【ISC2015】视神经超声检查有助于预测卒中患者的死亡风险

纳什维尔——2015国际卒中大会（ISC2015）上的一项研究显示，应用视神经超声评估包绕视神经的神经鞘有助于发现急性卒中患者几日内或几个月内的死亡风险。

这项新型研究旨在应用非侵袭性方法快速发现存在颅内压升高风险的卒中患者，颅内压水平可反映卒中严重性，较高的颅内压是死亡的主要原因。佛罗里达州盖恩斯维尔市佛罗里达大学医学院的助理教授Vishnumurthy S. Hedna（MD）是这项研究首席研究员，他说，评估视神经鞘的厚度可能是检查颅内压是否升高的一种简易方法。

Hedna说：“视神经超声可用于检查大脑有无肿胀，肿胀有时会在大卒中后发生。这可通过超声成像查看眼部后方神经的直径，因为脑部肿胀时，压力会传导至眼部。医生可据此应用降低脑部压力的药物治疗卒中。”

这项研究纳入佛罗里达大学杉德思医院的86例卒中患者，这些患者被怀疑在卒中后颅内压逐渐升高。研究者应用眼部超声评估视神经鞘。

研究发现，随后因血管栓塞卒中死亡的患者神经鞘直径平均为5.82mm，幸存者为5.33mm；因出血性卒中死亡的患者神经鞘直径平均为6.23mm，幸存者为5.72mm。

神经鞘每增加1mm，血管栓塞卒中患者6个月内死亡的风险增加3倍；出血性卒中患者的死亡风险增加5倍。大多数死亡发生在患者入院后1个月内。这项研究还显示，神经鞘越粗，患者6个月后重度失能的可能性越大。

视神经超声是一种床旁常规应用的安全检查；行检查时将凝胶涂敷在闭合的眼睑上并将超声探头置于其上。Hedna说：“眼部超声简单易行，许多研究已经表明这种操作容易学会。其他的方法可能是侵袭性的、有辐射的，而且不符合成本效益。”

Hedna称，目前颅内压测量方法包括直接脑室穿刺或脊椎穿刺；而这项研究结果在未来可能会帮助医生在为患者进行初次检查时，在不进行侵袭性检查的情况下即可确定风险水平，并在必要时，尽早开始监测颅内压、用药降低颅内压、颅内引流减少液体积聚，或者改换治疗方案。

研究者在患者因卒中入院后第一天和第二天测量每侧眼部神经鞘直径两次，大多数患者测得8个值。该研究对死亡风险的预测主要是基于第二天的测量值，但是对于很快就死亡的患者和很快从重症监护转出的患者仅有一个测量值。研究者现在仍在研究第一天和第二天是神经鞘测量值的差异是否与患者的死亡或失能相关。

调查组计划的研究是，根据神经检查结果异常和神经鞘增粗对患者的脑部液体积聚进行治疗与仅应用常规治疗的患者相比，是否会影响患者的表现。卒中影响最严重的患者“可能是那些在其后病程中一直需要用药降低脑部水肿的患者。我们感觉测量视神经鞘直径也仅仅是帮助医生及早做出决定。”

他说，超声检查仅仅是在卒中发生不久时进行才有价值。卒中后脑部肿胀常常会在第三天至第四天达到峰值，所以超声检查应在急性卒中的情况下应用。

共同作者包括Vaibhav Rastogi（M.D）、Emily Weeks（M.P.H）以及Rohit Pravin Patel（M.D.），作者声明见摘要。该研究无外部资助。

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NASHVILLE, Tenn., Feb. 11, 2015 – Using optic ultrasound to measure the sheath of a nerve that connects the eye and brain can help identify acute stroke patients most at risk of dying within days or months, according to research presented at the American Stroke Association’s International Stroke Conference 2015.

The new study aimed to quickly and noninvasively identify stroke patients who are at risk from increased pressure inside the skull – which is thought to reflect stroke severity and is the major cause of death. Measuring the thickness of the optic nerve sheath may be a simple test for increased intracranial pressure, said Vishnumurthy S. Hedna, M.D., lead researcher and assistant professor of neurology at the University of Florida College of Medicine in Gainesville, Fla.

 “Ultrasound on the optic nerve can be used to test your brain for swelling, which sometimes occurs after a major stroke,” Hedna said. “This can be done by looking at the nerve diameter behind your eye with ultrasound images, since it is thought that when your brain swells, pressure gets transmitted towards your eyes,” Hedna said. “This would help doctors treat your stroke with medications that would reduce brain pressures.”

The study involved 86 patients at the University of Florida’s Shands Hospital in Gainesville, Fla., who were suspected of having a buildup of pressure in the skull after their stroke. Researchers used ocular ultrasound (ultrasound assessment of the eyes) to measure the sheath that encases the optic nerve.

For patients who later died of a stroke due to a blood vessel blockage, average diameter of the nerve sheath was 5.82 millimeters, versus 5.33 millimeters in those who survived. In patients with a bleeding stroke, average diameter was 6.23 millimeters for those who died, versus 5.72 for survivors.

For every millimeter bigger the nerve sheath diameter was, the risk of death within six months was four times as high in patients whose stroke was due to a blood vessel blockage, and six times as high in patients who had a bleeding stroke. Most of the deaths occurred within a month of patients’ hospitalization. The study also suggested that the larger the nerve sheath measurement, the more disabled a patient was likely to be six months later.

Optic ultrasound is a safe, routine bedside test that is performed using gel and a device placed on closed eyelids, Hedna said. “Optic ultrasound is easy to do, and has been described in many studies as easily teachable. Other methods are invasive, involve radiation, and are not cost-effective.”

Currently, intracranial pressure is monitored directly from within the skull or with a spinal tap. In the future, the findings could help doctors assign risk levels to patients during their initial exam without performing invasive testing, and when needed, act earlier to monitor intracranial pressure, give medicine to diminish it, place a drain in the head to reduce fluid buildup, or otherwise change management of the patient, Hedna said.

The researchers measured two dimensions of the nerve sheath in each eye on both the first and second day a patient was hospitalized after a stroke, totaling eight measurements for most patients. The study based its estimates of death risk mainly on measurements taken on day two, but for patients who soon died or were quickly discharged from intensive care, only one day’s measurements were available. The researchers are still studying whether differences in optic nerve sheath diameter from day one to day two were related to patients’ risk of death or disability.

The team plans to study whether treating patients for fluid buildup on the brain based on an abnormal neurological exam plus a bigger nerve sheath affects how they fare, compared with patients who have usual care. The most severely impaired patients “are probably the ones who would get medications to decrease brain edema later in the course of their illness anyway,” Hedna said. “We feel the optic nerve sheath diameter would just help the clinician make the decision sooner.”

The ultrasound test is likely to be useful in stroke care only when given soon after stroke injury, he said. “Brain swelling after stroke usually peaks between three to four days, hence its use in the acute stroke setting.”

Co-authors are Vaibhav Rastogi, M.D.; Emily Weeks, M.P.H.; and Rohit Pravin Patel, M.D. Author disclosures are on the abstract. No outside funding reported.

Copyright © 2015 Elsevier Inc. All rights reserved.