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Hypertension affects approximately one-third of Americans. An additional 30% are unaware that they harbor the disease. Significantly increased blood pressure constitutes a hypertensive emergency that could lead to end-organ damage. When organs such as the brain, heart, or kidney are affected, an intervention that will lower the blood pressure in several hours is indicated. Several pharmacologic options are available for treatment, with intravenous antihypertensive therapy being the cornerstone, but there is no standard of care. Careful consideration of each patient’s specific complaint, history, and physical examination guides the emergency physician through the treatment algorithm.

Brugada syndrome describes the syndrome of sudden cardiac death in the setting of the following electrocardiographic findings: right bundle branch block pattern with ST-segment elevation in the right precordial leads. The right bundle branch block may be incomplete while the ST segment elevation is minimal. The electrocardiographic findings are not constant. Patients suspected of having Brugada syndrome should be promptly referred for electrophysiological testing and treatment. Rapid referral and placement of an implantable cardioverter defibrillator (ICD) is associated with an excellent prognosis, whereas failure to diagnose this condition is associated with a high risk for sudden death. Therefore, it is imperative that all emergency physicians be familiar with the typical ECG manifestations of Brugada syndrome. Three illustrative cases are presented with a review of the syndrome. (Am J Emerg Med 2003;21:146-151. Copyright 2003, Elsevier Science (USA). All rights reserved.)

This study reports our findings from 22 patients (ages ranging from 42 to 73 yr; mean = 55.2) with recalcitrant idiopathic Parkinson's disease (PD) who received implants of fetal ventral mesencephalic tissue using an MRI-guided stereotactic procedure and who have been followed for at least 6 mo postoperatively, employing the guidelines established by the Core Assessment Program for Intracerebral Transplantations. Evaluations were videotaped and were performed both on and off levodopa medications. To date, we have seven patients with 24 mo, three with 18 mo, three with 12 mo, and nine with 6 mo of postsurgical assessments. Comparing surgical outcomes to levels prior to fetal transplants we found: 1) mean levodopa levels were reduced 46% at 6 mo, 12% at 12 mo, 20% at 18 mo, and 54% at 24 mo; 2) Unified Parkinson's Disease Rating Scale (UPDRS) scores with patients on levodopa were improved by an average of 38% (6 mo), 50.2% (12 mo), 69.3% (18 mo), and 73.9% (24 mo), while off medication scores showed reductions ranging from 24.7% at 6 mo to 55.1% at 24 mo. Other measures, including Hoehn-Yahr staging, Activities of Daily Living, and dyskinesia rating scales, were also significantly improved following fetal transplants. Timed motor tasks (finger dexterity, supination-pronation, foot tapping, and Stand-Walk-Sit) performance also demonstrated highly significant improvements. Patient's self-rating scores indicated that the patients typically perceived substantial improvements in their condition. However, substantial variability in the improvements following surgery still persists and range from nominal improvements in performance to significant changes that can be classified as altering the overall lifestyle of the patients. To date, 4 of the 22 subjects were considered by the physicians to be nonresponders; that is, there were no clinically relevant improvements in these patients' conditions.

The effect of varying the volume of grafted fetal mesencephalic tissue was studied in patients with idiopathic Parkinson's disease in a single-blinded study. Evaluations were performed according to the Core Assessment Program for Intracerebral Transplantation and videotaped both prior to transplantation and in 3-month intervals after transplantation. One group, low-volume grafts (six subjects; mean age, 57.2 years), received ventral mesencephalon grafts from one to two donors with an approximate volume up to 20 mm3, while the second group, high-volume grafts (seven subjects; mean age, 59.5 years), received ventral mesencephalon grafts from three or more donors with an approximate volume of 24 mm3. Both groups of patients demonstrated significant improvement over presurgical baseline scores on all major parameters. The high-volume group had significantly greater improvements on all the UPDRS scores and also better performance on a variety of motor performance tasks over that seen among low-volume patients. These results indicate that variations of fetal graft volume do have an impact on clinical outcome.

Cross-sectional analysis of CBF values was carried out among 668 volunteers and patients. Subjects were subdivided according to age, gender, and degree of cerebrovascular disease, ranging from healthy volunteers with or without risk factors for stroke to patients with multi-infarct dementia. Four-year longitudinal analysis was also carried out on 230 individuals from the original sample, Decrements in CBF values were evidenced by both cross-sectional and longitudinal analysis in relation to advancing age, progressive cerebrovascular disease, and dementia. Regional, age-related CBF declines in healthy volunteers were heterogeneous, possibly related to changes in levels of functional activity within different brain regions.

A 7-year prospective study among 181 neurologically normal elderly volunteers (mean age, 70.6 years) revealed an incidence of 3.3, or 0.47 new cases per year, for Alzheimer's disease (SDAT) and 5.5, or 0.78 new cases per year, for multi-infarct dementia (MID). The unusually high incidence of MID is considered to reflect preselection of a large percentage of volunteers (48.6) with risk factors for (but without symptoms of) atherothrombotic stroke. Of 88 volunteers at risk of stroke, 11.4 developed MID within 7 years. In MID patients, cerebral blood flow (CBF) values began to decline around 2 years before onset of symptoms, while in SDAT patients, CBF levels remained normal until symptoms of dementia appeared; thereafter, CBF declined rapidly.

In order to standardize and quantify diagnostic information derived from medical histories and case reports given by demented patients, their families or care‐providers, a questionnaire has been developed containing 94 questions. The output is categorized by computer into graphic clinical scales which correlate and weigh information relating to seven of the most common causes of dementia. The present investigation assesses the validity of predictive diagnostic classifications derived from the clinical scales tested on admission by correlating them later with final diagnoses determined independently by thorough clinical evaluation including standard diagnostic tests, computed tomography and nuclear magnetic resonance scans. Results of 101 healthy, neurologically normal, age‐matched volunteers and 140 patients representative of the more common forms of dementia indicate that correct diagnostic identification was: 75% for dementia secondary to Parkinson's disease, 100% for Huntington's disease, 90.2% for Alzheimer's disease, 82.4% for multi‐infarct dementia, 90.0% for posttraumatic dementia, 77.8% for normal‐pressure hydrocephalus and 85.7% for Wernicke‐Korsakoff dementia. Correct diagnostic assignment was highly significant (P < .0005). The screening questionnaire may prove to be a useful and standard diagnostic tool for clinicians and investigators concerned with epidemiology, prevention and treatment of dementia.

• Possible effects of chronically elevated serum cholesterol and triglyceride levels on measurements of cerebral blood flow were investigated by between-group comparisons of individuals, with and without hyperlipidemia, among 56 neurologically normal elderly volunteers and among 102 age-matched patients with symptoms of transient ischemic attacks (TIAs). Results demonstrated significantly higher levels of serum cholesterol and triglyceride among the TIA patients compared with randomly selected agematched normal controls of similar educational and environmental backgrounds. Cerebral blood flow levels were reduced among groups of TIA patients with elevated levels of either cholesterol or triglycerides compared with the TIA patients with normal lipid levels. Similar trends were seen among normal volunteers, but these did not reach levels of statistical significance because of the limited numbers available. Analysis of frequency distributions for risk factors other than hyperlipidemia indicated that hypertension, atherosclerotic heart disease, diabetes mellitus, and cigarette smoking were also more prevalent among TIA patients than among age-matched normal controls.

This paper describes a technique for using twin element antennas (dipoles and slots) to increase the efficiency of antennas fabricated on electrically thick dielectric substrates. We present calculations which show that the efficiency of both the slot and dipole antennas can be increased by the proper spacing of elements placed broadside to each other. We consider the use of substrates that are odd integral multiples of a quarter of a dielectric wavelength thick and give results for an e=4 substrate with thicknesses of one, three, and five quarter wavelengths. These thicknesses can be used when working at millimeter wave frequencies and yield substrate dimensions which can be handled and processed easily, while still yielding radiation-to-air efficiencies of about 70%. We also show calculated beam patterns for the elements which appear to be suitable for imaging array applications.

Nineteen patients with sudden onset of impaired recent memory, cerebellar ataxia, peripheral neuropathy, and other signs of Wernicke-Korsakoff syndrome (WKS) were treated and examined prospectively for 3 months. Serial studies included histories, neurological examinations, cognitive capacity screening examinations (CCSE), computed tomography (CT) scans, and measurements of regional CBF. Patients were detoxified and withdrawn from sedatives before CBF measurements were examined. Treatment included alcohol withdrawal, nutritious diet, and 300 mg thiamine daily. Before treatment CCSE scores and blood flow values of both white and gray matter were reduced, particularly within both temporoparietal regions. After treatment of compliant patients (n = 10), white and gray matter blood flow increased concurrently with improved CCSE scores. Abnormal eye signs, ataxia, peripheral neuropathy, and performance of activities of daily living also improved. Cerebral atrophy and ventricular enlargement measured by CT decreased. Early recognition and treatment of WKS in compliant patients permit rapid reversals of cognitive and neurological impairments associated with increased blood flow of gray and white matter and improvements of brain atrophy measured by CT scanning.

Among neurologically normal volunteers approaching age 65 with an option for retirement, a four‐year prospective longitudinal study was designed to examine effects of different levels of physical activity on cerebral perfusion by between‐group comparisons. After the fourth year, cognitive performance was also tested. Three groups were compared, each composed of 30 elderly volunteers, assigned as follows: Group 1, who continued to work; Group 2, who retired but participated in regular physical activities; and Group 3, who retired but did not participate in regular, planned physical activities. Retirees who elected to become physically inactive exhibited significant declines in cerebral blood flow (CBF) throughout four years of follow‐up. Those who continued to work or retirees who elected to participate in regular activities sustained more constant CBF levels. Active retirees and those who continued to work also scored better on cognitive testing after the fourth year of follow‐up compared to inactive retirees.

Seventy multi‐infarct dementia patients were randomized into an aspirin‐treated group and an untreated control group for an exploratory investigation to determine any effects of 325 mg aspirin daily on cognitive performance. The control group did not receive placebo but evaluations were carried out in a blinded manner. The index group (N = 37, mean age 67.1 years) received 325 mg of aspirin by mouth once daily while the control group (N = 33, mean age 67.6 years) was followed and treated in a similar manner except that they received no aspirin. Both groups had comparable risk factors for stroke, which were treated similarly, as well as comparable initial cerebral blood flow values, as measured by the 133xenon inhalation method, and initial scores on Cognitive Capacity Screening Examination testing. Patients were evaluated at intervals of one year. Significant improvements were demonstrated for cerebral perfusion values (P < .0001) and cognitive performance scores (P < .0001) among aspirin‐treated patients compared to untreated controls at each of three annual follow‐up evaluations. Both men and women benefited from aspirin therapy and their quality of life and independence appeared to be improved, which was not apparent in the control group. Daily aspirin appears to improve or stabilize declines in cerebral perfusion and cognition among patients with multi‐infarct dementia.

Effects of chronic cigarette smoking on cerebrovascular responsiveness of volunteers at risk for stroke and not at risk for stroke were evaluated by serial measurements of cerebral blood flow using the 133Xe inhalation method. Resting gray matter blood flow values (Fg) measured while breathing room air were compared with Fg values measured during inhalation of either 5 per cent CO2in air or 100 per cent O2. Changes in Fg values during inhalation of 5 per cent CO2were used to estimate cerebral vasodilator capacitance, and those during inhalation of 100 per cent O2were used to estimate cerebral vasoconstrictor capacitance. Results indicated that chronic cigarette smokers have both reduced vasodilator (P< 0.01) and reduced vasoconstrictor (P< 0.02) capacitance when compared with nonsmokers of the same ages regardless of whether or not other risk factors for stroke were present. Vasodilator capacitance to 5 per cent CO2inhalation was reduced among smokers compared with nonsmokers of the same age by 48 per cent in non‐risk subjects and 56 per cent in risk‐factored subjects, while vasoconstrictor capacitance to 100 per cent O2inhalation among smokers was decreased by 24 per cent in non‐risk subjects and 34 per cent in risk‐factored subjects. In risk‐factored subjects, combined effects of smoking and other risks appeared to be additive.

Regional cerebral blood flow values were measured utilizing the 133Xe inhalation method in patients with multi‐infarct dementia (MID) (n= 22, age 67.4 ± 9.8 years), in patients with senile dementia of Alzheimer type (SDAT) (n= 36, age 63.8 ± 8.0) and in age‐matched normal healthy volunteers (n= 50, age 67.5 ± 9.3). Mean hemispheric gray matter flow values were significantly reduced in MID (P< 0.01) and SDAT (P< 0.01) patients compared with age‐matched normal volunteers. In normal volunteers, mean flow values showed gradual declines with advancing age (r= −0.44, P< 0.005). In MID patients there were significant decreases in flow values with advancing age (r= −0.43, P< 0.05), but flow values were consistently lower than in age‐matched normals. Reductions of flow were most evident in the distribution of both middle cerebral arteries. Unlike MID patients, patients with SDAT had diffusely reduced flow values over all age ranges without correlation with advancing age. Reductions of mean flow values in both dementia groups were significantly correlated with severity of dementia (P< 0.05 for both groups). Cerebral blood flow reductions related to the aging process also contribute to decreased cerebral perfusion in patients with MID. This is not true in SDAT, where the disease process itself pre‐empts cerebral blood flow reductions attributable to aging.

Neurotoxic effects of habitual alcohol consumption were investigated by correlating the subjects' estimates of abstinence or frequency and amount of alcohol consumed with measurements of gray matter blood flow utilizing the 133Xe inhalation method. Two hundred and twenty‐two subjects were studied, including 136 healthy subjects, 82 subjects with well‐established risk factors for stroke (hypertension, hyperlipidemia, heart disease, and diabetes mellitus), and four subjects with chronic alcoholic dementia of the Wernicke‐Korsakoff type. Subjects were classified according to average quantitative amounts of alcohol consumed per day, week, or month for the past five years. Comparisons of mean values for hemispheric gray matter blood flow indicated significant inverse relationships with the average amounts of alcohol consumed. This linear relationship occurred regardless of whether or not other risk factors were present and indicated that alcohol itself was a risk factor reducing gray matter blood flow and had additive effects of reducing cerebral blood flow further when combined with other risk factors. Patients who had chronic Wernicke‐Korsakoff syndrome had the most severely reduced blood flow levels, as might be predicted from extrapolation of the regression line comparing cerebral blood flow values with the degree of chronic alcohol consumption.

Summary Previous studies have demonstrated that externally measured magnetic field patterns are indicative of activity in the vicinity of the right hippocampal formation during infrequent and unpredictable intrusions or omissions of visual stimuli in an oddball evoked response paradigm. These fields occur coincident with late endogenous evoked potential components that are consistently recorded in similar situations. In the present study, magnetic fields temporally corresponding to the late P300 component of simultaneously recorded evoked potentials were accounted for by sources in the vicinity of the left and right hippocampus in addition to previously reported sources in the vicinity of the primary visual cortex. Projection of these sources onto MRIs suggested that both hippocampal structures are simultaneously active and that there is an amplitude and strength-related dominance of the right hippocampal sources to visual stimulation.

Summary The replicability of dipole localizations between sessions in an unselected group of subjects was studied. Auditory evoked magnetic fields (AEMFs) in response to contralaterally and ipsilaterally presented 1 kHz tone bursts were recorded from the right hemisphere of 12 subjects with normal hearing in two replicate sessions several days apart. Three long-latency components of the AEMF were studied, occurring at latencies near 50 msec (P1m), near 100 msec (N1m) and near 165 msec (P2m). A spherical model of the head was used to fit equivalent-current dipoles to the data. Statistical analysis of dipole parameters revealed virtually no differences between the two testing sessions. The variability between sessions had a mean absolute difference of 3 to 10 mm for the spatial parameters. Comparison of dipole parameters between components showed that there was a replicable, but nonsignificant, trend for a difference in the location of the N1m from contralateral vs. ipsilateral stimulation, and a statistically significant confirmation that the P2m is located anterior to the N1m for contralateral stimulation. Magnetic resonance images from each subject were used to locate the dipoles near the primary auditory cortex in the Sylvian fissure.

Cerebral blood flow (CBF) was measured by the 133Xe inhalation method in patients with multi‐infarct dementia (MID, N= 26), Alzheimer's dementia (AD, N= 19), and among age‐matched, neurologically normal, healthy volunteers (N= 26). Cognitive performance was assessed in all subjects using the Cognitive Capacity Screening Examination (CCSE). Cerebral vasomotor responses were calculated from differences in values of mean hemispheric gray matter blood flow (ΔCBF) measured during inhalation of 100% oxygen (hyperoxia) compared with CBF measured while breathing room air. Significant correlations were found between CCSE performance and vasomotor responsiveness in patients with MID (P< .01), but not in patients with AD or in neurologically normal volunteers. Loss of vasomotor responsiveness is an indicator of cerebrovascular disease with rigidity and/or loss of reactivity of cerebral vessels, which impairs cerebrovascular responses to situational demands and predisposes to cerebral ischemia. Loss of cerebral vasomotor responsiveness among MID patients, which is a biologic marker of cerebrovascular disease, provides confirmatory evidence of the vascular etiology of MID and assists in separating MID from AD patients.

Local cerebral blood flow (LCBF) and local tissue:blood partition, coefficient (LΛ) values were measured during CT scanning while patients with different types of Parkinson's syndrome (N= 14) inhaled a contrast mixture of 35–37 per cent stable xenon gas in oxygen. Single‐compartment analysis fitted to infinity was used to calculate LΛ and LCBF values. Results were compared with results from normal age‐matched volunteers (N= 24). Mean hemispheric (p< 0.05) and subcortical (p< 0.05) gray matter LCBF values were reduced in idiopathic Parkinson's disease (N= 11), compared to values from age‐matched normals. Regionally, LCBF reductions included frontal (p< 0.001), parietal cortex (p< 0.05), caudate (p< 0.05), lentiform nuclei (p< 0.001) and thalamus (p< 0.05) reductions. LΛ values were normal. Unilateral tremor and/or rigidity correlated directly with reduced LCBF in contralateral lentiform (p< 0.01) and caudate (p< 0.01) nuclei. In postencephalitic Parkinsonism (N= 1) LCBF reductions were diffuse, with normal LΛ values. In the akinetic form of Parkinsonism (N= 1) associated with lacunar infarcts, LCBF and LΛ reductions were patchy. In Parkinsonism following carbon monoxide poisoning (N= 1), LCBF values of gray and white matter were diffusely reduced and LΛ values were reduced in both pallidal regions. When dementia was present together with Parkinsonism (N= 3), LCBF reductions were more diffuse and severe. Dopaminergic deficiency correlated directly with reduced LCBF values, reflecting the severity of Parkinsonism. J Am Geriatr Soc 33:413, 1985

• Magnetoencephalography offers the possibility of localizing accurately and noninvasively the source of intracranial currents associated with normal and abnormal brain activity. The purpose of this study was to assess the validity and across-subject reliability of localization of cortical sources responding to ipsilateral and contralateral auditory stimulation. Magnetic evoked fields to both stimulation conditions were measured in eight consecutive normal subjects, and the cortical sources of these fields were estimated on the basis of these measurements. Subsequent projection of the source location coordinates onto magnetic resonance images showed that in all subjects the sources were accurately estimated to fall in the vicinity of the auditory cortex and that two separate sources may account for the response to ipsilateral and contralateral stimulation.

• Brain atrophy estimated by computed tomographic (CT) scanning and mean hemispheric and regional gray matter cerebral blood flow (CBF) values were measured in patients with mild to moderate Huntington's disease (HD) (N = 16) using the xenon Xe 133 inhalation method and in asymptomatic blood relatives at risk from HD (N = 6) using both the xenon Xe 133 inhalation and the stable xenon CT contrast CBF methods. Results were compared with measurements in two groups of age-matched normal volunteers (N = 48 and N = 42, respectively). Significant brain atrophy in the vicinity of both caudate nuclei was present in patients with HD but not in at-risk individuals. Mean hemispheric xenon Xe 133 CBF values were reduced in patients with HD but seemed to be normal in at-risk individuals. In HD, reductions in CBF were found in both frontotemporal regions. Correlations were found between severity of dementia estimated by reductions of Mini-Mental Status Questionnaire scores and reductions of either mean hemispheric or regional frontotemporal CBF values in HD. The CT estimates of brain atrophy and three-dimensional CBF by stable xenon-contrast measurements were normal in asymptomatic individuals at risk from HD.

Effects of chronic cigarette smoking on cerebral blood flow were investigated by measuring gray matter blood flow (Fg) using xenon 133 inhalation among 192 volunteers without cerebrovascular symptoms. There were 108 normal, healthy volunteers; 84 had risk factors for stroke (hypertension, hyperlipidemia, diabetes mellitus, and/or heart disease). Of both risk and nonrisk groups, 75 were habitual smokers (0.5 to 3.5 packs per day for 25 years). Comparisons of mean Fg values for both hemispheres showed significant reductions related to tobacco consumption and risk factors for stroke. Multiple-regression equations using smoking, age, risk, and alcohol consumption indicated a combined R2 value of 0.22. Smoking seems to be a potent risk factor decreasing cerebral blood flow probably by enhancing cerebral arteriosclerosis. Chronic cigarette smoking in persons with other risk factors further reduced Fg values in an additive manner when compared with subjects who had corresponding risk factors who did not smoke.(JAMA 1983;250:2796-2800)

A cross-sectional study of cerebral blood flow (CBF) levels in 268 neurologically normal volunteers contrasting nonsmokers, smokers who quit, and current cigarette smokers indicated that subjects who quit smoking had significantly higher cerebral perfusion levels than subjects who had continued to smoke but remained lower than subjects without a history of cigarette smoking. All subjects were matched for age and sex, and smoking groups were matched for duration and amount of smoking. A prospective study of 11 subjects who were able to stop smoking in which CBF levels were available both antecedent to and following cessation of the habit indicated that significant gains occurred in cerebral perfusion levels within one year following cessation of smoking. A control group of 22 subjects who continued to smoke (matched for age, sex, duration of smoking, and duration of time between baseline and follow-up) showed no change in CBF values. A correlation between magnitude of CBF change and duration of cessation of cigarette smoking demonstrated a significant linear increase in CBF during the one-year period. These results suggest that elderly individuals who have smoked for three to four decades can benefit substantially by abstaining from cigarette smoking and that significant improvement in cerebral circulation occurs within a relatively short period.(JAMA 1985;253:2970-2974)

Underwater sparks have long been used by the geophysical prospecting community as a source of intense low‐frequency sound. While bubble hydrodynamic models are well developed, the mechanism of transferring energy from the thermal power input, through the various energy conversion channels, to the work done by the bubble has not been adequately studied. In this work an abinitio model of the bubble dynamics, including blackbody ablation, ionization, dissociation, and radiative transport, is developed. This model is a first step in enumerating the important physical mechanisms within bubbles generated by underwater sparks. The predictions of this model are compared with experimental results. Experimental work is still needed to validate the model, and to determine if and how model parameters related to actual physical parameters and measurable effects. © 1996 Acoustical Society of America.

A cohort of 52 patients (30 men and 22 women) with multi-infarct dementia (MID) has been followed up prospectively for a mean interval of 22.2 months. Clinical course has been documented by serial history taking and interviews and neurological, medical, and psychological examinations, and correlated with measurements of cerebral blood flow. The clinical course and cognitive performance have been compared with those of age-matched normal volunteers and patients with Alzheimer's disease. Patients with MID were subdivided into hypertensive and normotensive groups, and also into those displaying stabilized or improved cognition and those whose condition deteriorated. Among hypertensive patients with MID, improved cognition and clinical course correlated with control of systolic blood pressure within upper limits of normal (135 to 150 mm Hg), but if systolic blood pressure was reduced below this level, patients with MID deteriorated. Among normotensive patients with MID, improved cognition was associated with cessation of smoking cigarettes.(JAMA 1986;256:2203-2209)

A group of 51 neurologically normal, middle-aged and elderly volunteers (aged 35–86 years; mean age 63.24 years) with and without risk factors for stroke were given annual tests of cerebral vasomotor reactivity to assess any changes in the cerebral vascular capacitance associated with advancing age that might alter cerebral vasomotor reactivity. Cerebral vasomotor reactivity was estimated as the difference in bihemisphere gray matter CBF measured by the 133Xe inhalation method in the steady state breathing room air, followed by a second measurement during inhalation of 100% oxygen. There were significant and progressive reductions in cerebral vasomotor reactivity during the 4-year longitudinal study. Positive linear correlations were apparent between initial steady-state mean bihemisphere gray matter CBF levels and degrees of vasomotor reactivity, suggesting that the Law of Initial Value plays an important role. This should be borne in mind when analyzing scores of cerebral vasomotor reactivity. In the present communication, analysis of covariance was used to correct for influences of initial CBF levels on vasomotor responses tested while breathing pure oxygen.

Twenty severe chronic alcoholic patients with signs of neurotoxicity but without Wernicke-Korsakoff syndrome were treated by abstinence from alcohol and examined prospectively at intervals thereafter. Serial examinations included detailed medical histories, neurological examinations, cognitive capacity screening examinations, computed tomography scans with measurements of sulcal and ventricular volume, and measurements of regional CBF. All sedatives were withdrawn before CBF measurements were made. Before treatment, gray matter blood flow values were significantly reduced compared with those of age-matched normal volunteers, but white matter blood flow values were normal and the ventricles were enlarged. After abstinence from alcohol, mean gray matter blood flow values and brain volume both increased significantly.

Five cases of mobile cecum syndrome are presented. These patients all presented with chronic right lower quadrant abdominal pain with associated abdominal distention and symptomatic relief after passing flatus or having a bowel movement. Three patients had preoperative barium enemas demonstrating abnormal mobility of the cecum. On exploration, all patients were found to have the cecum and ascending colon unattached to the lateral peritoneum for 15 to 18 cm. All patients were treated by cecopexy, using a lateral peritoneal flap for fixation, and all have had relief of their pain. This technique is described and illustrated. Cecopexy is an effective method of fixing the cecum and prevents subsequent cecal volvulus. The diagnosis of mobile cecum syndrome should be considered in patients with chronic right lower quadrant pain.

Utilizing the high spatial and temporal resolution of magnetoencephalography in conjunction with magnetic resonance images, the current study explored the underlying electrical patterns of cortical excitation during both contralateral and ipsilateral auditory stimulation. Instead of studying only the peaks of the N100 component of the evoked magnetic field, a 30-msec window was chosen about the area where the peaks occurred and the intracranial sources generating that component were estimated at successive 5-msec intervals. Results indicated that the sources for both contralateral and ipsilateral conditions were best represented as a continuous movement of activation in an anterior–inferior direction along the superior surface of the temporal lobe. Although the peak magnetic fields of the N100 to contralateral stimulation were of shorter latency and higher amplitude, the generating sources of both had very similar time-dependent movement patterns, and comparisons of source localizations were dependent on the latency at which they were contrasted.

The arc phase of an electrical discharge in salt water is investigated using a 1‐D nonlinear fluid model in cylindrical (r) coordinates. For most electrode geometries, the arc phase is more accurately modeled using a cylindrical geometry compared to the usual and simpler to implement spherical model. This is due to the fact that until the bubble radius is comparable to the distance between electrodes, the preferred geometry is cylindrical. Both the bubbles external (water) and internal (dissociated water and plasma) are discretized and modeled with nonlinear fluid equations. The model includes the energy flow from the capacitor, into the plasma arc through its resistivity, and then finally into the hydroacoustic pulse. Simulation results will be compared to experiments. Also the efficiency of various electrode configurations will be investigated. [Work supported by the Office of Naval Research.]

Experimental and theoretical investigation of an array of spark sources has yielded information about the mutual effects of sources in close proximity, and about the acoustic spectra and radiation pattern. High‐speed photographs have been taken of several shots to supplement the calculations and acoustic data. Preliminary results indicate that the enhancement of particular output characteristics is feasible, and that this enhancement hinges on the interaction of multiple radiating bubbles in a particular way. Theoretical calculations and experimental data are compared.

The internal structure of the arc phase of a high‐voltage discharge in water is characterized by the evolution of water molecules into atomic and ionic components. However, the spatial distribution of these components, in addition to the temperature, vary considerably due to the influx of mass at the bubble boundary. The physical and acoustical properties of this bubble are investigated through the use of a newly developed nonlinear 1‐D fluid code. The model includes dissociation and ionization (through +2 for oxygen), thermal conduction, mass influx due to blackbody radiation at the bubble boundary, and a complete electrical model which includes the calculation of the electrical resistivity of the bubble due to both neutrals and ions. Preliminary results show interesting acoustical phenomena including strong acoustical pulses bouncing inside the bubble. These shock waves reflect off the bubble boundary, forming an inward propagating wave not unlike that of an implosion. The nonlinear inviscid fluid equations are also used to evolve the water exterior to the bubble boundary. [Work supported by the Office of Naval Research.]

In Reply.—We wish to thank Dr Cohen for his interest in our article entitled "Improved Cognition After Control of Risk Factors for Multi-infarct Dementia." We agree that multiple bilateral cerebral embolism from cardiac disease with dysrhythmia may be a cause of MID, but it is relatively rare (2% in our series of patients). Such cases due to cardiac emboli are being investigated in our ongoing prospective studies of stroke and MID. In the series of patients we described in our article, cases of MID due to cardiac emboli were excluded. Only two of the most common forms of MID were considered in our article, those due to multiple lacunar infarctions and to watershed cerebral infarcts associated with occlusive disease of the carotid arteries. We agree that heart disease is an important risk factor associated with stroke and MID. We also agree that treatment of heart disease and cardiac dysrhythmias