Prevention and Management of Stroke in Sickle Cell Disease

Abstract

Sickle Cell Disease(SCD) is one of the most common hemoglobinopathies in the world which causes stroke. The management of stroke depends on the manifestations and the age of the patient. Especially in childhood, anatomic and physiological abnormalities of CNS may be a predisposing factors. Stroke mostly affects the distal segments of the Internal Carotid Artery, but also middle and anterior segments of the cerebral arteries are involved. The most important predisposing factors are the arterial malformations, stenosis and obstructions in cranial arteries, generally involving Internal Carotid Artery, frequently Proximal Middle Cerebral or Anterior Cerebral Arteries. After infarcts at brain vessels, most frequent clinical findings are hemiparesis or hemiplegia, impaired speech, focal seizures, gait disturbances. Risk factors for predisposing stroke are prior transient ischemia, baseline Hb decrease, acute chest sydrome within previous two weeks, systolic blood pressure rises, leucocyte increases. The patient with silent stroke or transient ischemic attacks may be asymptomatic or without neurological symptoms. Neuroimaging abnormalities may be seen without significant clinical findings in children with SCD. We talk about silent stroke if there are neuroradiological abnormalities without clinical findings. Children with silent strokes are more prone to new strokes. If there is a significant stroke a ischemic stroke often present with focal neurological signs and symptoms. If patient is asymptomatic or have suspected stroke, first step may be performance of Transcranial Doppler Ultrasonography (TCD). Children with time-averaged mean velocity (TAMV), measured in Middle Carotid Artery or in distal internal carotid Artery abnormally elevated, defined as TAMV ≥ 200 cm/sec, have sixfold increase for stroke than those with normal TAMV ≤ 170 cm/sec. For these patients under the risk of stroke, chronic blood transfusion is recommended for prevention of primary stroke events. Because of high oxygene demand in children, the child with SCD who also has anemia is at particular risk. The management of acute stroke includes to rule out hemorrhage, stabilize vital signs, careful use of hydration and RBCs transfusion. Exchange blood with normal RBCs is mandatory; it will improve tissue perfusion and oxygenation. Long-term management of stroke is directed to prevent recurrences with fluids supplementation, a chronic transfusion programme at least for 6 months with exchange transfusion or erythrocytapheresis for reducing the HbS under 30%. After 3 years of HbS levels to be maintained <30%, the HbS leveles can be raised safely to less than 50% if the patient has remained neurologically stable. Indefinite chronic transfusion programme was advised for the patients with abnormal TCD values. Hydroxyurea (HU) is an alternative therapy in reducing TCD values and to try to increase HbF improving the clinical outcome. Periodical cranial Doppler ultrasound examination and selective red blood cell transfusions ‘d be useful for stroke prevention.镰状细胞病(SCD)是世上最常见的血红蛋白病，可致中风 中风防治受症状表现和病人的年龄所左右。 尤其对于患儿，中枢神经系统的组织异常和生理异常可能是诱病因素。 中风通常影响颈内动脉的末端，但也会牵连到脑动脉的中段和前段。 中风最重要的诱病因素有动脉畸形、器官狭窄和大脑动脉阻塞，一般和到颈内动脉有关，但牵连到大脑中动脉或大脑前动脉更为常见。 脑血管梗塞后，通常临床发现轻偏瘫或偏瘫、语言障碍、病灶性颠痫和步态障碍等。 诱病性中风具有的风险包括：前两周内引起短暂性局部缺血、血红蛋白含量减少和急性胸痛综合症，然后导致收缩压升高和白血球增加。 轻度中风或短暂性脑缺血发作的患者可能无症候或无神經症狀。 在没重大临床发现的情况下，镰状细胞病患儿可做脑神经成像检查，异常亦会发现。 下边我们将讨论无临床表现情况下神经放射性异常。 轻度中风的患儿再次中风的可能性很大。 如果中风严重，脑缺血的出现经常伴随着局部性神經系統症候和症状 如果患者无症候或疑似中风，首先应进行经颅多普勒超声（TCD）检查。 在异常抬升的中动脉或内动脉末端测量时间平均血流速度(TAMV)，结果为TAMV ≥ 200 cm/sec，该患者中风的可能性是正常情况（TAMV ≤ 170 cm/sec）的六倍。建议对有中风危险的患者采取慢速输血的方法，以防止主要中风事件。 由于儿童对氧的需求量高，患镰状细胞病同时伴有贫血的儿童危险系数尤其高。 急性中风防治的措施包括：排除溢血的可能性、稳定生命体征、谨慎利用水和作用和（血红细胞）RBCs输血 必须使用正常的RBCs交换血液；提高组织灌注和氧化作用。 中风的长期防治旨在阻止再次补充液体，用交换输血或红细胞除去法慢速输血至少6个月，以便把血红蛋白含量减少到30%以下。 血红蛋白含量 < 30% 保持3年后，如果患者神经稳定，可将其升高到50%以下。 TCD值不正常的患者，建议采取不定期慢速输血程序。 作为降低TCU值的备用疗法，羟基脲（HU）尝试提高HbF的含量，达到改善临床结果的目的。 防止中风有效的措施包括定期对大脑进行多普勒超声检查和有选择性的进行血红细胞输血。