John P. Conomy

Comparison of the Hemodynamic Changes Produced by Electrical Stimulation of the Area Postrema and Nucleus Tractus Solitarii in the Dog

Previous studies have implicated the area postrema (AP) as a site responsible for the centrally mediated neurogenic effects of angiotensin II. To clarify further its possible role in the central control of blood pressure, stainless steel electrodes were lowered stereotaxically into the AP of morphine-chloralose-anesthetized dogs after surgical exposure of the walls of the 4th ventricle just anterior to the obex. In all experiments, large pressor responses were obtained at a relatively low stimulus strength (range: 20-80 μA, 20-60 Hz); the increases in pressure (average: 30 ± 4 mm Hg) were rapid in onset and sustained for the 10- to 20-second duration of the stimulus. Hemodynamically, the pressor response during AP stimulation was due to increases in both cardiac output (+211 ± 37 ml/ min) and peripheral resistance (+0.81 ± 0.33 U). An increase in heart rate contributed to the onset but not the plateau of the pressor response. Reconstruction of electrode tracts in all experiments corrobo-rated that these pressor responses originated in the AP. The specificity of these cardiovascular responses was confirmed further by repeating the same kind of stimuli with electrodes placed in the nucleus tractus solitarii (NTS). In contrast to the effects obtained during AP stimulation, bradycardia (-41 ± 6 beats/min) and hypotension (-29 ± 5 mm Hg) were characteristic features. The fall in blood pressure during NTS stimulation was secondary to the pronounced bradycardia and decreased cardiac output. The data suggest that the AP is part of a previously unrecognized pathway which is distinct from the primary baroreflex pathway with relays in the adjacent NTS. Circ Res 45:136-143, 1979

Quantitative assessment of cutaneous sensory function in subjects with neurologic disease

Based upon techniques devised for the behavioral study of cutaneous sensation in monkeys, a method has been developed which studies quantitatively cutaneous sensation in man. The techniques is analogous to the von Békésy method of audiometry and employs a subject-operated stimulus and signalling divice. In tests utilizing electrical stimulation of the skin surfaces the subject serves as his own control for comparison of one cutaneous zone with another and from one trial session to another. A permanent, written record of stimulus and nonverbal perceptual response is produced in this instrumental method which permits statistical analysis of responses. The analysis includes determination of cutaneous sensory thresholds, limits of stimulus intensity during detection, duration of perception, detection cycle rates, and persistence indices. This instrumental method of cutaneous sensory assessment is quantifiable, free of verbal bias, and repeatable in terms of defined stimulus strengths. In applied clinical studies, patients with peripheral nerve lesions show elevations of perceptual thresholds, reduced numbers of detection-disappearance cycles per unit time, prolonged, contorted decay slopes, and occasionally persistence of perception in the absence of stimulation. Patients with central lesions have variable threshold abnormalities, but little slowing of cycle rate or perceptual persistence. These quantitative sensation parameters can be evaluated longitudinally during the course of an illness and its treatment. The method has potential use in the investigation of basic aspects of sensation and its interactions with behavior.

The brain and arterial hypertension: new direction in an old relationship.

In the minds of most neurologists, the association of the terms “brain” and “arterial hypertension” suggests the influence of blood pressure upon the brain. Arterial hypertension all too frequently disturbs the function and wrecks the structure of the human brain through mechanisms of vascular impairment. Cerebral infarction and hemorrhage are the end stages, representing the structural worst of a very bad lot of brain-vascular effects. Traditional and well-substantiated neurologic thinking dictates, therefore, that arterial hypertension and the brain are related to each other in a casual way, in the direction that “arterial hypertension leads to the ruin of the brain.” Arterial hypertension Brain disorder

Emergency management of the patient with SEIZURES: Part 1. Classification and Treatment System, Common Seizure Disorders

Emergency treatment of the patient with convulsions can be based on a simple system of classification according to seizure type—isolated, series with interim consciousness, or continuous (with or without consciousness). Seizure disorders commonly seen in the emergency room include drug or alcohol withdrawal epilepsy and febrile seizures in children.

Emergency management of the patient with SEIZURES

The most common form of status epilepticus encountered in the hospital emergency room is generalized tonic-clonic seizures of a continuous type. This alarming form of epilepsy is the most hazardous in terms of morbidity and mortality and provides the most opportunity for therapeutic error. In treatment, the physician should use only those drugs with which he is familiar.

Impact of arterial hypertension on the brain

Even mild arterial hypertension dramatically increases the risk of vascular brain disease. Cerebral infarction is most commonly attributable to large-vessel thromboembolic disease. Lacunar infarcts, due to lipohyalin degeneration of vessel walls, are a particular hazard in the hypertensive patient. Hypertensive encephalopathy is associated with hypertension from any cause and may occur at any age. Brain hemorrhage is associated with arterial hypertension and is almost always fatal, regardless of treatment. Hypertension plays a major causal or complicating role in all cerebrovascular disease. The decline in the incidence of stroke over the past decade coincides with improving detection and treatment of hypertension.