Watershed cerebral infarction

Introduction to cerebral infarction in watershed area The cerebral infarction in the watershed area, or watershed infarction (WI), refers to the cerebral infarction that occurs at the junction of the two major arterial distribution areas of the brain. It occurs mostly in the larger arterial blood supply junction of the brain, regardless of the cause, It is different from cerebral thrombosis and cerebral embolism in terms of pathogenesis, pathology and clinical features. It is mainly located in the marginal zone between the large cortical arterial blood supply area and the basal ganglia arteriolar blood supply area, so it is also called marginal cerebral infarction. It can occur on one side of the cerebral hemisphere, or it can occur on both sides of the cerebral hemisphere, but it is more common on one side of the cerebral hemisphere, and the incidence rate accounts for about 10% of ischemic cerebrovascular disease. The most common cause is blood pressure reduction caused by various reasons, or insufficient blood supply to a certain arterial trunk, so that the blood supply to the proximal end of the artery is acceptable, and the blood supply to the peripheral marginal zone of the distal end is reduced, thereby causing ischemic cerebral infarction. The concept of brain watershed infarction has only been accepted by clinicians in recent years, and thus has become a consensus type of cerebral infarction, more common in the elderly over 60 years old. In recent years, with the application of brain CT scan and brain MRI examination in clinic, the location and extent of the lesion can be clearly displayed, and the etiology, pathology and clinical features of the lesion are further recognized, and it is increasingly valued by clinical research. basic knowledge The proportion of illness: 0.004% Susceptible people: more common in the elderly Mode of infection: non-infectious Complications: Hypertension Diabetes

Causes of cerebral infarction in watershed area

(1) Causes of the disease

The etiology of brain watershed infarction is currently unclear. The following factors may be related to brain watershed cerebral infarction, such as paroxysmal hypotension, carotid stenosis or occlusion, vascular microembolism, hypoxemia, polycythemia, abnormal platelet function, etc. In particular, paroxysmal hypotension, carotid stenosis or occlusion and vascular microembolization are more important and may be the main cause of the disease.

1. Hypotension: The cerebral blood circulation is part of the systemic circulation, and the brain watershed area is farthest from the heart. It is most susceptible to the effects of circulating blood pressure or effective circulating blood volume. The brain is the advanced center of the nervous system, and its metabolic activity is particularly strong. The energy demand is the highest, and the brain tissue is almost anaerobic and glucose-free. The energy is continuously supplied by the circulating blood flow. When the circulating blood pressure drops or the circulating blood volume suddenly decreases, for example, if the dose of antihypertensive drugs is too large or inappropriate, it is easy. It causes blood pressure to drop in a short period of time. When it reaches a certain level and lasts for a certain period of time, especially in the boundary area between the two cerebral arteries, it is easy to be ischemic, that is, avascular necrosis of the brain occurs. The underlying cause is myocardial ischemia, arrhythmia, and uprightness. Hypotension, excessive antihypertensive therapy and diabetes complicated with autonomic dysfunction, brain CT scan or brain MRI showed a brain infarction in the watershed.

2. Carotid stenosis or occlusion: atherosclerosis and other causes can cause carotid stenosis or occlusion, most lesions occur at the beginning of the internal carotid artery, when the stenosis reaches more than 50% of the normal lumen, the pressure at the distal end of the blood vessel Affected, on the basis of the hemodynamic disorder and the unsound collateral circulation is likely to lead to brain watershed infarction.

3. Vascular microembolism: The plug is derived from the heart wall thrombus, aortic atherosclerosis, platelet embolus, cholesterol crystal, fat embolus, cancer embolus, etc., can selectively enter the brain surface artery, resulting in the watershed end Vascular ischemia, which persists for a certain period of time and reaches a certain level, can lead to brain watershed infarction.

4. Heart disease and hemorheological changes: the cerebral perfusion pressure caused by the disease is reduced or the thrombus selectively enters the final blood vessel of the watershed, leading to brain watershed infarction, and hemorheological changes also play an important role in brain watershed infarction. The role, mainly blood viscosity and increased hematocrit are easy to cause brain watershed infarction.

5. Anatomical variation of the posterior communicating artery: the posterior communicating artery connects the internal carotid artery with the vertebral-basal artery, which is the passage of the anterior and posterior half of the Willis ring. After the occlusion of one of the internal carotid arteries, the patient's cerebral perfusion is dependent on the side of the other side. The branch blood flow is mainly completed by the Willis ring artery. It is reported that, like the posterior posterior communicating artery diameter 1mm, it can protect the cerebral perfusion and avoid brain watershed infarction. As the lateral posterior artery diameter is <1mm or absent, the brain is prone to occur. Watershed infarction.

6. Cerebral atherosclerosis: cerebral atherosclerosis usually occurs later, plaques appear after 40 years of age, lesions are most prominent in the Willis ring and middle cerebral artery, according to recent reports, the beginning of the internal carotid artery and The atherosclerotic lesions inside the skull are quite common, and there may be varying degrees of stenosis, plaque hemorrhage, ulcers and wall thrombosis. Due to cerebral stenosis, brain tissue is prone to brain atrophy due to chronic long-term blood supply. The cerebral atherosclerosis causes the lumen to be highly narrow, resulting in insufficient blood supply to the brain, especially in the watershed.

7. Other causes

1 increased blood lipids: hypercholesterolemia, hypertriglyceridemia, easily lead to cerebral atherosclerosis, increased blood viscosity, leading to the formation of cerebral infarction,

2 Diabetes: Diabetes not only causes microvascular disease, but also causes macrovascular disease. These changes lead to atherosclerosis and microcirculatory disorders, abnormal lipoprotein metabolism, immune abnormalities and smooth muscle damage, which promote ischemic cerebrovascular disease.

(two) pathogenesis

The main cause of brain watershed infarction is circulatory hypotension, stenosis or occlusion of the brain, and heart disease. Atherosclerosis is an important underlying cause.

Brain watershed infarction may be related to hemodynamic disorder. Hypotension is one of the main causes. Brain watershed infarction is mainly located between the large cortical arterial blood supply area and the marginal brain tissue between the basal ganglia arteriolar blood supply area. With the wide application of brain CT scan and brain MRI examination, the lesion morphology can be clearly displayed, which provides reliable help for studying the clinical features of brain watershed infarction.

Studies have shown that most patients with brain watershed infarction suffer from hypertension, 1 h to 4 days before the onset of brain watershed infarction, some patients have a significant drop in blood pressure, after the onset, the patient is recurrent or persistent hypotension.

Under normal oxygen partial pressure and glucose content, 20% of total cardiac output enters the cerebral blood circulation, the average cerebral blood flow is (50±5) ml/(100g brain tissue·min), and the brain tissue energy is 33.5J. / (100g brain tissue · min), glucose brain consumption is 4 ~ 8g / h, 24h 115g, if the blood is completely interrupted, 8 ~ 12s oxygen depletion, 5min nerve cells begin to bechemic necrosis, so when the circulating blood pressure drops Or the blood volume of the circulation suddenly decreases to a certain extent for a certain period of time, especially in the boundary area between the two cerebral arteries, which is very easy to be ischemic, that is, the ischemic necrosis of the brain tissue occurs.

Most patients are located at the junction of the middle cerebral artery and other arteries. The average blood flow velocity of the middle cerebral artery of patients with brain watershed infarction is slowed down, which is proportional to the degree of blood pressure drop. According to the hemodynamic principle, cerebral vascular resistance = mean arterial pressure / mean blood flow velocity, cerebral blood flow = mean blood flow velocity × middle cerebral artery cross-sectional area, it is speculated that the average blood flow velocity of the middle cerebral artery can reflect the influence of cerebral blood flow on the tissue supply in the marginal zone of arterial distribution, and a small number of patients with cerebellar lesions also Coexisting basal ganglia, thalamic infarction, may be related to distant dysfunction, so the blood flow velocity of the middle cerebral artery is related to the occurrence of brain watershed infarction, and is greatly affected by blood pressure. It has been confirmed that the main arterial end supplying the cerebral cortex is soft. The membranes are anastomosed to each other, and the end of the artery supplying the deep brain is generally free of anastomotic blood vessels. Therefore, when the blood pressure drops, the blood supply area at the end of the deep brain tissue is most prone to ischemia, and the cerebral blood flow is automatically regulated due to the decrease of cerebral vascular compliance. Upward range, redistribution of blood flow in the skull base artery, systemic hypoxia and metabolic disorders, blood flow of the patient Learn reserve capacity decreased significantly, not even fluctuations in blood pressure, cerebral perfusion pressure may also change, to reduce cerebral blood flow, causing ischemic cerebrovascular accident.

Prevention of cerebral infarction in watershed area

Treatment for hypertension, atherosclerosis, hyperlipidemia, diabetes, heart disease and carotid stenosis should be strengthened.

Pay attention to changing bad habits, moderate physical activity, avoid bad habits such as smoking, alcoholism, binge drinking, overeating, mainly low-fat, low-calorie, low-salt diet, and have enough high-quality protein, vitamins, cellulose and Trace elements.

Complications of cerebral infarction in watershed Complications, hypertension, diabetes

Because patients with watershed infarction often have history of hypertension, diabetes, heart disease, etc., they often have clinical manifestations of primary disease, such as clinical manifestations of hypertension, clinical manifestations of diabetes, and clinical manifestations of heart disease.

Symptoms of cerebral infarction in the watershed area Common symptoms Chronic atherosclerotic sensory disorder Intelligent disorder Hypertension

1. Main clinical manifestations: common in elderly people over 60 years old, clinical symptoms and signs are more complicated, blood pressure is lower when the incidence is more common, general performance may include: disturbance of consciousness, speech disorder, motor aphasia, transcortical motility Aphasia, nomenclature aphasia, hemianopia, movement disorders, sensory disturbances, convulsions, mental retardation, mental disorders, personality changes and positive pyramidal tract signs.

Because of the different positioning characteristics of the site, it depends mainly on the location and extent of the damage, but the cerebral cortex watershed cerebral infarction often has no symptoms. The main clinical features include: more onset in sleep or blood pressure control is too low; acute onset, disturbance of consciousness No or less, can have mental, personality changes or extrapyramidal symptoms of cerebral infarction, post-watershed cerebral infarction, subcortical cerebral infarction and basal ganglia watershed cerebral infarction.

(1) Pre-watershed cerebral infarction: the pre-cortical type refers to the infarct zone located in the superficial region between the anterior cerebral artery and the middle artery. It is mainly characterized by limb paralysis, rare facial paralysis, and half of the symptoms are accompanied by paresthesia. Hemispherics are associated with cortical motor aphasia and mental retardation, and non-dominant hemisphere lesions often have affective disorders.

(2) Post-watershed cerebral infarction: the post-cortical type refers to the superficial layer of the infarct zone between the middle cerebral artery and the posterior cerebral artery, often manifested as hemianopia with macular avoidance, in addition, common cortical sensory disturbance, Hemiplegia is mild or no, the dominant hemisphere is manifested as cortical-type sensory aphasia, occasional apraxia, nearly half may have emotional apathy, but also cortical sensory aphasia - apathy - simple aphasia, non-dominant hemisphere lesions There is contralateral space neglect and lack of disease.

(3) subcortical watershed cerebral infarction: the subcortical upper type refers to the infarction located between the deep and shallow branches of the middle cerebral artery, affecting the white matter of the lateral ventricle and basal ganglia, and the fibers in the basal nucleus are concentrated. Hemiplegia and partial sensory disturbances often occur, and dominant hemispheric lesions often have speech disorders.

(4) basal ganglia watershed cerebral infarction: the infarct of the brain watershed area under the curtain, is the ischemic infarction between the arteries of each group in the basal ganglia, with cerebellar watershed infarction more common, clinically often have simple partial movement and sensory disturbance It can also be seen as a simple central facial paralysis. The clinical symptoms and signs between the various types are sometimes not characterized. The diagnosis depends on brain CT scan or brain MRI.

3. Domestic sub-divisions are divided into the following types. This type of classification may be more convenient for brain CT scans and brain MRI examinations.

(1) The anterior cerebral artery and the marginal zone of the middle cerebral artery cortical branch. The infarction is located beside the sagittal sinus on the convex surface of the brain, which is called the pre-watershed infarction.

(2) The middle cerebral artery and the posterior cerebral artery cortex marginal zone, the infarction is located in the fan-shaped zone at the posterior end of the lateral ventricle, called the posterior upper watershed infarction.

(3) The anterior, middle, and posterior arteries provide blood for the top, sacral, and occipital triangle, and the infarction is located at the outer edge of the lateral ventricle, called the posterior watershed infarction.

(4) The curved zone of the middle cerebral artery cortical branch and the deep perforating branch is called the subcortical watershed infarction.

(5) The marginal zone at the end of the main arteries of the cerebellum is called the submental watershed cerebral infarction.

Examination of cerebral infarction in watershed area

Hemorheological examination: may have abnormalities such as high blood lipids, increased hematocrit, and elevated blood sugar.

1. Brain CT scan: Brain CT scan is one of the main bases of brain watershed infarction. It is a low-density foci that is located at the border junction of the main arteries of the brain. It is wedge-shaped, wide-edge outward, and sharp-pointed inward. CT The signs are the same as general cerebral infarction.

(1) Pre-watershed cerebral infarction: Infarction occurs in the marginal zone of the anterior cerebral artery and the middle cerebral artery cortex, which is equivalent to the mid-media, wedge-shaped, with the tip facing the lateral ventricle, the bottom facing the cortical surface, and the upper and lower centers returning to the upper part. Before and after the movement, the clinical manifestations were hemiplegia (lower limbs), hemipline loss, transcortical motor aphasia and mental retardation.

(2) Post-watershed cerebral infarction: Infarction occurs in the marginal zone of the posterior cerebral artery and the middle cerebral artery cortex, often at the junction of the occipital occipital region, which is wedge-shaped and pointed toward the ventricle. The clinical manifestations are hemianopia or quadrant blindness, cortical-like sensation. Obstacles, hemiparesis, transcortical sensory aphasia, etc.

(3) subcortical watershed cerebral infarction: infarction occurs in the marginal zone of the middle cerebral artery cortex and deep perforator, mainly located in the basal ganglia and lateral ventricle, can be connected into a linear or intermittent infarct, clinical manifestations of hemiplegia Non-cortical sensory disturbances, dominant hemispheric lesions may have language disorders.

(4) basal ganglia watershed cerebral infarction: brain MRI examination is superior to brain CT scan.

2. Brain MRI examination: It shows that the lesion is clearer than the brain CT scan, which can partially replace cerebral angiography, especially for posterior fossa lesions, which is superior to brain CT scan, and MRI can show lesions on the axial, coronal and sagittal planes. It is easy to judge the position and shape more accurately, such as the three-dimensional MR blood flow imaging through the brain watershed infarction Willis ring, while observing the cerebral infarction, the diagnosis of brain atypical watershed infarction not in the important watershed area Significant.

3. For cerebral aortic stenosis, cerebral atherosclerosis, cerebral vascular malformations, etc., blood vessel examinations such as Doppler ultrasound (TCD) and/or digital subtraction angiography (DSA), magnetic resonance vessels should be performed. Imaging (MRA).

4. Cardiac disease and blood pressure examination: All patients should pay attention to blood pressure examination, 24 hours of dynamic blood pressure observation if necessary, cardiac examination mainly includes electrocardiogram examination, cardiac ultrasound examination, etc. Some patients have abnormal manifestations of electrocardiogram, such as coronary blood supply Insufficient, left ventricular hypertrophy, atrioventricular block, myocardial infarction, paroxysmal tachycardia, atrial fibrillation, etc.

5. Fundus examination: mainly the manifestation of retinal atherosclerosis in the fundus, that is, the arterial lumen is thinned, the reflection of the arterial wall is enhanced, and the reflective band is widened, which can be expressed as a copper wire-like change. In severe cases, the artery is stiff and silvery. Such changes, arteriovenous cross-invasion, arterial compression of the vein to the deep retina of the retina, the vein can be pressed like a pen tip, and the severe one shows the atherosclerosis such as interruption or dislocation of the vein.

Diagnosis and diagnosis of cerebral infarction in watershed area

Diagnostic criteria

According to the pathogenesis and etiology of brain watershed cerebral infarction, patients with hypertension, atherosclerosis, hyperlipidemia, coronary heart disease or diabetes, etc., which cause cerebral atherosclerosis or a history of heart disease, suddenly appear neurological signs, such as Speech disorders, motor aphasia, transcortical motor aphasia, nomenclature aphasia, hemianopia, dyskinesia, sensory disturbances, convulsions, mental retardation, mental disorders, personality changes and positive pyramidal tract signs, and even disturbances of consciousness, should be considered The possibility of cerebrovascular disease, brain CT scan and brain MRI is the main diagnostic method necessary.

For the case of watershed cerebral infarction, attention should be paid to the cause, such as transcranial Doppler ultrasound, digital subtraction angiography (DSA), magnetic resonance blood flow imaging (MRA), electrocardiography, echocardiography and hemorheology. In order to clarify the cause and prevent recurrence.

Differential diagnosis

1. Cerebral hemorrhage: In the event of activity or emotional agitation, most have a history of hypertension and blood pressure fluctuations, acute onset, headache, vomiting, disturbance of consciousness are more common, brain CT scan can be seen high-density hemorrhage.

2. Brain tumor: slow-progressive cerebral infarction, attention to brain tumor differentiation, primary brain tumor incidence is slow, brain metastasis tumor is sometimes similar to acute cerebrovascular disease, brain CT scan should be done in time, if brain tumor and cerebral infarction can not Identification, it is best to do brain MRI to confirm the diagnosis.

3. Pay attention to the identification of other types of cerebral infarction.

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