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Biomedical subjects

Y H Sohn

Publications and source records attributed to Y H Sohn.

At least 19 recordsLinked to original sources
PubMed1995

Relationship between the auditory P300 and the procedural memory function in drug-naive patients with Parkinson's disease.

We evaluated and compared procedural memory and auditory P300 event-related potential in age-matched normal controls (n = 15) and drug-naive patients with Parkinson's disease (n = 16). We used Gollin's incomplete picture test for visual procedural memory function and Tower of Hanoi puzzle for visuomotor procedural memory function. The mean latency of P300 was significantly prolonged in the Parkinsonian group than in the controls. In the neuropsychology test, the patients group revealed selective impairment of visuomotor procedural memory against preserved visual procedural memory. In the patients group, the latency of P300 was inversely correlated with performance of visuomotor procedural memory. These results suggest that prolonged auditory P300 event-related potential show the dysfunction of visuomotor procedural memory in the basal ganglia, which appears to be more selectively impaired than visual procedural memory in drug-naive patients with Parkinson's disease.

Event-Related Potentials, P300↗
PubMed1994

Wearing-off fluctuations in Parkinson's disease: contribution of postsynaptic mechanisms.

Wearing-off phenomenon that complicates levodopa therapy of Parkinson's disease has been attributed to a reduction in striatal dopamine storage due to the progressive degeneration of presynaptic dopaminergic terminals. To determine whether postsynaptic mechanisms also contribute to these response fluctuations, the duration of the antiparkinsonian response in parkinsonian patients grouped by disease severity was compared following discontinuation of a steady-state optimal-dose infusion of apomorphine. Although the plasma half-life of this dopamine receptor agonist remained constant, its mean efficacy half-time declined from 66 minutes in early, levodopa-naive patients to 33 minutes in advanced, complicated parkinsonians (p < 0.005). Since the motor effects of apomorphine do not depend on the presence of dopaminergic terminals, changes at the postsynaptic level undoubtedly contribute to the diminished response duration. The only slightly greater attenuation of levodopa's motor effects observed previously under similar conditions suggests these postjunctional alterations, possibly involving relatively plastic striatal dopaminoceptive systems, account for most of the shortening in the duration of levodopa action that underlie wearing-off fluctuations.

Apomorphine↗
PubMed1994

Levodopa peak response time reflects severity of dopamine neuron loss in Parkinson's disease.

We measured the time to peak antiparkinson response following injection of levodopa or apomorphine in 57 patients with Parkinson's disease. The peak response time for levodopa fell from 53 +/- 6.5 minutes in patients at Hoehn and Yahr stage I-II, and 28 +/- 4.8 minutes in those at stage IV (p < 0.0005). There was a significant correlation between levodopa peak response time and symptom duration (r = 0.65; p < 0.0001), but there was no relation between apomorphine peak response time and measures of disease severity. Peak response time to levodopa appears to reflect predominantly the status of compensatory presynaptic dopaminergic mechanisms and thus may provide an index to the degree of dopamine neuron degeneration in parkinsonian patients.

Apomorphine↗
PubMed1991

Effect of apraclonidine hydrochloride on acute introacular pressure rise after argon laser iridotomy.

To determine the effect of apraclonidine hydrochloride on the acute intraocular pressure (IOP) rise after argon laser iridotomy (ALI), a double-masked comparative study was carried out. Twenty-nine eyes (20 patients) with angle-closure glaucoma underwent ALI. Eighteen eyes were treated with apraclonidine, and the remainder received a placebo 1 hour before and immediately after ALI. The mean IOP increase in the apraclonidine group was lower than that in the placebo group at each postlaser interval (p less than 0.01). Although the average value of the maximal increases of IOP after ALI in the apraclonidine group was 4 mmHg, that in the placebo group was 16 mmHg. In the placebo group, 27.3% (3 out of 11 eyes) experienced an IOP rise greater than or equal to 10 mmHg. However, that kind of IOP rise was not found in the apraclonidine group (0 out of 18 eyes) (p less than 0.01). Ocular or systemic side effects were not found in a series of examinations in both groups. Therefore, apraclonidine proved to be effective in lowering the IOP rise after ALI.

Acute Disease↗
PubMed1991

Benign brainstem hemorrhage simulating transient ischemic attack.

A 48-year-old hypertensive man had sudden onset of symptoms suggesting vertebrobasilar insufficiency, which were transient in nature lasted for only 4 hours. Brain computed tomography revealed a small hematoma in the pontomedullary junction. This is an uncommon presentation of benign brainstem hemorrhage simulating transient ischemic attack. We propose that computed tomographic scan using thin slices of 3mm to 5mm thickness at the level of brainstem is required before starting anticoagulation therapy for vertebrobasilar transient ischemic attack.

Brain Stem↗
PubMed1990

Effect of capsular infarct size on clinical presentation of stroke.

We reviewed the medical records and cranial computed tomograms of 74 patients with acute capsular infarcts to investigate the correlation between infarct size and clinical symptoms. Average infarct size varied significantly by clinical syndrome; patients with sensorimotor stroke had the largest infarcts, patients with pure motor hemiparesis had middle-sized infarcts, and patients with ataxic hemiparesis or the dysarthria-clumsy hand syndrome had the smallest infarcts. Although it has been proposed that the type of lacunar syndrome is determined entirely by the infarct location, our results suggest that infarct size is another important factor influencing the clinical presentation of lacunar syndromes.

Adult↗
PubMed1990

A case of Leigh's disease with initial manifestation of dystonia.

A case of Leigh's disease (subacute necrotizing encephalomyelopathy) is reported with such noteworthy features as early onset, dystonia, paraparesis the presence of low attenuation areas in both basal ganglias on computerized tomography of the brain and the presence of a high signal intensity in both basal ganglias in T2 weighted image by MR. The electron microscopic findings of muscle biopsy are suggestive of pleoconial mitochondrial myopathy.

Basal Ganglia↗
PubMed1987

Pressure-flow relations across the normal mitral valve.

The stenotic mitral valve area is a major determinant of the atrioventricular pressure-flow relation, and mean atrioventricular pressure gradient is proportionate to the square of mean flow rate. In the absence of obstruction, this relation is linear. The effect of the normal mitral valve area on this pressure-flow relation has not been previously examined. Pulsed Doppler studies of transmitral flow were performed simultaneously with thermodilution cardiac outputs in 25 patients in sinus rhythm and with no valvular disease. Mean flow rate was determined as thermodilution stroke volume/diastolic filling period measured by Doppler. Several instantaneous pressure gradients were estimated from multiple velocity measurements using the modified Bernoulli equation and were plotted against time. Mean pressure gradient was estimated by dividing the area under the pressure-time curve by the diastolic filling period. Average and standard deviation of mean flow rate and pressure gradient was 223 +/- 70 ml/s and 1.4 +/- 0.8 mm Hg, respectively. There was an excellent linear correlation between these 2 parameters (r = 0.91, SEE = 30 ml/s). This confirms the linear relation of mean pressure gradient to mean flow rate in the absence of obstruction. The excellent correlation, obtained without considerations of individual variations of valve area, suggests that this relation is independent of valve area, under normal physiologic conditions.

Blood Flow Velocity↗
PubMed1987

Reversible arrhythmias observed in patients treated with recombinant alpha 2 interferon.

We have treated 25 patients, 7 with breast cancer and 18 with non-Hodgkin's lymphoma, with recombinant alpha 2 interferon. In 5 patients we observed cardiac arrhythmias that were unexpected and required treatment. No deaths have occurred that we can attribute to interferon, though 1 patient had to be resuscitated. Age, prior cardiac disease, prior treatment with doxorubicin, and interferon dose appear to be predisposing factors for this toxicity.

Aged↗
PubMed1986

Left ventricular mass and systolic performance in chronic systemic hypertension.

This study was undertaken to define the relation between the extent of left ventricular (LV) hypertrophy and ventricular systolic performance in patients with chronic systemic hypertension. Ninety patients with chronic systemic hypertension were compared with 41 normal subjects as determined by angiography. LV mass was estimated from the M-mode echocardiogram. Patients were separated into 3 groups: those with LV mass of less than 2 (group I, n = 58), 2 to 4 (group II, n = 21) and more than 4 (group III, n = 11) standard deviations above mean normal. The ratio of preejection period to LV ejection time (PEP/LVET), percent shortening of the echocardiographic internal diameter (% delta D) and velocity of circumferential shortening (Vcf) were used as indexes of LV systolic performance. The frequency of abnormality, expressed as percent of patients in groups I, II and III, was 33%, 55% and 85% for PEP/LVET, 15%, 35% and 72% for % delta D, and 0%, 15% and 55% for Vcf. For each group PEP/LVET was the most frequently abnormal measure and Vcf was the least frequent abnormality. Calculation of peak and end-systolic wall stress was used as an index of the adequacy of LV hypertrophy. This index was significantly reduced in group I, did not differ from control in group II and was significantly increased in group III, indicating that hypertrophy was appropriate to wall tension in groups I and II. It is concluded that the occurrence of LV dysfunction with increasing LV mass in patients with moderate LV hypertrophy (group I and II) reflects a deficiency in intrinsic contractile performance of the hypertrophied myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Range ambiguity in pulsed Doppler ultrasound: the ambiguity clarified?

Pulsed Doppler ultrasound (PW) can be used to determine the location of frequency shifts within the cardiac chambers or great vessels. However, it is possible to record similar frequency shifts at sample volume locations distal to their original site; this is referred to as range ambiguity (RA). Eleven patients were studied with combined Doppler and two-dimensional echocardiography (2-D) to determine the circumstances in which RA occurs. Mapping of various flow patterns with PW was performed in each of four 2-D views beginning at 2 cm distances from the transducer and at subsequent 1-cm intervals until the maximal range of the PW was achieved. Range ambiguity was demonstrated only in the four-chamber view in patients with enlarged cardiac chambers or if an abnormal flow pattern was present. The site of origin of the ambiguous signals was dependent on the pulse repetition frequency (PRF) employed. Range ambiguity occurs more often when a relatively high PRF is used. Range ambiguity may be used for mapping of abnormal flow beyond the range of PW or for recording of high velocities at sample volumes far from the transducer without frequency aliasing.

Aged↗
PubMed1984

Identification of patients with improved survival following coronary bypass surgery.

This study was designed to determine whether left ventricular performance measured noninvasively from the systolic time intervals could identify patients in whom coronary bypass surgery may improve survival. 71 patients with two- or three-vessel disease undergoing coronary bypass surgery were compared with 78 matched medically treated patients. All patients had recuperated from myocardial infarction by a mean of 17.6 months when systolic time intervals were performed. Surgical and medical patients were classified preoperatively into those with normal and those with abnormal left ventricular performance by preejection period/left ventricular ejection time (PEP/LVET less than or equal to 0.42 and greater than 0.42, respectively). Survival was analyzed by life table and log-rank test. Cumulative 5-year survival in patients with normal left ventricular performance was not statistically different in surgical and medical groups (96 vs. 93%, respectively). In contrast, cumulative survival in patients with abnormal left ventricular performance was significantly greater in the surgical group when compared to the medical group (84 vs. 62, p less than 0.01). Among the patients with abnormal left ventricular function, the mean PEP/LVET and the average vessel disease were not different in the medical and surgical groups. Multivariate analysis of 17 other clinical and laboratory risk variables were not different between these two groups. It is concluded that coronary bypass surgery my improve survival in patients with two- or three-vessel disease and left ventricular dysfunction.

Actuarial Analysis↗
PubMed1982

Value of positive myocardial technetium-99m-pyrophosphate scintigraphy in the noninvasive diagnosis of cardiac amyloidosis.

Ten consecutive patients with tissue-proven amyloidosis, seven of whom presented with congestive heart failure, were found to exhibit intense diffuse uptake of technetium-99m-pyrophosphate (Tc-99m-PYP) on cardiac radionuclide imaging. The patients exhibited echocardiographic and systolic time interval abnormalities suggesting combined restrictive and congestive cardiomyopathic changes. On M-mode echocardiograms, there was symmetrically increased thickness of the interventricular septum and left ventricular (LV) posterior wall in diastole (10 of 10), decreased fractional shortening of the LV minor axis diameter in systole (eight of nine), and decreased percent thickening of the LV minor axis diameter in systole (eight of nine) and LV posterior wall (10 of 10) in systole. Three patients demonstrated enlarged LV end-diastolic diameter. All 10 patients had abnormal PEP/LVET and eight had shortened LVETI. When combined with noninvasive tests of LV performance, positive myocardial pyrophosphate (PYP) scanning provides a new and useful adjunct in the diagnosis of amyloid heart disease.

Aged↗
PubMed1982

The QT greater than QS2 syndrome: a new mortality risk indicator in coronary artery disease.

In the normal population the duration of electrical systole (QT) is shorter (mean -26 +/- 13 ms, 1 standard deviation) than that of electromechanical systole (QS2), which it closely parallels throughout the range of resting heart rate. This close association prompted the hypothesis that the duration of QT may be more closely linked physiologically to QS2 than to the heart rate and hence may provide a more potent prognostic indicator than the relation of QT to heart rate. The present study was designed to test this hypothesis. On hundred stable patients 14 months after myocardial infarction were followed up an average of 43 months. Twenty patients had prolongation of QT relative to QS2 (QT greater than QS2) and 13 patients had long QT corrected for heart rate (QTc). There were 20 deaths (16 sudden). The cumulative 5 year survival rate was 35% in patients with QT greater than QS2 and 91% in patients with QT greater than or equal to QS2 (p less than 0.001). There was no significant difference in survival in patients with long QTc compared with patients with normal QTc (69 versus 82%). Univariate and multivariate analysis for the association of QT greater than QS2 with known risk factors, clinical descriptors, drug therapy, systolic time intervals (preejection period/left ventricular ejection time), and frequency of 1, 2 and 3 vessel coronary occlusive artery disease revealed that only the presence of abnormal preejection period/left ventricular ejection time added significantly to the presence of QT greater than QS2 in stratifying 5-year survival into high and low risk groups. Thus, in patients with coronary artery disease, the presence of QT greater than QS2 provides a new risk indicator that is more potent than QT corrected for heart rate.

Aged↗
PubMedDate not supplied

Prolonged ictal amnesia with transient focal abnormalities on magnetic resonance imaging.

A previously healthy woman had a prolonged amnestic state caused by complex partial status epilepticus with bilateral mesiotemporal lobe involvement confirmed by EEG with nasopharyngeal electrodes. A magnetic resonance imaging (MRI) scan obtained shortly after recovery from the amnesia showed reversible focal abnormalities consisting of increased signal intensity on T2-weighted scan in the mesiotemporal lobe.

Adult↗