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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Doppler detection of venous and arterial gas emboli has been recognized since 1968. The technology has been applied using 5-MHz ultrasound to study decompression sickness and monitor cardiopulmonary bypass and intracranial surgery. Since the advent of transcranial Doppler, which requires the use of lower ultrasonic carrier frequencies to penetrate the temporal bone, the detection of particulates moving in the bloodstream has been available. Using 2 MHz, microembolic signals have been detected in a variety of clinical situations, including cardiac conditions known to have high probabilities to produce embolic stroke. The basic features of a Doppler embolic signal have been clarified, and many investigators are applying the technology to determine the clinical significance of the detected emboli and their use in diagnosis and medical and surgical treatments. The basis for automatic sizing, counting, and characterizing the emboli is under development. The applications of Doppler detection of emboli will range from diagnosis and localization of embolic sources to improvement in surgical techniques and adjustments in medical treatments. (ECHOCARDIOGRAPHY, Volume 13, September 1996)
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PMID:Detection of Embolism with Doppler Ultrasound: A Review. 1144 64

Patent foramen ovale (PFO) is implicated in platypnea-orthodeoxia, stroke and decompression sickness (DCS) in divers and astronauts. However, PFO size in relation to clinical illness is largely unknown since few studies evaluate PFO, either functionally or anatomically. The autopsy incidence of PFO is approximately 27% and 6% for a large defect (0.6 cm to 1.0 cm). A PFO is often associated with atrial septal aneurysm and Chiari network, although these anatomic variations are uncommon. Methodologies for diagnosis and anatomic and functional sizing of a PFO include transthoracic echocardiography (TTE), transesophageal echocardiography (TEE) and transcranial Doppler (TCD), with saline contrast. Saline injection via the right femoral vein appears to have a higher diagnostic yield for PFO than via the right antecubital vein. Saline contrast with TTE using native tissue harmonics or transmitral pulsed wave Doppler have quantitated PFO functional size, while TEE is presently the reference standard. The platypnea-orthodeoxia syndrome is associated with a large resting PFO shunt. Transthoracic echocardiography, TEE and TCD have been used in an attempt to quantitate PFO in patients with cryptogenic stroke. The larger PFOs (approximately > or =4 mm size) or those with significant resting shunts appear to be clinically significant. Approximately two-thirds of divers with unexplained DCS have a PFO that may be responsible and may be related to PFO size. Limited data are available on the incidence of PFO in high altitude aviators with DCS, but there appears to be a relationship. A large decompression stress is associated with extra vehicular activity (EVA) from spacecraft. After four cases of serious DCS in EVA simulations, a resting PFO was detected by contrast TTE in three cases. Patent foramen ovales vary in both anatomical and functional size, and the clinical impact of a particular PFO in various situations (platypnea-orthodeoxia, thromboembolism, DCS in underwater divers, DCS in high-altitude aviators and astronauts) may be different.
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PMID:Patent foramen ovale: a review of associated conditions and the impact of physiological size. 1152 6

The significance of patent foramen ovale (PFO) in the pathophysiology of Type II decompression sickness (DCS) remains controversial. PFOs are common, occurring in approximately one quarter of the normal population, thus making right-to-left shunting of venous gas emboli (VGE) a theoretical concern in both hyper- and hypobaric situations. Despite this high prevalence of PFO in the general population, and the relatively common occurrence of venous gas bubbles in diving and altitude exposures, the incidence of Type II DCS in diving or with altitude is remarkably low. Although the literature supports a relationship between the presence and size of PFO and cryptogenic stroke, and an increased relative risk of Type II DCS with a PFO in divers, the absolute increase in risk accrued is small. Hence, the value of screening is also controversial. This paper presents a summary of the literature on PFOs and DCS in animals, and in human altitude and diving, focusing on the latter; as well the analogous literature on cryptogenic stroke. The results of an examination of the literature on detection of, screening for, and treatment of PFOs is also presented.
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PMID:A review of the relationship between patent foramen ovale and type II decompression sickness. 1176 13

A new test developed to characterize the bending properties of treated or virgin hair fibers is described. The device consists of a pendulum that bends a sample made up of 39 parallel hair fibers at each swinging stroke. Hair bending stiffness can be assessed by the number of strokes observed until the pendulum stops. The mechanical behavior of natural hair fibers is related to their geometric characteristics. The effects of various hair treatments can be assessed by this method.
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PMID:A new approach to the bending properties of hair fibers. 1177 53

Pulmonary barotrauma-induced cerebral arterial gas embolism (CAGE) continues to complicate compressed gas diving activities. Inadequate lung ventilation secondary to inadvertent breath holding or rapid buoyant ascent can quickly generate a critical state of lung over-pressure. Pulmonary over-pressurization may also occur as a consequence of acute and chronic pulmonary pathologies. Resulting barotrauma frequently causes structural failure within the terminal distal airway. Respiratory gases are then free to embolize the systemic circulation via the pulmonary vasculature and the left heart. The brain is a common target organ. Bubbles that enter the cerebral arteries coalesce to form columns of gas as the vascular network narrows. Small amounts of gas frequently pass directly through the cerebral circulation without occlusion. Larger columns of gas occlude regional brain blood flow, either transiently or permanently, producing a stroke-like clinical picture. In cases of spontaneous redistribution, a period of apparent recovery is frequently followed by relapse. The etiology of relapse appears to be multifactoral, and chiefly the consequence of a failure of reperfusion. Prediction of who will relapse is not possible, and any such relapse is of ominous prognostic significance. It is advisable, therefore, that CAGE patients who undergo spontaneous recovery be promptly recompressed while breathing oxygen. Therapeutic compression will serve to antagonize leukocyte-mediated ischemia-reperfusion injury; limit potential re-embolization of brain blood flow, secondary to further leakage from the original pulmonary lesion or recirculation of gas from the initial occlusive event; protect against embolic injury to other organs; aid in the resolution of component cerebral edema; reduce the likelihood of late brain infarction reported in patients who have undergone spontaneous clinical recovery; and prophylax against decompression sickness in high gas loading dives that precede accelerated ascents and omitted stage decompression.
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PMID:Pulmonary barotrauma-induced cerebral arterial gas embolism with spontaneous recovery: commentary on the rationale for therapeutic compression. 1184 83

There are only a few reported cases of psychiatric disorders presenting a s decompression sickness (DCS). Previous reports indicate that DCS can result in personality change, depression, Munchausen's syndrome, and pseudo stroke. We report two cases of acute psychoses that occurred following diving as suspected DCS and were treated with hyperbaric oxygen, which did not improve the psychotic features. One patient had symptoms of DCS including myalgias, weakness, and fatigue; however the symptoms were inconsistent. The symptom onset and nitrogen loading from his dive profiles made the diagnosis of DCS unlikely. The second patient exhibited mild joint pain, fatigue, and psychosis that was temporally associated with diving but no other symptoms of DCS. Following a detailed medical evaluation we determined that these two patients did not have DCS or arterial gas embolism (AGE). Although it is highly unlikely that a pure psychotic episode will arise as a result of DCS, physicians caring for divers with symptoms of DCS or AGE and acute psychosis may consider a trial of recompression therapy while completing the medical evaluation. Divers with acute psychosis without signs and symptoms and benign dive profiles are unlikely to have DCS or AGE.
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PMID:Acute psychosis associated with diving. 1206 50

Two hundred and fifty-one patients with a persistent foramen ovale (PFO), mean age 43.3 +/- 12.4 years, underwent catheter closure between 6/1995 and 6/2001. One hundred and forty-one had an ischemic stroke, 99 a transient ischemic attack (TIA) or prolonged reversible ischemic neurologic deficit, 5 peripheral arterial embolism, 4 suffered from decompression sickness after diving and 2 had transient global amnesia. Fifty-nine of them had multiple events in spite of antiplatelet or anticoagulant therapy. The patients received five different devices: 13 Rashkind Occluders, 20 Amplatzer septal Occluders, 109 Amplatzer PFO-Occluders, 73 CardioSEAL and 36 STAR-Flex devices. Time of fluoroscopy was 8.3 +/- 4.5 min. In three patients a device embolized and had to be removed from the groin vessels. We saw five inguinal or retroperitoneal venous hematomas with the need for operation in one patient. One early and one late perforation of the left atrium caused by a guide wire and a left-atrial disc, respectively, also needed surgery. Fourteen patients had documented late arrhythmias. Six patients with atrial fibrillation needed drugs or cardioversion while the other patients with runs of supraventricular tachycardia, atrial flutter and multiple extrasystoles needed no therapy. On transesophageal echocardiography (TEE) 6 months after implantation we found four significant residual leaks. These patients had the defect closed with a second device. In addition a secundum atrial septal defect (ASD) was closed in 17 patients (mean age 38 +/- 10.5 years) with Amplatzer septal Occluders (12) and CardioSEAL devices (5). These patients had experienced eight strokes and nine TIAs, 3 of them had had multiple events. Two of these patients had a significant residual defect and one had atrial flutter following the procedure. Two hundred and two PFO-patients and 12 ASD patients were followed for 6-62 (24.6 +/- 14.2) months; 2 died due to a traffic accident and a myocardial infarction, respectively. Four patients had another neurologic event following PFO-closure. We now overlook 210 patients with 348.6 symptom-free patient years and have a 1-year recurrence rate of neurologic events of 1.9%. Catheter closure of the PFO and atrial septal defect is a simple, effective and quick method which ensures a high closure rate, avoids life-long anticoagulation and has a low recurrence rate of neurologic events.
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PMID:[Interventional occlusion of foramen ovale and atrial septal defects after paradoxical embolism incidents]. 1244 68

The role of patent foramen ovale (PFO) in cryptogenic stroke is still debated, but from recent follow-up studies it seems that the amount of right-to-left shunt (RLS) and the association with atrial septal aneurysm (ASA) are major determinants of stroke recurrence. PFO and RLS through the atrial chambers have been recently studied in a number of conditions not or marginally related to cerebrovascular disease. Historically the first studies addressed the presence of RLS in scuba divers as a possible abnormality related to decompression sickness (DS) of unknown aetiology. Despite initial debate there is now robust evidence to claim that patency of foramen ovale increases the risk of developing DS by two and half to four times. Patients with PFO-related DS tend to have early occurrence of symptoms after surfacing and a clinical presentation that indicates brain or upper cervical spinal cord involvement. Recent reports suggest that divers with hemodynamically significant RLS may have an increased risk of developing clinically asymptomatic multiple brain lesions. PFO has been found in patients suffering from migraine with aura with approximately the same frequency as that encountered in cryptogenic stroke patients. This finding has prompted speculations on the possible role of RLS in increasing the stroke risk in migraineurs and in the pathophysiology of the aura. Recent reports showing that migraine with aura is dramatically improved after transcatheter closure of PFO suggest that migraine with aura may indeed be triggered by humoral factors that reach the brain by escaping the pulmonary filter. A RLS is involved in a rare condition known as platypnea-orthodeoxia and perhaps underlies an increased risk of cerebral complications after major orthopedic surgery. Valsalva-like activities often precede the occurrence of attacks of transient global amnesia (TGA) and abnormalities consistent with hypoperfusion of deep limbic structures have been reported during a typical TGA episode. This had raised the hypothesis that TGA may be triggered by paradoxical embolism of platelets aggregates in the posterior circulation, but the search for an increased frequency of PFO in TGA patients has yielded conflicting results. Conditions that determine an increase in pulmonary pressure may facilitate the opening of the virtual interatrial valve and thus promoting shunting of blood to the left heart chambers which in turn might contribute to further desaturation of arterial blood. It is therefore not surprising that RLS has been found in 70% of patients with chronic obstructive pulmonary disease and increased pulmonary pressure and in the same proportion of patients with obstructive sleep apnoea, a condition that ultimately may result in pulmonary hypertension. In conclusion, from the evidence gathered so far the picture is emerging of an important role of PFO in a number of non-stroke conditions, either as causative factor or as associated condition predisposing to complications. The availability of simple diagnostic techniques such as transcranial Doppler (TCD) to assess RLS will undoubtedly contribute a great deal of knowledge on the relevance in medicine of this hitherto neglected condition.
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PMID:Clinical impact of patent foramen ovale diagnosis with transcranial Doppler. 1247 Aug 46

Although diving with compressed air is generally safe, neurological problems resulting from infarction in SCUBA diving are well known, including arterial gas embolism and decompression sickness (caisson's disease, bends) involving the brain and spinal cord. While air gas embolism forms the overwhelming majority of causes for stroke in divers, internal carotid artery (ICA) dissection is another potential mechanism for central nervous system infarction in the setting of SCUBA diving. A 38 year-old female, who presented with complaints of headache, nausea, vomiting, and left sided hemiparesis after rapid ascent to the surface from a depth of 120 feet of seawater was initially treated for decompression illness in a hyperbaric chamber. Further neurological workup revealed a right ICA dissection. This case demonstrates the dangers of ICA dissection following rapid ascent to the surface from underwater and emphasizes an interesting presentation of stroke associated with SCUBA diving.
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PMID:Internal carotid artery dissection in stroke from SCUBA diving: a case report. 1267 Jan 19

Thin section electron micrographs of rapidly fixed Chlamydomonas cells were used to establish a relationship between flagellar bends and orientation of the central pair microtubule complex. Using conditions that preserve flagellar waveforms during both forward swimming (asymmetric bends) and backward swimming (symmetric bends), we found that central pair orientation differs in bent regions and straight regions. During forward swimming, a plane through the two central pair microtubules is parallel to the bend plane throughout principal bends, in both effective stroke and recovery stroke phases of the beat cycle. In these curved segments, the C1 microtubule always faces the outer edge of the curve. This parallel orientation twists in straight regions both proximal and distal to bends. During backward swimming episodes induced by photoshock, when Chlamydomonas flagella beat with principal and reverse bends of similar magnitude, the central pair twists by 180 degrees between successive bends. These observations support a model in which central pair orientation in Chlamydomonas is linked to doublet-specific dynein activation, and bend propagation is linked to rotation of the central pair complex.
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PMID:Orientation of the central pair complex during flagellar bend formation in Chlamydomonas. 1450 9


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