Lipohyalinosis

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Lipohyalinosis is a cerebral small vessel disease affecting the small arteries, arterioles or capillaries in the brain. Originally defined by C. Miller Fisher as 'segmental arteriolar wall disorganisation', it is characterized by vessel wall thickening and a resultant reduction in luminal diameter. Fisher considered this small vessel disease to be the result of hypertension, induced in the acute stage by fibrinoid necrosis that would lead to occlusion and hence lacunar stroke. However, recent evidence suggests that endothelial dysfunction as a result of inflammation is a more likely cause for it. This may occur subsequent to blood–brain barrier failure, and lead to extravasation of serum components into the brain that are potentially toxic. Lacunar infarction could thus occur in this way, and the narrowing – the hallmark feature of lipohyalinosis – may merely be a feature of the swelling occurring around it that squeezes on the structure.

Contents

Misuse of the term

C. Miller Fisher had decided to make lipohyalinosis a substitute term for fibrinoid necrosis. Fisher had done this because "of what he perceived to be the general agreement that the affected arteriolar segments also contained lipid". [1] This has caused some issues with the usage of the term lipohyalinosis. "Because of its use by some earlier authors, Fisher included "hyalinosis" in the list of synonyms that also included the term "fibrinoid"". [1] This means that people often associate hyalinosis and hyaline with lipohyalinosis and consider them the same thing. [1] The misuse of the term lipohyalinosis also has meant that many cerebral vessel pathology have been incorrectly described as lipohyalinosis. [2] This misuse of lipohyalinosis may cause issues for accurate diagnosis and therefore treatment of specific conditions if used incorrectly on a patient.[ citation needed ]

Hypertension

Hypertension is a strong risk factor. So-called deep-perforating arteries – relatively small arteries branching off of relatively large arteries (most commonly the lenticulostriate arteries from the middle cerebral artery) – are especially prone. [3] Uncontrolled hypertension and diabetes are both risk factors for this condition.[ citation needed ]

When Fisher observed the relationship between lacunar infarcts and lipohyalinosis, he also noted the relation to hypertension. It has been found that "The strong association between lipohyalinosis and hypertension documented by Fisher has been confirmed in several studies". [4] These studies have shown hypertension can cause lipohyalinosis because of the way hypertension changes blood vessels' structure. "Vascular remodelling of small and large vessels provoked by arterial hypertension is the initial step in the development of atherosclerosis and lipohyalinosis." [5] More specifically, "Hypertension alters the structure of blood vessels by producing vascular hypertrophy and remodeling and by promoting atherosclerosis in large cerebral arteries and lipohyalinosis in penetrating arterioles". [6] Chronic hypertension even produces arteriolar changes like lipohyalinosis that makes the blood vessel very susceptible to rupture. [6] The relationship between lipohyalinosis and hypertension is well documented and confirmed by various studies. [ citation needed ]

Furthermore, "In the microscopic level of small arteries or arterioles, hypertension also generates specific vasculopathies such as lipohyalinosis and thus causing lacunar infarctions". [6] Hypertensions and lacunar infarcts and lacunar stroke are related. This means hypertension is a start to a chain reaction. From lipohyalinosis to lacunar infarctions that may eventually lead to stroke, hypertension, uncontrolled, can cause a lot of damage to the brain.[ citation needed ]

Lacunar infarcts

Lacunar infarcts are a result of atherosclerosis (microthrombi) and lipohyalinosis. These affect the deep structures of the brain and may leave small (~5mm) cavity lesions. Small lacunar infarcts are "caused by various arterial disorders, the most frequent of which include microatheroma, lipohyalinosis, fibrinoid necrosis, and Charcot-Bouchard aneurysm". [7]

Lipohyalinosis was considered the most common cause for lacunar infarcts. [7] Fisher observed through autopsy studies that lacunar infarcts are caused by processes he described as segmental arterial disorganization, fibrinoid degeneration, and lipohyalinosis. [2] [8] Fisher's work in this area has been invaluable, but in more recent research into this area with new technology has brought up questions if lipohyalinosis is really the main cause of lacunar infarcts or lacunar stroke. Some new research now suggests that microatheroma may now be considered the main cause in that it is "now thought to be the most common mechanism of small vessel occlusion..." [6] These new findings have to be looked into more closely to determine if microatheroma is the main cause of lacunar infarcts or lacunar stroke or if Fisher's work still stands as it has for many years that lipohyalinosis is one of the main causes.[ citation needed ]

Cognitive decline

In a study done in 2003, researchers had found that their "data indicate that widespread small vessel lesions due to both [cerebral amyloid angiopathy] and [arteriosclerosis/lipohyalinosis] may play a critical role in the development of [Alzheimer disease]". [9] This means lipohyalinosis may be a huge factor in Alzheimer's disease and cognitive decline in general.[ citation needed ]

There have also been other studies that link cerebral small vessel diseases to cognitive decline and lipohyalinosis being a cerebral small vessel disease, is included in those as well. Cerebral small vessel disease is a major cause of cognitive decline in the older populations. [10] [11] The results from a small pilot study had found that "Participants showed some decreases in executive functioning, attention, processing speed, and memory retrieval, consistent with previous literature" and that "Performance on a computer-administered cognitive measure showed a slight overall decline over a period of 8–28 months". [10] Cerebral small vessel disease has caused, even if it is slight, a decline in cognition and has in this study and other studies like it.[ citation needed ]

Other

There are many other conditions and diseases that are related to lipohyalinosis. Below are the names of a few that are related to it and what they are. [ citation needed ]

Leukoaraiosis

Leukoaraiosis is a disease found in the brain and is very visible on CT or MRI scans. "Leukoaraiosis, or periventricular white matter disease, is the result of multiple small-vessel infarcts within the subcortical white matter... The pathophysiologic basis of the disease is lipohyalinosis of small penetrating arteries within the white matter, likely produced by chronic hypertension." [12]

Chronic familial lipohyalinosis

Chronic familial lipohyalinosis is a rare inherited variant.[ citation needed ]

Related Research Articles

Thrombus Blood clot

A thrombus,, colloquially called a blood clot, is the final product of the blood coagulation step in hemostasis. There are two components to a thrombus: aggregated platelets and red blood cells that form a plug, and a mesh of cross-linked fibrin protein. The substance making up a thrombus is sometimes called cruor. A thrombus is a healthy response to injury intended to stop and prevent further bleeding, but can be harmful in thrombosis, when a clot obstructs blood flow through healthy blood vessels in the circulatory system.

Arteriosclerosis Thickening, hardening and loss of elasticity of the walls of arteries

Arteriosclerosis is the thickening, hardening, and loss of elasticity of the walls of arteries. This process gradually restricts the blood flow to one's organs and tissues and can lead to severe health risks brought on by atherosclerosis, which is a specific form of arteriosclerosis caused by the buildup of fatty plaques, cholesterol, and some other substances in and on the artery walls. It can be brought on by smoking, a bad diet, or many genetic factors.

Vascular dementia (VaD) is dementia caused by problems in the supply of blood to the brain, typically a series of minor strokes, leading to worsening cognitive abilities, the decline occurring step by step. The term refers to a syndrome consisting of a complex interaction of cerebrovascular disease and risk factors that lead to changes in brain structures due to strokes and lesions, resulting in changes in cognition. The temporal relationship between a stroke and cognitive deficits is needed to make the diagnosis.

Binswangers disease Medical condition

Binswanger's disease, also known as subcortical leukoencephalopathy and subcortical arteriosclerotic encephalopathy (SAE), is a form of small vessel vascular dementia caused by damage to the white brain matter. White matter atrophy can be caused by many circumstances including chronic hypertension as well as old age. This disease is characterized by loss of memory and intellectual function and by changes in mood. These changes encompass what are known as executive functions of the brain. It usually presents between 54 and 66 years of age, and the first symptoms are usually mental deterioration or stroke.

Cerebrovascular disease Condition that affects the arteries that supply the brain

Cerebrovascular disease includes a variety of medical conditions that affect the blood vessels of the brain and the cerebral circulation. Arteries supplying oxygen and nutrients to the brain are often damaged or deformed in these disorders. The most common presentation of cerebrovascular disease is an ischemic stroke or mini-stroke and sometimes a hemorrhagic stroke. Hypertension is the most important contributing risk factor for stroke and cerebrovascular diseases as it can change the structure of blood vessels and result in atherosclerosis. Atherosclerosis narrows blood vessels in the brain, resulting in decreased cerebral perfusion. Other risk factors that contribute to stroke include smoking and diabetes. Narrowed cerebral arteries can lead to ischemic stroke, but continually elevated blood pressure can also cause tearing of vessels, leading to a hemorrhagic stroke.

Arteriole Smaller branches of Arteries in the Capillaries

An arteriole is a small-diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillaries.

Ischemia Restriction in blood supply to tissues

Ischemia or ischaemia is a restriction in blood supply to any tissues, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism. Ischemia is generally caused by problems with blood vessels, with resultant damage to or dysfunction of tissue i.e. hypoxia and microvascular dysfunction. It also means local hypoxia in a given part of a body sometimes resulting from constriction. Ischemia comprises not only insufficiency of oxygen, but also reduced availability of nutrients and inadequate removal of metabolic wastes. Ischemia can be partial or total blockage. The inadequate delivery of oxygenated blood to the organs must be resolved either by treating the cause of the inadequate delivery or reducing the oxygen demand of the system that needs it. For example, patients with myocardial ischemia have a decreased blood flow to the heart and are prescribed with medications that reduce chronotrophy and ionotrophy to meet the new level of blood delivery supplied by the stenosed so that it is adequate.

Infarction Tissue death due to inadequate blood supply

Infarction is tissue death (necrosis) due to inadequate blood supply to the affected area. It may be caused by artery blockages, rupture, mechanical compression, or vasoconstriction. The resulting lesion is referred to as an infarct (from the Latin infarctus, "stuffed into").

Hypertensive kidney disease Medical condition

Hypertensive kidney disease is a medical condition referring to damage to the kidney due to chronic high blood pressure. It manifests as hypertensive nephrosclerosis. It should be distinguished from renovascular hypertension, which is a form of secondary hypertension, and thus has opposite direction of causation.

Perivascular space

A perivascular space, also known as a Virchow–Robin space, is a fluid-filled space surrounding certain blood vessels in several organs, including the brain, potentially having an immunological function, but more broadly a dispersive role for neural and blood-derived messengers. The brain pia mater is reflected from the surface of the brain onto the surface of blood vessels in the subarachnoid space. In the brain, perivascular cuffs are regions of leukocyte aggregation in the perivascular spaces, usually found in patients with viral encephalitis.

Hypertensive emergency Condition of markedly elevated blood pressure with diastolic pressure typically greater than 120 mm Hg

A hypertensive emergency is very high blood pressure with potentially life-threatening symptoms and signs of acute damage to one or more organ systems. It is different from a hypertensive urgency by this additional evidence for impending irreversible hypertension-mediated organ damage (HMOD). Blood pressure is often above 200/120 mmHg, however there are no universally accepted cutoff values. Signs of organ damage will be discussed below.

Intraparenchymal hemorrhage Medical condition

Intraparenchymal hemorrhage (IPH) is one form of intracerebral bleeding in which there is bleeding within brain parenchyma. The other form is intraventricular hemorrhage (IVH).

Arteriolosclerosis Medical condition

Arteriolosclerosis is a form of cardiovascular disease involving hardening and loss of elasticity of arterioles or small arteries and is most often associated with hypertension and diabetes mellitus. Types include hyaline arteriolosclerosis and hyperplastic arteriolosclerosis, both involved with vessel wall thickening and luminal narrowing that may cause downstream ischemic injury. The following two terms whilst similar, are distinct in both spelling and meaning and may easily be confused with arteriolosclerosis.

Cerebral infarction Medical condition

A cerebral infarction is the pathologic process that results in an area of necrotic tissue in the brain. It is caused by disrupted blood supply (ischemia) and restricted oxygen supply (hypoxia), most commonly due to thromboembolism, and manifests clinically as ischemic stroke. In response to ischemia, the brain degenerates by the process of liquefactive necrosis.

Watershed stroke Medical condition

A watershed stroke is defined as a brain ischemia that is localized to the vulnerable border zones between the tissues supplied by the anterior, posterior and middle cerebral arteries. The actual blood stream blockage/restriction site can be located far away from the infarcts. Watershed locations are those border-zone regions in the brain supplied by the major cerebral arteries where blood supply is decreased. Watershed strokes are a concern because they comprise approximately 10% of all ischemic stroke cases. The watershed zones themselves are particularly susceptible to infarction from global ischemia as the distal nature of the vasculature predisposes these areas to be most sensitive to profound hypoperfusion.

Lacunar stroke Medical condition

Lacunar stroke or lacunar cerebral infarct (LACI) is the most common type of ischemic stroke, resulting from the occlusion of small penetrating arteries that provide blood to the brain's deep structures. Patients who present with symptoms of a lacunar stroke, but who have not yet had diagnostic imaging performed, may be described as suffering from lacunar stroke syndrome (LACS).

Complications of hypertension

Complications of hypertension are clinical outcomes that result from persistent elevation of blood pressure. Hypertension is a risk factor for all clinical manifestations of atherosclerosis since it is a risk factor for atherosclerosis itself. It is an independent predisposing factor for heart failure, coronary artery disease, stroke, kidney disease, and peripheral arterial disease. It is the most important risk factor for cardiovascular morbidity and mortality, in industrialized countries.

A silent stroke is a stroke that does not have any outward symptoms associated with stroke, and the patient is typically unaware they have suffered a stroke. Despite not causing identifiable symptoms, a silent stroke still causes damage to the brain and places the patient at increased risk for both transient ischemic attack and major stroke in the future. In a broad study in 1998, more than 11 million people were estimated to have experienced a stroke in the United States. Approximately 770,000 of these strokes were symptomatic and 11 million were first-ever silent MRI infarcts or hemorrhages. Silent strokes typically cause lesions which are detected via the use of neuroimaging such as MRI. The risk of silent stroke increases with age but may also affect younger adults. Women appear to be at increased risk for silent stroke, with hypertension and current cigarette smoking being amongst the predisposing factors.

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy Medical condition

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), is disease of the arteries in the brain, which causes tissue loss in the subcortical region of the brain and the destruction of myelin in the CNS. CARASIL is characterized by symptoms such as gait disturbances, hair loss, low back pain, dementia, and stroke. CARASIL is a rare disease, having only been diagnosed in about 50 patients, of which ten have been genetically confirmed. Most cases have been reported in Japan, but Chinese and caucasian individuals have also been diagnosed with the disease. CARASIL is inherited in an autosomal recessive pattern. There is currently no cure for CARASIL. Other names for CARASIL include familial young-adult-onset arteriosclerotic leukoencephalopathy with alopecia and lumbago without arterial hypertension, Nemoto disease and Maeda syndrome.

Hypertension and the brain

Hypertension is a condition characterized by an elevated blood pressure in which the long term consequences include cardiovascular disease, kidney disease, adrenal gland tumors, vision impairment, memory loss, metabolic syndrome, stroke and dementia. It affects nearly 1 in 2 Americans and remains as a contributing cause of death in the United States. There are many genetic and environmental factors involved with the development of hypertension including genetics, diet, and stress.

References

  1. 1 2 3 Rosenblum, William I. "Fibrinoid Necrosis of Small Brain Arteries and Arterioles and Miliary Aneurysms as Causes of Hypertensive Hemorrhage: A Critical Reappraisal." Acta Neuropathologica 116, no. 4 (October 2008): 361–69. https://doi.org/10.1007/s00401-008-0416-9.
  2. 1 2 Lammie, G Alistair. “Pathology of Small Vessel Stroke.” British Medical Bulletin 56, no. 2 (2000): 296–306.
  3. ↑ Brenner D, Labreuche J, Pico F, et al. "The renin-angiotensin-aldosterone system in cerebral small vessel disease". J Neurol. May 2, 2000
  4. ↑ Coca, Antonio, ed. Hypertension and Brain Damage. Updates in Hypertension and Cardiovascular Protection Ser. Cham: Springer, 2016.
  5. ↑ Droste, D. W., M. A. Ritter, R. Dittrich, S. Heidenreich, T. Wichter, M. Freund, and E. B. Ringelstein. "Arterial Hypertension and Ischaemic Stroke." Acta Neurologica Scandinavica 107, no. 4 (April 2003): 241–51. https://doi.org/10.1034/j.1600-0404.2003.00098.x.
  6. 1 2 3 4 Aiyagari, Venkatesh, and Philip B. Gorelick, eds. Hypertension and Stroke: Pathophysiology and Management. 2nd ed. Clinical Hypertension and Vascular Diseases. Humana Press, 2016.
  7. 1 2 Lastilla, Marcello. “Lacunar Infarct.” Clinical & Experimental Hypertension 28, no. 3/4 (April 2006): 205–15. https://doi.org/10.1080/10641960600549082.
  8. ↑ Caplan, Louis R. “Lacunar Infarction and Small Vessel Disease: Pathology and Pathophysiology.” Journal of Stroke 17, no. 1 (January 2015): 2–6. https://doi.org/10.5853/jos.2015.17.1.2.
  9. ↑ Thal, Dietmar Rudolf, Estifanos Ghebremedhin, Mario Orantes, and Otmar D. Wiestler. “Vascular Pathology in Alzheimer Disease: Correlation of Cerebral Amyloid Angiopathy and Arteriosclerosis/Lipohyalinosis with Cognitive Decline.” Journal of Neuropathology & Experimental Neurology 62, no. 12 (December 1, 2003): 1287–1301. https://doi.org/10.1093/jnen/62.12.1287.
  10. 1 2 Baker, John G., Amy J. Williams, Catalina C. Ionita, Peterkin Lee-Kwen, Marilou Ching, and Robert S. Miletich. “Cerebral Small Vessel Disease: Cognition, Mood, Daily Functioning, and Imaging Findings from a Small Pilot Sample.” Dementia and Geriatric Cognitive Disorders EXTRA 2, no. 1 (April 18, 2012): 169–79. https://doi.org/10.1159/000333482.
  11. ↑ Østergaard, Leif, Thorbjørn S Engedal, Fiona Moreton, Mikkel B Hansen, Joanna M Wardlaw, Turgay Dalkara, Hugh S Markus, and Keith W Muir. "Cerebral Small Vessel Disease: Capillary Pathways to Stroke and Cognitive Decline." Journal of Cerebral Blood Flow & Metabolism 36, no. 2 (February 2016): 302–25. https://doi.org/10.1177/0271678X15606723.
  12. ↑ Kasper, Dennis, Anthony Fauci, Stephen Hauser, Dan Longo, J. Larry Jameson, and Joseph Loscalzo, eds. "Cerebrovascular Diseases." In Harrison's Principles of Internal Medicine, 19th ed. McGraw-Hill Medical.
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