OVERVIEW
Cerebral Watershed Infarction (CWSI) is defined as localized ischemia in the watershed zone or marginal zone between adjacent vascular supply zones. It can occur unilaterally or bilaterally and accounts for approximately 10% of all cerebral infarctions.
Causes
1. Diseases of cerebrovascular itself
Carotid artery stenosis is closely related to CWSI, when the stenosis of extracranial segment of internal carotid artery is more than 50%, and at the same time there is a drop in blood pressure, it is easy to have low perfusion in the watershed area, and it is easy to form CWSI. the development of the collateral circulation and the Willis ring has a significant impact on the perfusion in the watershed area, when the internal carotid artery is severely stenosed or occluded, the collateral and the Willis ring provide the main perfusion, and when the collateral circulation and the Willis ring is poorly developed, it is not necessary to have the collateral circulation and the Willis ring. When the collateral circulation and the Ring of Willis are poorly developed, this can lead to a susceptibility to infarction especially in the watershed region.
2. Hypotension or decreased cardiac output
Various causes of low blood pressure and reduced cardiac output in the circulation can cause CWSI, and they are often common causes, including: cardiac surgery, excessive blood loss during various other surgical procedures, vasodilation caused by various drugs, shock syncope of various causes, cardiac arrest, severe arrhythmia, spontaneous fluctuating hypotension, etc. These causes cause a reduction in blood pressure and blood flow slows down, leading to a reduction in blood flow to distal vessels, resulting in cerebral tissue infarction. Reduced blood flow, so that the brain tissue infarction.
3. Microemboli theory
Microemboli can reach the end of arterial branches with blood flow, often in the vascular branches in the junction area between the anterior cerebral artery and the middle cerebral artery blood supply. Microemboli are not easy to be cleared by stagnant blood flow, which can easily lead to the formation of CWSI.
Symptoms
Watershed cerebral infarction is predominantly over 60 years of age, with no gender difference. Most often there is carotid artery stenosis, lower blood pressure and decreased cardiac output. Common sites are the marginal zone between the middle cerebral artery and the anterior cerebral artery, the marginal zone between the middle cerebral artery and the posterior artery or the anterior middle and posterior cerebral arteries, and the marginal zone between the cortical and deep-penetrating branches of the middle cerebral artery. Clinical symptoms often have a stroke-like onset, and most often there is no impairment of consciousness. Combined with CT, it can be categorized into the following common types:
1. Pre-cortical type
It is a watershed cerebral infarction in the blood-supplying area of the anterior and middle cerebral arteries, located in the middle frontal gyrus, and in the shape of a band or wedge. Clinical manifestations are central hemiparesis and hemiplegia mainly in the upper limbs and hemiplegia, usually without facial and tongue palsy, and there may be affective disorders, strong grip reflex and focal epilepsy. Transcortical motor aphasia may be seen in the primary lesion, while quadriplegia and intellectual disability or dementia may be seen in the bilateral lesion.
2. Post-cortical type
It is a watershed area between the middle and posterior cerebral arteries or cortical branches of the anterior middle and posterior cerebral arteries. The lesions are located in the parieto-occipito-temporal junction area, and hemiplegia is the most common, with lower quadrant blindness being the most common. Cortical sensory deficits hemiparesis is mild or absent. Emotional apathy is present in about 1/2 of the cases, and there may be memory loss and Gerstmann’s syndrome (impaired angular gyrus). Difficulty in word recognition and transcortical sensory aphasia are seen in the dominant lesion, and somatosensory deficits are occasionally seen in the non-dominant side.
3. Subcortical type
The subcortical type is a watershed area between the cortical branches of the anterior middle and posterior cerebral arteries and the deep perforating branches, or between the return branch of the anterior cerebral artery (Heubner’s artery) and the middle cerebral artery (Doubt’s artery). The infarcted lesion is located in the deep part of the brain, white matter shell nucleus caudate nucleus, etc. Pure motor light hemiparesis or (and) sensory impairment involuntary movement may occur.
Examination
General routine examinations include blood pressure, blood lipids, blood glucose, blood homocysteine, blood viscosity measurement, plasma fibrinogen, antinuclear antibodies, C-reactive protein, electrocardiogram, and cardiac ultrasound. Cranial CT, cerebral angiography and magnetic resonance examination of watershed cerebral infarction are the same as cerebral thrombosis examination.
1. Cranial CT
Watershed cerebral infarction is a low-density area in the brain parenchyma, and the CT plane in the watershed area of the cerebral vessels shows a cusp toward the side, and the base of the ventricle toward the basal ganglia area of the wedge-shaped band in front of the chondrum, which may be irregularly formed into a sheet-like low-density shadow.
2. Angiography
Angiography can clearly show occlusion or obvious stenosis at the end of 2 neighboring vessels without embolus finding.
Diagnosis
According to the history and clinical manifestations, the diagnosis can be made by referring to the auxiliary examinations, as the onset of stroke is usually without consciousness disorder.
Treatment
1. The same treatment as cerebral thrombosis.
2. Respond to the various causes of the disease.
Actively search for the causes of the disease and treat the symptoms, including correcting the patient’s hypercoagulable state, replenishing blood volume, maintaining stable blood pressure, etc. Treatment of heart disease and intracranial and extracranial arterial lesions can help reduce the incidence of CWSI. For hypertensive patients, treatment with angiotensin-converting enzyme inhibitor antihypertensive drugs can simultaneously reduce the risk of coronary events and ischemic stroke.
3. Rehabilitation
(1) Preventing and controlling low blood pressure in the elderly, especially in cases of fever, diarrhea, infusion reaction and heart disease, and immediately replenishing and expanding fluid to maintain blood pressure if necessary.
(2) Strengthen the functional training of calculation, memory, speech and limbs.
(3) Hyperbaric oxygen therapy.
(4) Electrotherapy, acupuncture, massage and physiotherapy.