Perspectives in Medicine最新文献

Transcranial color-coded duplex ultrasonography (TCCS) enables the visualization of basal cerebral arteries through the intact skull by color-coding of blood flow velocity. The arteries of the circle of Willis can be identified by their anatomic location with respect to the brain stem structures and by the determination of the flow direction. TCCS is an important neuroimaging method due to its excellent time resolution. In addition to the diagnostics of intracranial vascular disease, this technique is valuable in intensive care and stroke units, e.g. for follow-up examinations in vasospasm after subarachnoid hemorrhage, and for intraoperative monitoring as well. In difficult anatomical conditions, the application of echo contrast agents can improve the diagnostic reliability of the examination. This paper reviews the examination technique and the clinical application of this method in routine cerebrovascular diagnostics.

Objective

Navigated transcranial magnetic stimulation (nTMS) is a newly evolving technique. Despite its supposed purpose of preoperative mapping of the central region, little is known about further applications as well as the accuracy compared to more commonly used modalities like direct cortical stimulation (DCS) and functional MRI (fMRI).

Methods

We examined 30 patients with tumors in or close to the precentral gyrus as well as in the subcortical white matter motor tract using nTMS with the Nexstim eXimia system. Data was sent to the neuronavigation system and correlated with intraoperative direct cortical stimulation.

Results

In the cases of lesions of the precentral gyrus, preoperative motor cortex characterization correlated well with intraoperative DCS with a deviation of 4.5 ± 3.5 mm. When comparing nTMS with fMRI however, deviation was quite larger with 9.6 ± 7.9 mm for upper and 15.0 ± 12.8 mm for lower extremity. In patients with subcortical lesions DTI fiber tracking was performed using nTMS mapping as seed region, which resulted in a subjectively more specific presentation of the corticospinal tract compared to conventional fiber tracking and caused less interobserver variability.

Conclusion

Navigated TMS correlates well with DCS as the best established standard despite many factors, which are supposed to contribute to inaccuracy of the method. Moreover, nTMS-aided DTI fiber tracking is user-independent and, therefore, a method for further standardization of DTI fiber tracking.

Evaluation of optic nerve sheath by means of optic nerve ultrasonography (ONUS) is a reliable tool for assessment of patients with increased intracranial pressure. The aim of this study was to present the usefulness of optic nerve sheath ultrasonography in patients with brain death.

Ten patients with brain death as a result of traumatic or non-traumatic causes were evaluated by ONUS. Optic nerve sheath diameter (ONSD) was measured with a 12 MHz linear ultrasound probe (Terason T3000, Teratech Corporation, USA). The probe was adjusted to give a suitable angle for displaying the entry of the optic nerve into the globe, at the depth of 3 mm behind the globe. For each optic nerve four measurements were made, twice in transversal and twice in the sagittal plane, by rotating the probe clockwise. Mean ONSD for brain death patients were compared with mean ONSD of 17 healthy controls.

Ten individuals (7 males) with confirmed brain death (5 due to neurotrauma, 2 due to subarachnoid hemorrhage, 2 as a result of ischemic strokes and one of parenchymal hemorrhage), were evaluated. On the left side mean ONSD was 0.71 ± 0.06 cm on transversal plane and 0.72 ± 0.04 cm on sagittal plane. On the right side mean ONSD was 0.73 ± 0.05 cm on transversal plane and 0.73 ± 0.06 on sagittal plane. In controls left mean ONSD was 0.51 ± 0.05 cm on transversal plane and 0.55 ± 0.06 cm on sagittal plane. On the side right mean ONSD was 0.52 ± 0.05 cm on transversal plane and 0.54 ± 0.07 on sagittal plane. Mean ONSD in brain death was 0.72 ± 0.05 cm and 0.53 ± 0.06 cm in controls (p < 0.01).

Measurements of ONSD may be useful in distinguishing brain death persons from healthy controls.

The significance of cerebrovascular disorders is steadily increasing due to the demographic changes in western industrial societies. Therefore the implementation of telemedical networks seems tempting to improve deliverance of specialised stroke care in non-urban areas. Networks like TEMPiS, located in the rural area of south-eastern Bavaria, have shown to deliver high experienced stroke therapy to underserved areas.

Mandatory for a high quality of supply is the appropriate technical equipment. Moreover, beside the teleconsultations, a continuous training should be performed. Mobile solutions allow more flexibility for the teleconsultants.

Carotid intima–media thickness (cIMT) and carotid plaque are ultrasound imaging measures of carotid atherosclerosis and strong predictors of future stroke, myocardial infarction and vascular death. The use of ultrasound measures of cIMT and carotid plaque as a screening tool in clinical practice however have been extremely limited by a lack of recognition of its value by medical communities, health care policy makers and a lack of reimbursement by third-party payers engaged in the delivery of vascular imaging services. This review addresses the role of cIMT and plaque in vascular disease risk prediction. Recent data from large population based studies on reclassification of the vascular risk using carotid ultrasound imaging markers is presented. In addition, the common clinical scenarios for the appropriate use of cIMT in clinical setting are summarized according to the recent study conducted by the Society of the Atherosclerosis Imaging and Prevention in collaboration with the International Atherosclerosis Society. This presentation is intended to provide a practical guide for use of cIMT and plaque to clinicians to promote optimal clinical use of cIMT and to researchers to direct cIMT and plaque research towards investigating environmental and genetic factors of a complex disorder – subclinical atherosclerosis – leading to future genetic discoveries and new anti-atherosclerotic therapies.

Takayasu arteritis is a panaortitis, more frequent in Japan, South-East Asia India and Mexico, that presents in the 2nd or 3rd decade of life with a non-specific inflammatory phase, then vascular stenosis with ‘pulselessness’ with collateral development. Clinical features include reduced/absent pulses, bruits, hypertension, aortic regurgitation, neurological symptoms from ischemia. While the gold standard for diagnosis is arteriography, magnetic resonance angiography and ultrasonography are now widely used due to their non-invasive nature. Steroids are the cornerstone of medical therapy; cytotoxics may be used for failures. Surgery or angioplasty may be needed for severe vascular stenosis.

Several studies have demonstrated the value of ultrasound perfusion imaging to visualize the area of perfusion deficit in patients with acute ischemic stroke.

Triggered high mechanical index (MI) imaging, which uses contrast microbubble destruction to analyze bolus contrast kinetics in the brain parenchyma, was used in these studies. Recently high sensitive, low MI imaging was introduced. With this new technology real-time bolus kinetics as well as refill kinetics could be analyzed without triggering. In the early phase of ischemic stroke, ultrasound perfusion imaging is useful in detecting the area of perfusion deficit and to assess outcome prognosis of the patient. This bedside technology is available for use in the stroke unit when patients with acute ischemic stroke undergo a color-coded duplex work-up to evaluate their vascular status.

In Russia brain death diagnostic is still under great public attention. In such environment confirmatory tests are absolutely necessary. Aim of our study is to investigate the cerebral blood flow in brain death using color-coded duplex sonography. The sonographic study of 20 patients with brain death was performed and included transcranial and extracranial color duplex sonography. All patients were untrepanized. The following parameters were measured – presence of reverberating flow, Vmax ranges.

Results: At baseline TCDS revealed both MCA in all patients, and the BA in 18 patients. Oscillating flow with Vmax −32 ± 12 sm/s in MCA was found. Reverberating flow in the proximal segment of ICA and in the V2 segment of VA was found in all patients. Vmax ranges were 96 ± 27 sm/s in ICA and 58 ± 17 sm/s in VA. After 6 h TCDS was successful in 16 patients. In all of 16 cases blood flow in the MCA as a systolic peak or reverberating flow was detected. Basilar system study was successful in 12 cases. In all vessels blood flow was as systolic peaks.

Extracranial ICA and VA were visualized in all cases. In the ICA and V2, V3 segments of the VA reverberating flow were detected. Vmax was 47 ± 25 sm/s in ICA and 35 ± 17 sm/s in VA. In BD color duplex scanning reveals oscillating flow or systolic spikes in distal ICA, VA, intracranial vessels. In TCDS, the most common finding is MCA with reverberating flow. The optimum combination is extracranial and intracranial scanning in the early stages of BD.

Paradoxical embolism is a possible cause of ischemic stroke, particularly in younger patients without any other cause, i.e. cryptogenic stroke, and a patent foramen ovale is the most frequently assumed cause. The contrast transcranial Doppler monitoring mode has a sensitivity that is comparable to contrast transesophageal echocardiography for detection of a right-to-left shunt, however, the contrast transesophageal echocardiography remains the “golden standard” for the detection of a patent foramen ovale. Diagnostic studies that can identify a patent foramen ovale may be considered for prognostic purposes. In most cases, however, it is difficult to establish a firm etiological association and the debate about medical or interventional management is ongoing. Other possible causes of right-to-left shunting leading to cerebral complications like pulmonary arteriovenous malformations have also been noted but are rarely discussed.

Sonothrombolysis is a novel therapy for recanalization of acute intracranial arterial occlusion. So far, safety and efficacy has been shown for transcranial ultrasound with diagnostic probes in combination with standard thrombolysis treatment. However, there are several new developments including special designed ultrasound probes, microspheres for enhancement of the thrombolytic effect of ultrasound and other new approaches. This review provides an overview of current evidence from randomized controlled trials and perspectives on this topic.