid cell leukodystrophy are presented. The brain stem auditory evoked responses (BAERs) and the flash visual evoked potentials (VEPs) were abnormal. Repeated cranial CT scans showed multiple areas of increased attenuation and progressive cerebral atrophy. These evoked potential and CT scan patterns occurring concomitantly in an infant are suggestive of globoid cell leukodystrophy.

Electroencephalography↗

PubMed1986

Quantitative analysis of intracranial circulation using rapid-sequence DSA.

By using a high-frame-rate technique, intravenous digital subtraction angiography (IVDSA) of the intracranial circulation was performed in patients with transient ischemic attacks and asymptomatic bruits. Twenty patients with normal carotid arteries or mild stenosis of no hemodynamic significance were selected as a control group to evaluate the effect of carotid stenosis on the difference between hemispheres in the peak arrival time (delta TMAX) of the contrast bolus. Data were obtained for the anterior (ACA), middle (MCA), and posterior (PCA) cerebral artery distributions. Raw data of the time-density curve in a region of interest were analyzed by polynomial curve-fitting techniques to obtain the peak arrival time (TMAX). The delta TMAXs for normal middle, anterior, and posterior distributions were 0.140 +/- 0.119 sec, 0.152 +/- 0.146 sec, and 0.189 +/- 0.187 sec, respectively. Eleven patients with tight carotid stenosis or occlusion whose delta TMAX fell outside the normal range as established from the 20 control patients were analyzed with regard to ischemic symptoms. The delta TMAXs of the MCA, ACA distributions in the asymptomatic patients with tight carotid stenosis or occlusion were 0.653 +/- 0.379 sec and 0.118 +/- 0.159 sec, respectively; p less than 0.001 in the MCA when compared with controls. The delta TMAXs of the MCA, ACA distribution in the symptomatic patients with tight carotid stenosis or occlusion were 1.31 +/- 0.13 sec and 0.525 +/- 0.079 sec, respectively; p less than 0.001 in the MCA and ACA distributions when compared with controls. Quantitative analysis of this type of physiologic data may enable the detection of patients with carotid stenosis who are well compensated by collateral flow from those who are poorly compensated and at risk for possible infarction on a hemodynamic basis. Serial followup DSA studies in patients with asymptomatic bruits may help to correlate the progression of extracranial carotid stenosis and the status of intracranial collateral reserves.

Adult↗

PubMedDate not supplied

A cliniconeuroradiologic approach to third cranial nerve palsies.

Sixty-three patients with third cranial nerve palsies (CNPs), either isolated (31) or in association with other neurologic deficits (32), underwent neuroophthalmologic and neuroradiologic evaluation. Discrepancies between the clinical and radiologic evaluations were analyzed and useful clinical presenting symptoms were identified. Microvascular infarction secondary to diabetes mellitus and/or hypertension was the most common cause in patients with isolated third CNP, and extensive neuroradiologic evaluation is not indicated in this subgroup. The overall diagnostic yield of high-resolution CT for isolated third CNPs was low (30%), but improved to 60% if diabetes and hypertension were excluded. However, CT was highly sensitive (90%) in those patients with third CNPs associated with additional neurologic deficits. The status of the pupil in and of itself cannot be the sole determinant as to whether angiography is indicated to exclude an aneurysm. Careful ophthalmologic observation and relating the severity of pupillomotor dysfunction to extraocular ophthalmoplegia is mandatory to determine the logical sequence of radiologic evaluation. Retroorbital pain taken in isolation is a nonspecific presenting symptom and has differential diagnostic value only if it is correlated temporally with the onset of third CNP and the presence or absence of additional cranial nerve deficits.

Adolescent↗

PubMedDate not supplied

Difficulties in diagnosing congenital posterior fossa fluid collections after shunting procedures.

The differential diagnosis of retrocerebellar fluid collections in infants is important because of the prognostic implications. Usually the diagnoses are easy; however, shunting of the lateral ventricles or of the fluid collections may alter the appearance of the lesions, precluding accurate diagnosis. Under such circumstances a careful study of all the sequential radiologic studies is necessary.

Cerebellum↗

PubMedDate not supplied

MR evaluation of neurovascular lesions after endovascular occlusion with detachable balloons.

Three patients with surgically inaccessible giant carotid aneurysms/pseudoaneurysms and one patient with carotid cavernous fistula had endovascular occlusion with detachable silicone balloons filled with Cholografin. MR was performed before the procedures in three cases and again 18 hr to 44 days after embolization in all four cases. The age-related changes of arterial thrombi, as well as the optimal timing and value of different pulse sequences in the noninvasive follow-up, were evaluated. Arterial thrombi have some characteristics in common with intracerebral hematomas, being isointense on T1-weighted spin-echo images during acute phase and subsequently acquiring hyperintense signals on both T1- and T2-weighted spin-echo images during the subacute and chronic phases. Additional observations are that (1) hyperacute (less than 24 hr old) thrombus is hyperintense on T2-weighted spin-echo sequences; (2) hemosiderin is less conspicuous in chronic intraluminal thrombi than in intracerebral hematomas of comparable size; and (3) thrombosis is initiated at a site remote from the apex of the aneurysm and then progresses centripetally. The Cholografin-filled balloon is hypointense to gray matter on T1-weighted spin-echo images and isointense to both hyperacute and chronic thrombus on T2-weighted spin-echo images. The optimal timing and sequence for MR follow-up of a thrombosed aneurysm with conventional spin-echo technique is beyond 7 days on T1-weighted spin-echo images. The in vivo appearance of Cholografin-filled silicone balloons does not change appreciably on T1- and T2-weighted spin-echo sequences up to 6 weeks if filled according to the manufacturer's specification.

Adult↗

PubMedDate not supplied

Endovascular packing of carotid bifurcation aneurysm with polyester fiber-coated platinum coils in a rabbit model.

PURPOSE: To assess the value of endovascular packing of intracranial bifurcation aneurysms with commercially available coils. METHODS: Carotid bifurcation aneurysms were surgically created in 12 New Zealand rabbits with subsequent assessment of the extent of aneurysm ablation following endovascular packing with polyester fiber-coated platinum coils. RESULTS: Follow-up angiograms obtained from 29 to 108 days postprocedures showed various degrees of aneurysm ablation. Complete obliteration of aneurysm dome occurred in seven out of eight rabbits, while ablation of aneurysm neck was successful in only one out of eight. No spontaneous thrombosis was observed in seven control animals over a 3-month period. Coils of various configurations used in this experiment all maintained stable intraaneurysmal position. Histologic examination of treated aneurysms consistently demonstrated extensive proliferation of spindle cells on the coil surface and in interstices between coils with channels lined by cells resembling endothelial cells. Organized thrombus was not a prominent feature. CONCLUSION: Endovascular packing of human bifurcation aneurysms with current commercially available polyester fiber-coated platinum coils may not result in complete obliteration of the aneurysm with reendothelialization occurring across the aneurysm neck.

Animals↗